Determining amino content.

Question

1mL of Standard Glycine (7.5mg mL-1) was diluted into a 100mL volumetric flask. One standard had 0.30mL of the diluted standard glycine and 0.20mL of distilled water.

How would I calculate the amount of glycine in μmol? I am a bit confused with the calculation

Answer 1

Starting with the original standard of 7.5 mg/ml and taking 1 ml (7.5 mg) and diluting to 100 ml gives you 7.5mg/100 ml.

7.5 mg/100 ml = 0.075 mg/ml

Taking 0.3 ml of this gives you 0.075 mg/ml x 0.3 ml = 0.012 mg in the 0.3 ml

Adding this to 0.20 ml d.H2O now gives you 0.012 g in 0.5 ml = 0.012mg/0.5 ml = 0.024 mg//ml

To convert this to umoles/ml use the molar mass of glycine (75 g/mol = 75 mg/mmol = 75 ug/umol)

0.024 mg/ml x 1 mmole/75 mg x 1000 umole/mmole = 0.32 umoles/ml

So, to answer your question, the amount of glycine will depend on the volume you use.  If you use the entire 0.5 ml (0.2 ml + 0.3 ml d.H2O) you will have 0.32 umoles glycine. 

 

Hope this answers your question.