SSCE VCE Chemistry Investigation Design: Aspartame is an ingredient in so

Question

Aspartame is an ingredient in some soft drinks. Aspartame is unstable in some conditions and reacts to form four main products. One of the products of aspartame breakdown is 5-benzyl-1,3-dioxo-2-piperazineacetic acid (DKP). It is thought that DKP may be harmful to humans.

A student, Kim, investigates the effect of storage temperature on the rate of production of DKP from aspartame in lemonade. Experimental data is obtained using high-performance liquid chromatography (HPLC) to analyse the aspartame and DKP content in lemonade samples.

HPLC calibration

Kim first calibrated the HPLC using the following method:

1. Prepare and refrigerate a standard solution of pure aspartame with a concentration of 1000 mg L⁻¹.
2. Transfer a 10.00 mL aliquot of the pure aspartame solution into a 1.000 L volumetric flask.
3. Fill the volumetric flask up to the 1.000 L mark with deionised water and shake the flask.
4. Inject a sample of the diluted aspartame solution into the HPLC to obtain a chromatogram.
5. Repeat steps 1-4 with DKP.

The following two calibration chromatograms were obtained.

[Refer to the chromatograms for Aspartame and DKP]

Analysis of lemonade samples

Kim then followed the method given in steps 6–14 to investigate the rate of production of DKP from aspartame in lemonade at different storage temperatures.

6. Open a can of lemonade.
7. Transfer a 10.00 mL aliquot of lemonade from the can into a 1.000 L volumetric flask.
8. Fill the volumetric flask up to the 1.000 L mark with deionised water and shake the flask.
9. Inject a sample of the diluted lemonade into the HPLC using the same operating conditions used during calibration.
10. Set up three water baths at temperatures of 15 °C, 25 °C and 35 °C.
11. Place the can of lemonade in each of the three water baths, ensuring that the initial temperature of the lemonade is the same in each.
12. Remove samples of 10.00 mL from each water bath after 0, 1, 2 and 3 days, replacing the can in the water bath after each sample is removed.
13. After three days, take one each water bath and follow steps 6–9.

Aspartame is an ingredient in some soft drinks - VCE - SSCE Chemistry - Question 9 - 2021 - Paper 1

Worked Solution & Example Answer:Aspartame is an ingredient in some soft drinks - VCE - SSCE Chemistry - Question 9 - 2021 - Paper 1

Rate of production of DKP

Change in concentration of DKP (over time)

Join the SSCE students using SimpleStudy...