Exposure to 4,4'-methylenediphenyl diisocyanate (MDI) during moulding of rigid polyurethane foam: determination of airborne MDI and urinary 4,4'-methylenedianiline (MDA)

Occupational exposure to 4,4'-methylenediphenyl diisocyanate (MDI) was measured during moulding of rigid polyurethane foam. The aim of the study was to find out whether an MDI-derived urinary amine metabolite could be detected in the urine of workers exposed to apparently low levels of MDI. Airborne MDI was sampled on 1-(2-methoxyphenyl)-piperazine (2MP)-impregnated glass fibre filters and determined by high-performance liquid chromatography (HPLC) using ultraviolet (UV) and electrochemical (EC) detection. The limit of detection of MDI was 3 ng ml-1 for a 20 microliters injection. The precision of sample preparation, expressed as relative standard deviation (RSD), was 1.3% with UV detection and 2.1% with EC detection at a concentration of 70 ng MDI ml-1 (n = 6). The 2MP-MDI derivative was stable at +4 degrees C up to eight weeks. The accuracy of the method was validated in an international quality control programme. Workers (n = 57) from three different factories participated in the study. Urinary 4,4'-methylenedianiline (MDA) metabolite was determined after acid hydrolysis as heptafluorobutyric anhydride derivatives by gas chromatography-mass spectrometry using chemical ionisation and monitoring negative ions. The limit of detection in urine was 0.2 nmol l-1. The precision of six analyses for a urine sample spiked to a concentration of 1 nmol l-1 was 29% (RSD). The MDI concentrations were below the limit of detection in most (64%) of the air samples collected in the worker's breathing zone. Still, detectable amounts of MDA were found in 97% of the urine samples. Monitoring of urinary MDA appears to be an appropriate method of assessing MDI exposure in work environments with low or undetectable MDI concentrations in the workplace air.     

Pharmacokinetics of clenbuterol in the ostrich.

The aim of this study was to investigate the pharmacokinetics of clenbuterol in the ostrich as no such data is available. Clenbuterol (2 mg) was given as a single oral dose to nine ostriches. Blood samples were collected over a period of 96 h after administration and urine for a period of 5 d. Plasma and urine samples were frozen at -20 degrees C pending analysis. Clenbuterol was quantified using a gas chromatograph-mass selective detector. The method for quantification of clenbuterol in plasma was validated by analysing spiked quality control samples at different concentrations. The limit of quantification was determined to be 0.75 ng ml-1 with an absolute recovery of more than 80%. The geometric mean maximum plasma clenbuterol concentration was 4.40 ng ml-1 with 3.0 h as the median time for maximum concentration. The plasma elimination half-life was 19.7 h. The clenbuterol concentration was above 0.75 ng ml-1 in plasma for 48 h and above 1.0 ng ml-1 in urine for 5 d. These data can be useful in residue analysis for clenbuterol in ostriches.     

Production of monoclonal antibody and development of enzyme-linked immunosorbent assay for kanamycin in biological matrices

Monoclonal antibodies (MAbs) against kanamycin were prepared by using a kanamycin-bovine gamma-globulin conjugate for the immunization of mice. Splenocytes from BALB/c immunized mice were fused with P3X63Ag8U.1 myeloma cells. This resulted in two hybridoma cell lines. Fifty per cent inhibition concentrations (IC50) for the MAbs were 2 and 5 ng ml-1. One MAb (IC50 = 2 ng ml-1) was named #22 and was used to develop quantitative assays for kanamycin by means of an enzyme-linked immunosorbent assay (ELISA). The detection limit was 0.2 ng ml-1 and the standard deviations were 0.2-4.4% for intra-assay and 0.6-4.7% for inter-assay, respectively. The detection limits using peroxidase were 4 ppb in cattle milk, cattle plasma, cattle urine, swine plasma, swine urine and chicken plasma. Using the MAb #22 produced, a rapid test kit based on an immunochromatographic method was developed. The detection limits using the kit were 50 ppb in cattle milk, cattle plasma, cattle urine and chicken plasma.     

High-performance liquid chromatographic method for the determination of 9-(4-hydroxy-3-hydroxymethylbut-1-yl)guanine (BRL-39123) in human plasma and urine

A rapid, sensitive and reliable reversed-phase high-performance liquid chromatographic (HPLC) method with UV detection has been developed for the assay of a novel anti-herpes agent, 9-(4-hydroxy-3-hydroxymethylbut-1-yl)guanine (BRL-39123), in human plasma and urine. The drug and the internal standard, the structural analogue BRL-42377, were extracted from the biological matrix by adsorption on a cation-exchange column and were subsequently eluted under alkaline conditions prior to HPLC. The method is reproducible, with coefficients of variation of ca. 5%, and linear from 0.1 to at least 30 micrograms ml-1 in plasma and from 50 to at least 2000 micrograms ml-1 in urine. The method has been used extensively to measure BRL-39123 in plasma and urine samples generated during clinical studies and is adequate for defining pharmacokinetics at projected therapeutic doses.     

Sensitive fluorimetric determination of formaldehyde by the co-quenching effect of formaldehyde and sulfite on the fluorescence of tetra-substituted amino aluminium phthalocyanine

A novel and sensitive fluorimetric method was developed for the determination of formaldehyde based on the co-quenching effect of formaldehyde and sulfite on the fluorescence of tetra-substituted amino aluminium phthalocyanine. Formaldehyde in the concentration range 0.040-1.19 micrograms ml-1 can be determined with a limit of detection of 7.5 ng ml-1. The relative standard deviation for nine replicate measurements of 80.0 ng ml-1 formaldehyde is 1.8%. The method was applied to the analysis of real samples with satisfactory results.     

Determination of proteins at nanogram levels with Bordeaux red based on the enhancement of resonance light scattering

A simple, sensitive and selective method was proposed for the determination of proteins by using a resonance light scattering technique. The weak resonance light scattering (RLS) of Bordeaux red (BR) can be enhanced greatly in the pH range 3.87-3.96 by the addition of micro amounts of proteins, resulting in four characteristic peaks in the wavelength range 250-600 nm. At the maximal wavelength of 363 nm, the enhanced RLS is proportional to the concentration of proteins in the range 0.12-10.8 microg ml-1 for bovine serum albumin (BSA) and 0.24-18.0 microg ml-1 for human serum albumin (HSA). The detection limits were 40.0 and 52.9 ng ml-1 for BSA and HSA, respectively. The present method has been applied to the determination of total proteins in human serum, urine and saliva samples. The obtained results are in good agreement with those obtained by the Bradford method with relative standard deviations (R.S.D.) of 0.9-2.3%.     

Carbon paste electrodes modified with Bi(2)O(3) as sensors for the determination of Cd and Pb

Carbon paste electrodes bulk-modified with Bi(2)O(3)were used for the determination of Cd(II) and Pb(II). The best composition was 1% (wt%) Bi(2)O(3) in the paste. The measurements were made by differential pulse voltammetry in the potential range from -1.2 V to -0.3 V. The peak potential of the reoxidation of Cd is -0.85 V, and of Pb -0.60 V vs. SCE. The lowest concentration that could be determined was 5 microg L(-1) of both metals (preconcentration time 240 s), the relative standard deviation was 3.5%-5.0% (four determinations). The correlation coefficient ( r(2)) of the calibration curves was 0.9966 (for Cd) and 0.9971 (for Pb). The Bi(2)O(3)-modified electrode could be used for the analysis of drinking water, mineral water and urine.     

Indirect Trace Determination of Ethylenediminetetraacetic Acid (Edta) in Water by Potentiometric Stripping Analysis

Abstract

An analytical method for indirect trace determination of ethylenediaminetetraacetic acid (EDTA) in water, by potentiometric stripping analysis is described. Excess Bi(III) was added to form a 1:1 complex with EDTA at pH 2.3. The uncomplexed Bi(III) was then deposited on a glassy carbon electrode at a potential of ?0.40 V vs. SCE and subsequently stripped potentiometrically using potassium dichromate as oxidant. The stripping time of uncomplexed Bi(III) was recorded. The Concentration of EDTA in the sample was determined from the concentration of added Bi(III) and the potentiometrically stripped Bi(III) at ?0.4 V by the standard addition method. The relative standard deviation for EDTA concentration of 95 ppb and 4.5 ppb was 1.9% and 2.6%, respectively. The detection limit was about 1 ppb EDTA for a deposition time of 3 minutes.     

Adsorptive preconcentration for voltammetric measurements of trace levels of chlorprothixene

The psychotherapeutic drug chlorprothixene is shown to adsorb strongly onto a glassy carbon surface in an open circuit. By using this phenomenon to preconcentrate the drug at a glassy carbon electrode prior to differential-pulse voltammetric measurements, sensitivity at the ppb level is readily achieved. The adsorptive stripping response was evaluated with respect to electrolyte, solution pH, accumulation time, concentration dependence and other variables. A linear peak current-concentration relationship was observed up to 1 microgram ml-1 of chlorprothixene; the relative standard deviation (at the 0.6 microgram ml-1 level) is 3.2%. For a preconcentration time of 10 min, the detection limit was found to be 2 ng ml-1. The open circuit preconcentration/medium exchange/voltammetric scheme was used to eliminate interference from sample solutions. The application of the method to human urine samples is described.     

Atomic absorption spectrometric determination of trace zinc in alloys and biological samples after preconcentration with [1-(2-pyridylazo)-2-naphthol] on microcrystalline naphthalene

An atomic absorption spectrometric method for the determination of trace amounts of zinc after adsorption of its [1-(2-pyridylazo)-2-naphthol] complex on microcrystalline naphthalene has been developed. This complex is adsorbed on microcrystalline naphthalene in the pH range 3.5-7.5 from large volumes of aqueous solutions of various alloys and biological samples with a preconcentration factor of 40. After filtration, the solid mass consisting of the zinc complex and naphthalene was dissolved with 5 ml of dimethylformamide and the metal was determined by flame atomic absorption spectrometry. Zinc can alternatively be quantitatively adsorbed on [1-(2-pyridylazo)-2-naphthol]-naphthalene adsorbent packed in a column and determined similarly. About 0.5 ng of zinc can be concentrated in a column from 200 ml of aqueous sample, where its concentration is as low as 2.5 pg ml-1. The calibration curve is linear in the range 0.1-6.5 ng ml-1 in dimethylformamide solution. Eight replicate determinations of 2 ng ml-1 of zinc gave a mean absorbance of 0.145 with a relative standard deviation of 1.5%. The sensitivity for 1% absorption was 0.061 ng ml-1. Various parameters, such as the effect of pH and the interference of a number of metal ions on the determination of zinc, have been studied in detail to optimize the conditions for the determination of zinc in various standard complex materials.     

Fast urinary screening for paracetamol using on-line microwave assisted hydrolysis and spectrophotometric detection

A fully automated urinary screening system for paracetamol and its metabolites is proposed. The method comprises on-line acid microwave assisted hydrolysis of the drug to p-aminophenol followed by reaction with o-cresol in alkaline medium. The indophenol blue dye formed can be continuously monitored at 620 nm. The detection limit achieved, 0.1 microgram ml-1, allows a high dilution of the samples, thus reducing potential interferences from the sample matrix (mainly protein degradation during urine hydrolysis). The proposed screening system also possesses an adequate selectivity, as the major interferent, epinephrine, is tolerated at concentrations higher than those that could be found in the positive urine samples. The reproducibility, expressed as relative standard deviation, was 3.0% and the sample frequency 20 h-1. The reliability of the method was established at five concentrations (between 0.5 and 4 times the detection limit). Finally, it was applied to the screening of several human urine samples. The results obtained were compared with those provided by batch acid hydrolysis, and were similar in all instances.     

Use of photochemical reactions in flow injection: determination of oxalate in urine

The use of photochemical reactions in flow injection (FI) is reported. The irradiation of an FI reactor with a suitable source facilitates the development of the iron(III)-oxalate reaction, allowing the amperometric determination of the anion in the range 1.0-13.0 micrograms ml-1, with a relative standard deviation of 1.1% and a sampling frequency of 40 h-1. The proposed method was applied successfully to the determination of oxalate in urine samples.     

Electrochemical oxidation at carbon paste electrode of tacrine and 1-hydroxytacrine and differential pulse voltammetric determination of tacrine in pharmaceuticals and human urine

The electrochemical oxidation of tacrine and its 1-OH-metabolite, has been studied by cyclic voltammetry and differential pulse voltammetry by using carbon paste electrodes. The peak current-concentration relationship was found to be linear up to 20 micrograms ml-1 with detection limits of 0.06 microgram ml-1 for tacrine and 0.18 microgram ml-1 for 1-OH-tacrine and quantitation limits of 0.20 microgram ml-1 for tacrine and 0.37 microgram ml-1 for 1-OH-tacrine. A method for determining tacrine by differential pulse voltammetry in pharmaceuticals and human urine, in the presence of 1-OH-tacrine, has been developed.     

Determination of carphedon in human urine by solid-phase microextraction using capillary gas chromatography with nitrogen-phosphorus detection

Carphedon is a phenyl derivative of nootropil and is effective in increasing physical endurance and cold resistance, and is used for amnesia treatment. Carphedon was extracted from human urine samples by solid-phase microextraction with a 65 microns carbowax-divinylbenzene-coated fiber. This analysis was performed by using capillary gas chromatography with nitrogen-phosphorus detection and optimized at pH 9.6, 30% NaCl, immersion time 10 min and desorption in the GC injector at 250 degrees C for 3 min. The regression equation for carphedon showed good linearity in the range from 0.1 to 10 micrograms ml-1 for human urine samples. The limit of detection was 0.01 microgram ml-1. The developed method is more sensitive and simpler in sample preparation than liquid-liquid extraction and can be applied to doping analysis for stimulants.     

Column chromatographic pre-concentration of iron(III) in alloys and biological samples with 1-nitroso-2-naphthol-3,6-disulphonate and benzyldimethyltetradecylammonium-perchlorate adsorbent supported on naphthalene using atomic absorption spectrometry

The solid ion-pair material produced from the reaction between benzyldimethyltetradecylammonium chloride (BDTA) and sodium perchlorate on naphthalene provides the basis for a simple, rapid and selective technique for pre-concentrating iron from up to 500 ml of aqueous solution. Iron reacts with disodium 1-nitroso-2-naphthol-3,6-disulphonate (Nitroso-R salt) to form a water-soluble coloured chelate anion. The iron chelate anion forms a water-insoluble, stable iron-Nitroso-R-BDTA complex on naphthalene packed in a column. Trace amounts of iron are quantitatively retained on naphthalene in the pH range 3.5-7.5 and at a flow-rate of 1-2 ml min-1. The solid mass is dissolved out from the column with 5 ml of N,N-dimethylformamide and iron is determined by means of an atomic absorption spectrometer at 248 nm. The calibration graph is linear for concentrations of iron over the range of 0.5-20 micrograms in 5 ml of final solution. The standard deviation and relative standard deviation were calculated. The detection limit of the method was 0.0196 micrograms ml-1 of iron. The sensitivity for 1% absorption was 0.072 microgram ml-1 (0.165 microgram ml-1 by direct atomic absorption spectrometry of aqueous solution). The proposed method was applied to the determination of iron in standard alloys and biological samples.     

Determination of arsenic in biological fluids by electrothermal atomic absorption spectrometry

A procedure for the determination of the total content of arsenic in urine, serum and blood by electrothermal atomic absorption spectrometry (ETAAS) is described. Zeeman correction is used to compensate the high background signals. The samples are diluted (1 + 1 for urine and 1 + 3 for both serum and blood samples) in a medium containing 0.1% w/v Triton X-100 before being introduced directly into the furnace. A solution containing 15% w/v hydrogen peroxide, 0.65% w/v nitric acid and 0.5% w/v nickel is also introduced into the atomizer by means of a separate injection. Calibration is carried out against aqueous standards for blood and serum samples and using the standard additions method for urine samples. The detection limit is 20 pg (2 ng ml-1). The reliability of the procedure is checked by analyzing three certified reference materials and by recovery studies.     

Determination of three anabolic compounds in calf urine by liquid chromatography with photodiode-array detection

A method for the determination of three anabolic hormones (diethylstilbestrol, dienestrol and trenbolone) in calf urine is described. After enzymatic hydrolysis, the samples were cleaned up by C18 solid-phase extraction. Drugs were extracted with hexane and analyzed by isocratic elution on a Discovery RP-Amide C16 5 microns column with photodiode-array detection at 240 and 347 nm. Both retention time and UV spectra were used for identification. Detection limits for the HPLC system were calculated to be 0.3 ng injected for all analytes in the standard mixture. However, for urine samples these limits increased because of the presence of unidentified matrix components. After extraction from urine, the limits of detection for the whole analytical procedure were 5 and 10 ng injected for trenbolone and stilbenes, respectively. The average recoveries of the hormones from spiked samples were in the range 53.1-56.7% with RSD between 11.3 and 14.5% for the whole procedure in the concentration range 25-2.5 ng ml-1.     

Determination of copper in white-metal bearing alloys

A method is proposed for the determination of copper in white-metal bearing alloys by direct controlled-potential electrolysis with a tantalum cathode at -0.32 V vs. SCE in a sulphate/bisulphate buffered electrolyte (pH 2) with fluoroboric acid and sodium tartrate as masking agents. Only Bi(III) interferes. Any co-deposited Bi can be corrected for by its spectrophotometric determination with Semi-Xylenol Orange after preconcentration with La(III) as carrier, from an ammoniacal solution containing the redissolved deposit. Any residual Cu(II) in the electrolyte is determined by spectrophotometry with 2,9-dimethyl-1, 10-phenanthroline. The standard deviation of this method has been found to be 0.03 mg (n = 12) and its relative standard deviation from 0.03 to 0.17%. It has been successfully used for referee analysis and certification of standard reference materials.     

氢化物发生-原子荧光光谱法测定1：5万区域地质调查样品中的As、Sb、Bi、Hg等4种元素

建立了氢化物发生-原子荧光光谱法测定1∶5万区域地质调查样品中的As、Sb、Bi、Hg等4种元素的分析方法,通过采用王水(1+1)分解样品,在盐酸(5%)介质中用硼氢化钾作为还原剂对As、Sb、Bi、Hg等4种元素进行氢化物发生-原子荧光光谱法测定。方法检出限为0.008 9(As)、0.008 1(Sb)、0.008 1(Bi)、0.001 7(Hg)μg/g,测定结果的相对标准偏差(RSD,n=12)为0.82%～7.6%,准确度△lgC=-0.01～0.02。方法简便、成本低,检测结果准确,检出限、准确度及精密度均能达到行业规范要求,适用于1∶5万区域地质调查样品水系沉积物、土壤中As、Sb、Bi、Hg等4种元素的测定。     

原子荧光光谱法测定以磷块岩为原料制备磷酸中的砷

本文利用以水作载流的氢化物发生-原子荧光光谱仪测定了以磷块岩为原料自制的磷酸中的砷（As）。利用硫酸法溶融磷块岩自制出磷酸,优化仪器的工作条件,通过条件实验选择出适用于测定砷所需的盐酸和5% L（+）-抗坏血酸-5% 硫脲的用量。原子荧光光谱法测定结果如下：在0.5 ng·mL-1 ~ 8.0 ng·mL-1浓度范围内线性相关系数R2=0.99996;检出限为0.0018 ng·mL-1,样品的相对标准偏差（RSD）为0.82 %,样品的加标回收率在92.4 % ~ 103.4 %。通过与电感耦合等离子体发射光谱法（ICP-OES）比对,结果一致。