Sample Preparation for Drug Analysis

SAMPLE PREPARATION FOR HPLC ANALYSIS OF DRUG PRODUCTS... 

Urine analysis for illegal drugs is increasingly performed in forensic laboratories (especially in Japan). Gas chromatography-mass spectrometry (GC-MS) is extensively used because of its versatility and reliability. By way of sample preparation for GC analysis, conventional liquid-liquid extraction has a widespread use, but it is not only laborious but also environmentally unfriendly due to the consumption of considerable amounts of organic solvents. Therefore, microintegration of the sample preparation procedure is required. 

Marko, V., Soltes, L., and Radova, K. 1990. Polar interactions in solid-phase extraction of basic drugs by octadecylsilanized silica, 7. Chromatog. Sci., 28 403 06. McDowall, R. D. 1989. Sample preparation for biomedical analysis, 7. Chromatog.,... 

As well as sampling, another important aspect of sample preparation for drug analyses is the homogenisation of a subsequent extraction of the sample. This step is necessary, particularly if we have a powder that is not homogenous. A number of homogenisation techniques are available in drug analysis and these are summarised in Table 11.1. 

The sample preparation for the analysis of dmgs in biological fluids consists of a number of operations that are used for the release of the drug from a conjugate or biological matrix removal of endogenous compounds that could interfere with the assay and techniques for liquid handling. 

Figure 3.1 A hair sample from a suspected drug user is prepared for forensic analysis. As hair grows, it incorporates small amounts of chemicals that are produced when drugs are broken down in the body. To identify these drugs, the hair is first cut into pieces and soaked in a liquid solvent The solvent removes the traces of drug metabolites from the hair so that they can be identified by chromatography and mass spectrometry.

Barbiturates can be prepared for HPLC analysis by dissolution of the drug sample in methanol at a chosen concentration, followed by removal of any sofid particulate material by filtration, etc. A typical set of HPLC operating conditions used for the analysis of barbiturates is shown in Table 9.4. 

Extraction can be used as an efficient and selective sample preparation method before analysis by chromatographic, spectroscopic, electroanalytical, or electrophoretic methods (see for example [5-10]). International norms from the International Standards Organization, US Food and Drug Administration, and US Environmental Protection Agency recommend application of extraction methods in analysis of food products and environmental and pharmaceutical samples. Novel ideas and new views concerning extraction have led to many controversies about terminology and to reallocation and softening of the boundaries between extraction and other analytical sample treatment techniques. 

Membrane filtration is a widely used but narrowly understood technique for sample preparation in chemical analysis. This section has the goal of providing some basic information to aid in the use of filtration tools with drug impurities. Many of the common sample preparation approaches described elsewhere in this chapter, such as liquid extraction, supercritical fluid extraction, and accelerated solvent extraction are effective at removing the dissolved analytes of interest from the matrix while leaving behind many poorly soluble or insoluble matrix components. In contrast, filtration is designed to remove these suspended particles from the extract prior to subsequent analytical steps. Unfiltered samples can destroy the performance of a downstream analytical technique such as HPLC or optical spectroscopy.68,69... 

McDowall, R. D., Doyle, E., Murkitt, G. S., and Picot, V. S. 1989. Sample preparation for the HPLC analysis of drugs in biological fluids, J. Pharmaceut. Biomed. Anal., 7 1087-1096. 

Kinsella B, O Mahony J, Malone E, Moloney M, Cantwell H, Furey A, Danaher M, Current trends in sample preparation for growth promoter and veterinary drug residue analysis, J. Chromatogr. A 2009 1216 7977-8015. 

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