ABSTRACT
Testing for substances of abuse in bio«uids has great forensic relevance. e need for testing arises in many di’erent situations: identifying drugs of abuse, supporting or denying a person’s statement that they have or have not taken drugs, or determining what drug may have caused an overdose. Many methods, notably commercially produced immunoassays that
Introduction 113 NMR 114
eory 114 Isotope Used in the Study of Drugs by NMR 115 Solvent Suppression Techniques 116
Classical Presaturation Experiments 116 WET (Water Suppression Enhanced through T1 E’ects) 116 WATERGATE (WATER Suppression through GrAdient Tailored Excitation) 117 Excitation Sculpting 117 PURGE (Presaturation Utilizing Relaxation Gradients and Echoes) 117
NMR Probe Improvement 118 NMR Studies on Human Urine 118
Commonly Abused Types of Drugs in Urine and Current Methodologies for Testing 118 Range of Detectable Drugs in Urine 119
NMR Studies on Other Bio«uids 122 Quantitation Studies 122 Advantages and Limitations of NMR 124 Coupled Techniques: LC-NMR and LC-NMR-MS 126 References 127
may be used in workplace testing, or gas chromatography-mass spectrometry (GC-MS), which is commonly used in forensic laboratories, have already been well researched and accepted in the scientic community. However, these methods are prone to certain downfalls. Immunoassays are presumptive tests that are not denitive and are subject to high rates of false negatives or false positives due to cross-reactivity or adulterants in the samples tested [1]. Chromatographic methods require sample preparation such as extraction and derivatization of the compounds and extensive operator training; they are also time consuming. In addition, GC-MS instrumentation may not be readily available when it is necessary to determine the cause of an overdose in a timely manner for proper medical treatment [2]. Nuclear magnetic resonance (NMR) spectroscopy has many advantages. It allows positive identications, very little sample preparation or operator training is needed, and a spectrum can be gathered in only a few minutes. NMR spectroscopy also shows signals from all NMR-active materials, and therefore is not limited to screening for specic drugs. It is widely used in the eld of metabonomics for studying metabolites in biological samples [3]. NMR spectroscopy has also been used to identify compounds in urine from intentional and unintentional overdoses [2] [4] [5] [6] [7]. is chapter focuses on the use of magnetic resonance spectroscopy as a tool for the identication and quantitation of drugs in bio«uids.
