1. Dangerous new drug
‘crystal blue’

2. Links to 2015 A levels
Practical techniques to be completed by candidates:
• use laboratory glassware apparatus for a variety of experimental techniques to include serial dilutions
• separate biological compounds using thin layer/paper chromatography or electrophoresis
• use microbiological aseptic techniques, including the use of agar plates and broth
• use ICT such as computer modelling, or data logger to collect data, or use software to process data
One major change to the new exam specifications is the addition of a practical endorsement to the examined content, which will be given as pass/ fail.
In the core / required practicals specified by the Department for Education in their document, ‘GCE AS and A level subject content for biology, chemistry, physics and psychology’ published in April 2014 , one is that students should ‘separate biological compounds using thin layer/paper chromatography or electrophoresis’. Electrophoresis is obviously one practical component where the ABE program can support teachers and students in the new A level practical endorsement requirements.
There are other areas of the practical endorsment, where kit loans and consumable supplies from the ABE program can be used to help schools. Shown in slide – cover.
From the ‘GCE AS and A level subject content for biology, chemistry, physics and psychology’ document issued by the Department for Education in April 2014,
Appendix 5c – Use of apparatus and techniques – biology

3. Scenario
Crystal blue can be added to drinks for colour and the ultimate experience.
Safe up to a certain concentration and then lethal.

4. Practical work Prepare serial dilutions of crystal blue
Construct a standard curve
Calculate the concentration of an unknown sample
Provide data for the Police

5. Serial dilutions
A serial dilution is any dilution where the concentration decreases by the same quantity in each successive step.
9 parts diluent
1 part sample
If a solution has a 1/10 dilution the number represents 1 part of the patient sample added to 9 parts of diluent.
The final dilution is found by multiplying each of the dilutions together.
What would the final dilution be after 5 successive 1/10 dilutions?

6. Serial dilutions 9 parts diluent 1 part sample 9 parts diluent
1 in 10
1/10
1 in 10
1/100
1 in 10
1/1,000
1 in 10
1/10,000
1 in 10
1/100,000
10-1
10-2
10-3
10-4
10-5

7. Serial dilutions
5 successive ‘doubling dilutions’ (1/2 dilutions) were made. What was the final dilution?
1 part diluent
1 part sample
1 part diluent
1 part sample
1 part diluent
1 part sample
1 part diluent
1 part sample
1 part diluent
1 part sample
1 in 2
1/2
1 in 4
1/4
1 in 8
1/8
1 in 16
1/16
1 in 32
1/32

8. Serial dilutions: practise

10. Spectrophotometer 0.54 Prism Lens Sample Detector Readout Slit
Light source

11. Spectrophotometer 0.54 DCPIP absorbs light at 600 nm
Light source
Lens
Prism
Detector
0.54
Readout
Slit
Sample
DCPIP absorbs light at 600 nm
100% transmission = no absorption of light by sample
0% transmission = sample absorbs all light

12. Spectrophotometer 0.54 Light source Lens Prism Detector Readout Slit
Sample
The spectrophotometer can determine the concentration of a known chemical substance, by measuring the intensity of light detected.
More light detected = less concentrated
Less light detected = more concentrated

13. Paper
A new spectrophotometric assay for measuring pyruvate dehydrogenase complex activity: a comparative evaluation
Chen-Juan Ke,a   Ya-Hui He,b   Hong-Wu He,c   Xu Yang,a  Rui Li*a and   Junlin Yuan*a  
Show Affiliations
Anal. Methods, 2014,6,