Determination of cyanide by a highly sensitive indirect spectrophotometric method

Complexation of Pd(2+) with cyanide inhibits the extraction of the palladium complex of 5-phenylazo-8-aminoquinoline. This effect is used for the indirect spectrophotometric determination of cyanide at the mug level. Cyanide in industrial waste water and in sea-water is determined after distillation as HCN from the sample and collection in sodium hydroxide solution.     

Determination of cyanide by an indirect spectrophotometric method using 5-Br-PADAP

Complexation of Ni(2+) with cyanide inhibits its colour reaction with 5-Br-PADAP and this reaction is used in the spectrophotometric determination of cyanide at the ug level. Cyanide in industrial waste waters is determined after an initial transfer as hydrogen cyanide from the sample into sodium hydroxide solution with a stream of air.     

Solvent extraction flow-injection manifold for the simultaneous spectrophotometric determination of free cyanide and thiocyanate ions based upon on-line masking of cyanides by formaldehyde

This study reports a sensitive solvent extraction flow-injection (FI) method for the simultaneous spectrophotometric determination of free cyanide and thiocyanate in human saliva and pralidoxime solutions. Cyanide and thiocyanate form colored (λ_max=540 nm) ternary complexes with copper and 2,2′-dipyridyl-2-quinolylhydrazone (DPQH) that are extractable into chloroform. The determination of thiocyanates in the presence of cyanides is accomplished after on-line masking of the latter with formaldehyde through a binary inlet static mixer (BISM). Total thiocyanates and cyanides are determined in a second run, without the use of the masking agent. The proposed method allows the determination of the analytes in the range of 0-4 mg l⁻¹ thiocyanates and 0-3 mg l⁻¹ cyanides, with the 3σ detection limits being 0.007 and 0.004 mg l⁻¹, respectively. The precision of the method (s_r<1.0% at 1 mg l⁻¹ CN⁻ or SCN⁻, n=12 in both cases) and the sampling rates were quite satisfactory (60 injections per hour). The method was applied to the analysis of human saliva and pralidoxime solutions and gave recoveries in the range of 98.0-102.2% for both analytes whereas the mean relative error was e_r=1.7%.     

Determination of pentachlorophenol by flow-injection analysis with spectrophotometric detection

Two FIA methods for the determination of pentachlorophenol, based on its oxidizing-condensation reaction with 4-aminoantipyrine in aqueous medium and spectrophotometric detection in the conventional and stopped-flow modes, are described. In both cases the calibration graphs are linear in the range from 1.0 to 60.0 mug/ml pentachlorophenol, with sampling rates of 48 and 28 samples/hr for triplicate analysis, respectively. Interferences from phenol and other chlorophenols have been evaluated. The stopped-flow method is particularly useful for determining pentachlorophenol in commercial formulations containing no more than 15% of other chlorophenols.     

Simultaneous spectrophotometric determination of cyanide and thiocyanate after separation on a melamine-formaldehyde resin

A simple indirect spectrophotometric method for the determination of cyanide, based on the oxidation of the cyanide with chlorine (Cl(2)) is described. The residual chlorine is determined by the color reaction with o-tolidine (3,3'-dimethylbenzidine). The maximum absorbance for Cl(2) is at 437 nm. A linear calibration graph (0-4.0x10(-5) M CN(-)) is obtained under optimal reaction conditions at room temperature and pH 11-12. The stoichiometric mole ratio of chlorine to cyanide is 1:1. The effective molar absorptivity for cyanide is 5.87x10(4) l mol(-1) cm(-1) at pH 1.6. The limit of quantification (LOQ) is 3.6x10(-7) M or 9.4 ppb. Effects of pH, excess reagent, sensitivity, reaction time and tolerance limits of interferent ions are reported. The method was applied to the determination of cyanide in a real sample. The basic interferent usually accompanying CN(-), i.e. thiocyanate, is separated from cyanide by sorption on a melamine-formaldehyde resin at pH 9 while cyanide is not retained. Thiocyanate is eluted with 0.4 M NaOH from the column and determined spectrophotometrically using the acidic FeCl(3) reagent. The initial column effluent containing cyanide was analyzed by both the developed chlorine-o-tolidine method and the conventional barbituric acid-pyridine (Spectroquant 14800) procedure, and the results were statistically compared. The developed method is relatively inexpensive and less laborious than the standard (Spectroquant) procedure, and insensitive to the common interferent, cyanate (CNO(-)).     

Determination of cyanide using flow-injection multisensor system

A flow-injection multisensor system (FIMS) comprising potentiometric sensors of different types for determination of free cyanide activity in basic solutions for extraction of noble metals was developed. The solvent polymeric membrane sensors based on metalloporphyrin and crystalline sensors were combined in the sensor system. The system allowed determination of cyanide activity in the range 10⁻⁴–1 mol l⁻¹ with an error less than 5% in individual cyanide solutions and acceptable precision (about 20%) in process liquids. The system was able to analyse up to 20 samples per h. The FIMS was also applied to detecting of silver ions in the presence of cyanide. Chalcogenide glass sensor was used as the detector that ensured the precision of 20%.     

The effect of barbituric acid concentration in the spectrophotometric determination of cyanide and thiocyanate by the pyridine-barbituric acid method

Summary The König reaction forms the basis of many analytical methods including those for the determination of chlorine, nicotinic acid, thiocyanate and cyanide. The colorimetric methods have, however, been plagued with various problems such as the use of hazardous, often carcinogenic compounds, and the instability of the final color formed as well as of the color reagent itself.Using a mixture of pyridine, hydrochloric acid and barbituric acid as the color reagent, the present study shows the effect of barbituric acid concentration on the intensity and stability of the color complex. The problems associated with the use of barbituric acid can be attributed mainly to the high concentration used by previous workers. A color reagent containing about 0.1% (w/v) barbituric acid shows marked improvements in color intensity and stability as well as reagent stability.     

Determination of hydrazine derivatives by flow-injection analysis with spectrophotometric detection

Flow-injection analysis for the determination of hydrazine derivatives based on their nucleophilic substitution reaction with 4-chloro-5,7-dinitrobenzofurazan in aqueous medium, and spectrophotometric detection has been described. The calibration graphs were linear in the range from 0.15 to 4.0 mug ml(-1) of hydrazine derivatives, with sampling rates of up to 28-32 samples h(-1). Interferences from amino compounds, benzoic acids, aliphatic amines and ammonia have been evaluated. The procedure has been applied to the determination of hydrazine derivatives in serum, urine, appressin drugs and artificial mixtures.     

流动注射后化学发光法测定盐酸阿比朵尔

研究了盐酸阿比朵尔在鲁米诺-K3Fe(CN)6化学发光反应体系中的后化学发光反应. 据此建立了测定盐酸阿比朵尔的流动注射后化学发光分析法. 方法的线性范围为6.0×10-9～1.0×10-7 g/mL, 检出限(3σ)为2×10-9 g/mL. 对4.0×10-8 g/mL的盐酸阿比朵尔溶液连续11次平行测定, RSD=1.3%. 方法已用于盐酸阿比朵尔胶囊及尿样中盐酸阿比朵尔含量的测定. 在对这一后化学发光反应的动力学性质、化学发光光谱、紫外可见吸收光谱以及一些相关问题研究的基础上, 提出了可能的反应机理.     

流动注射化学发光抑制法测定阿魏酸钠

提出了Fe2+-H2O2-亚甲基蓝化学发光新体系并用于阿魏酸钠的测定。实验发现,在酸性介质中,Fe2+-H2O2体系可与亚甲基蓝反应产生极强的化学发光,阿魏酸钠对此化学发光具有显著的抑制作用。据此,结合流动注射技术,建立了阿魏酸钠化学发光分析新方法。研究了影响化学发光强度的因素,化学发光信号的降低值(ΔI)与阿魏酸钠浓度在4.5×10-6～4.5×10-5mol/L范围内呈良好的线性关系,方法的检出限为7.0×10-7mol/L。对4.8×10-6mol/L的阿魏酸钠进行了11次平行测定,其RSD=0.8%,该法已用于片剂中阿魏酸钠含量的测定。     

Determination of iodine value fatty acids by a flow-injection method

An automated method for determining the iodine value for various industrial fatty acids is described. The method is based on flow-injection techniques and the chemistry is a modified version of the standard Wij's solution method. The system is fully computerized with an AIM-65 microcomputer. Two detection system, u.v.-visible absorbance and potentiometric sensing, are compared. Results comparable to the conventional method are obtained. Continuous-run sample throughput rates of 12 h^?1 are eralistic.     

Flow injection spectrophotometric determination of cyanide by the phenolphthalin method

The phenolphthalin method for the determination of cyanide has been modified and adapted to a continuous flow system based on the flow injection principle. Aqueous cyanide samples are injected into a carrier stream (0.001 M NaOH), which is then merged with the combined reagent stream of phenolphthalin and carbonate buffer (pH 10.3), and the mixture is passed through an on-line cupric sulfide packed column. The resulting phenolphthalein (the oxidized form of phenolphthalin) is measured in a flow-through spectrophotometer at 552 nm, to determine the cyanide content. The chemical factors and flow injection analysis (FIA) variables influencing the system are discussed. The calibration graph is linear from 0.6 to 4.3 ppm cyanide. At a sampling rate of about 70 samples h(-1) with 50 mul sample injections, precision was about 1% relative S.D.     

Determination of uranium in seawater by flow-injection preconcentration on dodecylamidoxime-impregnated resin and spectrophotometric detection

A flow injection method has been developed for the determination of uranium in seawater combining the on-line preconcentration with spectrophotometric detection. An aliquot (10 mL) of the seawater sample adjusted to pH 5.5 was injected into the analytical system and uranium was adsorbed on the column packed with styrene-divinylbenzene copolymer resin (Bio-Beads SM-2) modified with dodecylamidoxime which showed high selectivity to uranium. Uranium was then eluted with 0.01 M hydrochloric acid and detected spectrophotometrically after the reaction with Chlorophosphonazo III. Interference from calcium and strontium was masked with cyclohexanediaminetetraacetic acid added to the chromogenic reagent solution. The sample throughput, the detection limit (3σ), and the preconcentration factor were 23 per hour, 0.13 μg/L, and 20, respectively, when the sample injection volume was kept at 10 mL. The precision at the 2 μg/L level was less than 4% (RSD). The proposed method was applied to the determination of uranium in the seawater samples collected off the Boso peninsula, Japan and the uranium concentration was found to be ca. 3 μg/L, which is close to the literature data. The yield of the recovery test ranged from 95% to 99%.     

流动注射化学发光法检测甲基嘧啶磷残留

研究发现,在碱性介质中甲基嘧啶磷能够有效增强鲁米诺-H2O2体系的化学发光。据此,结合流动注射分析法,建立了测定甲基嘧啶磷的流动注射化学发光分析方法,并对可能的反应机理进行了探讨。考察了甲基嘧啶磷-鲁米诺-H2O2体系的化学发光反应动力学以及反应体系pH、鲁米诺浓度、H2O2浓度、流速、进样体积等因素对化学发光的影响。结果表明:在最佳条件下,甲基嘧啶磷在5.0×10-8～1.0×10-5g/mL的浓度范围内与发光强度呈良好的线性关系,检出限(S/N=3)为2.5×10-8g/mL。将该体系应用于加标小麦样品测定,回收率为94.7%～113.0%,相对标准偏差为2.2%～3.6%。     

Spectrofluorimetric flow-injection determination of cyanide

The spectrofluorimetric determination of cyanide (0.1–20 μg ml^?1) with pyridoxal and pyridoxal-5-phosphate by a normal flow-injection method and a stopped-flow procedure is reported. The large number of interfering species in the normal method is significantly decreased by the use of the stopped-flow method. The relative standard deviation is <2%.     

Determination of mimosine by a sensitive indirect spectrophotometric method

A simple and sensitive indirect spectrophotometric method is described for the determination of mimosine based on its reaction with diazotized sulfanilamide (DZSAM). DZSAM couples with N-(1-naphthyl)ethylenediamine (NEDA) forming a pink colored azodye, absorbing maximally at 540 nm (ε_max=27 mM⁻¹ cm⁻¹). In the present method, mimosine was first reacted with known excess of DZSAM and the unreacted DZSAM was determined by coupling with NEDA. The reaction of mimosine with DZSAM proceeded optimally at neutral pH. The decrease in absorbance of the DZSAM-NEDA-coupled product obeyed Beer’s law in the concentration range of 0.005-0.15 μg ml⁻¹ of mimosine. The present method was applied to estimate mimosine in plant extracts containing lesser than 0.05 μg ml⁻¹ with recovery at 99±0.41%. The method described is superior to other reported methods in terms of ease of adaptability and sensitivity.     

Determination of palladium with thiocyanate and rhodamine b by a solvent-extraction method

Sensitive spectrophotometric and spectrofluorimetric procedures for the determination of palladium have been developed, based on solvent-extraction of the ion-pair formed between Rhodamine B and the anionic complex of Pd(II) with thiocyanate. With an organic to aqueous phase-volume ratio of 1:5, the molar absorptivity is 9.0 x 10(4) l.mole(-1).cm(-1) and the absorbance of the reagent blank is 0.026. Spectrophotometrically, palladium can be determined in the range 0.1-8.8 mug. Spectrofluorimetrically, it can be determined over the range 0.04-1.5 mug. The spectrophotometric procedure has been applied to the determination of palladium in dental alloys, organopalladium compounds and hydrogenation catalysts.