催化光度法测定痕量钼──钼(Ⅵ)－盐酸联氨－橙黄Ⅳ催化光度新体系

基于盐酸介质中,钼(Ⅵ)催化盐酸联氨还原橙黄Ⅳ的反应,建立了动力学分光光度法测定痕量钼的新方法。本法检出限为3.7×10^-3μg/mL,测定钼量范围为0.025～1.8μg/mL;已将此法用于测定绿豆中的钼及钼酸铅和钼酸钡的溶度积。     

Catalytic spectrophotometric determination of molybdenum (VI) with the hydrazine-metanil yellow system

A new catalytic Spectrophotometric method for the determination of trace amounts of molybdenum (VI) has been proposed. The method is based on the catalytic effect of Mo(VI) on the reduction of metanil yellow by hydrazine dihydrochloride. Under experiment condition, the linear range of determination is 20–160 ng/mL for molybdenum and the detection limit is 11.2ng/mL. The method has been used to determine trace molybdenum in bean samples with the recovery of 96.0–99.0%, with relative standard deviations of 1.50–2.53%.     

Flow-Injection Catalytic Spectrophotometric Determination of Trace Amounts of Nitrite

ABSTRACT

A flow-injection catalytic spectrophotometric method is proposed for the determination of nitrite based on its catalytic effect on potassium bromate oxidation of acridine orange in phosphoric acid medium. The reaction is monitored spectrophotometrically by measuring the decrease in absorbance of acridine orange at 491.5 nm coupling with the stopped-flow technique. The calibration curve was linear between 3.4 and 65 ng/mL, and the detection limit was 2.2 ng/mL. Up to 30 samples can be analyzed per hour with a relative precision of ca. 1.9%. The proposed method was successfully applied to the determination of nitrite in waters and food samples with satisfactory results.     

Kinetic-Spectrophotometric Determination of Molybdenum(VI) Based on Its Catalytic Effect on the Thionine-Hydrazine Reaction

Abstract

A kinetic method for the determination of trace amounts of Mo(VI) (0.05-4 μg ml^?1) based on its catalytic effect on the reduction of thionine by hydrazine monochloride in strongly acidic media is reported. The reaction is monitored spectrophotometrically by measuring the decrease in absorbance of thionine at 605 nm after a fixed time (5 min.). The detection limit of the method is 23 ng ml^?1 and the relative standard deviation (RSD) for 0.05 μg ml^?1 of Mo(VI) is 1.2% (n=7). The method is almost free from interferences, especially from large amounts of tungsten. The procedure was successfully applied to the determination of trace amounts of molybdenum in steel.     

Spectrophotometric determination of trace amounts of molybdenum (VI) based on catalytic reduction of safranine by hydrazine dihydrochloride

Summary A simple and rapid kinetic method for the determination of traces of molybdenum (0.1–4.0 g/ml) based on its catalytic effect on the reduction of safranine by hydrazine dihydrochloride is reported. The reaction is monitored spectrophotometrically by measuring the decreasing absorbance of safranine at 520 nm by the fixed time method. The method is sensitive, precise and free from interferences from many anions and cations. The experimental limit of detection is 100 ng/ml and the relative standard deviation for 1.0 g/ml Mo(VI) is 1.56%. The procedure was successfully applied to the determination of molybdenum in a steel alloy.     

Catalytic Kinetic Determination of Trace Amounts of Copper with Polarographic Detection

Abstract

This method is based on the catalytic effect of copper(II) on the redox reaction between acid chrome dark blue and ascorbic acid in acetic acid-sodium acetate buffer solution and 1,10-phenanthroline as an activator. Acid chrome dark blue exhibits a sensitive polarographic wave at -0.375V Vs. SCE and change of acid chrome dark blue concentration is traced by a polarographic detection technique. The detection limit and the linear range of copper(II) are 2.34ng/ml and 5 to 50ng/ml respectively. This new catalytic method has been applied to the determination of copper in human hair, with satisfactory results.     

Adsorbing colloid flotation separation and polarographic determination of Mo(VI) in water

A method is described for the flotation and determination of Mo(VI) in water at ng/ml levels. Mo(VI) is preconcentrated and separated by adsorbing colloid flotation employing aluminium(III) hydroxide as collector and sodium lauryl sulphate as surfactant at pH 5.3 ± 0.1. The molybdenum content in the froth is estimated by using the catalytic wave of Mo(VI) in the presence of nitrate by charging current compensated d.c. polarography (CCCDCP) or differential pulse polarography (DPP). The effect of variables such as pH, ionic strength, concentration of collector and surfactant, time of stirring and gas flow-rate on the recovery of Mo by flotation is reported. The effects of various cations and anions on the flotation and determination of Mo are studied. This method is employed for the determination of molybdenum in natural fresh water samples.     

A Complexo-Ion Exchange Method for the Sensitive and Selective Detection Of Iron (III) and Molybdenum(VI) on Antimony(V) Silicate Beads

Abstract

A highly sensitive and selective spot test method has been developed for iron(III) and molybdenum(VI) with a limit of detection 0.01 μg per 0.02 ml and 0.001 μg per 0.02 ml for Fe(III) and Mo(VI) respectively on the beads of antimony(V) silicate cation exchanger. The method utilizes the adsorption ion-exchange properties of antimony(V) silicate and the complex forming ability of sodium diethyldithiocarbamate.     

Enhanced sensitivity for the differential pulse polarographic determination of Mo(VI) based on adsorption catalytic current

A differential pulse polarographic (DPP) method based on the adsorption catalytic current in a medium containing chlorate and 8-hydroxyquinoline (oxine) is suggested for the determination of molybdenum(VI). Experimental conditions such as pH and the composition of supporting electrolyte have been optimized to get a linear calibration graph at trace levels of Mo(VI). The sensitivity for molybdenum can be considerably enhanced by this method. The influence of possible interferences on the catalytic current has been investigated. The sensitivity of the method is compared with those obtained for other DPP methods for molybdenum. A detection limit of 1.0 × 10^–8 mol/L has been found.     

Ultra trace analysis of molybdenum by differential pulse polarography and adsorptive stripping voltammetry in the presence of 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone

Summary Different polarographic and voltammetric techniques for the determination of molybdenum at the trace level have been investigated. As a result, a new high-sensitivity procedure for the determination of molybdenum by adsorptive stripping voltammetry was developed. The method is based on the reaction of molybdenum(VI) with 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone (chloranilic acid) to produce a complex which is absorbed onto mercury at –0.20 V (vs. Ag/AgCl, 3 mol/l KCl) from pH 2.7 solution. The cathodic stripping peak at –0.62 V can be used to determine molybdenum with a detection limit of 0.02 ng/ml after 5 min deposition time. The relative standard deviation for the determination of 0.1 ng/ml Mo after 5 min stirred collection was 6.6%. Interference from various inorganic ions and organic substances are reported. The method was applied to the determination of molybdenum traces in waters; interfering organic substances in polluted waters were destroyed by oxidative digestion in a microwave oven.     

Determination of trace molybdenum in biological and water samples by graphite furnace atomic absorption spectrometry after separation and preconcentration on immobilized titanium dioxide nanoparticles

A new method has been developed for the determination of trace molybdenum based on separation and preconcentration with TiO₂ nanoparticles immobilized on silica gel (immobilized TiO₂ nanoparticles) prior to its determination by graphite furnace atomic absorption spectrometry (GFAAS). The optimum experimental parameters for preconcentration of molybdenum, such as pH of the sample, sample flow rate and volume, eluent and interfering ions, have been investigated. Molybdenum can be quantitatively retained by immobilized TiO₂ nanoparticles at pH 1.0 and separated from the metal cations in the solution, then eluted completely with 0.5 mol L^?1 NaOH. The detection limit of this method for Mo was 0.6 ng L^?1 with an enrichment factor of 100, and the relative standard deviation (RSD) was 3.4% at the 10 ng mL^?1 Mo level. The method has been applied to the determination of trace amounts of Mo in biological and water samples with satisfactory results.     

An HPLC Method for Measuring 5-Fluorouracil in Plasma

Abstract

5-Fluorouracil in plasma was determined by extraction with methyl isobutyl ketone, evaporation of the ketone, and reverse phase high performance liquid chromatography of the evaporation residue. With UV detection at 280 nm the lower limit of detection is 10.0 ng/ml and interfering peaks eliminated. The method is highly reproducible.     

Differential Pulse Polarographic Determination of Trace Molybdenum in Uranium with α-Benzoinoxime Extraction

A method for the determination of trace molybdenum in uranium is described based on its specific catalytic reduction wave in the presence of nitric acid. Molybdenum is separated from uranium by α-benzoin oxime extraction and determined by differential pulse polarography. As lower as 1 ng/ml of Mo(VI) is determinable and 98% of recovery can be obtained at present work.     

Double indication in catalytic—kinetic analysis; Determination of iron(III), cyanide and molybdenum(VI)

The reactions in catalytic—kinetic methods are followed simultaneously with two independent indication systems. The information delivered by the two indication methods can be used alone or in combination for the determination of the catalyst or the inhibitor. The following examples illustrate the method: the determination of iron(III) by its catalytic action on the decomposition of hydrogen peroxide (thermometric and biamperometric indication)in the range 10–100 ng Fe/6 ml; the determination of cyanide which inhibits the catalytic activity of copper on the decomposition of hydrogen peroxide thermometric and biamperometric indication) in the range 2–60 μg CN^-/7 ml; and the determination of molybdenum based on the Landolt-type system iodide—bromate— ascorbic acid (thermometric and photometric indication) in the range 0.8–40 μg Mo/8 ml.     

Determination of Trace Amounts of Acetaldehyde Using a Novel Chemiluminescence Reaction

Abstract

The chemiluminescent reaction of iso-propyl alcohol with C10^?-H₂O₂ is enhanced by acetaldehyde. This provides a new method for the determination of trace amounts of acetaldehyde. The detection limit is 0.08ng/ml acetaldehyde and the linear dynamic range is 0.5ng/ml to 1000 ng/ml. The method results in good selectivity and has been satisfactorily applied to the determination of traces of acetaldehyde in waste water samples.     

Polarographic Determination of Inorganic Phosphorus in Phytic Acid

Abstract

A method for the determination of inorganic phosphorus in phytic acid by polarography was developed. The mechanism of Mo/Sb/P polarographic behaviour has been studied. It is one of the most sensitive analytical methods of phosphorus at present. The limit of detection is 8x10^?9 g/ml. This method has been used in the determination of inorganic phosphorus in phytic acid and result is found satisfactory.     

High Performance Liquid Chromatoraphic Determination of R-831, A New Antiallergic Agent,in Dogs and Humans

Abstract

A simple, selective and sensitive HPLC method has been developed to measure R-831 levels in dogs and humans. It is an internal standard technique with a single step extraction and one wash. Samples are chromatographed on a reversed-phase system with ultraviolet detection. The lowest detectable concentration for plasma is 25 ng R-831/ml with a 1 ml sample and the linear range is 25–8000 ng R-831/ml. The lowest detectable concentration for urine is 250 ng R-831/ml with a 0.1 ml sample and the linear range is 250–8000 ng R-831/ml. This method has been used to quantitate levels of R-831 in bioavailability and toxicity studies in dogs, and in pharmacokinetic and efficacy studies in humans.     

Sequential Extraction-Spectrofluorimetric Determination of Mercury Using Cryptand Ethers

Abstract

A spectrofluorimetric study of the extraction of mercury with 1,2-dichloroethane as an ion-pair formed between the cryptand 2.2.1-mercury complex and the eosinate counter-ion is described.

The detection limit for mercury is 0.7 ng/ml, and the linear working range up to 125 ng/ml of mercury.

The relative standard deviation is found to be 2.0% at the 100 ng/ml level. The proposed method has been tested for the determination of mercury in coal.     

HPLC Determination of Ochratoxin A in a Low Volume of Human Blood Serum

Abstract

A high‐performance liquid chromatography (HPLC) method has been developed for the determination of ochratoxin A (OTA) in human blood serum. Samples were purified on a C18 solid phase extraction column. The developed method required a relatively low serum volume (0.5 ml). Significant correlation (r of 0.998) was found over the range from 0.10 to 8 ng/ml, with a detection limit of 0.1 ng/ml and better performance in terms of precision and accuracy. Mean recoveries at 0.5 and 2 ng/ml were respectively 69.7±1.2 and 71.9±2.8%. This method was used as a rapid and noninvasive tool to assess human exposure to OTA. Among 40 analyzed serum samples, 27.5% were found to contain OTA with levels going from 0.1 to 11.98 ng/ml with a mean concentration of 0.73±2.35 ng/ml.     

A New Method for the HPLC Analysis of Pt(II) in Urine

Abstract

An analytical method has been developed to measure Pt(II) in urine via derivatization and UV or HPLC analysis. A measured quantity of urine is heated briefly with diethyl ammonium diethyl-dithiocarbamate, and the resulting Pt(Et₂NCS₂)₂ is extracted into a measured volume of chloroform. Concentrations of Pt(II) are determined by UV absorption at 346 nm or by reverse phase HPLC analysis. The detection limit for Pt(II) as its dithiocarbamate is ～ 1 ng by HPLC; the concentration limit for HPLC analysis by direct extraction was ～ 25 ng/ml. Chromatographic response was linearly related to Pt(II) concentration over the range 100-4, 000 ng/ml; dilution of more concentrated samples has extended this range to at least 30, 000 ng/ml. This method has been applied to the analysis of Pt(II) in the urine of patients who have received cis-dichlorodiamniineplatinum(II) (CDDP) chemotherapy.