Extraction techniques drug analysis

High performance liquid chromatography (HPLC) can rapidly separate drugs and metabolites from endogenous compounds in biological fluids. Fractions are readily collected and thus HPLC has been used in cannabinoid work to purify biological fluid extracts prior to analysis by techniques offering either more sensitive or specific detection than has been available for LC. 

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. 

LC/MS/MS to support the clinical development [104-108]. The conventional sample preparation procedures require labor-intensive sohd-phase extraction (SPE) sample pretreatment steps and extensive method development time for the LC/MS drug analysis. One of the popular alternatives to SPE is the resurgence of the on-line SPE or column switching techniques [109-111]. More recently, this strategy has been further developed to determine the drug candidates in human plasma by LC/MS/MS analysis [104,109,112]. 

One of the most crucial considerations in proteomic analysis is sample preparation because this will ultimately dictate the number and type of proteins that can be processed. The first priority is to establish the precise protein system to be studied [e.g., will this be a comprehensive and exhaustive catalogue of every expressed protein within a tissue or cellular extract, or is only a small subset of a cellular proteome (e.g., only phosphoproteins or membrane-bound proteins) sufficient for analysis ]. Whether a full or partial proteome, or even a limited number of specific proteins is required for analysis, it is crucial that the extraction technique provide maximal protein recovery while preserving the integrity of the protein complex to be examined. Furthermore, the method of preparation must be totally compatible with the separation methods to be used. This is particularly important for separation technologies that are reliant on protein-protein interactions or drug/ligand/antibody, etc. interactions. Poor recovery of proteins is clearly... 

In the numerous studies on the analysis of theophylline in biological fluids, only a few HPLC systems have been used. However, a variety of sampling techniques have been described, ranging from direct injection of plasma to solvent extraction techniques. These techniques will be discussed briefly later (see below). Whereas series of drugs has been reported not to interfere with the analysis of theophylline18,27,33,35.48,68,75,96,104,105,106,111,1127 122.126.127.128.1S6.160.183.191.193.196> some drugs interfere, e.g. aBtpic1ll1n and methi-... 

Campfns-Falco, R Herraez-Herndndez, R. Sevillano-Cabeza, A. Solid-phase extraction techniques for assay of diuretics in human urine samples. J.Liq.Chromatogr., 1991, 14, 3575-3590 [SPE hydrox-yethyltheophylline (IS) extracted acetazolamide, amiloride, bendroflumethiazide, bumetanide, chlorthalidone, ciclothiazide, ethacrynic acid, furosemide, hydrochlorothiazide, probenecid, spironolactone] Shah, V.R Walker, M.A. Prasad, V.K. Application of flow programming in the analysis of drugs and their metabolites in biological fluids. J.Liq.Chromatogr., 1983, 6, 1949-1954 [urine plasma also chlorothiazide, hydrochlorothiazide]... 

Extraction techniques—in particular, liquid-liquid extraction and solid phase extraction—are used in toxicological analysis and some drug analysis prior to chromatographic analysis. The process of extraction is used to extract organic substances, such as drugs, directly from body fluids and tissues. The two main types of extraction used in these types of analyses are liquid-liquid extraction and solid phase extraction. 

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. 

See alsa Chromatography Multidimensional Techniques. Environmental Analysis. Extraction Solid-Phase Extraction. Food and Nutritional Analysis Sample Preparation Contaminants Pesticide Residues. Forensic Sciences Drug Screening in Sport Illicit Drugs. Herbicides. Liquid Chromatography Instrumentation Clinical Applications Food Applications. Mass Spectrometry Peptides and Proteins. Pesticides. Pharmaceutical Analysis Sample Preparation. Proteomics. Sample Handling Automated Sample Preparation. Water Analysis Organic Compounds. 

One of the first applications of CI-SIM to drug analysis involved the development of an analytical technique to quantitate selected anti-neoplastic agents (20). To test the method, an equimolar mixture of 5-fluoro-2 -deoxyuridine, 6-mercaptopurine ribonucleoside and arabinosylcytosine were added to mouse serum. Extraction and flash methylation yielded the methylated derivatives (15, 16 and respectively Fig. 7) which could be separated by GC. Th selected ion profiles of this extract, obtained by monitoring the MH of each derivative are shown in Fig. 8. This method has been used for the quantitation of arabinosylcytosine in mice serum (20). 

Amphetamines have also been extensively analyzed by GC-MS [2,32-36]. Recent work has focused on improvements in derivatization procedures [13], extraction techniques [1,33,35,36], and optimizing ionization parameters [14]. Solid-phase microextraction was utilized for headspace analysis of urine to determine both amphetamine and methamphetamine [32], In conjunction with the use of pentadeuterated methamphetamine as an internal standard, LODs were obtained as low as 0.1 llg/ml for both compounds monitored in the SIM mode and using isobutane CL This method was found to be 20 times more sensitive than traditional headspace analysis of urine without SPME extraction [32]. Even lower limits of detection were obtained utilizing derivatization of amphetamine and methamphetamine with propylchloroformate and LLE of the propylcarbamate derivatives from urine [13]. When deuterated amphetamine and methamphetamine were used as internal standards, the LODs were 25 ng/ml for both drugs the LOD improved to 5 ng/ml when Wpropylamphetamine was used as the internal standard. In this case, ions were formed via El and SIM was used (Fig. 4) [13]. This method was shown to be rugged and relatively free from potential interferences from other related drugs. 

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