Determination of traces of sulfur in selenium by molecular emission cavity analysis

The selenium sample (ca. 1 mg) containing 40–90 μg g^-1 sulfur is decomposed in a combustion apparatus and the evolved sulfur dioxide is adsorbed on about 30 mg of silica gel. The silica gel is deposited in a cavity and the sulfur is determined by molecular emission cavity analysis. Incomplete sulfur recoveries (86 ± 4%) caused by incomplete conversion to sulfur dioxide necessitate a correction factor.     

Determination of traces of phenol in waters by molecular emission cavity analysis

Tribromophenol is produced from phenol (10^-5—10^-6 M), filtered off and determined by production of InBr emission at 376 nm in an air—hydrogen—nitrogen flame. Recoveries of 97—99% were obtained from spiked lake water.     

Determination of selenium in water samples by molecular emission cavity analysis after coprecipitation

Selenium (0.2–5 ppb) is coprecipitated with hydrated iron(III) oxide, dissolved in acid, reprecipitated as the element and determined by molecular emission cavity analysis. For a 250-ml water sample, the detection limit is 0.2 ppb. For <5 ppb selenium there is no need for coprecipitation.     

Determination of thiamine using continuous flow molecular emission cavity analysis

A continuous flow method for the determination of thiamine hydrochloride (20.0-240.0 microgram ml(-1), 5.9 x 10(-5)-7.1 x 10(-4)m) is described. The sample was mixed with an excess of sodium hydroxide and remained in the delay coil for 20 min at 90 degrees C. The solution was then mixed with an excess of orthophosphoric acid and the hydrogen sulphide evolved was transferred continuously into the cavity to generate a molecular++ emission of S2. The analysis is completely automated, requires no sample pre-treatment and samples can be analysed at a rate of 30 samples h(-1) with a relative error of 1-2%. The method was evaluated by carrying out an interference study with common excipients and other water-soluble vitamins, a recovery study and by the analysis of commercial formulations. Results compared well with those obtained using the official method. The method was also applied to content uniformity tests.     

Indirect determination of cyanide by molecular emission cavity analysis

Nanogram amounts of cyanide were indirectly determined by molecular emission cavity analysis. The method is based on the reaction of cyanide with sulphite-formaldehyde addition compound and the measurement of the S₂ emission produced either from the sulphite released or from the addition compound. The relative standard deviations are 2.13% and 1.66% and the recoveries are 99% and 100% using the released sulphite peak and the addition compound peak, respectively. Potential interfering anions were investigated.     

Determination of nanogram amounts of bromide and chloride by molecular emission cavity analysis based on gallium halide emission

By measuring the GaBr emission enhanced by iodide at 350 nm in a carbon cavity heated by a hydrogen/argon flame, 0–60 ng of bromide is determined with a detection limit of 0.5 ng μl^?1. In a similar way, gallium (0–20 ng) can be determined with a detection limit of 0.15 ng μl^?1. Interferences are reported. Chloride (0–1200 ng) is determined by means of GaCl emission; the detection limit is 50 ng μl^?1.     

Indirect determination of amino acids by molecular emission cavity analysis

An indirect method for the determination of ca. 10^?4 M amino acids is described which is based on the reaction of the latter with 2,4,6-trinitrobenzene-1-sulphonic acid at pH 11.7 and the measurement of the S₂ emission in a hydrogen-nitrogen flame that is produced from the resulting compound after the addition of hydrochloric acid. The optimum conditions for the determination of amino acids were investigated. The amino acids examined were glycine, alanine, valine, methionine, serine, threonine and histidine.     

Continuous-flow molecular emission cavity analysis for sulphide

Sulphide (1–10 μg ml^?1) is determined by mixing the sample with an excess of orthophosphoric acid in a segmented continuous-flow system. The hydrogen sulphide evolved is swept into the cavity for generation of S₂ emission. The analysis is completely automated, requires no sample pretreatment and samples can be analyzed at 24 h^?1.     

流动注射光度法测定药物中的盐酸氯丙嗪

在pH 4.04的HAc-NaAc缓冲液中, 刚果红与盐酸氯丙嗪在室温下迅速结合生成缔合物, 且缔合物在480 nm处有最大吸收. 基于此建立了流动注射光度法测定药物中盐酸氯丙嗪的含量. 方法线性范围为0.25～50.0 μg/mL, 检出限为0.082 μg/mL, 测定频率达80次/h.     

The determination of inorganic sulphate in urine by molecular emission cavity analysis

Summary Urinary sulphate is determined by 100-fold dilution with 0.1M phosphoric acid, and measurement of the S₂ emission at 384 nm generated in a MECA cavity placed in hydrogen-nitrogen-air flame.

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Zusammenfassung Im Harn enthaltenes Sulfat wird bestimmt, indem man mit 0,1M Phosphorsäure hundertfach verdünnt und die S₂-Emission bei 384 nm bestimmt, die sich nach Anbringung der Probe in einer MECA-Vertiefung² in einer Wasserstoff-Stickstoff-Luft-Flamme einstellt.

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Dedicated to Prof. Hans Lieb on the occasion of his 90th birthday.     

Determination of sulphur anions by flow injection with a molecular emission cavity detector

A molecular emission cavity detector is attached to a flow injection system for the determination of sulphide, sulphite and sulphate in the ranges 2–130, 3–150 and 5–250 ng S, respectively, in 3-μ1 samples. The sample throughput is abort 100 h^?1. Resolution of mixtures of these anions is also possible, based on the sequential appearance of their S₂ emission peaks. The use of a hydrogen peroxide carrier stream allows the determination of total sulphur.     

The determination of inorganic phosphorus compounds by using molecular emission cavity analysis

The chemical and spectral interferences on the HPO emission within the cavity are investigated. Alkali metals, copper, manganese, iron and sulphate all interfere spectrally, and the alkali metals also suppress the HPO emission. A standard addition method after a batch ion-exchange resin treatment of the sample solution is proposed for the determination of phosphorus (1–1000 mg l^?1 P) in solutions of inorganic samples (e.g., rocks).     

Determination of benzhexol hydrochloride in tablets by high-performance liquid chromatography

Separation on a LiChrosorb C₂ reversed-phase column with methanolic ammonium dihydrogenphosphate as eluent provides a simple determination of benzhexol hydrochloride in tablets containing 2–5 mg of the drug. Common excipients do not interfere.     

Determination of chlorthalidone and clonidine hydrochloride in tablets by HPLC

A rapid, reversed-phase high performance liquid chromatographic method is described for the determination of chlorthalidone and clonidine hydrochloride combinations in tablets. Individual tablets or composite samples were sonicated in water, diluted with methanol, and filtered prior to chromatographing. Chlorthalidone, formulated at 15 mg/tablet, was chromatographed on octadecylsilyl-bonded, 5 to 6-micrometers, spherical silica with 50% methanol in water mobile phase. Clonidine hydrochloride, formulated at 0.1 or 0.2 mg/tablet, was chromatographed on trimethylsilyl-bonded, 5 to 6-micrometers, spherical silica with 65% methanol in pH 7.9 phosphate buffer mobile phase. Both were determined with a spectrophotometric detector at 254 nm. Mean recoveries of the drugs from six synthetic tablet samples were 100.3% for chlorthalidone and 99.7% for clonidine hydrochloride (at 0.1 mg/tablet level) with coefficients of variation of 0.79 and 1.55%, respectively.     

Continuous-flow molecular emission cavity analysis for organic sulphur compounds by alkaline hydrolysis

Alkaline hydrolysis of various organic sulphur compounds (thioacetamide, thiosemicarbazide, thiodiacetic acid and dithiooxamide) in a continuous-flow analyzer produces sulphide which can be removed from the solution after acidification. Hydrogen sulphide evolved is measured by molecular emission cavity analysis. Samples can be analyzed at a rate of 30 h^?1 with a relative error of 1–2%.     

Determination of some organophosphorus insecticides by flow injection with a molecular emission cavity detector

The determination is based on the measurement of HPO emission at 528 nm in a H₂/N₂ flame. Organophosphorus insecticides are extracted with hexane/dichloromethane at pH < 7, the solvent is evaporated, and the residue is dissolved in ethanol. Up to 2 μl of the solution is injected into the flow system. Mixtures of dicrotophos, dimethoate, malathion and parathion were determined.     

Determination of some phosphorus-containing compounds by flow injection with a molecular emission cavity detector

The use of molecular emission cavity analysis combined with a flow-injection system for the determination of nanogram amounts of some organophosphorus compounds and phosphorus oxo-anions is described. Sensitivit, calibration linearity, precision and detection limits were measured for each compound. Simultaneous determinations of some ternary mixtures of these compounds are also described. Sample throughput is 20 h^?1.     

Effect of sulphite on the determination of sulphide by continuous-flow molecular emission cavity analysis Determination of both anions in admixture

The effect of sulphite on the determination of sulphide after acidification and molecular emission cavity analysis is investigated. This severe spectral interference can easily be overcome and, therefore, the determination of sulphide and sulphite in admixtures in feasible. This is accomplished by the addition of sodium chloroacetate, which reacts with sulphide in alkaline medium to produce thiodiacetate. A simple method is derived which allows the successful determination of both anions in admixture. The procedure is applied to a variety of synthetic mixtures with an average relative error of 1.3% for sulphite and 2.7% for sulphide.     

Optimisation of sulphur emission in molecular emission cavity analysis: Effects of variation in cavity position and phosphate addition

Temperature profiles are measured for hydrogen flames used for m.e.c.a. and discussed in terms of the emission intensities produced by some sulphur compounds in different regions of the flame. The effect of addition of phosphoric acid or phosphate buffers on sulphates and ammonium thiocyanate is re-examined and the enhancing effect of “residual phosphate” discussed.     

Continuous flow molecular emission cavity analysis of cephalosporins by alkaline degradation to sulphide

A continuous flow method for the determination of some cephalosporins (cephradine, cephalexin, cephalosporin C, cefadroxil, cephapirin and cephalothin) in the general range 10.0-250.0 micrograms ml-1 is described. The sample is mixed with sodium hydroxide and remains for 20 min at 90 degrees C in the delay coil of an air-segmented system. The solution is then mixed with an excess of orthophosphoric acid, and the hydrogen sulphide evolved is continuously transferred into the cavity for generation of the S2 molecular emission. The analysis is automated, requires no sample pre-treatment and samples can be analysed at a rate of 30 per hour with a relative error of 1-2%. The method was evaluated by carrying out recovery experiments and by the analysis of commercial formulations. Results agreed well with those obtained by the standard methods.