Acidic analytes drugs

In practice, the majority of TLC separations are qualitative or semiquantitative (visual comparison) in nature. However, modern computer-controlled densitometers are now available that scan sample and calibrator chromatograms in tracks on HPTLC plates and provide quantitative capabilities. Clinically relevant analytes that have been measured by TLC include amino acids, bile acids, carbohydrates, drugs, fipids, glycolipids, phospholipids, porphyrins, prostaglandins, steroid hormones, purines, pyrimidines, derivatives of nucleic acid, and urinary organic acids. The advantages of TLC include simphcity, rapidity, versatility, ability to process a large number of samples... 

Electrophoresis on a macro scale has been applied to a variety of difficult analytical separation problems inorganic anions and cations, amino acids, catecholamines, drugs, vitamins, carbohydrates, peptides, proteins, nucleic acids, nucleotides, polynucleotides, and numerous other species. A particular strength of electrophoi esis is its unique ability to separate charged macromolecules of interest to biochemists, biologists, and clinical chemists. For many years, electrophoresis has been the powerhouse method of separating proteins (enzymes, hormones, antibodies) and nucleic acids (DNA, RNA), for which it offers unparalleled resolution. ... 

Electrophoresis on a macro scale has been applied to a variety of difficult analytical separation problems inorganic anions and cations, amino acids, catecholamines. drugs, vitamins, carbohydrates, peptides, proteins, nucleic acids, nucleotides, polynucleotides, and numerous other species. 

The utility of TLC in metabolic diseases, illicit drug use, toxicology, including mycotoxins, environmental injuiy, and particularly analytical drug characterization, and quantitation, both diagnostically and for regulatory purposes, is well-documented (8,65,66). The further application of TLC to nucleic acids has a significant literature that we document extensively. 

Vitamins and Other Nutrients in Food Matrices see also Section 6.3. Food matrices are available with values assigned for vitamins, carotenoids, fatty acids, cholesterol, natural toxins, veterinary drugs, and hormone residues. The NIST food matrix SRMs for vitamins include coconut oil (SRM 1563), infant formula (SRM 1846), and baby food composite (SRM 2383) (particularly for carotenoids). Fatty acids and cholesterol are the primary analytes of interest in meat homogenate (SRM 1546) and diet... 

The most critical decision to be made is the choice of the best solvent to facilitate extraction of the drug residue while minimizing interference. A review of available solubility, logP, and pK /pKb data for the marker residue can become an important first step in the selection of the best extraction solvents to try. A selected list of solvents from the literature methods include individual solvents (n-hexane, " dichloromethane, ethyl acetate, acetone, acetonitrile, methanol, and water ) mixtures of solvents (dichloromethane-methanol-acetic acid, isooctane-ethyl acetate, methanol-water, and acetonitrile-water ), and aqueous buffer solutions (phosphate and sodium sulfate ). Hexane is a very nonpolar solvent and could be chosen as an extraction solvent if the analyte is also very nonpolar. For example, Serrano et al used n-hexane to extract the very nonpolar polychlorinated biphenyls (PCBs) from fat, liver, and kidney of whale. One advantage of using n-hexane as an extraction solvent for fat tissue is that the fat itself will be completely dissolved, but this will necessitate an additional cleanup step to remove the substantial fat matrix. The choice of chlorinated hydrocarbons such as methylene chloride, chloroform, and carbon tetrachloride should be avoided owing to safety and environmental concerns with these solvents. Diethyl ether and ethyl acetate are other relatively nonpolar solvents that are appropriate for extraction of nonpolar analytes. Diethyl ether or ethyl acetate may also be combined with hexane (or other hydrocarbon solvent) to create an extraction solvent that has a polarity intermediate between the two solvents. For example, Gerhardt et a/. used a combination of isooctane and ethyl acetate for the extraction of several ionophores from various animal tissues. 

Recent developments in drug discovery and drug development spurred the need for novel analytical techniques and methods. In the last decade, the biopharmaceutical industry set the pace for this demand. The nature of the industry required that novel techniques should be simple, easily applicable, and of high resolution and sensitivity. It was also required that the techniques give information about the composition, structure, purity, and stability of drug candidates. Biopharmaceuticals represent a wide variety of chemically different compounds, including small organic molecules, nucleic acids and their derivatives, and peptides and proteins. 

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