Determination of bencyclane in human plasma by means of capillary gas chromatography and nitrogen-phosphorus selective detection

A sensitive and specific method for the determination of bencyclane in human plasma is presented. Bencyclane was extracted from human plasma with two 3-ml volumes of isooctane and was shaken for 10 min. The organic phase was separated and evaporated to dryness at 40 degrees C under a nitrogen stream. The residue was dissolved and an aliquot was injected into the gas chromatograph. The separation was performed with a DB-17 column with helium as the carrier gas. Nitrogen-selective detection was performed. The quantification was performed with the signal output. The limit of detection was 1 ng/ml.     

Excretion of iodide in 24-h urine as determined by ion-pair reversed-phase liquid chromatography with electrochemical detection

A simple method is presented for the routine analysis of iodide in urine. After a one-step sample clean-up, iodide was separated by ion-pair reversed-phase liquid chromatography and detected electrochemically with a silver electrode. The coefficient of variation of a single analysis of iodide in a pooled urine sample (530 nmol/l) was 7.6%. The detection limit, derived from a signal-to-noise ratio of 3, was 3 pmol, corresponding to 0.06 mumol/l. The recovery of iodide added to urine was 96 +/- 7%. The accuracy of the method was assessed by analysing ten different samples with neutron activation analysis. The data obtained with the two methods showed a high correlation (r = 0.991) and did not differ significantly. Excretion of iodide in samples of 24-h urine from a free-living population was shown to have a log-normal distribution and to be higher in men than in women. The iodide/creatinine ratio was independent of sex and increased with age.     

A cleaner and simple spectrophotometric micro-fluidic procedure for copper determination using nitroso-R salt as chromogenic agent

A cleaner and simple spectrophotometric method using microflow analysis (muFA) was performed. It consisted of a T-junction with microcoil on a polymethyl methacrylate (PMMA) chip which was fabricated by laser ablation and a molded polydimethylsiloxane (PDMS) as top plate. The fabricated PMMA chip was integrated with light emitting diode (LED) as light source and spectrometer as detector. The proposed device was applied to determining copper in water samples using nitroso-R salt as chromogenic reagent at 495nm. It was found that the proposed muFA system was with less reagents and samples consumption with tiny waste generation. The relative standard deviation (R.S.D.) was less than 2% (n=11) with the percentage recovery of 98.0+/-1.7% (n=7). The linear range for determination of copper in water samples was over the range of 0.05-3.0mugmL(-1) with a correlation coefficient (r(2)) of 0.999. The limit of detection (3sigma) was 47ngmL(-1) with a sample throughput of 30h(-1).     

Immobilization of ultra-thin layer of monoclonal antibody on glass surface

When preparing an affinity column and a biosensor, it is desirable to immobilize a unimolecular layer of pure protein on a matrix. In this work, we tried to immobilize a monoclonal antibody on a surface of a glass test-tube as a model, to confirm the stability of this ultra-thin layer by an enzyme immunoassay, and to estimate the thickness of the layer on a slide glass by Fourier transform infrared reflection spectrometry. A new test-tube was washed and dried. The tube was filled with 5% 3-aminopropyltriethoxysilane. The 3-aminopropylsilylated surface was treated with glutaraldehyde and 5.6.10(-2) mg/ml solution of a normal mouse monoclonal antibody. The Schiff base between glutaraldehyde and the antibody was further reduced with 7.9.10(-3)% NaBH4. The tube was washed with 0.05% Tween 20 to block non-specific binding. The antibody immobilized on the surface was measured by an enzyme immunoassay based on a reaction of anti-mouse immunoglobulin G labelled with alkaline phosphatase, with which p-nitrophenol was produced from p-nitrophenylphosphate as a substrate. Meanwhile, various amounts of the antibody were immobilized on slide glasses in the same manner. The antibody on each surface was measured by Fourier transform infrared reflection spectrometry. The antibody immobilized under the final conditions was detectable by the enzyme immunoassay, and stable at 4 degrees C for ten days. The antibody on the slide glass was a unimolecular layer, as judged from the Fourier transform infrared spectra referred to -CONH- band semiquantitatively. Thus, we found the optimal conditions for immobilizing an ultra-thin layer of the monoclonal antibody on the glass surface.(ABSTRACT TRUNCATED AT 250 WORDS)     

柱后衍生高效液相色谱法测定鸡肉中莫能菌素残留量

样品用甲醇－水溶液匀浆、提取后过滤,再用二氯甲烷进行液－液萃取,然后通过Ｓｅｐ－Ｐａｋ柱进一步净化。净化后的样液与香兰素衍生试剂在酸性和加热条件下进行柱后衍生,反应产物在５２０ｎｍ波长处测定。衍生剂：香兰素３０．０ｇ＋浓硫酸２０ｍＬ＋甲醇９５０ｍＬ,流速：０．７ｍＬ／ｍｉｎ;色谱柱：μ－ＢｏｎｄａｐａｋＴＭＣ１８３．９ｍｍｉ．ｄ．×３００ｍｍ,或相当的色谱柱;流动相：Ｖ（甲醇）Ｖ（水）Ｖ（磷酸）＝９４０６０１,流速０．７ｍＬ／ｍｉｎ;柱后反应室：体积大于１．４ｍＬ的不锈钢管（３００ｃｍ×１ｍｍｉ．ｄ．）。     

Determination of starane (fluroxypyr) herbicide using flow injection spectrophotometry.

The starane herbicide was spectrophotometrically determined by the diazotization method in a flow injection assembly. Since starane is a substituted pyridyl compound the NH2 group at the p-position was exploited for diazotization. Starane was diazotized with nitrite and the diazotized product is coupled with beta-naphthol. The absorbance of the resulting azo dye was measured at 395 nm with a molar absorptivity of 1.5 x 10(4) L mol(-1) cm(-1). The calibration graph was linear over the range of 0.6 to 10 microg/mL, with a relative standard deviation (RSD) of 1.67% and a sampling through put of 60 samples h(-1). The % recovery for the determination of starane was found to be 96%. The method was successfully applied to the determination of the active ingredient of starane herbicide in its formulation as well as in food samples.     

A new evaporation procedure for monitoring of iodine-125 in liquid waste

A simplified monitoring method of 125I in liquid waste was devised. The waste water of 200 cm3 was taken on a Saran (polyvinylidene chloride) film covering a stainless steel vat. A stable iodine (20 mg) and sodium hydroxide (1 mmol) was added. The water was evaporated using an infra-red lamp. After heating to dryness, the Saran film was folded and transferred into a polyethylene tube. The radioactivity of 125I was counted with a well type NaI(Tl) scintillation counter. When a multi-channel analyzer was available for counting, an absolute decay rate of 125I was calculated with single and sum photo-peak counts. The radioactivity of 125I counted by a single-channel counter must be corrected with the counting efficiency of about 55%, with a special emphasis of a self absorption of photons. The recovery of 125I for concentrations below the permissible level was more than 98%.     

Solid-phase reactors as high stability reagent sources in flow analysis: selective flow injection spectrophotometric determination of cysteine in pharmaceutical formulations

The flow injection spectrophotometric determination of cysteine was carried out by reaction with cobalt(II) ions entrapped in a polymeric material and filling a packed-bed reactor; the released cobalt(II) complexed with the amino acid was monitored at 360 nm. The method worked with a high repeatability, even with independent reactors, days and solutions. Selectivity of the procedure was tested with twenty different foreign compounds found in pharmaceutical formulations containing cysteine, parent amino acids included; no serious interferences were observed. The calibration graph for cysteine was linear over the range 1-90 micrograms ml-1 with a relative standard deviation of 0.8% at 60 micrograms ml-1 (n = 158). The calculated sample throughput was 90 h-1. The method was applied to determine the content of cysteine in pharmaceutical formulations.     

Determination of nitrite by inhibition of the chemiluminescence of acriflavine in a flow-injection assembly

The indirect determination of nitrite was performed with a flow-injection assembly on the basis of the inhibition of the analytical output obtained in a luminometer by oxidation of acriflavine. The acriflavine solution merged with the nitrite and the resulting mixture was injected into a pure water stream. This solution merged with the oxidant solution (potassium permanganate in sulfuric acid medium) and the resulting chemiluminiscence was affected (inhibited) by the presence of nitrite after reaction with the aminoacridine. The method was applicable over the range 10-800 microg l(-1) of nitrite with a correlation coefficient of 0.9960. The relative standard deviation was 1.4% and the throughput was 76 samples h(-1). The influence of foreign substances was also tested. A solid-phase reactor, filled with Amberlite IRA-900, was inserted in the assembly for the on-line preconcentration of nitrite; the analytical output resulted in an increase of up to 11.5-fold. The method was applied to the determination of nitrites in residual waters, industrial formulations and soil samples.     

Two-stage extraction preconcentration and HPLC determination of phenol and 1-naphthol in aqueous solutions

The extraction of phenol and 1-naphthol with isomolar mixtures of ethyl acetate and hexane under batch conditions and with tributyl phosphate impregnated into a polyurethane foam under batch and dynamic conditions was studied. A procedure for determining phenol and 1-naphthol in aqueous samples was developed including their dynamic recovery on a column packed with polyurethane foam impregnated with tributyl phosphate, elution with a 0.1 M NaCl solution of pH 12.5–13.0, extraction with a mixture of ethyl acetate and hexane, and separation by normal-phase high-performance liquid chromatography (HPLC) with UV-detection. The overall preconcentration coefficient was 250. The detection limits were 2.5 μg/L. The relative error of determination was lower than 18%. The time of one determination was 2–2.5 h.     

Quantitative determination of L-DOPA in tablets by high performance thin layer chromatography

A densitometric high performance thin-layer chromatographic (HPTLC) method was developed and validated for quantitative analysis of L-DOPA in tablets. Chromatographic separation was achieved on precoated silica gel F 254 HPTLC plates using a mixture of acetone-chloroform-n-butanol-acetic acid glacial-water (60:40:40:40:35 v/v/v/v/v) as mobile phase. Quantitative analysis was carried out at a wavelength of 497 nm. The method was linear between 100 and 500 ng/microL, with a correlation coefficient of 0.999. The intra-assay variation was between 0.26 and 0.65% and the interassay was between 0.52 and 2.04%. The detection limit was 1.12 ng/microL, and the quantification limit was 3.29 ng/microL. The accuracy ranged from 100.40 to 101.09%, with a CV not higher than 1.40%. The method was successfully applied to quantify L-DOPA in real pharmaceutical samples, including the comparison with HPLC measurements. The method was fast, specific, with a good precision, and accurate for the quantitative determination of L-DOPA in tablets.     

On-line complexation/preconcentration system for the determination of lead in wine by inductively coupled plasma-atomic emission spectrometry with ultrasonic nebulization

An on-line lead preconcentration and determination system implemented with inductively coupled plasma-atomic emission spectrometry (ICP-AES) with ultrasonic nebulization (USN) in association with flow injection was studied. For the preconcentration of lead, a Pb-quinolin-8-ol complex was formed on-line at pH 6.8 and retained on Amberlite XAD-16 resin. The lead was removed from the microcolumn by countercurrent elution with nitric acid. A total enhancement factor of 225 was obtained with respect to ICP-AES with pneumatic nebulization (15.0 for USN and 15.0 for the column). The detection limit for Pb for the preconcentration of a 10 mL wine sample was 0.15 microg/L. The precision for 10 replicate determinations at a Pb level of 25 microg/L was a relative standard deviation of 2.5%, calculated from the peak heights obtained. The calibration graph obtained by using the preconcentration system for lead was linear with a correlation coefficient of 0.9995 for levels near the detection limit up to > or = 1000 microg/L. The method was successfully applied to the determination of lead in wine samples.     

Determination of mercury in industrial workplaces by collection on activated carbon,solvent extraction and cold-vapour atomic-absorption spectrometry

A method for the determination of mercury in workplace environments in a chlor-alkali plant was optimized. Mercury was collected on activated carbon with a personal sampling pump at a flow-rate of 0.5 l/min, then the carbon was mineralized by heating with potassium permanganate and sulphuric acid. The mercuric ion was next chelated with ammonium pyrrolidinedithiocarbamate and extracted with methyl isobutyl ketone at acidic pH (1.6–5). The chelate in the extract was decomposed with sulphuric acid and the mercuric ion reduced to the metal with stannous chloride. The mercury was determined by coldvapour atomic-absorption spectrometry (CVAAS). The calibration graph was linear up to 5 ng/ml Hg in the initial solution, the relative standard deviation was 4.5% (for 2 ng/ml) and the detection limit was 0.14 ng/ml. All the figures of merit are referred to the initial sample. The proposed method gave good accordance with CVAAS without extraction.     

碱性橙与蛋白间的特异性与非特异性作用荧光光谱比较

将碱性橙与抗体的作用、碱性橙与牛血清白蛋白(BSA)间的作用分别作为特异性作用和非特异性作用模型,采用荧光光谱法固定激发波长为280 nm,扫描不同温度下碱性橙与抗体和牛血清白蛋白两种相互作用,在300～600 nm的发射波长,比较了两种相互作用的差异.结果表明,碱性橙与抗体结合为单一的静态猝灭过程,二者之间的作用力主要为静电作用力;在溶液中,二者以摩尔比1∶1结合,结合常数为3.88×104 L/mol(25.C),3.73×104 L/mol(37.C)和2.35×104 L/mol (45.C);碱性橙距抗体分子色氨酸残基最短距离(r)为5.52 nm.碱性橙与BSA的结合也为静态猝灭,作用力为静电作用力.但碱性橙与抗体作用过程中形成了激基复合物,与BSA则不形成激基复合物.     

A 50% n-octylmethyl, 50% diphenyl-polysiloxane as stationary phase with unique selectivity for gas chromatography

An n-octylmethyl, diphenyl-polysiloxane called SOP-50-Octyl was prepared by a condensation reaction of bis(dimethylamino) n-octylmethylsilane with diphenylsilanediol. The resulting copolymer was a gum with high molecular weight and was obtained with a yield of 80%. 1H and 29Si NMR spectroscopy revealed that the copolymer was a 52% octylmethyl, 48% diphenyl-polysiloxane with random microstructure. Small cyclic impurities could be almost quantitatively removed via a purification step. SOP-50-Octyl was used as stationary phase for the preparation of wall coated open tubular fused silica capillary columns for gas-liquid chromatography. The capillary columns exhibited high separation efficiency and high inertness. The stationary phase offered a unique selectivity due to its unique composition. The Rohrschneider-McReynolds constants indicated a low overall polarity in spite of the high phenyl content, as the polarity was distinctly decreased by the octyl substituent. Furthermore, the octyl substituent was responsible for a high column bleed, reducing the maximum allowable operating temperature to 280 degrees C. The elution temperatures of apolar compounds were increased due to increased interaction of the octyl substituent with the analytes. Some applications with volatile and semi-volatile organic compounds illustrate that SOP-50-Octyl is an excellent choice for confirmational analyses.     

高效液相色谱法测定环氧树脂粘接剂中的双酚A

建立了进出口建筑用环氧树脂粘接剂中双酚A的高效液相色谱-荧光检测法。对提取方法和色谱条件进行了研究,结果表明采用乙醇超声提取样品15min可获得良好的提取效果。以乙腈和水为流动相,采用梯度洗脱可消除样品的基质干扰。方法对环氧树脂粘接剂中双酚A的定量限(LOQ)为0.5 mg/kg,在2～4000 ng/mL范围内,线性相关系数为0.9996。在5个添加水平下回收率在89.1%～100.8%之间。     

Determination of lead in seawater by flow-injection on-line preconcentration-electrothermal atomic absorption spectrometry after coprecipitation with iron(III) hydroxide.

A flow-injection on-line preconcentration-electrothermal atomic absorption spectrometric (ETAAS) method coupled with a coprecipitation method has been developed for the determination of lead in seawater. The combination of two preconcentration procedures, coprecipitation with iron(II) hydroxide and solid-phase extraction with a lead-selective resin, Pb-Spec, allowed the determination of lead at the ng kg(-1) level. Lead in 250 g of a sample solution was collected by coprecipitation with 10 mg of iron. The precipitate was dissolved in 25 ml of 1 mol l(-1) nitric acid; then, a 4-ml aliquot of the sample solution was introduced into the flow-injection system to preconcentrate and separate lead from iron on a Pb.Spec microcolumn. The sorbed lead was eluted with a 1.0 x 10(-4) mol l(-1) EDTA solution. The 30-microl portion of the eluate corresponding to the highest analyte concentration zone was injected into a graphite furnace. The overall enhancement factor was about 200 for 250 g of the sample. The average and standard deviation of ten blank values obtained were 1.7 ng and 0.38 ng, respectively. The recovery was 93.7 +/- 5.0% for seawater spiked with 20 ng kg(-1) lead. The proposed method is applicable to the analysis of seawater for lead at slightly higher levels.     

Interference by the Catecholic Cephalosporin BRL-41897-A with Diagnostic Clinical Chemistry Assays

The catecholic cephalosporin BRL-41897-A, was investigated for in vitro interference with commonly used clinical chemistry assays. An important finding was a negative interference with the enzymatic cholesterol assay that incorporates the Trinder reaction, in which hydrogen peroxide produced by an oxidase drives the oxidative coupling of a phenol with 4-aminophenazone to produce a colored quinoneimine. The suspected interference by BRL-41897-A with the Trinder reaction was investigated using a uricase driven system in which the phenol reagent was substituted or combined with BRL-41897-A. The results indicate that BRL-41897-A competes with the phenol component to react preferentially with 4-aminophenazone to produce a quinoneimine of low absorptivity. Further investigations conducted with similar enzymatic assays for creatinine, cholesterol, triglycerides, and uric acid showed the interference varied substantially with analyte and was dependent on analyte concentration.     

Determination of Phenols and Cresols in Urine by Gas Chromatography

Abstract

A rapid, simple, and sensitive method was developed for the determination of three cresol isomers and phenol in urine. The sample was spiked with m-chlorophenol, as internal standard, and hydrolyzed with sulfuric acid at ambient temperature. The hydrolyzed solution was saturated with ammonium sulfate and extracted with ethyl acetate. The extract was injected without derivatization into a gas chromatograph fitted with a flame ionization detector and a glass column packed with 0.1% SP 1000 on Carbopack C. All four analytes, which eluted within 13 minutes, were quantified from standard curves.

The method was evaluated by analysis of spiked urine pools from laboratory workers and samples of urine from workers in a coal gasification plant.     

Deposition of nanosized latex particles onto silica and cellulose surfaces studied by optical reflectometry

Deposition of positively charged nanosized latex particles onto planar silica and cellulose substrates was studied in monovalent electrolyte solutions at pH 9.5. The deposition was probed in situ with optical reflectometry in a stagnation point flow cell. The surface coverage can be estimated reliably with island film theory as well as with a homogeneous film model, as confirmed with atomic force microscopy (AFM). The deposition kinetics on the bare surface was of first order with respect to the particle concentration, whereby the deposition rate was close to the value expected for a perfect collector. The efficiency coefficient, which was defined as the ratio of the experimental and theoretical deposition rate constants, was in the range from 0.3 to 0.7. Subsequently, the surface saturated and a limiting maximum coverage was attained (i.e., blocking). These trends were in qualitative agreement with predictions of the random sequential absorption (RSA) model, where electrostatic interactions between the particles were included. It was observed, however, that the substrate strongly influenced the maximum coverage, which was substantially higher for silica than for cellulose. The major conclusion of this work was that the nature of the substrate played an important role in a saturated layer of deposited colloidal particles.