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) |
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Authors: | Suni Niina M Lindfors Pia Laine Olli Ostman Pekka Ojanperä Ilkka Kotiaho Tapio Kauppila Tiina J Kostiainen Risto |
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Institution: | aDivision of Pharmaceutical Chemistry, University of Helsinki, P.O. Box 56, Helsinki FI-00014, Finland;bHjelt Institute, Department of Forensic Medicine, University of Helsinki, P.O. Box 40, Helsinki FI-00014, Finland;cLaboratory of Analytical Chemistry, Department of Chemistry, University of Helsinki, P.O. Box 55, Helsinki FI-00014, Finland |
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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. |
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Keywords: | Ambient mass spectrometry Desorption electrospray ionization Desorption atmospheric pressure photoionization Matrix effect Drug analysis |
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