Flotation-spectrophotometric method for determining palladium by means of the ion-association complex of pentabromopalladate(II) with Rhodamine 6G

The conditions for the formation of a suitable coloured palladium ion-association complex with a basic dye have been examined, and a spectrophotometric method developed for the determination of palladium with bromide and Rhodamine 6G (R6G). Benzene is used for flotation and dimethylformamide for dissolution of the ion-association complex. The molar absorptivity is 3.0 x 10(5) l. mole(-1).cm(-1) at 53Onm. Beer's law is obeyed up to a palladium concentration of 0.3 mug/ml. The composition of the complex is [R6G(+)](3)[PdBr(3-)(5)]. Platinum interferes severely but other platinum metals interfere to a lesser degree. The method has been applied to the determination of traces of palladium in metallic platinum after a preliminary separation with nickel dimethylglyoximate as collector.     

铜(Ⅱ)-硫氰酸盐-乙基紫-微乳液分光光度法测定钢样中的微量铜

在非离子型微乳液(OP/n-C5H11OH/n-C7H16/H2O)存在下,Cu2+与硫氰酸盐形成络阴离子[Cu(SCN)4]2-,在pH 3.6乙酸盐缓冲溶液中,该络阴离子再与乙基紫(EV)形成吸附型离子络合物,该络合物的组成为[Cu(SCN)4]2-:EV=1:2,最大吸收波长为660nm,表观摩尔吸光系数ε660为1.08×l05L.mol-1.cm-1,Cu2+含量在1.7～18.0μg/50 mL范围内符合比尔定律,检出限为0.5μg/50 mL,用该方法测定了钢中的铜,相对标准偏差小于2%。     

Extractive spectrophotometric determination of trace amounts of iron(III) with benzyltriethylammonium chloride

The ion-association complex formed between a thiocyanato-iron(III) ion and a benzyltriethylammonium ion is extracted into 1,2-dichloroethane, and its absorbance at 476 nm is used for determination of the iron. Beer's law is obeyed up to about 4 mug/ml iron concentration in the final solution. The molar absorptivity is 2.79 x 10(4) l.mole(-1).cm(-1).     

Indirect determination of arsenic by flotation spectrophotometry

An indirect method of arsenic determination in the submicrogram range via the determination of molybdenum is presented here. High sensitivity is achieved by combination of the chemical amplification during formation of dodecamolybdoarsenic acid (arsenic: molybdenum ratio 1 12) with multiplication due to the formation of ion-association complexes during flotation-spectrophotometric molybdenum determination with crystal violet (molar ratio 1 2). Thus, the amplification factor relating to arsenic is 24.Dodecamolybdoarsenic acid is formed in a weakly acidic medium and is quantitatively extracted byn-butanol. Back extraction of the heteropoly acid to the aqueous phase and its simultaneous destruction provides the basis for the reaction of released molybdate ions with thiocyanate ions. The molybdenum-thiocyanate complex forms a sparingly soluble ion-association complex with crystal violet which can be floated with toluene on the phase boundary (film flotation). After separation of the aqueous phase the floated molybdenum compound is dissolved in acetone and the resulting free crystal violet ions are subjected to photometric determination at 590 nm as equivalent of the concentration of arsenic. The molar absorptivity of crystal violet is 3.2 · 10⁵1 · mol^–1 · cm^–1. Beer's law is obeyed in a concentration range from 0.01 to 1 g Mo · ml^–1 (0.001–0.1 g As · ml^–1). The resulting detection limit for arsenic is 1 ng · ml^–1.     

Resonance Rayleigh-scattering method for the determination of sildenafil citrate in a pharmaceutical formulation using Evans blue.

A highly sensitive resonance Rayleigh-scattering (RRS) method for the determination of sildenafil citrate has been developed, based on the fact that sildenafil (Sild) reacted with Evans Blue (EB) to form an ion-association complex in pH 1.1 - 4.6 aqueous solution. This resulted in a significant enhancement of the RRS intensity, and a new spectrum appeared. The wavelength of the maximum RRS was at 365 nm, and other scattering peaks were at 400, 442, 470 and 534 nm, respectively. The intensity of RRS was directly proportional to the concentration of Sild in the range 0 - 11.5 microg ml(-1), and the detection limit for Sild (3 sigma) was 30.3 ng ml(-1). The composition of the ion-association complex was Sild:EB = 1:1, as established by Job's method. The method had good selectivity and could be applied to the determination of Sild in the aqueous phase without using organic solvent extraction. The method was simple and rapid. In addition, the reaction mechanism and the reason for RRS enhancement were considered.     

Spectrophotometric determination of arsenic in water samples based on micro particle formation of ethyl violet-molybdoarsenate.

In this study, a simple and sensitive method for the determination of arsenic in water samples was developed. The method is based on the formation of micro particles of Ethyl Violet and molybdoarsenate, which gives an apparently homogeneous blue color to the solution. The absorption of the excess dye gradually decreases due to its conversion to a colorless carbinol species under strongly acidic conditions. Consequently, the sufficiently low reagent blank enables the spectrophotometric determination of arsenic with the detection limit of 4 microg l(-1). The coefficient of variation for the spectrophotometry at 50 microg l(-1) was 3.5% (n = 5). Furthermore, it is possible to detect concentrations as low as 10 microg l(-1) of arsenic visually. Our method will be useful as a simple, rapid, and cost-effective field test of arsenic, requiring no complex apparatus or skilled laboratory support.     

A study of the composition and properties of the ion-association complex of Rhodamine B with silicomolybdic acid, with a view to its analytical application

The composition of the ion-association complex of Rhodamine B with silicomolybdate has been examined by Job's method and spectrophotometric titration. The ratio of Rhodamine B to silicon in the complex is 4 : 1. The same ratio is obtained by analysis of the crystalline complex. The composition of the complex is identical in aqueous medium, an organic solvent (ethanol) and in the crystalline state (C(28)H(30)N(2)O(3))(4)SiMo(12)O(40)). The complex is stable in the organic solvent and has its absorption maximum at 555 nm and a molar absorptivity of 5 x 10(5) 1.mole(-1)cm(-1). The complex can be advantageously used for the determination of silicon.     

Spectrophotometric determination of tungsten in ores and steel by chloroform extraction of the tungsten-thiocyanate-diantipyrylmethane complex

A method for determining up to about 6% of tungsten in ores and mill products is described. It is based on the extraction of the yellow tungsten(V)-thiocyanate-diantipyrylmethane ion-association complex into chloroform from a 2.4M sulphuric acid-7.8M hydrochloric acid medium containing ammonium hydrogen fluoride as masking agent for niobium. The molar absorptivity of the complex is 1510 1. mole(-1).mm(-1) at 404 nm, the wavelength of maximum absorption. Moderate amounts of molybdenum and selenium may be present in the sample solution without causing appreciable error in the result. Interference from large amounts is avoided by separating these elements from tungsten by chloroform extraction of their xanthate complexes. Large amounts of copper interfere during the extraction of tungsten because of the precipitation of cuprous thiocyanate. Common ions, including uranium, vanadium, cobalt, titanium, arsenic and tellurium, do not interfere. The proposed method is also applicable to steel.     

Spectrophotometric and derivative spectrophotometric determination of iron by extraction of the iron(II)-TPYZ-picrate ion-association complex

A solvent extraction-spectrophotometric determination of microamounts of iron has been developed, based on the formation of an ion-association complex of iron(II) with 2,4,6-tris(2'-pyridyl)-1,3,5-triazine as primary ligand and picrate as counter-ion, which is extracted into 1,2-dichloroethane. The complex is formed at pH 4.0-7.0 and the iron concentration can be determined by measuring the absorbance directly in the organic phase. The apparent molar absorptivity is 2.2 x 10(5) l.mole(-1).cm(-1). As the method is practically free from interferences it was applied to the determination of iron in different biological and inorganic samples. Although the proposed method is very sensitive it can be further sensitized by employing the derivative spectrophotometric technique.     

Extractive-spectrophotometric determination of molybdenum as an ion-association complex with thiocyanate and adogen

A selective and sensitive method is described for the determination of trace amounts of molybdenum, based on its reaction with thiocyanate and its extraction (into toluene) as an ion-association complex formed with adogen (methyltrioctylammonium chloride). The molar absorptivity is 2.13 x 10(4) l.mole(-1).cm(-1) at lambda(max) 467 nm. The method has been applied to molybdenum determination in steels.     

Resonance Rayleigh scattering method for the determination of trace amounts of cadmium with iodide-basic triphenylmethane dye systems

In dilute phosphoric acid solution, cadmium (II) reacts with a large excess of I- to form [CdI4]2- which reacts further with basic triphenylmethane dyes such as crystal violet (CV), ethyl violet (EV), methyl violet (MV), brilliant green (BG) or malachite green (MG) to form an ion-association complex. This results in a significant enhancement of resonance Rayleigh scattering (RRS) intensity and the appearance of new RRS spectra. The characteristics of RRS spectra of the ion-association complexes, the influencing factors and the optimum conditions of these reactions have been investigated. The intensity of RRS is directly proportional to the concentration of cadmium from 0 to 60 ng mL(-1) for EV and MV systems, 0 to 80 ng mL(-1) for CV system, and 0 to 100 ng mL(-1) for BG and MG systems. The methods exhibit high sensitivities and the detection limits for cadmium are between 0.35 and 2.00 ng mL(-1) depending on the different reaction systems. The new RRS method was applied to the direct determination of traces of cadmium in pure zinc and synthetic water samples.     

Indirect determination of cyanide in water by atomic-absorption spectrophotometry

An indirect method for determination of trace cyanide in water by atomic-absorption spectrophotometry is described. Cyanide forms a stable complex anion with Pd in alkaline solution. This complex anion can form an ion-association complex with tetra-alkylammonium ions which can be extracted into n-butyl alcohol with an efficiency higher than 90%. The extract can be analysed directly for palladium (and hence indirectly for cyanide) by flame atomic-absorption spectrophotometry. The detection limit for cyanide by this method is 0.1 mug ml in the n-butyl alcohol extract. Beer's law is obeyed for 0.13-9 mug of CN(-) per ml of n-butyl alcohol. Several foreign ions do not interfere.     

The determination of thallium(III) with the 2,2'-bipyridyl-iron(II) chelate

A spectrophotometric determination of thallium (III), based on solvent extraction of an ion-association pair formed between the cationic 2,2'-bipyridyl-iron(II) chelate and the anionic thallium(III) bromide complex is described. The best extractant is 1,2-dichloroethane and extraction is possible over the pH range 2.5–6.7. The composition of the extracted species was confirmed, and conditions were established for the extraction over the concentration range 7.9·10^-6–3.5·10^-5M of thallium in aqueous solution.     

A highly sensitive colour reaction for Se(IV) with the iodide-rhodamine B-PVA system Spectrophotometric determination of trace amounts of selenium in water

A highly sensitive spectrophotometric method for determination of selenium(IV) has been developed, based on Se(IV) oxidation of I(-) to I(-)(3) in a weak-acid medium, then formation of the 1:1 ion-association complex of I(-)(3) with Rhodamine B in the presence of poly(vinyl alcohol). The molar absorptivity is 1.97 x 10(5)l.mole(-1).cm(-1). Preconcentration of Se(IV) and elimination of interfering ions is achieved by an improved thiol cotton method, so the determination has very good selectivity. Se(IV) at mug/l. levels in tap water, hot-spring water and river water has been satisfactorily determined by the method.     

蒸馏-催化极谱法测定复杂物料中微量砷

提出了用催化极谱法测定复杂物料中微量砷的含量。选择测定的溶液介质中含碲(Ⅳ)硫酸溶液5mL和150g.L-1碘化钾溶液5mL。仪器扫描速率为250mV.s-1,并采用二阶导数测定。试样(0.01～1.0g)用氯酸钾0.5g、氢氟酸5滴、硝酸5～10mL溶解,用蒸馏法分离其中的砷。砷的质量浓度在0.4mg·L-1以内与相应的峰电流呈线性关系。按此方法测定了12个矿样中砷含量,其测定值与已知值相符。方法的回收率在97%～100%之间,相对标准偏差(n=6)在2.3%～7.2%之间。     

甲苯咪唑与曙红Y相互作用的共振瑞利散射、倍频散射和荧光光谱及其分析应用

在pH值3.4~3.9的Britton-Robinson(BR)缓冲介质中,甲苯咪唑(MBZ)与曙红Y(EY)反应形成1:1的离子缔合物,体系反应不仅导致荧光光谱的猝灭,还使共振瑞利散射(RRS)和倍频散射(FDS)显著增强,最大的RRS峰位于326 nm处。 荧光猝灭法、RRS法、FDS法的检出限分别为32.31、7.24和11.65 μg/L,其中RRS法的灵敏度最高。 实验讨论了反应的最佳条件以及共存物质的影响。 该方法用于甲苯咪唑片剂以及尿样中MBZ的测定,结果令人满意。     

〔I2Br〕- 与某些碱性三芳基甲烷染料的水相显色反应及其应用于碘的分光光度测定

研究〔I2Br〕-络阴离子与乙基紫、结晶紫、维多利亚蓝4R等碱性三芳基甲烷染料在聚乙烯醇存在下的离子缔合反应的条件、分光光度特征和分析化学性质。结果表明,在稀磷酸介质中,当形成上述离子缔合络合物时,溶液均发生明显的颜色变化。不同染料体系的摩尔吸光系数在2.6×104～6.2×104L*mol-1*cm-1之间,以乙基紫体系灵敏度最高。碘离子浓度在0～1.6mg/L（乙基紫体系）、0～1.4 mg/L（结晶紫体系）和0～0.8 mg/L(维多利亚蓝体系)符合比耳定律,可用于水相直接显色测定碘离子。方法也有良好的选择性,较大量的其他卤离子、一些无机酸根以及一定量的常见金属离子不干扰。用于海带、紫菜和黄豆中碘离子的测定,结果较为满意。     

Spectrophotometric determination of tantalum in ores and mill products with brilliant green after separation by methyl isobutyl ketone extraction of tantalum fluoride

A method for determining ~ 0.001% or more of tantalum in ores and mill products is described. After fusion of the sample with sodium carbonate, the cooled melt is dissolved in dilute sulphuric-hydrofluoric acid mixture and tantalum is separated from niobium and other matrix elements by methyl isobutyl ketone extraction of its fluoride from 1M hydrofluoric acid-0.5M sulphuric acid. The extract is washed with a hydrofluoric-sulphuric acid solution of the same composition to remove co-extracted niobium, and tantalum is stripped with dilute hydrogen peroxide. This solution is acidified with sulphuric and hydrofluoric acids and evaporated to dryness, and the residue is dissolved in oxalic-hydrofluoric acid solution. Tantalum is ultimately determined spectrophotometrically after extraction of the blue hexafluorotantalate-Brilliant Green ion-association complex into benzene from a 0.05M sulphuric acid-0.5M hydrofluoric acid-0.2M oxalic acid medium. The apparent molar absorptivity of the complex is 1.19 x 10(4) l.mole(-1).mm(-1) at 640 nm, the wavelength of maximum absorption. Common ions, including iron, aluminium, manganese, zirconium, titanium, molybdenum, tungsten, vanadium, tin, arsenic and antimony, do not interfere. Results obtained by this method are compared with those obtained by an X-ray fluorescence method.     

Photometric Determination of Trace Arsenic in Aqueous Media

A new procedure has been proposed for the photometric determination of arsenic as its compounds with tetrazolium salts. The choice of 5(1,3-benzadioxole-5-yl)-2-(4-iodophenyl)-3-phenyl-2H-tetrazolium chloride as a reagent for arsenic has been substantiated. The developed scenario of sample preparation involves the gas extraction of arsenic as arsine from the reaction mixture and its absorption isolation from the gas phase into a reagent solution in a 10 : 3 : 12 water–butanol-1–dimethyl sulfoxide mixture. The procedure provides the determination of from 1 to 120 g/L arsenic.     

A selective extraction system for trace amounts of silver

Silver can be extracted from near-neutral aqueous solution into nitrobenzene as the ion-association system formed between its 1,10-phenanthroline complex and bromopyrogallol red. In the presence of EDTA, mercury(II) and bromide ions as masking agents, the extraction system is highly selective. Of 42 ions examined, only thiosulphate and large amounts of gold interfere. The colour system is very sensitive (ε = 32,000). Also, it can readily be applied to the indirect determination of concentrations of cyanide down to 0–026 ppm by determination of an added excess of silver.