Al(III) in water can be detected by adding the reagent 8-hydroxyquinoline (HQ) a

Question

Al(III) in water can be detected by adding the reagent 8-hydroxyquinoline (HQ) and measuring the absorbance of the A1(HQ)3 complex. Measuring absorbance in a cell with a 5.00 cm cell path and plotting A versus known micromolar concentrations of Al(III) gives a slope of 0.340 and an intercept of 0.092. Calculate the Al(III) concentration of a sample which gives an Absorbance of 0.879 If the standard deviation of the blank measurement is 0.004, what is the limit of detection for this method in micromolar A1(III)? Calculate the molar absorptivity of the A1(HQ)_3 complex.

Explanation / Answer

7. a) A = cl         (Beer's law)

slope = l = 0.34

or, = 0.34/5

We get,

A = cl

or, 0.879 = [0.34/5 ] * c * 5

or, c =concentration = 0.299 M

b. limit of detection = (3*standard deviation) / slope

= 3* 0.004/0.34

= 0.035 M

= 35294 micromolar

c. A = cl              (Beer's law)

slope = l = 0.34

or, molar absorptivity, = 0.34/5 = 0.068 M-1.cm-1

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