In biological fluids

The third method is of limited application and is used only in special cases, The second is the most accurate and rapid method, and is of considerable technical importance. The chemical method (described below), although less accurate than the polarimetric method, is of great value for the estimation of sugars in biological fluids. In fact, for such purposes, it is often to be preferred to the polarimetric method owing to the probable presence of other substances having high optical rotations. 

J. Chamberlain, Mnalysis of Drugs in Biological Fluids, CRC Press, Boca Raton, Fla., 1985. 

For more specific analysis, chromatographic methods have been developed. Using reverse-phase columns and uv detection, hplc methods have been appHed to the analysis of nicotinic acid and nicotinamide in biological fluids such as blood and urine and in foods such as coffee and meat. Derivatization techniques have also been employed to improve sensitivity (55). For example, the reaction of nicotinic amide with DCCI (AT-dicyclohexyl-0-methoxycoumarin-4-yl)methyl isourea to yield the fluorescent coumarin ester has been reported (56). After separation on a reversed-phase column, detection limits of 10 pmol for nicotinic acid have been reported (57). 

Ion Selective Electrodes Technique. Ion selective (ISE) methods, based on a direct potentiometric technique (7) (see Electroanalytical techniques), are routinely used in clinical chemistry to measure pH, sodium, potassium, carbon dioxide, calcium, lithium, and chloride levels in biological fluids. 

DIRECT POTENTIOMETRIC DETERMINATION OF SULFATE CONTENT IN BIOLOGICAL FLUIDS (URINE)... 

One of the important problems in the diagnosis of different disease in their early stages is the determination of bio-active substances in biological fluids. We are currently interested in applying capillary electrophoresis (CE) as technique for the rapid and highly efficient separation of corticosteroids in semm and urine. Steroids can analyze by MEKC. 

We have developed the method of the determination of steroids in biological fluids (semm and urine) by MEKC with on-line concentration (sweeping) with detection limit for about 3 ng/ml (S/N=3). 

The pur pose of work is to develop the technique of separ ation of purine bases (caffeine, theophylline, theobromine) and the technique of detection of purine bases in biological fluid by TLC using micellar mobile phases containing of different surfactants. 

On the basis of the received data, simple, expressive procedures for the coulometric determination of the antioxidants mentioned above in biological fluids and pharmaceuticals have been proposed. 

Histamine is the biological amine, playing an important role in living systems, but it can also cause unnatural or toxic effects when it is consumed in lai ge amounts. It can occur with some diseases and with the intake of histamine-contaminated food, such as spoiled fish or fish products, and can lead to undesirable effects as headache, nausea, hypo- or hypertension, cai diac palpitations, and anaphylactic shock syndrome. So, there is a need to determine histamine in biological fluids and food. 

The pH scale is widely used in biological applications because hydrogen ion concentrations in biological fluids are very low, about 10 M or 0.0000001 M, a value more easily represented as pH 7. The pH of blood plasma, for example, is 7.4 or 0.00000004 M H. Certain disease conditions may lower the plasma pH level to 6.8 or less, a situation that may result in death. At pH 6.8, the H concentration is 0.00000016 M, four times greater than at pH 7.4. 

Most biotin-dependent carboxylations (Table 18.5) use bicarbonate as the carboxylating agent and transfer the carboxyl group to a substrate earbanion. Bicarbonate is plentiful in biological fluids, but it is a poor electrophile at carbon and must be activated for attack by the substrate earbanion. 

The aromatic portion of the molecules discussed in this chapter is frequently, if not always, an essential contributor to the intensity of their pharmacological action. It is, however, usually the aliphatic portion that determines the nature of that action. Thus it is a common observation in the practice Ilf medicinal chemistry that optimization of potency in these drug classes requires careful attention to the correct spatial orientation of the functional groups, their overall electronic densities, and the contribution that they make to the molecule s solubility in biological fluids. These factors are most conveniently adjusted by altering the substituents on the aromatic ring. 

Immunoaffinity extraction combined on-line with LC in conjunction with MS (108 -110) or tandem MS (111, 112) has also been demonstrated for the determination of analytes in biological fluids. Obviously, such systems offer a very high... 

K. Eanbeck-Vallen, J. Carlqvist and T. Nordgren, Determination of ampicillin in biological fluids by coupled-column liquid cliromatography and post-column derivatiza-tion , 7. Chromatogr. 567 121-128 (1991). 

J. V. Posluszny and R. Weinberger, Determination of dmg substances in biological fluids by direct injection multidimensional liquid cliromatography with a micellar cleanup and reversed-phase cliromatography , Awa/. Chem. 60 1953-1958(1988). 

T. Seki, K. Yamaji, Y. Orita, S. Moriguchi and A. Sliinoda, Simultaneous determination of uric acid and creatinine in biological fluids by column-switching liquid cliromatogra-phy with ulti aviolet detection , 7. Chromatogr. A 730 139-145 (1996). 

The therapeutic utility of systemically administered ASON had been limited by their short plasma half life (sometimes even less than 3 min). This is due to their sensitivity to nuclease digestion. When the first-generation ASON were chemically modified, e.g., by replacing the oxygen in the phosphodiester bond with sulfur (phosphorothiorate) they obtained an increased stability in biological fluids while their antisense effect has been maintained. First-generation agents can be delivered via intravitreal injection, parenterally, by topical cream, enema, and inhaled aerosol. These antisense... 

For quantitative work, it is necessary to estimate the concentration of 5-amino-l-(P-D-ribofuranosyl)imidazole in aqueous solution. It seems that the only available method is the Bratton-Marshall assay, which was originally developed for the estimation of arylamines in biological fluids. The principle of the method is the spectrometric estimation of a salmon-pink colored dyestuff obtained by diazotation in situ, followed by coupling with /V-( 1 -naphthyl)ethyl-enediamine.65 The only remaining problem then is to know the molar extinction of this dye because pure samples of AIRs are not available. A value of 16800 at 520 nM was obtained for the dyes prepared from a model compound, 5-amino-l-cyclohexylimidazole-4-carboxylic acid (54), which is crystalline. A comparable molar extinction can be expected for the dye prepared from imidazole 55, if the carboxyl group does not exert too much influence on the chromophore. Actually, its influence is perceptible even with the naked eye, the dyestuff prepared from 53 having a somewhat different, wine-red color, with max>520 nM. The molar extinction for 55 is 17400 at 500 nM. When the decarboxylation of 54 was conducted under mild acidic conditions (pH 4.8, 50°C, 1 hour), estimation of 5-aminoimidazole 55 by the Bratton-Marshall method led to the conclusion that the reaction was almost quantitative.66 Similar conditions for the final decarboxylation were adopted in the preparation of samples of AIRs labeled with stable isotopes.58... 

Of particular interest in brevetoxin research are the diagnosis of intoxication and identification of brevetoxins and their metabolites in biological fluids. We are investigating the distribution and fate of radiolabeled PbTx-3 in rats. Three model systems were used to study the toxicokinetics and metabolism of PbTx-3 1) rats injected intravenously with a bolus dose of toxin, 2) isolated rat livers perfused with toxin, and 3) isolated rat hepatocytes exposed to the toxin in vitro. 

Gases that participate in chemical reactions typically are at pressures different from one bar. Substances in solution are likely to be at concentrations different from one molar. For example, a biochemist who wants to know what processes are spontaneous under physiological conditions will find that the substances dissolved in biological fluids are rarely at one molar concentration. How does AG vary with changes in molarity and pressure Recall that enthalpy is virtually independent of concentration but that entropy obeys Equation ... 

Natelson, S. A rapid method for the estimation of urea in biological fluids as the urea diacetyl complex. 

---