1. Kumazawa T, Sato K, Seno H et al. (1994) Positive and negative ion mass spectrometry of ten xanthine derivatives and their rapid clean-up with Sep-Pak C18 cartridges from biological samples. Forensic Sci Int 68:53–67
2. Kuroiwa Y, Yoshida T (1997) Alkaloids. In: Brandenberger H, Maes RAA (eds) Analytical Toxicology for Clinical, Forensic and Pharmaceutical Chemists. Walter de Gruyter, Berlin, pp 621–661
3. Naito H (2001) Poisoning of Industrial Products, Gases, Pesticides, Drugs, and Natural Toxins. Cases, Pathogenesis and Its Treatment, 2nd edn. Nankodo Co., Ltd., Tokyo, pp 386–388 (in Japanese)
4. Bauza MT, Smith RV, Knutson DE (1984) Gas chromatographic determination of pentoxifylline and its major metabolites in human breast milk. J Chromatogr 310:61–69
5. Verebey K, DePace A (1998) Rapid confirmation of enzyme-multiplied immunoassay test (EMIT) for phencyclidine-positive urine samples with capillary gas chromatography-nitrogen-phosphorus detection. J Chromatogr 427:151–156