Speciation of arsenic in body fluids

Inorganic arsenic is metabolized by consecutive reduction and methylation reactions to dimethylated arsenic (DMA), and then excreted into the urine mostly in the form of DMA. Therefore, arsenic metabolites in the body fluids and organs/tissues are present in the form of inorganic (arsenite and arsenate) and methylated arsenics (MMA and DMA). Although pentavalent arsenics can be present mostly in the form of free ions, trivalent ones may be present more in the forms conjugated with thiol groups of glutathione (GSH) or proteins. Arsenic in the body fluids (plasma, bile and urine) is present in the soluble forms and can be speciated on ion exchange columns by HPLC with on-line detection by an inductively coupled argon plasma-mass spectrometer (ICP-MS). Free forms of arsenite, arsenate, and monomethylarsonous, monomethylarsonic, dimethylarsinous and dimethylarsinic acids in the body fluids have been demonstrated to be speciated simultaneously within 10 min or so on both anion and cation exchange columns together with arsenobetaine (AsB) and arsenocholine (AsC). Trivalent arsenics conjugated with GSH were eluted in intact forms on an anion exchange column but were liberated into free forms on a cation exchange column. Thus, free and GSH-conjugated arsenic metabolites in the bile and urine have been speciated simultaneously on ion exchange columns by HPLC-ICP-MS.     

Immunoaffinity CE in clinical analysis of body fluids and tissues

This paper reviews immunoaffinity CE procedures developed since 1998 for drug, hormone, and disease marker analyses of body fluids and tissues. Immunoaffinity CE and related techniques are described. Examples of clinical applications are included.     

Kinetics of Glucose Mutarotation in Aqueous Urea Solutions

Kinetics of glucose mutarotation in water-urea mixtures with urea concentrations of 0-15 mol % was studied in the temperature range 283-308 K. It was found for the first time that the rate of mutarotation increases with increasing concentration of urea in water. It was established that urea molecules along with water molecules affect directly the reaction rate via specific solvation. The fact that the activation parameters are almost independent of the concentration of urea was explained in terms of preservation of the structure of the solutions in the composition range studied.     

Mutarotation of fructose thiosemicarbazone and its 4-substituted homologs

Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 565–566, April, 1992.     

Simultaneous voltammetric determination of prednisone and prednisolone in human body fluids

A sensitive, rapid and reliable electrochemical method based on voltammetry at single wall carbon nanotube (SWNT) modified edge plane pyrolytic graphite electrode (EPPGE) is proposed for the simultaneous determination of prednisolone and prednisone in human body fluids and pharmaceutical preparations. The electrochemical response of both the drugs was evaluated by osteryoung square wave voltammetry (OSWV) in phosphate buffer medium of pH 7.2. The modified electrode exhibited good electrocatalytic properties towards prednisone and prednisolone reduction with a peak potential of ∼−1230 and ∼−1332 mV respectively. The concentration versus peak current plots were linear for both the analytes in the range 0.01-100 μM and the detection limit (3σ/slope) observed for prednisone and prednisolone were 0.45 × 10⁻⁸, 0.90 × 10⁻⁸ M, respectively. The results of the quantitative estimation of prednisone and prednisolone in biological fluids were also compared with HPLC and the results were in good agreement.     

Detection and determination of antimalarial drugs and their metabolites in body fluids

This review of methods for determining antimalarial drugs in biological fluids has focused on the various analytical techniques for the assay of chloroquine, quinine, amodiaquine, mefloquine, proguanil, pyrimethamine, sulphadoxine, primaquine and some of their metabolites. The methods for determining antimalarials and their metabolites in biological samples have changed rapidly during the last eight to ten years with the increased use of chromatographic techniques. Chloroquine is still the most used antimalarial drug, and various methods of different complexity exist for the determination of chloroquine and its metabolites in biological fluids. The pharmacokinetics of chloroquine and other antimalarials have been updated using these new methods. The various analytical techniques have been discussed, from simple colorimetric methods of intermediate selectivity and sensitivity to highly sophisticated, selective and sensitive chromatographic methods applied in a modern analytical laboratory. Knowledge concerning the method for a particular study is determined by the type of application and the facilities, equipment and personnel available. Often is it useful to apply various methods when conducting a clinical study in malaria-endemic areas. Field-adapted methods for the analysis of urine samples can be applied at the study site for screening, and corresponding blood samples can be preserved for subsequent analysis in the laboratory. Selecting samples for laboratory analysis is based on clinical, parasitological and field-assay data. The wide array of methods available for chloroquine permit carefully tailored approaches to acquire the necessary analytical information in clinical field studies concerning the use of this drug. The development of additional field-adapted and field-interfaced methods for other commonly used antimalarials will provide similar flexibility in field studies of these drugs.     

The Mutarotation of Fructose and the Invertase Hydrolysis of Sucrose

Abstract

Studies by GLC and GLC/MS of the mutarotation of fructose in water have been made to determine equilibrium composition as a function of temperature. The major components are β-fructo-pyranose, β-fructofuranose and α-fructofuranose in agreement with studies in the literature. There are small amounts of the α-fructopyranose and the open-chain ketone form. The major change during mutarotation is the ring size change for β-fructopyranose → β-fructofuranose, but other changes contribute. For this reason, polarimetric rate studies of this system as a simple first-order equilibrium process are not valid. Hydrolysis of sucrose catalyzed by invertase has been accomplished to the extent of 99% in 1 min. The mutarotation of glucose and fructose were then studied without the complication of further production of the products from sucrose. The enzymatic cleavage is stereo-specific to provide retained configuration in α-glucopyranose and β-fructofuranose which each mutarotate to equilibrium. The mutarotation lag was demonstrated and its importance to sucrose hydrolysis discussed.     

Enantioselective determination of drugs in body fluids by capillary electrophoresis

During the past decade, chiral capillary electrophoresis (CE) emerged as a promising, effective and economic approach for the enantioselective determination of drugs in body fluids, hair and microsomal preparations. This review discusses the principles and important aspects of CE-based chiral bioassays, provides a survey of the assays developed and presents an overview of the key achievements encountered. Applications discussed encompass the pharmacokinetics of drug enantiomers, the elucidation of the stereoselectivity of drug metabolism and bioanalysis of drug enantiomers of toxicological and forensic interest.     

Determination of thallium in autopsy tissues and body fluids by spectrophotometric technique

Microchimica Acta - A sensitive and specific Spectrophotometric technique for the determination of microgram amounts of thallium in autopsy tissues and body fluids is described. The material is...     

Determination of antiviral nucleoside analogues AM365 and AM188 in perfusate and bile of the isolated perfused rat liver using HPLC

Development, validation and application of an HPLC assay for new antiviral nucleoside analogues AM365 and AM188 in isolated perfused rat liver perfusate and bile were performed. An analytical column (Phenosphere-NEXT, 250 x 4.6 mm, C(18), 4 microm, Phenomenex) was used in tandem with a guard column (4 x 3 mm, C(18), Phenomenex) and operated at 25 degrees C. The mobile phase [methanol:10 mmol/L sodium orthophosphate buffer (pH 7.0), 15:85, v/v] was pumped at 1 mL/min. The signal from a diode array detector was collected from 190 to 300 nm. The chromatogram was processed at 220 and 252 nm for AM365 and AM188, respectively. The HPLC method was validated by six intraday and seven interday runs. Standard curves were linear in the range 0.125-8.00 microg/mL for AM365 and AM188, and the lower limit of quantification for AM365 and AM188 was 0.125 microg/mL. Mean interday precision and accuracy of IPL perfusate quality control samples were within 8.8%, and mean intraday precision and accuracy were within 13.1%. The assay has been successfully used in the study of metabolism and disposition of AM365 in the isolated perfused rat liver.