Analytical Chem istry - DePauw University

624 Analytical Chemistry 2.0[quinine] (mg/mL) I f1.00 10.113.00 30.205.00 49.847.00 69.8910.00 100.0After ingesting 10.0 mg of quinine, a volunteer provided a urine sample24-h later. Analysis of the urine sample gives an relative emission intensityof 28.16. Report the concentration of quinine in the sample in mg/L andthe percent recovery for the ingested quinine.relative emission intensity1008060402000 2 4 6 8 10μg quinine/mLIt can take up 10–11 days for the body tocompletely excrete quinine.So l u t i o nLinear regression of the relative emission intensity versus the concentrationof quinine in the standards gives a calibration curve with the followingequation.I f= 0. 124 + 9.978×µgquininemLSubstituting the sample’s relative emission intensity into the calibrationequation gives the concentration of quinine as 2.81 mg/mL. Because thevolume of urine taken, 2.00 mL, is the same as the volume of 0.05 MH 2 SO 4 used in extracting quinine, the concentration of quinine in theurine also is 2.81 mg/mL. The recovery of the ingested quinine is281 . µ g1 mg× 200 . mL urine×ml urine1000 µ g× 100 = 0. 0562%10.0 mg quinineingested10F.4 Evaluation of Photoluminescence SpectroscopySc a l e o f Op e r a t i o nSee Figure 3.5 to review the meaning ofmacro and meso for describing samples,and the meaning of major, minor, and ultratracefor describing analytes.Photoluminescence spectroscopy is used for the routine analysis of traceand ultratrace analytes in macro and meso samples. Detection limits forfluorescence spectroscopy are strongly influenced by the analyte’s quantumyield. For an analyte with F f > 0.5, a picomolar detection limit is possiblewhen using a high quality spectrofluorimeter. For example, the detectionlimit for quinine sulfate, for which F f is 0.55, is generally between 1 partper billion and 1 part per trillion. Detection limits for phosphorescenceare somewhat higher, with typical values in the nanomolar range for lowtemperaturephosphorimetry, and in the micromolar range for room-temperaturephosphorimetry using a solid substrate.