Here is a student procedure to measure nicotine in urine. A 1.00-mL sample of biological fluid was placed in a 12-mL vial containing 0.7 g Na2CO3 powder. After 5.00 μg of the internal standard 5-aminoquinoline were injected, the vial was capped with a Teflon-coated silicone rubber septum. The vial was heated to 80ºC for 20 min and then a solid-phase microextraction needle was passed through the septum and left in the headspace for 5.00 min. The fiber was retracted and inserted into a gas chromatograph. Volatile substances were desorbed from the fiber at 250ºC for 9.5 min in the injection port while the column was at 60ºC. The column temperature was then raised to 260ºC at 25ºC/min and eluate was monitored by electron ionization mass spectrometry with selected ion monitoring at m/z 84 for nicotine and m/z 144 for internal standard. Calibration data from replicate standard mixtures taken through the same procedure are given in the table..

(a) Why was the vial heated to 80ºC before and during extraction?
(b) Why was the chromatography column kept at 60ºC during thermal desorption of the extraction fiber?
(c) Suggest a structure for m/z 84 from nicotine. What is the m/z 144 ion from the internal standard, 5-aminoquinoline?

Urine from an adult female nonsmoker had an area ratio m/z 84/144 0.51 and 0.53 in replicate determinations. Urine from a nonsmoking girl whose parents are heavy smokers had an area ratio 1.18 and 1.32. Find the nicotine concentration (μg/L) and its uncertainty in the urine of each person.

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Nicotine in urine (ug/L) Area ratiom/z 84/144 12 51 102 157 205 0.056, 0.05 0.402 0.39, 0.684, 0.66 1.0, 1.063 1.27, 1.35, NH2 CH3 5-Aminoquinoline CgHgN2 Nicotine