Mg ct1506 im by design2pro

» Month 2015 » June 2015

CT2 »

First Rock From the Sun

» Features

» Departments

CT4 Cannabis Testing Opens Up a Whole New Market

CT7, CT13 » New Products CT14 » Column Corner CT15 » Index & Chrom Online

CT8 X-Ray Spec Easily Analyzes Battery Components CT10 Exploiting the Potential of GPC/SEC for Polymer Analysis

Cover Story

Chromatography Techniques » June 2015

First Rock from the Sun Thanks to a slew of carefully designed scientific instruments on the MESSENGER spacecraft, we now know more than ever about the innermost planet of our solar system. »

by Michelle Taylor, Editor-in-Chief

riginally commissioned for a oneyear risky mission to Mercury, the MESSENGER spacecraft successfully operated for four years, transmitting extraordinary scientific findings about a planet we knew virtually nothing about previously. After using the last of its propellant and therefore no longer able to maintain a stable orbit, MESSENGER, after 10 years (seven in transit), slammed into the surface of Mercury traveling about 8,750 mph on April 30, 2015 at 3:26 EDT. “For the first time in history, we now have real knowledge about the planet Mercury that shows it to be a fascinating world as part of our diverse solar system,” said John Grunsfeld, associate administrator for the Science Mission Directorate at NASA, in a statement. “While spacecraft operations will end, we are celebrating MESSENGER as more than a successful mission. It’s the beginning of a longer journey to analyze the data that reveals all the scientific mysteries of Mercury.” The MErcury Surface, Space ENvironment, GEochemistry and Ranging (MESSENGER) spacecraft traveled a total of 4.9 billion miles—a journey that included 15 trips around the sun and ABOVE: Artist's impression of the MESSENGER spacecraft in orbit at Mercury. flybys of Earth once, Venus twice and Mercury COVER: These images show spectrometer readings measuring Mercury’s atmothree times—before it was inserted into Mercury’s sphere and surface composition. Photos: NASA/Johns Hopkins University Applied orbit in March 2011. Physics Laboratory/Carnegie Institution of Washington. Based on NASA’s numerous proposals and which explains both the seven years in transit and many flybys of studies, it was established that inserting a spacemultiple planets, did the trick. craft into orbit around Mercury was going to be extremely difficult. As the planet closest to the sun, Mercury is most subjected The payload to the sun’s powerful gravitational pull. In fact, Mercury travels MESSENGER is only the second spacecraft sent to Mercury. at an average speed of 106,000 mph. MESSENGER had to gain Mariner 10 flew past the planet three times in 1974 and 1975, tremendous speed to catch up with the planet, something that was mapping about 40 percent of its surface. Fortunately, in the three quite difficult, even given NASA’s advanced propulsion systems. If decades since Mariner 10 flew, space technology (and overall techMESSENGER approached on a direct path from Earth, it would nology) advanced enough to allow a more complex MESSENGER be accelerated by the sun’s gravity and pass Mercury too quickly to gather much more data. to orbit it. The spacecraft, which was designed and built at the Johns But Chen-wan Yen, an engineer from NASA’s Jet Propulsion Hopkins University Applied Physics Laboratory (APL), featured Laboratory, came up with a trajectory that relied on gravity assists many technology firsts. The most prominent among them was from Venus and Mercury. The resulting “loop-de-loop” path,

June 2015

» Chromatography Techniques

Cover Story

tribution, including varithe development of a vital ations in the thickness of heat-resistant and highly its crust. reflective ceramic cloth sunshade that isolated the spacecraft’s instruments and The biggest findings electronics from direct solar MESSENGER’s bigradiation, which was imporgest finding is an ironic tant given Mercury’s proximone—the planet closest ity to the sun. For example, to the sun contains ice. according to APL and NASA, Thanks to the tilt of the front side of the sunshade Mercury’s rotational axis, experienced temperatures which is almost zero, the in excess of 570 F, whereas craters at the planet’s the majority of components poles never see sunlight. in its shadow operated near From Mercury’s orbit, room temperature (68 F). MESSENGER looked The success in both design down at the planet’s poles and implementation of the and confirmed that the sunshade will help inform permanently shadowed future designs for planetary craters have temperatures missions within the solar less than -280 F, and water system. ice is stable on their dark The sunshade protected inner surfaces. Data indithe following instruments: cated the ice in the polar • Mercury Dual Imaging regions could be more This mosaic of Caloris basin is an enhanced-color composite overlain on System (MDIS): Widethan two miles thick. a monochrome mosaic. The color mosaic is made up of images obtained and narrow-angle imagers when both the MESSENGER spacecraft and the sun were overhead, conMESSENGER also ditions best for discerning variations in brightness. Photo: NASA that mapped landforms, caught sight of a mystracked variations in surterious dark material face spectra and gathered topographic information. covering most of the ice deposits. While researchers are still not • Gamma-ray and Neutron Spectrometer (GRNS): This instrusure exactly what it is, the layer supports the theory that organic ment detected gamma rays and neutrons that were emitted compounds and water were transferred from the outer solar sysby radioactive elements on Mercury’s surface or by surface tem to the inner planets, ultimately leading to life on Earth. elements that had been stimulated by cosmic rays. It was used Details on Mercury’s unique exosphere was another pivotal to map the relative abundances of different elements, and was find by MESSENGER. MESSENGER determined the chemical integral in finding ice at Mercury’s poles. composition of the exosphere to be hydrogen, helium, sodium, • X-ray Spectrometer (XRS): Gamma rays and high-energy potassium and calcium. It also monitored the material as it was X-rays from the Sun, striking Mercury’s surface, cause the surstretched out into a comet-like tail as long as 2 million km due face elements to emit low-energy X-rays. XRS detected these to the extreme space weather, including solar wind bombardemitted X-rays to measure various elements in the materials of ment, solar radiation and meteoroid vaporization. Mercury’s crust. The technological advancements of MESSENGER allowed • Magnetometer (MAG): This instrument mapped Mercury’s it to see much more than the 40 percent Mariner 10 had previmagnetic field and found regions of magnetized rocks in the ously mapped. This spacecraft photographed the entirety of the crust. Caloris basin, one of the largest impact basins in the solar sys• Mercury Laser Altimeter (MLA): By bouncing light off the tem. This allowed the spacecraft to spot volcanic vents around planet’s surface and gathering it after it had been reflected, this the rim of the basin, proving that volcanism helped shape the instrument provided detailed information on the height of surface of Mercury. landforms on Mercury’s surface. Highly accurate descriptions Even before MESSENGER, scientists hypothesized that of Mercury’s topography ensued. Mercury—a planet whose core makes up 60 to 70 percent of its • Mercury Atmospheric and Surface Composition mass—was shrinking. MESSENGER’s images of Mercury’s cliffs, Spectrometer (MASCS): This spectrometer, which was sensicalled lobate scarps, confirmed previous theories—to an extent. tive to light from the infrared to the ultraviolet, determined the Thanks to the cooling of Mercury’s oversized core, images characteristics of the atmosphere surrounding Mercury and showed that the total contraction of the planet is actually two to established the presence of iron and titanium minerals. seven times greater than researchers previously thought. • Energetic Particle and Plasma Spectrometer (EPPS): EPPS Earth’s magnetic field is generated by the planet’s churning measures the composition, distribution and energy of charged hot, liquid-iron core via magnetic dynamo. Mercury’s iron core particles (electrons and various ions) in Mercury’s magnetowas supposed to have finished cooling long ago, and therefore sphere. stop generating magnetism. However, much to the puzzlement • Radio Science (RS): Using the Doppler Effect, RS meaof scientists, that is not the case. MESSENGER confirmed that sured slight changes in the spacecraft’s velocity as it orbited Mercury’s magnetic field is not a relic of the past, but is indeed Mercury. This allows scientists to study Mercury’s mass disgenerated by an active dynamo in the planet’s core.

CT4

Chromatography Techniques » June 2015

Cannabis Testing Opens Up a Whole New Market Not just for illegal or medicinal use anymore, the cannabis testing industry is poised for a breakthrough as it finds its foothold in analytical science. »

by Michelle Taylor, Editor-in-Chief

iven recent law and attitude changes in the United States, the cannabis industry is on the rise—which means the cannabis testing industry is likewise growing. From analyzing potency and pesticides to testing for terpenes and residual solvents, chromatography is aptly suited to the analytical needs of the cannabis testing industry. Chromatography Techniques Editor-inChief Michelle Taylor recently spoke with Amanda Rigdon, GC Columns Product Manager at Restek Corp., for her input on the past, present and future of the cannabis testing market.

G Amanda Rigdon, GC Columns, Restek Corp.

Q: You’ve been doing medical cannabis testing for years, but now that cannabis is legal in some states, how does that affect the future of your product development? A: The fact that cannabis has been legalized in some states has really helped our product development efforts. The reason for this is that as additional states legalize cannabis, more labs spring up, bringing more customer views and needs to the table. For example, knowing that one lab is running a specific list of cannabinoids isn’t really helpful for developing standards, but once we see multiple labs running that same list, we know that there is a real market need for that list of cannabinoids. Additionally, as regulations begin to be put into place in different states like Colorado and Washington, we can get an even clearer picture of where the industry is heading in terms of methods and analytes. However, there is another side to that coin. Right now, state regulations differ from state to state, and they’re somewhat in flux, meaning that methods and analyte lists are still changing. While this is a challenge in terms of product development, in my mind, it’s a fun place to be because right now we’re witnessing the birth of a new analytical industry. Q: What impacts do you see cannabis legalization having on the overall scientific industry? A: While cannabis legalization may give birth to an industry

that rivals the size of the organic food industry, I’m not sure the cannabis industry will have an earth-shattering impact on the overall scientific industry. My prediction is that as the cannabis industry matures and continues to legitimize, the overall scientific industry will begin to view it as just another market segment, much like the food or nutraceutical industry. Granted, there may be a larger population of laid-back, long-haired scientists in the industry (which I think is great), but in reality, cannabis analysis methods are no different than analysis methods in any other industry segment today. We’re still just quantifying analytes in a matrix. Don’t get me wrong—I think that this will be a good thing. Once the overall scientific industry begins to view the cannabis analytical industry as just another market segment, the legitimate cannabis labs out there should begin to receive the respect and support they deserve. Q: Now that cannabis is legal in some states, do you expect an uptick in instrumentation and consumables specific for cannabis testing? Do you expect the extra attention to come with a wave of enhanced scientific methods/instruments? A: I believe there will definitely be an uptick in specialized instruments and consumables for the cannabis analytical industry. In fact, we can already see this happening with the introduction of numerous “cannabis analyzers.” While some of these analyzers may work just fine, the quantitative accuracy of some of these “analyzers” is dubious at best. Right now, this specialized equipment is preying on the relative inexperience of much of the cannabis analytical industry, but as the industry matures, I can see other, more legitimate consumables, sample prep products and standards being introduced to address the analytical needs for cannabis-specific methods. Additionally, as methods become more standardized, I can see some quantitative analyzers based on existing instrumentation being introduced for the more common methods, such as potency. This being said, I can’t see a whole lot of enhanced instrumentation being developed for this industry. As I said before, the methods used by this industry aren’t really very different than those used for food or nutraceuticals. As regulations for food and nutraceuticals evolve, instrumentation will evolve with them, and will most likely continue to be suitable for cannabis analyses.

June 2015

Q: There have been arguments from some that don’t consider cannabis testing a legitimate subset of scientific testing. How do you respond to that? A: Honestly, I’m not sure how that can be an argument. Cannabis testing involves quantification of analytes in a matrix. I’m not sure how this definition fails to fall under “legitimate scientific testing.” If the argument is that some cannabis testing labs aren’t interested in obtaining accurate results and instead only want to report potency numbers that will sell more product, then my answer to that would be yes, I’m sure there are labs like that out there. However, we have to remember that this is an infant market operating under heavy restrictions, considerable legal risk and a decades-old stigma. As the market matures, regulations will also mature, and the focus will solidify where it should be: consumer safety, product quality and product consistency. Right now, I work with many laboratories that operate for this purpose and generate data that I, as an experienced analytical chemist, would trust. As time goes on, the labs operating for the purpose of moving product will either go away because of violations of regulations or will improve their practices to bring them in line with scientific standards. This is why cannabis testing needs to be recognized by both regulators and the scientific industry as a legitimate subset of scientific testing. If we continue to ignore the industry, these less-than-trustworthy labs will continue to operate, putting consumers at risk. I would argue that if the food or nutraceutical industry was less regulated than it is currently, we would enjoy much less safety when consuming these products. Many of the improvements in regulation for food safety have come from collaboration between scientists and regulators—I see a great possibility here for cannabis safety as well.

» Chromatography Techniques

Q: What are common methods currently used in the analytical side of the cannabis industry? A: The most common method by far right now is potency analysis. This method measures the level (usually reported in percent) of a variety of cannabinoids in various cannabis products. Many states where cannabis is legal require potency testing for all cannabis products sold in dispensaries. Most states usually only require reporting for tetrahydrocannabinol (THC) and cannabidiol (CBD) and their associated acids, tetrahydrocannabinolic acid and cannabidiolic acid, but some labs choose to quantify other cannabinoids, such as cannabigerol (CBG) and cannabichromene (CBC). This testing can be performed via gas chromatography or liquid chromatography on matrices ranging from plant material to foods to topical creams. The other two common methods used by the cannabis testing industry are residual solvent analysis and terpene analysis. Residual solvent analysis is the measurement of organic solvents present in cannabis concentrates, which are highly concentrated products extracted from cannabis plant material via solvent or supercritical fluid extraction. This test is performed only on cannabis concentrates via GC. Terpene analysis is the measurement of flavor and fragrance compounds that occur in the cannabis plant (terpenes). Terpenes contribute to the overall flavor profile of various cannabis strains and are suspected to enhance some of the medicinal benefits of cannabis. Terpenes are usually measured in plant material or concentrates via GC or LC. Q: What are some of the challenges with current methods? A: Based on what I see in the market, the main challenge with current methods is sample preparation. The imagination of the production side of the cannabis industry seems unlim-

CT5

CT6

Chromatography Techniques » June 2015

ited, which results in a constant influx of new and challenging matrices. On any given day, a cannabis testing lab can encounter matrices ranging from plant material, to gummy bears, to topical creams and soaps. Sample preparation methods for all of these matrices will differ, and labs under a time crunch don’t have time to develop new sample preparation methods every day. Another challenge is the regulations concerning pesticide analysis. While some states have released lists of allowed pesticides for cannabis producers, there seems to be little guidance on how testing should be performed. Are there allowable limits for these pesticides? Which pesticides should be monitored outside of the allowed list? And of course, sample preparation for analysis of ppb levels of pesticides can be more challenging than sample preparation for analysis of percent levels of cannabinoids. Q: Every scientist wants faster results—more samples in less time for less money. How do you solve this equation in cannabis testing? A: Restek Corp. is helping cannabis labs solve the equation for running more samples in less time for less money by combining efficient methods with workflow optimization. The Innovations Lab at Restek has over two centuries of combined chromatography experience across multiple industries. We’ve drawn on our experience in other industries to develop fast, easy, time-saving methods that can be combined on the fewest instrument platforms possible. For example, we have developed fast headspace methods for residual solvents and terpenes that require little to no sample preparation on the same column and instrument platform to help cannabis labs make full use of the headspace instrument required for residual solvent analysis. On the LC side, we have developed an extremely fast potency method that can be performed on any conventional HPLC system without the need for more expensive UHPLC instrumentation. Q: What is your advice to both startup and well-established cannabis testing laboratories? A: If I could give one piece of advice to startup labs, it would be this: do a lot of research before starting up your lab. If you’re considering purchasing a refurbished instrument, check into the company you’re considering purchasing from, check to make sure you can still purchase parts for your refurbished instrument. How will the refurbished instrument be serviced? Are you sure that guy you know really knows how to service a two decade old

instrument? Make sure to research the methods you’re planning to implement so you know you’re purchasing an appropriate instrument. If you don’t have much chromatography experience, take a day or two to read up on basic chromatography. There are a ton of free, useful resources available to help you learn the basics of chromatography. My advice to well-established cannabis testing labs is to keep looking into streamlining and improving your methods. Never stop asking questions. Is there a faster way to run a specific analysis? Can multiple analyses be combined on one instrument? Can your sample preparation methods be improved to keep your instruments and consumables cleaner? If you’re encountering ion suppression for your pesticides analysis, is there an improved sample preparation method? Q: You recently took part in the first annual Emerald Conference, exploring the science of cannabis testing. Can you share some insights, analysis and/or trends that came out of that conference? A: The Emerald Conference in January of this year was an amazing experience! It really validated my views that the cannabis testing industry has made great strides toward proper, legitimate science for the purpose of consumer safety. The atmosphere at the Emerald Conference was more professional than some other conferences I’ve attended for well-established industries. The conference wasn’t a congregation of potheads—it was a conference of scientific professionals gathered to share insights and network with their peers. One trend I saw at the conference was an overall agreement that better, more accurate methods were required by the industry if it was to continue to grow. A major insight for me was the realization that there is a disconnect between the production/sales side of the cannabis industry and the testing side. While producers and dispensaries want some testing to be performed on their product, some are unwilling to pay a fair price for high-quality, accurate testing. In my opinion, this contributes to some labs practicing less-than-optimal science in order to drive down costs or to give producers and/or dispensaries the answer they’re looking for. Until we mitigate this through education or regulation, labs dedicated to good science may suffer. Q: Are there future conferences planned? A: The last time I spoke to the conference organizers, they were in the midst of planning for the 2016 Emerald Conference, so yes, there are future conferences planned at this time. I know I will be attending, and based on what I heard from conference attendees in January, attendance will definitely grow.

CT7

Chromatography Techniques » June 2015

New Products TOF/MS Easily IDs Unknown Analytes LECO’s Pegasus GC-HRT 4D combines comprehensive GCxGC with high-performance time-of-flight mass spectrometry. The TOF/MS provides scientists with the ability to investigate complex samples and identify unknown analytes with confidence. These advances in technology are paired with the company’s ChromaTOF-HRT brand software with High Resolution Deconvolution, which is tailored to get the most out of high-resolution data using NIST and accurate mass libraries. User workflows are enabled by features such as pseudo-molecular ions via chemical ionization, leveraging retention time matching, isotope patterns and mass accuracy of deconvoluted fragments—all leading to confident identification of unknown species. The TOF/MS has mass accuracies of 1 ppm. LECO Corp. www.leco.com, 800-292-6141

Analyzers Specifically Designed for Gasification Apps Henniker Scientific’s Veraspec range of Molecular Beam Gas Analyzers has been extended to meet the specific demands of reaction monitoring in pyrolysis and gasification research applications. The product range comprises high-performance gas sampling systems designed for the analysis of high-pressure reaction processes up to atmospheric pressure. The systems are particularly suited to the study of gas kinetics of atmospheric reactions, clusters and high-pressure plasmas. The series features the proprietary 19-mm MAX quadrupole mass filter. The quadrupoles are available in mass range options up to 16,000 amu with ppb detection capability and resolution characteristics that include a single detector capable of measuring neutrals, positive ions and negative ions. The systems offer an unique cross-beam sampling configuration, which improves signal-to-noise over axial sampling arrangements. The Cross Beam Deflector Ionizer deflects ionized gas phase species through 90° with 100% efficiency, separating them from photons, metastables and molecular beam gases. This scheme, together with the heated inlet path, greatly reduces spurious background signal and maintains the integrity of the quadrupole mass filter for longer, allowing potentially harmful deposits to pass straight through and on to the ultra-high vacuum pumping system. Henniker Scientific Ltd. www.henniker-scientific.com, +44 0 1925 830771

Analytical HPLC Separations High Quality for Absolute Reliability You are searching for the right quality control in the production of pharmaceuticals, chemicals, or food and beverages? We offer you a comprehensive range of state-of-the-art analytical HPLC solutions, and dedicated application support to carefully analyze your analytical task.

www.merckmillipore.com/ analytical-hplc

EMD Millipore Corp. is a subsidiary of Merck KGaA, Darmstadt, Germany EMD Millipore and the M logo are trademarks of Merck KGaA, Darmstadt, Germany. © 2015 Merck KGaA, Darmstadt, Germany. All rights reserved.

CT8

Chromatography Techniques » June 2015

X-Ray Spec Easily Analyzes Battery Components X-ray photoelectron spectroscopy allows the intricate depth profiling of lithium batteries, revealing information on components and chemistries that can improve overall performance. »

by Tim Nunney, Thermo Fisher Scientific, Inc., Waltham, Mass.

he Thermo Scientific K-Alpha+ XPS system was used to analyze the surface of lithium-ion battery electrodes. Due to the air-sensitive nature of these materials, the K-Alpha vacuum transfer module was used to safely transport the samples from a glove box to the instrument without exposure to ambient atmosphere. This ensured that the surface was as representative of the electrode material as removed from the cell.

Introduction For a large number of applications, from automobiles to portable electronics, lithium-ion battery assembles have become the energy storage solution of choice. Lithium ion (Li-ion) battery cells are lightweight compared to other battery technology, which makes them appropriate for transport applications when combined with their relatively high-energy density, and can mitigate against their higher cost. Further improving the performance of Li-ion cells—for example, to increase energy density, reduce weight, decrease costs and improve recharge times—involves developing improvements to at least one of the core components of the cell, shown in Figure 1. When operating, lithium stored in the anode is oxidized, and the Li+ ions created transport through the electrolyte and separator film to the cathode. In the cathode, it is the anion that is oxidized, creating a compound that can store the arriving lithium ions. When the cell is recharged after use, the flow of

Figure 1: Li-ion cell in operation.

ions is in the opposite direction, and they are reduced back to lithium metal to be stored in the anode. The anode is typically made from graphite, with lithium intercalated into the graphite structure. The cathode is comprised of a lithium metal oxide, the exact composition of which varies depending upon the required characteristics of the cell. The most commonly used cathode materials are LiCoO2 (LCO – lithium-cobalt), LiMn2O4 (LMO – lithium-manganese), LiFePO4 (LFP – lithium-phosphate) and Li(NiMnCo)O2 (NMC – nickel manganese cobalt). These oxides change in stoichiometry depending on whether the cell is charged or discharged; i.e., if the flow of Li+ is to or from the cathode. A byproduct of the charge and discharge process is the formation of the solid-electrolyte interphase (SEI) layer on the anode. The formation and development of the SEI layer competes with the reversible lithium intercalation process. Over the lifetime of the battery the presence of the SEI will contribute to the lowering of capacity, and is a contributing factor to the ultimate failure of the cell. Understanding the SEI layer is critical—it can be controlled and therefore improve cell performance. XPS depth profiling offers a way of chemically characterizing the complex mix that The vacuum transfer module on the K-Alpha+ KPS system allows samples that have been prepared in an inert environment to be transferred into the spectrometer chamber without exposure to air.

June 2015

Âť Chromatography Techniques

Figure 3: Composition variation for the NMC components.

Figure 2: Survey spectra from pristine cathode (blue) and cycled cathode (red) samples.

By using the vacuum transfer module and the K-Alpha+ XPS system, it is possible to analyze Li-ion battery components. Analysis of unused and cycled cathode samples determined the expected variation in lithium content.

makes up the interphase layer, allowing identification of the chemistries that comprise the SEI.

Experimential Lithium is very sensitive to air and moisture. To analyze the electrode materials successfully, they need to be introduced into the K-Alpha+ XPS system without air exposure. To do this, the samples are loaded into the K-Alpha Vacuum Transfer Module (VTM) in a glove box. The VTM is evacuated in the glove box antechamber, and then transported to the XPS system. As the VTM is held together by air pressure, it automatically opens during the pump-down cycle in the K-Alpha+ and is therefore integrated into the standard, automated sample transfer process. In these experiments, two cathode samples were investigated. One sample was a pristine, unused sample; the other was from a cell that had been through several charge-discharge cycles, and was in a charged state when the cell was disassembled.

Results Survey spectra collected from the as-received cathode samples are shown in Figure 2. The cathode material is Li(NixMnyCoz)O2, prepared using a binder medium to hold the material together. The binder is a mixture of fluorine and oxygen-containing polymers, and for the pristine sample is evident as a significant amount of residue on the surface. This could be important during the first use of the cathode if the binder residue is mobile in the electrolyte or reacts to begin the formation of a surface layer that impedes ion transport. The cycled cathode still shows the presence of the binder, and also evidence of residue from the electrolyte at the surface. Figure 3 shows the variation in the NMC components of the two samples (excluding oxygen). The relative intensities of the Ni, Mn and Co components are very similar between the two samples, but the amount of Li detected is around 40 percent of that seen in the pristine cathode. This is as expected in a sample from a charged cell, where the Li ion transport has been toward the anode and away from the cathode, resulting in a depleted level of lithium in the cathode.

Chromatography is what we do and who we are. We are an independent, international, and diverse team of employee-owners. We live and breathe phase chemistry, peak separations, resolution, and inertness because while chromatography may be a necessary tool in your business, it is our business. And it is a business we serve with unrivaled Plus1 service, applications, and expertise. From LC to GC, Restek is your first and best choice for chromatography.

www.restek.com

CT9

CT10

Chromatography Techniques » June 2015

Exploiting the Potential of GPC/ SEC for Polymer Analysis The changing global economic picture, environmental pressures and growing demand for specialist applications are driving the requirement for a new generation of instrumentation for polymer development. »

by Stephen Ball, Product Marketing Manager for Nanoparticle and Molecular Characterization, Malvern Instruments, UK

cross the globe, synthetic (or man-made) polymers are used in substantial volumes for a diverse range of applications: for packaging and electrical insulation; in the formulation of paints, coatings and adhesives; to manufacture consumer goods; and produce man-made fibers for the textile industry. The vast majority of these polymers are produced from feedstocks derived from oil refining. This means the economics of production have been transformed in recent years as a result of dramatic changes in oil price. In addition, the synthetic polymer industry faces significant pressure to advance the sustainability agenda by developing polymers with a lighter environmental footprint. These include materials with higher performance/volume gearing for the production of lighter automotive components or more efficient packaging, and products with enhanced recyclability. Increasingly, the line between “natural” and synthetic polymers is blurred as technology is developed to make new polymers from naturally occurring feedstocks. Replacing fossil fuel-based polymers with renewable/ biopolymers, such as those derived from starch or cellulose, is a proven strategy for lightening the environmental load associated with polymer use. These trends, and the drive to commercialize smart new polymers for highly specialized applications, creates dynamism in the synthetic polymer industry, driving a requirement for analytical instrumentation that is sufficiently powerful and sensi-

tive to provide the information needed to progress. For polymer scientists, GPC/SEC (gel permeation chromatography/size-exclusion chromatography) is a valued analytical technique, primarily because of its ability to provide molecular weight (MW) distribution data.

Re-evaluating GPC GPC is a two-step process involving separation of the sample in a packed column on the basis of hydrodynamic size, and subsequent detection of the resulting stream. A traditional GPC/SEC setup uses a single concentration detector—typically a refractive index (RI) detector—to determine how much material there is in each sized fraction. These data generate a size distribution for the sample. This size distribution is usually converted into a MW distribution through a calibration exercise based on the measurement of relevant standards. MW and MW distribution are primary metrics for polymers because they directly impact almost all of the commercially useful properties they exhibit, from gas barrier performance to mechanical strength and melting properties. The need for MW data therefore runs from R&D—where it supports the development of new products and processes—through optimization and troubleshooting during manufacture, and product QC (since MW often forms part of the sales specification). Against a backdrop of substantial industry development, the limitations of this single detector approach are becoming increasingly problematic. One issue is that for many polymers, especially those that are new, there are few relevant standards. In the absence of a standard with a size/MW ratio similar to that of the material being analyzed, the MW data measured with a single concentration detector will be relative to the standard rather than absolute, a factor that can seriously inhibit the development of the structure-performance relationships needed for development. In addition, a single detector reveals very little information about other polymer characteristics, such as the extent of branching,

June 2015

» Chromatography Techniques

With this setup, the MW of the sample is determined directly by the LS detector without need for a closely similar calibration standard. A light scattering detector generates MW data from measurements of the light scattering pattern produced by a molecule, using the Rayleigh equation. Both weight-averaged and number-averaged MW distribution data are produced—Mw and Mn respectively. In this experiment, PMMA is observed to have the highest Mw (894.4 kDa), while that of PS is 249.7 kDa, and PVC is 227.1 kDa. The ratio of Mw/Mn quantifies the polydispersity of the polymer (PD), a measure of the breadth of MW spanned by the sample. All three Figure 1: Using a multi-detector array produces MW distribution data for PS polymers have a PD of around 2, indicating a broad (pink and purple), PMMA (green and black) and PVC (blue and olive) with no MW distribution. need for calibration. This simple series of experiments demonstrates one of the primary benefits of using a multi-detecwhich can be used to control product performance. tor array—the ability to measure the MW of any polymer, The use of an integrated multi-detector array, in place of a regardless of structure of elution volume, with a high degree of single detector, directly addresses these issues. The following studies show what this more modern approach to GPC/SEC can deliver.

Accurate, absolute MW measurement Three different polymer samples were analyzed using an OMNISEC GPC/SEC system from Malvern Instruments incorporating the OMNISEC REVEAL multi-detector array. This consists of up to four detectors: RI, light scattering (LS), UV and viscometer. The samples measured were a broad distribution polystyrene (PS), a broad distribution polymethyl methacrylate (PMMA) and a polyvinyl chloride (PVC). The samples were separated using two Viscotek T6000M columns with a mobile phase of tetrahydrofuran (THF) stabilized with 300 ppm butyl hydroxyl toluene (BHT). Full dissolution was ensured by leaving the samples overnight to dissolve. The detectors and columns were all maintained at a temperature of 35 C to ensure good sample separation and a stable baseline for each analysis. Figure 1 shows MW distribution data for the three samples expressed in the form of a weight fraction (Wf) overlay plot. Replica injections for each polymer illustrate the excellent reproducibility of the measurements. Table 1 shows the additional information provided by the GPC/SEC system for each polymer, which includes measurements of intrinsic viscosity (IV) and weigh average hydrodynamic radius (RHw).

Polystyrene

108,900 249,770 2.294

Polymethylmethacrylate 431,670 894,430 2.072

0.814

0.361

1.353

13.902

7.647

15.53

Parameter

Polystyrene

Mn (Da) Mw (Da) PD (Mw/Mn) Intrinsic viscosity (dL/g) Rhw (nm)

112,240 227,090 2.023

Table 1: Results from the measurement of three polymer samples using a multi-detector array include values of IV and RHw, alongside MW distribution data.

Figure 2: Triple detection chromatograms for three different polystyrene samples with the clean baselines and smooth traces that characterize successful GPC/SEC analysis.

CT11

CT12

Chromatography Techniques » June 2015

accuracy, even in the absence of relevant standard. One of the major advances in modern GPC/SEC systems is in the area of light scattering detector sensitivity. In combination with features that ensure a stable baseline for measurement, this sensitivity delivers the excellent reproducibility illustrated by these data. Such performance enables the differentiation of polymers that differ only slightly from one another, which can be helpful for understanding and unlocking the full potential of a new polymer, or when troubleshooting a polymerization process. Equally importantly, high sensitivity enables accurate measurement with very little sample—as little as 100 ng with the latest high-performance systems. This means that reliable data can be generated for a brand new polymer even when supplies are scarce.

Extending productivity Included in the multi-detector data presented above are values for IV, an inverse measure of density. Polymers with the same MW exhibit different IVs depending on the how they coil in solution, a behavior that is influenced by, for example, the extent of branching in the polymer backbone. Tighter coiling increases density and lowers IV. When MW is being independently measured using a LS detector, IV data from a viscometer can be used to investigate structural characteristics. Figure 2 shows triple detection chromatograms for three different polystyrene samples, one linear (unbranched, 2A), the second with a star-shaped, branched structure (2B), and the last a brominated linear polystyrene (2C). Table 1 summarizes the numerical data recorded. All samples were prepared and run under the same conditions as in the previous study using an OMNISEC GPC/SEC system. The clean baselines and smooth traces of the recorded chromatograms demonstrate the excellent performance of the GPC/SEC system and the successful analysis achieved. The numerical values presented in Table 1 indicate that the branched and brominated samples have a MW to IV ratio that is different from that of the linear pure polystyrene, suggesting that branching and bromination change the way in which the polymers coil in solution. The Mark Houwink (M-H) plot, a log-log graph of IV against MW, highlights these differences. The M-H plot shows that, at any given MW, the branched polystyrene has a lower IV than the linear analogue, indicating that it has a higher density and less open structure. This difference increases with increasing MW. In addition, the brominated sample exhibits a much lower IV than either of the others at all MWs. The substitution of hydrogen atoms (atomic mass = 1) on the styrene with bromine atoms (atomic mass = 79.9) means that brominated chains have a much higher MW than unbrominated analogues of equivalent length. This results in an increase in molecular density and a corresponding decrease in IV. Here then, two discrete effects are reducing IV—branching and substitution. However, the magnitude of the differences in each case is dependent on the level of branching or substitution. This raises the question of how to differentiate between these two effects. Figure 3 shows data collected using the UV-Vis photodiode array detector in the OMNISEC RESOLVE array, which collects high-quality spectral data to enable compositional differentiation of the eluting sample. The branched polystyrene produces a UV trace (3C) that is very different from that of the brominated sample (3A) but essentially identical to that of the linear polystyrene sample (3B). The observed reduction in IV with the branched sample can therefore be safely attributed to branching rather than to any difference in composition.

Figure 3: Data collected using the UV-Vis photo-diode array detector in the OMNISEC RESOLVE array.

The UV data for the brominated sample can be used to determine whether bromination is consistent as a function of MW, or whether higher/lower MW material is associated with more or less bromination. Such information can be valuable for the development of new materials or when troubleshooting polymerization control or QC issues since subtle differences in bromination reactions can trigger substantial and unacceptable differences in product performance.

Looking ahead As the polymer industry faces up to significant current and future challenges, more is required of the analytical techniques that it relies on. GPC/SEC is a technique that has evolved substantially from the single detector, calibration-based approach first established in the 1970s and 80s. Today’s fully integrated, multi-detector GPC/SEC systems offer levels of performance and informational productivity that ensure their place at the heart of the polymer developer’s toolkit. By enabling the accurate and reproducible measurement of MW, MW distribution, molecular size, IV and structural characteristics such as branching, modern GPC/SEC systems provide the information needed to drive product development and ensure that manufacturing processes are fully optimized to consistently deliver high performance products.

June 2015

» Chromatography Techniques CT13

New Products EDXRF Analyzers Measure Across Range of Matrices

Helium Ionization Detector is Small, Sensitive

Applied Rigaku Technologies’ Rigaku NEX QC Quant EZ series of low-cost, high-resolution benchtop energy dispersive X-ray fluorescence (EDXRF) elemental analyzers delivers measurements across a diverse range of matrices—from homogeneous liquids of any viscosity to solids, thin films, alloys, slurries, powders and pastes. The EDXRF series includes the NEX QC QuantEZ EDXRF spectrometer, optimized for routine quality control elemental analysis applications, and the NEX QC+ QuantEZ analyzer, designed for more demanding applications where analysis time and sample throughput are critical. Applied Rigaku Technologies, Inc. www.rigakuedxrf.com, 512-225-1796

VICI’s newest member of the Pulsed Discharge Detector (PDD) family is also the smallest and thriftiest. The miniPDD uses about one fifth (20 percent) the amount of helium as the VICI Valco D-3 and D-4 versions, giving up only a bit of sensitivity and dynamic range in return. It is approximately half the size of the D-4, but has nearly the same sensitivity—about 100 ppb for fixed gases. With its reduced size, weight and helium consumption, it is well suited to portable applications, or to any situation in which the high cost of helium becomes a consideration. Valco Instruments Co., Inc. www.vici.com, 800-367-8424

Sample System, MALDI Generate Highres Images Shimadzu Scientific Instruments’ iMLayer matrix vapor automated sample treatment (matrix deposition) system provides a precise, high-resolution method for high spatial resolution imaging mass spectrometry. Used in conjunction with the company’s MALDI-TOF mass spectrometers, the system uses vaporization to deposit matrix to tissue slices using what is called the “dry coat” method. In this method, matrix powder is heated under vacuum to the boiling point of the matrix crystals. The sample positioned above the matrix then becomes coated with a thin layer of matrix. A laser positioned above the sample is utilized to control the thickness of the matrix layer, resulting in reproducible matrix deposition. Shimadzu Scientific Instruments Inc. www.ssi.shimadzu.com, 800-477-1227

Gel Electrophoresis System Analyzes DNA Quickly The Qsep100 DNA Analyzer from Precision Biosystems uses micro-capillary gel electrophoresis combined with fluorescence detection to perform post-PCR separation, detect DNA and RNA fragments and assess the quality of genomic DNA. The system can perform 200 assays automatically as quickly as 2 min/sample. It resolves DNA fragments in the range of 10 to 20,000 base pairs (bp) with 2 to 4 bp resolution. The design features a disposable pen-shaped cartridge filled with gel that incorporates a short-fused silica capillary. The sample is automatically injected into the cartridge where it migrates through the capillary, and fragments are excited by a super-bright LED. Precision Biosystems www. precisionbiosystems.com, 888-490-4443

Plate is Sturdy Transportation Option

Gas Analyzers Feature Broad Pressure Range

Porvair Sciences’ glass vial storage plate combines 96 borosilicate glass vials of 700 µL into a rigid polypropylene carrier microplate to provide a solution for storage and transportation applications. The hard-wearing plate provides a zero-leachates solution for both UHPLC and storage scenarios, such as combinatorial chemistry, where broad chemical resistance and thermal stability is vital. The storage plates are less costly than solid glass plates and are precisely manufactured to comply with ANSI/ SLAS dimensions to ensure complete compatibility with automated equipment. The glass vial storage plates can be capped with a square-well cap mat. Porvair Sciences Ltd www.porvair-sciences. com, +44 1978 666240

Hiden Analytical’s QGA systems are suited for direct real-time analysis, quantification and control of gas-related processes ranging in pressure from 100 mbar to 50 bar. The benchtop mass spectrometer systems are coupled to the user process by an integral robust, flexible, quartz-lined heated capillary with sample consumption rates as low as 1 mL/min and response times as low as 150 msec. Process interface options enable analyses through the broad pressure regime, and are suited to diverse application areas including top-gas analysis, measurement of dissolved species, multi-stream monitoring of gas feed and process exhaust lines, process/thermal reaction studies and respiratory analysis. Hiden Analytical, Inc. www.HidenAnalytical. com, 888-964-4336

CT14

Chromatography Techniques » June 2015

COLUMNCORNER SPE Sorbent for Contamination-free Food To protect against contamination of the food chain, fast and cost-effective sample preparation is essential for the analysis of mycotoxins. The clean-up process of mycotoxins can be optimized using Agilent Bond Elut Mycotoxin, a solid phase extraction (SPE) sorbent that cleans up food extracts for improved trichothecene and zearalenone analysis. The sorbent is a proprietary silica-based ion exchange material, and method for extraction and cleanup is successful with a variety of food and grain sample types, including wheat, corn, durum, oats and bread. The benefits of employing this solution for the analysis of mycotoxins include: faster flow rates, good cartridge-to-cartridge reproducibility, reduced sample preparation time, less sample loss, more reliable data and greater stability. Agilent Technologies www.agilent.com, 408-345-8886

Sample Prep Guide Highlights Appropriate Techniques Phenomenex has published a sample preparation guide and selection tool to help scientists produce cleaner samples for more efficient chromatographic analysis. The use of sample preparation has been on the rise in recent years as analysts recognize that it produces better results while delivering cost savings and reducing wear and tear on LC, GC and MS instruments. The 50-page guide is available to download at www.phenomenex.com/ SPguide, or researchers may request the print version. The guide includes useful tools and resources to help select the most appropriate technique for any sample type. It also provides specific product recommendations and general methods and protocols for easy method development. A handy selection tool is also available for quick reference. Phenomenex offers a range of sample preparation techniques, including filtration, protein precipitation, QuEChERS, phospholipid removal, simplified liquid extraction and solid phase extraction. Sample preparation techniques can be tailored for many matrices and are used in a variety of industries, including forensics, environmental analysis and food quality and safety. Phenomenex www. phenomenex.com, 310-212-0555

HPLC Column Heater Warms to 90.0 C Torrey Pines Scientific’s EchoTherm HPLC Column Heater Model CO20 features a temperature range from room temperature to 90.0 C readable and settable to 0.1 C. The PID temperature control software regulates temperatures to ±0.1 C. Temperature accuracy and stability are ±0.1 C with a stable temperature indicator lamp on the front panel that lights when the target temperature is stable to within ±0.2 C. The unit holds columns up to 30 cm long by ¼" or 3/8" diameter in mounting clips provided with room for guard columns and fittings. Larger diameter columns may be used by removing the column clips that hold the smaller columns. The heater features simple controls, digital display of target and actual chamber temperatures, an injection counter, and 30-day timer with alarm and user settable auto-off. An accessory stand is also available. The unit operates from 12 VDC and comes with a benchtop universal power supply for use anywhere in the world, 3-wire AC line cord for the country of use, counter cable, 12-month warranty and instruction manual. The heater is UL, CSA and CE compliant. Torrey Pines Scientific, Inc. www.torreypinesscientific.com, 760-930-9400

MS Columns Boast High Thermal Stability Restek’s Rxi-1301Sil MS GC columns offer true cyano phase selectivity and high thermal stability, which ensures users get dependable, accurate MS results and increased uptime. Exceptionally high thermal stability allows for more aggressive thermal ramping to eliminate carryover of high molecular weight compounds between analyses. In addition to providing both stable 1301 selectivity and low bleed/high temperature limits, the column is designed to provide maximum inertness. Each MS column is tested with a QC mix that includes both acidic and basic probes to ensure inertness across multiple compound classes. Greater column inertness improves peak shape and response, ensuring more accurate quantitative results. The MS column is ideal for the analysis of multiple compound classes across a range of polarities and volatilities. Restek Corp. www.restek.com, 814-353-1300

CHROM CORNER Need more chromatography news? Check out the headlines below and then log on to www.chromatographytechniques.com for even more exclusive online content.

» Test Spots Cocaine Use from a

www.chromatographytechniques.com

Single Fingerprint

General Manager DAVID A. MADONIA 973-920-7048; david.madonia@advantagemedia.com

Research has demonstrated a new, non-invasive test that can detect cocaine use through a simple fingerprint. Using multiple types of MS, researchers tested the prints against more commonly used saliva samples to determine whether the two tests correlated. While previous fingerprint tests have employed similar methods, they have only been able to show whether a person had touched cocaine, and not whether they have actually taken the drug.

» GCMS With Raman Key to Finding Life on Mars A husband and wife have teamed up to improve the way scientists detect condensed aromatic carbon, thought to be a chemical signature of astrobiology. Craig Marshall is an expert in using Raman spectroscopy to look for carbonaceous materials, while Alison Olcott Marshall is a paleontologist interested in how the record of life gets preserved on Earth. The pair is known recently for overturning the idea that 3.5 billion-year-old specks found in rocks in Australia were the oldest examples of life on Earth.

» Ocean Has Hidden Fertilizer A new study by a research team from the Woods Hole Oceanographic Institution and Columbia University reveals a marine phosphorus cycle that is much more complex than previously thought. The work also highlights the important but previously hidden role that some microbial communities play in using and breaking down forms of this essential element.

Editorial Director BEA RIEMSCHNEIDER 973-920-7029; bea.riemschneider@advantagemedia.com Editor-in-Chief MICHELLE TAYLOR 973-920-7113; michelle.taylor@advantagemedia.com Associate Editor LILY BARBACK 973-920-7181; lily.barback@advantagemedia.com

100 Enterprise Drive, Suite 600 Rockaway, NJ 07866-0912 973-920-7000; Fax: 973-920-7541 Chief Executive Officer JIM LONERGAN Chief Operating Officer/Chief Financial Officer TERRY FREEBURG Chief Content Officer BETH CAMPBELL ADVERTISING/SALES IRENE DEVOS, Southeast 973-920-7187; irene.devos@advantagemedia.com

EDITORIAL INDEX Agilent Technologies . . . . . . . . . . .14

Porvair Sciences Ltd. . . . . . . . . . . .13

JOY DE STORIES, Mid-Atlantic 973-920-7112; joy.destrories@advantagemedia.com

Applied Rigaku Technologies, Inc. . . .13

Precision Biosystems . . . . . . . . . . .13

TRACI MAROTTA, Mid-Atlantic 973-920-7182; traci.marotta@advantagemedia.com

Henniker Scientific Ltd. . . . . . . . . . 7

Restek Corp. . . . . . . . . . . . . . . 4, 14

GREG RENAUD, Mid-Atlantic 973-920-7189; greg.renaud@advantagemedia.com

Hiden Analytical, Inc. . . . . . . . . . . .13

Shimadzu Scientific Instruments Inc.. .13

LECO Corp. . . . . . . . . . . . . . . . . . 7

Thermo Fisher Scientific, Inc. . . . . . . 8

LUANN KULBASHIAN, New England 973-920-7685; luann.kulbashian@advantagemedia.com

Malvern Instruments Ltd. . . . . . . . . .10

Torrey Pines Scientific, Inc. . . . . . . .14

NASA . . . . . . . . . . . . . . . . . . . . 2

Valco Instruments Co., Inc. . . . . . . . .13

Phenomenex . . . . . . . . . . . . . . . .14

TIM KASPEROVICH, Midwest 973-920-7192; tim.kasperovich@advantagemedia.com JOLLY PATEL, Midwest 973-920-7743; jolly.patel@advantagemedia.com FRED GHILINO, West 973-920-7163; fred.ghilino@advantagemedia.com List Rentals,

ADVERTISERS’ INDEX The Advertisers’ Index is provided as a reader service. Although every attempt has been made to make this index as complete as possible, the accuracy of all listings cannot be guaranteed.

Millipore Corp . . . . . . . . . . . . . . . . . . . .www.merckmillipore.com/analytical-hplc . . . . . . 7 Restek Corp. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . www.restek.com . . . . . . . . . . . . . . . 9, 16

INFOGROUP TARGETING SOLUTIONS Senior Account Manager, Bart Piccirillo, 402-836-6283; bart.piccirillo@infogroup.com Senior Account Manager, Michael Costantino 402-863-6266; michael.costantino@infogroup.com Reprints The YGS Group 1-800-290-5460 reprints@theygsgroup.com