Instability of calcium channel antagonists during sample preparation for LC–MS–MS analysis of serum samples  Ana B. Baranda, Rosa M. Alonso, Rosa M. Jiménez, Wolfgang Weinmann  Forensic Science International  Volume 156, Issue 1, Pages 23-34 (January 2006) DOI: 10.1016/j.forsciint.2004.11.014 Copyright © 2004 Elsevier Ireland Ltd Terms and Conditions

Fig. 1 Structures of the studied 1,4-dihydropyridines. Forensic Science International 2006 156, 23-34DOI: (10.1016/j.forsciint.2004.11.014) Copyright © 2004 Elsevier Ireland Ltd Terms and Conditions

Fig. 2 Degradation of the studied compounds in methanolic solution (20ng/ml) by exposure to (□) laboratory and (*) UV (254nm) light for 24h. Forensic Science International 2006 156, 23-34DOI: (10.1016/j.forsciint.2004.11.014) Copyright © 2004 Elsevier Ireland Ltd Terms and Conditions

Fig. 3 Degradation of the studied compounds in spiked plasma samples (20ng/ml) by exposure to laboratory light for 2h (▵). Area of a degradation product (○). Forensic Science International 2006 156, 23-34DOI: (10.1016/j.forsciint.2004.11.014) Copyright © 2004 Elsevier Ireland Ltd Terms and Conditions

Fig. 4 Overlayed chromatograms of 10μg/ml of lercanidipine in methanolic solution: (a) and of a methanolic solution of lercanidipine (10μg/ml) after 24h exposure to UV (254nm) light (b). Lercanidipine (Mw: 611, tR: 10.38min), P1 (Mw: 597, tR: 11.2min), P2 (Mw: 595, tR: 9.08min), P3 (Mw: 583, tR: 3.99min), P4 (Mw: 579, tR: 4.27min), P5/M1 (Mw: 609, tR: 10.77min), P6 (Mw: 567, tR: 2.99min), P7 (tR: 7.74min), P8 (Mw: 417, tR: 2.35min), P9 (Mw: 415, tR: 2.12min), P10 (Mw: 581, tR: 3.69min). Forensic Science International 2006 156, 23-34DOI: (10.1016/j.forsciint.2004.11.014) Copyright © 2004 Elsevier Ireland Ltd Terms and Conditions

Fig. 5 Scheme of degradation products obtained after the exposure of a methanolic solution of nisoldipine (10ng/ml) to UV light (254nm) for 24h. Order of the degradation products (P) according to the UV-response (peak area) obtained. Forensic Science International 2006 156, 23-34DOI: (10.1016/j.forsciint.2004.11.014) Copyright © 2004 Elsevier Ireland Ltd Terms and Conditions

Fig. 6 Scheme of degradation products obtained after the exposure of a methanolic solution of lercanidipine (10ng/ml) to UV light (254nm) for 24h. Order of the degradation products (P) according to the UV-response (peak area) obtained. Forensic Science International 2006 156, 23-34DOI: (10.1016/j.forsciint.2004.11.014) Copyright © 2004 Elsevier Ireland Ltd Terms and Conditions

Fig. 7 UV and MS spectra of the major photodegradation products of nisoldipine. UV-spectra: single and dotted lines correspond to the reference substance and the major degradation product, respectively. MS spectra: (a) mass spectra of nisoldipine and (b) mass spectra of first main degradation product. Upper and lower mass spectra were obtained at 20 and 50V declustering potential (DP), respectively, thus obtaining a higher degree of fragmentation in the lower spectra, which can be used for further structural identification. Forensic Science International 2006 156, 23-34DOI: (10.1016/j.forsciint.2004.11.014) Copyright © 2004 Elsevier Ireland Ltd Terms and Conditions

Fig. 8 UV and MS spectra of the major photodegradation products of lercanidipine. UV-spectra: single and dotted lines correspond to the reference substance and its degradation products, respectively. MS spectra: (a) mass spectra of second main degradation product, (b) mass spectra of lercanidipine, (c) mass spectra of first main degradation product using 20 and 50V declustering potential for the upper and lower mass spectra, respectively. Forensic Science International 2006 156, 23-34DOI: (10.1016/j.forsciint.2004.11.014) Copyright © 2004 Elsevier Ireland Ltd Terms and Conditions