CALCULATE THE CONCENTRATION OF A SAMPLE OF BOVINE SERUM ALBUMIN

Question

Calculate the concentration of a sample of bovine serum albumin (Mr 67,000) with an absorbance at 280 nm of 0.5, giving your answer in units of M (Molarity) (NOTE: ε at 280 nm = 1 cm3 mg-1 cm-1 and a cuvette of 1 cm path length (l) was used in the analysis). Do not approximate numbers. [5 marks]

Answer 1

Beer-Lamber law:  A = ecl

From previous question/answer, we found the concentration to be 0.5 mg/ml.  Converting this to moles/liter (M) is as follows:

0.5 mg/ml x 1 mmole/67,000 mg = 7.4627x10^-6 mmoles/ml = 7.4627x10^-3 mmoles/liter = 7.4627x10^-6 M

Not sure what it means "do not approximate numbers", because the absorbance has only 1 significant figure (0.5), so the answer should not have more than that.  It should be 7x10^-6 M or simply 7 uM.