Working standards are prepared for a standard curve from a 0.981mcg/mL coproporp

Question

Working standards are prepared for a standard curve from a 0.981mcg/mL coproporphyrin stock standard as shown below:

a) calculate the dilution of each working standard (express as a fraction, eg 1/2, 1/3)

b) calculate the concentration (in mcg/ml) of each working standard. (express the final answer in scientific notatin showing 2 decimal places to the right of the decimal point, eg, 5.22x 10-2)

Working Standard Volume of Coproporphyrin Stock Standard Volume of 0.1 mol/L HCl Final volume 1 1.0 ml of stock standard 4.0ml 5.0ml 2 1.0 ml of stock standard 9.0ml 10.0ml 3 2.0ml of standard 2 2.0ml 4.0ml 4 2.0ml of standard 2 6.0ml 8.0ml 5 2.0 ml of standard 4 2.0ml 4.0ml

Explanation / Answer

a) dilution factor=volume of stock/total volume

dilution factor of pre-diluted samples 1 =dilution factor 1*(volume of 1/total volume)

working std1) dilution factor=1.0ml/(1.0+4.0+5.0)ml=0.1

worknig std2) dilution factor=1.0ml/(1.0+9.0+10.0)ml=0.05

working std3) dilution factor=[2.0ml/(2.0+2.0+4.0)ml]*0.05=0.0125

working std4)) dilution factor=[2.0ml/(6.0+2.0+8.0)ml]*0.05=0.00625

working std 5) dilution factor=[2.0ml/(2.0+2.0+4.0)ml]*0.00625=0.00156

b) concentration of sample=concentration of stock*dilution factor

working std 1)concentration of sample=0.981mcg/mL *0.1=9.81*10^-2 mcg/ml

2) concentration of sample=0.981mcg/mL *0.05=4.90*10^-2 mcg/ml

3) concentration of sample=0.981mcg/mL *0.0125=1.23*10^-2 mcg/ml

4) concentration of sample=0.981mcg/mL *0.00625=6.13*10^-3 mcg/ml

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