An analysis of phosphorus species can be performed by a series of reactions usin
ID: 809084 • Letter: A
Question
An analysis of phosphorus species can be performed by a series of reactions using oxidized molybdenum. The resulting complex absorbs at a wavelength of 690nm. A patient excreted 1270.0mL of urine in a 24 hour period and the pH of the urine was 6.52. A 1.00mL aliquot of the urine was treated with molybdenum reagents and diluted to a volume of 50.00mL. A series of phosphate standards was treated in a similar manner. The absorbance of each solution at 690nm is given in the table below as measured against a blank.
Calculate the phosphate conecentration in the urine.
Analyte Concentration (ppm)
Absorbance
1.00
0.250
2.00
0.555
3.00
0.807
4.00
1.135
Patient sample
0.625
Analyte Concentration (ppm)
Absorbance
1.00
0.250
2.00
0.555
3.00
0.807
4.00
1.135
Patient sample
0.625
Explanation / Answer
by plotting the standered Analyte absorbance vs. its concentration we get a stright line. The equation of this line is
A=0.291*C-0.04. The sample concentration after dilution can be calculated from this equation, so it will be:
C=(A+0.04)/0.291=(0.625+0.04)/0.291= 2.285 ppm.
the sample concentration before dilution can be calculated by:
C1V1=C2V2
C1*1=2.285*50
C1= 114.261 ppm (phosphate conecentration in the urine)
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