title: Matrix effect in the analysis of drugs of abuse from urine with desorption atmospheric pressure photoionization-mass spectrometry (DAPPI-MS) and desorption electrospray ionization-mass spectrometry (DESI-MS).
abstract: We have studied the matrix effect within direct analysis of benzodiazepines and opioids from urine with desorption electrospray ionization-mass spectrometry (DESI-MS) and desorption atmospheric pressure photoionization-mass spectrometry (DAPPI-MS). The urine matrix was found to affect the ionization mechanism of the opioids in DAPPI-MS favoring proton transfer over charge exchange reaction. The sensitivity for the drugs in solvent matrix was at the same level with DESI-MS and DAPPI-MS (LODs 0.05-6 μg mL(-1)) but the decrease in sensitivity due to the urine matrix was higher with DESI (typically 20-160-fold) than with DAPPI (typically 2-15-fold) indicating better matrix tolerance of DAPPI over DESI. Also in MS/MS mode, DAPPI provided better sensitivity than DESI for the drugs in urine. The feasibility of DAPPI-MS/MS was then studied in screening the same drugs from five authentic, forensic post mortem urine samples. A reference measurement with gas chromatography-mass spectrometry (GC-MS) (including pretreatment) revealed 16 findings from the samples, whereas with DAPPI-MS/MS after sample pretreatment, 15 findings were made. Sample pretreatment was found necessary, since only eight findings were made from the same samples untreated.
authors.affiliation: Division of Pharmaceutical Chemistry, University of Helsinki, Helsinki, Finland.
authors.forename: Niina M
authors.initials: NM
authors.lastname: Suni
authors.forename: Pia
authors.initials: P
authors.lastname: Lindfors
authors.forename: Olli
authors.initials: O
authors.lastname: Laine
authors.forename: Pekka
authors.initials: P
authors.lastname: Ostman
authors.forename: Ilkka
authors.initials: I
authors.lastname: Ojanperä
authors.forename: Tapio
authors.initials: T
authors.lastname: Kotiaho
authors.forename: Tiina J
authors.initials: TJ
authors.lastname: Kauppila
authors.forename: Risto
authors.initials: R
authors.lastname: Kostiainen
mesh_terms: D000701:Analgesics, Opioid / Q000652:urine*; D001274:Atmospheric Pressure; D001569:Benzodiazepines / Q000652:urine*; D005554:Forensic Medicine; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D012997:Solvents / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization / Q000295:instrumentation / Q000379:methods*; D015813:Substance Abuse Detection / Q000379:methods*
chemical_list: D000701:Analgesics, Opioid; D012997:Solvents; D001569:Benzodiazepines