Vapor-phase infrared laser spectroscopy: from gas sensing to forensic urinalysis.
Numerous gas-sensing devices are based on infrared laser spectroscopy. In this paper, the technique is further developed and, for the first time, applied to forensic urinalysis. For this purpose, a difference frequency generation laser was coupled to an in-house-built, high-temperature multipass cell (HTMC). The continuous tuning range of the laser was extended to 329 cm(-1) in the fingerprint C-H stretching region between 3 and 4 microm. The HTMC is a long-path absorption cell designed to withstand organic samples in the vapor phase (Bartlome, R.; Baer, M.; Sigrist, M. W. Rev. Sci. Instrum. 2007, 78, 013110). Quantitative measurements were taken on pure ephedrine and pseudoephedrine vapors. Despite featuring similarities, the vapor-phase infrared spectra of these diastereoisomers are clearly distinguishable with respect to a vibrational band centered at 2970.5 and 2980.1 cm(-1), respectively. Ephedrine-positive and pseudoephedrine-positive urine samples were prepared by means of liquid-liquid extraction and directly evaporated in the HTMC without any preliminary chromatographic separation. When 10 or 20 mL of ephedrine-positive human urine is prepared, the detection limit of ephedrine, prohibited in sports as of 10 microg/mL, is 50 or 25 microg/mL, respectively. The laser spectrometer has room for much improvement; its potential is discussed with respect to doping agents detection.
Institute for Quantum Electronics, ETH Zurich, Schafmattstrasse 16, 8093 Zurich, Switzerland. richard.bartlome@alumni.ethz.ch
Richard
R
Bartlome
Julien M
JM
Rey
Markus W
MW
Sigrist
D004809:Ephedrine / Q000031:analogs & derivatives / Q000737:chemistry / Q000652:urine; D005740:Gases / Q000737:chemistry* / Q000652:urine*; D006262:Health; D006801:Humans; D007834:Lasers; D015394:Molecular Structure; D011336:Probability; D012680:Sensitivity and Specificity; D013055:Spectrophotometry, Infrared / Q000295:instrumentation* / Q000379:methods*; D013237:Stereoisomerism; D013696:Temperature; D016482:Urinalysis; D014556:Urine / Q000737:chemistry*; D014732:Vibration
D005740:Gases; D004809:Ephedrine