Introducing the OHAUS Guardian™ 3000 Hotplate Stirrer.

A hotplate stirrer is an important piece of kit to aid a laboratory technician’s daily work. For it to be useful, it must be reliable, robust and easy-to-use. The Ohaus Guardian™ 3000 hotplate stirrer is just the product, having recently been awarded the ASE Green Tick. The unit comes with an optional temperature probe which further improves its performance.

The ASE stated...

The Guardian 3000™ features a bright LCD display with easy-to-read temperature and speed settings, and intuitive icons.

The Guardian 3000™ has a large, easy to clean, ceramic heating plate, (178 mm square), stirs from 80 to 1600 rpm and offers a temperature range up to 500°C. Safety features include a hot top indicator light to protect the user; green indicator lights illuminate when unit is heating and stirring.

Can be used with the optional temperature probe for precise temperature control of your sample

Designed for economical heating and stirring in all laboratory settings

The Medline MS-100 is an analogue hotplate offering a large heating area of 180 x 180 mm with safe controlled heating up to 400°C.

Need help to decide between a heating mantle, stirrer or hotplate? We have written a handy guide to explain all the terminology, features and benefits and with our expert's top picks, to help you to make the right choice!

This is the Cole-Parmer Stuart SHP-200D-S, offering accurate temperature control and protection from over-heating, an easy-to-read digital screen, stirring speeds of up to 2000 rpm and mixing capability of up to 15 litres of liquid.

Scan to view our Hotplate/ Stirrer Buying Guide...

Ingredients:

• Soluble starch

• Room temperature water (few drops)

• Boiling water

• 100 mL measuring cylinder

• 150 mL beaker (or larger)

• Balance

• Spatula

• Weigh boat

• Stirring rod

• Pipette

• Heatproof gloves

• Goggles

1. Weigh out 1 g of soluble starch into a beaker.

Method:

3. Boil 100 mL water (measure into a measuring cylinder) and add the just boiled (still very hot) water to the starch paste.

2. Add enough room temperature water to make a paste.

4. Stir to mix and the solution will become clear.

5. Allow to cool and use as 1 % starch solution.

Making a starch solution without using hot water will result in a starch suspension and will not work in your experiments.

Making Agar for diffusion

You may be familiar with agar when used to grow bacterial cultures in microbiology, but a plain, technical, agar also exists which is agar without any nutrients. It can be used as a growth medium if you are adding your own mix of nutrients (for a specific microbiology practical for example) but more commonly it is used to make agar ‘jelly’ blocks for the students to observe diffusion.

Here we describe a method to make coloured agar blocks for diffusion studies.

Ingredients:

• Plain agar (technical agar/ agar agar) 20 - 25 g

• Distilled or deionised water

• Indicator solution 30 mL (see note below)

• Sodium hydroxide solution, 0.01 moldm-3 30 mL (see note below)

• Balance and weigh boat

• Hotplate stirrer

• Spatula

• Stirring rod and pipette

• Heatproof gloves

• Goggles

Method:

1. Weigh out 20 - 25 g (depending on the firmness of agar required) of plain agar powder into a large beaker or flask.

2. Make up to 1 litre with distilled/deionised water.

3. Stir, with heating, to mix and eventually the solution will become clear. This may take some time.

4. Allow to cool slightly (to around 50°C), add the sodium hydroxide solution and the indicator solution and mix.

5. Pour into the desired container and leave to set. Agar will set at around 45°C.

6. Once set, the coloured agar can be cut into blocks ready for the class, the diffusion investigation will require dilute acid (0.1 moldm-3 hydrochloric acid).

Alternative method:

• Make the agar up in water and add an indicator (30 mL) and sodium carbonate solution (30 mL 0.5 moldm-3) when the mix has cooled to around 50°C.

For more information on indicators and diffusion experiments with agar see Resource Hub

√ ELISA is a way of detecting proteins in a solution, using antibodies and linked to a colour changing enzyme-substrate marker.

√ The protein under test is bound to a solid surface (the bottom of a microplate) in one of 2 ways: directly to the plate (direct ELISA) or via a linked antibody (capture ELISA).

√ It is because of the highly specific nature of antibodies to their targets that this has become a hugely popular tool to detect levels of protein/peptide/antibodies and hormones in solution, and it is widely used in the medical and research industries.

√ Most ELISA kits intended for educational use will be direct ELISA with the base of the plate pre-prepared for the sample protein.

Applications of ELISA include:

1. Testing for antigens – The target antigen could be a virus, a food allergen or a drug.

2. Testing for antibodies in blood serum – examples of this would be HIV testing and COVID tests.

The basic steps to ELISA are:

1. Fix the antigen (protein sample) to the plate (‘coating/capture’).

2. Add a solution to block any unbound areas of the plate (‘blocking’). This can be an irrelevant protein, to which the antibody will not bind, or other solution.

3. Add the specific antibody that will bind to the protein, if present.

4. Add the antibody-enzyme complex.

5. Add the substrate that binds to the enzyme and if products are formed (if the substrate binds, i.e. if the protein is present) there will be a change of colour in the well of the plate.

6. There are kits available where you can also quantify the amount of protein present, using standard curve techniques.

A video is available to show the process using our Simulated ELISA Kit BT190000.

Most of us are now familiar with ELISA as a test for COVID-19 now

Our product specialists are happy to offer advice and training.