Dynamic sonication-assisted solvent extraction of organophosphate esters in air samples

A sensitive and selective method is presented for the determination of Zn-Bacitracin in adulterated animal feed by reversed-phase ion-pair high-performance liquid chromatography and post-column derivatization with o-phthalaldehyde prior to fluorescence detection. The calibration function was estimated to be between 8.0 and 65.0 mg l(-1) of Zn-BC. The detection and quantification limits of the chromatographic method were 2.5 and 7.5 mg 1(-1), respectively. Using the extraction procedure of Zn-Bacitracin from the feedstuff that we recently proposed and applying this new chromatographic method, it was possible to detect this antibiotic at levels below 5 mg kg(-1) in different kinds of feedstuffs with a standard deviation less than 6.0%.     

Blister-colorimetric determination of phosphate ions in water,agricultural samples,and biological samples

A procedure was proposed for the determination of phosphate ions in a blister cell (pellet cartridge) with a dry reagent mixture. The procedure is suitable for the quantitative determination of phosphate in different samples using a dry reagent mixture in an ampule or a blister without dissolving the reagents. After an ampule or a blister cell was opened and several drops of a test liquid were added, a color developed, whose intensity was proportional to the concentration of phosphate ions in the solution. The solution was then diluted to 2 mL with water and analyzed by photometry. The composition of the mixture was determined, and the procedure for the quantitative determination of phosphate ions was proposed; the procedure involves the formation and reduction of phosphomolybdic acid and the use of auxiliary reagents. The error of the colorimetric determination of phosphate ions in aqueous solutions, soil extracts, and urine was estimated with the participation of inexperienced operators.     

Assay of hydroxyfarrerol in biological fluids

A high-performance liquid chromatographic method for the determination of hydroxyfarrerol (IdB 1031) in biological samples was developed. IdB 1031 was first extracted by liquid-solid partition and the extracts were evaporated and analysed on a reversed-phase column under isocratic conditions, using either an electrochemical or a UV detector. The detection limit was ca. 5 ng/ml. Preliminary pharmacokinetic data showed that rats treated orally with 500 mg/kg had an average peak plasma concentration (Cmax) of 497 ng/ml after 2 h.     

Improvement of enantioselectivity of chiral organophosphate insecticide hydrolysis by bacterial phosphotriesterase

The bacterial phosphotriesterase (PTE) isolated from Flavobacterium sp. can catalyze the cleavage of the P-O bond in a variety of organophosphate triesters and has been shown to be an effective catalyst for the degradation of toxic organophosphate esters. Ethyl 4-nitrophenyl phenylphosphono-thioate (EPN) is a chiral organophosphate. Optical isomers of EPN show differences in their toxicity. R-EPN is known to be more toxic to hens and houseflies than S-EPN. We determined the K _i value of each enantiomer toward electriceel acetylcholinesterase. R-EPN (K _i=6 μM) inhibited acetylcholinesterase much more effectively than S-EPN (K _i=52 μM) did in vitro. Since PTE has been found to hydrolyze only the S-isomer of EPN, we attempted to alter the enantioselectivity of PTE in order to degrade toxic EPN enantiomer effectively. When PTE hydrolyzed EPN in the presence of dimethyl sulfoxide (DMSO), enzymatic activity toward S-EPN decreased linearly, but enzymatic activity toward R-EPN increased as a function of DMSO concentration. At 20% DMSO, the maximum activity was observed. The kinetic parameters of PTE to EPN isomers clearly indicated that in the presence of 20% DMSO, the enantioselectivity of PTE changed. The K _is value for R-EPN decreased from 0.24 to 0.03 mM, and the V _max value increased from 0.25 to 0.60 U/mg of protein. V _max/K _is values indicated that PTE preferred R-EPN over S-EPN in the presence of DMSO by a factor of 2.     

Gallium determination in biological samples

A sensitive, simple and time-saving method has been developed for the neutron activation analysis of gallium at concentrations around 10⁻⁴ ppm in biological tissues. After a 24-hour irradiation in a thermal neutron flux of 2.8·10¹³ n·cm⁻²·s⁻¹ and a purification by ion-exchange chromatography to eliminate troublesome elements such as sodium, iron and copper, the⁷²Ga activity is measured with enough accuracy for the method to be applicable in animal physiology and clinical toxicology.     

Determination of thallium in biological samples

Determination of thallium has become a major interest because of its high toxicity, especially as the monovalent cation. Thallium poisoning in the human body must be checked quickly by analysis of biological samples. This review highlights the development of highly sensitive detection techniques applied to the determination of thallium in biological samples, with or without pretreatment, based on the literature compiled in Analytical Abstracts from 1990.     

Isolation of thorium in biological samples

A scheme for the isolation of subpicogram to microgram amounts of thorium from bone and soft tissue samples is described. Thorium is first collected by co-precipitation with iron(III) hydroxide and then adsorbed by a cation-exchange resin column from a concentrated hydrochloric acid solution of the precipitate. A double precipitation is necessary for bone samples whereas a single precipitation suffices for liver samples. The thorium is eluted from the column with an ammonium carbonate solution which is then evaporated to dryness to effect the isolation. Good recoveries of thorium from bone samples are obtained.     

Recent progress of task‐specific ionic liquids in chiral resolution and extraction of biological samples and metal ions

Ionic liquids have been functionalized for modern applications. The functional ionic liquids are also called task‐specific ionic liquids. Various task‐specific ionic liquids with certain groups have been constructed and exploited widely in the field of separation. To take advantage of their properties in separation science, task‐specific ionic liquids are generally used in techniques such as liquid–liquid extraction, solid‐phase extraction, gas chromatography, high‐performance liquid chromatography, and capillary electrophoresis. This review mainly covers original research papers published in the last five years, and we will focus on task‐specific ionic liquids as the chiral selectors in chiral resolution and as extractant or sensor for biological samples and metal ion purification.     

Nitric oxide measurements in biological samples

The crucial role of nitric oxide (NO) in controlling many physiological functions in mammals is now established. To aid understanding this crucial role, sensitive and selective methods for its in vivo and in vitro detection are vital. The unique chemical and physical properties of NO set the tone for its detection strategies. This review summarizes different techniques and methodologies used in measuring NO in biological samples. Those include gas and liquid phase chemiluminescence, electron spin resonance spectroscopy, UV-visible spectroscopy, fluorescence, electrochemical sensors, and reporter cell assay. The principles, applications, merits, and limitations of each technique are discussed.     

Optimisation of a matrix solid-phase dispersion method for the determination of organophosphate compounds in dust samples

A fast and inexpensive sample preparation procedure based on the matrix solid-phase dispersion (MSPD) technique is proposed for the isolation of several organophosphate esters (mainly employed as flame retardants and plasticizers) from indoor dust samples. Extraction and clean-up were carried out in a single step and target compounds were determined by gas chromatography (GC) with nitrogen-phosphorus detection (NPD). The main parameters affecting extraction yield and selectivity, such as type and amount of dispersant material, clean-up co-sorbent and extraction solvent, were evaluated and optimised. Under final conditions, 0.5 g of dust were dispersed with equal amounts of anhydrous sodium sulphate and Florisil, and loaded on the top of a polypropylene cartridge containing 0.5 g of alumina. The dispersed sample was washed with 2 mL of n-hexane to remove the least polar interferences and analytes were eluted with 3 mL of acetone. Recoveries of the proposed method for spiked samples ranged from 80 to 116%, and the day-to-day variability remained between 5 and 10%. Data on levels of organophosphate species in dust from private houses and vehicle cabins are provided. In both cases, the lowest concentrations corresponded to the short chain, non-chlorinated, alkyl organophosphates, whereas mean values above 1 μg g⁻¹ were measured for the rest of analytes.     

The determination of tin in biological samples

A rapid method is described for the determination of tin in biological material, using¹²³Sn (T=40 m). The chemical procedure is based on the nearly quantitative extraction of tetravalent tin into toluene from an acid 1.3M iodide solution. The recovery is determined by spiking the solution with¹¹³Sn and measuring the activity of the^113mIn daughter in the counting sample. The lower limit of the determination is ?0.01μg. Results are given for standard kale powder and dried animal blood.     

Kinetic-coulometric determination of mercury in biological samples

A simple approximate calculation method is given which permits determina-tion of the maximal scan rates of potential allowable for distortion-free recording of current-voltage curves with X-Y recorders. For the calculations only the response time of the recorder, the wave shape and the scan rate of potential need be known. Stationary mercury electrodes and rapid polarography with a dropping mercury electrode at controlled drop times were examined. Electroanalytical implications are discussed, with particular emphasis on the rapid a.c. polarographic method with short controlled drop times and on stationary-electrode fundamental and second harmonic a.c. voltammetry. Theoretically and experimentally it has been shown that an X-Y recorder with 0.5–1.0-s response time can be used for scan rates up to about (50/nt') mV s^-1 with a.c. techniques and about (100/nt') mV s^-1 with d.c. polarography (t'= response time of recorder, n = number of electrons).     

Suitability of solid-phase microextraction for the determination of organophosphate flame retardants and plasticizers in water samples

The feasibility of solid-phase microextraction (SPME) for the determination of several organophosphorus flame retardants and plastizicers in water samples by gas chromatography-nitrogen phosphorous detection (GC-NPD) is evaluated. These compounds have a wide range of polarities and volatilities and require a thorough optimisation of the different SPME parameters. Considering also possible contamination and carryover sources, the best compromise microextraction conditions were found to be direct extraction of 22 ml samples, containing 300 mg/ml of NaCl, with a PDMS-DVB coated fibre at room temperature. Although equilibrium was not achieved, an extraction time of 40 min allowed obtaining a good sensitivity (quantification limits between 0.010 and 0.025 ng/ml), comparable to that achieved by solid-phase extraction (SPE) of 1l samples, producing both similar values of precision and accuracy. Furthermore, the SPME method has shown to be free of matrix effects, avoiding the need of employing the standard addition procedure for quantification, and was suitable for the determination of eight of the nine considered compounds. Only tris-(2-ethylhexyl)-phosphate was neither determinable by SPME nor by SPE. Finally, the application of the developed methodology to the analysis of wastewater samples, showed that important concentrations of these compounds (up to 10 ng/ml) have been detected in treated sewage water, being discharged into the aquatic environment.     

Enzymatic determination of citrulline in biological samples

Conclusions The newly developed method for the enzymatic determination of citrulline in biological specimens gives satisfying and reproducible results and is apt for measuring citrulline concentrations in the physiological as well as in the pathological range, for disease screening and probably can be utilized for automatic analysis.Since citrulline hydrolase is a fairly stable enzyme with no requirements for cofactors and not interfered by basic amino acids and urea, this method offers a true alternative to the citrulline-determinations employed previously.

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Enzymatische Bestimmung von Citrullin in biologischen Proben

     

GC-MS-SIM quantitation of amantadine in biological samples

Summary A simple, selective and sensitive method for the quantitation of amantadine in biological samples is described. After extraction from biological samples using a two-step procedure, amantadine is quantitatively converted into its isothiocyanate (NCS) derivative by treatment with carbon disulfide and then determined quantitatively using isobaric compounds, p-methoxyphenyl-ethylamine-NCS or N-acetylamantadine as external standards. The applicability of this method is illustrated by determining plasma levels of amantadine for pharmacokinetic studies and levels in dialysate samples of amantadine treated patients who were on dialysis machines.     

Substoichiometric determination of cadmium in biological samples

A method is suggested for the determination of submicrogram Cd in quantities by isotope dilution, using substoichiometric extraction into dithizone in chloroform. The applicability of the method was tested in biological samples. Extraction was carried out from a sodium acetate buffer betweenpH 9.7 and 12.0. With amounts of 0.2 μg of Cd, the S.E. was not greater than 0.01 μg. This method is suitable for large scale analysis of trace amounts of Cd in biological materials.     

Activation analysis of mercury in biological samples

A method has been developed for the determination of trace quantities of mercury in biological samples, in which homogeneous irradiation was achieved by introducing a rotating irradiation disk facility in the reactor pool water, and possible loss of mercury during chemical processing was reduced by using a simple procedure. This procedure involved the destruction of the sample in a reflux system with conc. HNO₃ or fuming HNO₃+H₂O₂ and subsequent isolation of mercury by spontaneous deposition on Cu sieves from dilute HNO₃(0.5–1.5N). The possibility of using Au or Co as standards, instead of mercury which is easily volatile, was also evaluated.