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.     

Sensitive flotation-spectrophotometric determination of gold, based on the gold(I)-iodide-methylene blue system

The gold(I)-iodide-Methylene Blue (MB) system is suitable for flotation separation and spectrophotometric determination of gold. Under the optimum conditions [(MB(+))(AuI(2)(-))].3[(MB(+))(I(3)(-))] is formed, and floated with cyclohexane. The product is dissolved in methanol and its absorbance measured. The molar absorptivity is 3.4 x 10(5)1.mole(-1).cm(-1) at 655 nm. The proposed method is more than three times as sensitive as the Rhodamine B method. Pt, Pd, Ag and Hg interfere seriously, and Ir, Rh, Bi and Cd to a smaller extent. Preliminary separation of gold by precipitation with tellurium as a collector is recommended. The method has been applied to determination of gold traces (about 1 x 10(-4)%) in a copper sample.     

Simultaneous determination of hexavalent and total chromium in water and plating baths by spectrophotometry

A new spectrophotometric determination method of hexavalent chromium in waste water and plating baths is described based on the oxidation of beryllon III by chromium(VI) in 0.02M sulphuric acid medium. The decrease in the absorbance of beryllon III was measured at 482 nm with an apparent molar absorptivity of 5.15 x 10(4)1.mole(-1).cm(-1). Beer's law was obeyed for chromium(VI) over the range 0-25 mug/25 ml. After the oxidation of Cr(III) to Cr(VI) by ammonium persulphate, total chromium can be determined. Therefore, chromium(III) can be calculated by subtracting chromium(VI) from total chromium. The detection limit is 0.015 and 0.020 mug/25 ml for chromium(VI) and total chromium, respectively. A sensitive spectrophotometric method for trace Cr(III) and Cr(VI) in waste water and plating baths was developed with good precision and accuracy. The reaction is also discussed.     

Studies and application of catalytic kinetic spectrophotometric determination of trace chromium(VI) sensitized by microemulsion medium

A new catalytic kinetic spectrophotometric method for the determination of trace amount of chromium (VI) in microemulsion medium has been developed. The method is based on the catalytic effect of chromium (VI) on the oxidation of nuclear fast red in the presence of Tween-80 microemulsion and HAc-NaAc buffer solution (pH = 5.2). The linear ranges are in the range of 0 approximately 0.0480 microg mL(-1) of Cr (VI) at 528 nm and the detection limit is 1.56x10(-9)g mL(-1). The method has been applied in determination of Cr (VI) in water and food samples with satisfactory results. The relative standard deviation is less than 4.6 % and the recovery is 93.5 approximately 104 %.     

Malachite green as a reagent for detection and spectrophotometric determination of chromium(VI)

A sensitive and inexpensive method of spectrophotometric determination of chromium(VI), based on the absorbance of its complex with malachite green and acetic acid at pH 2.5 is reported. The complex shows a molar absorptivity of 8 x 10(4) l.mole(-1) cm(-1) at 560 nm, using malachite green and acetic acid as reference solution. The effect of time, temperature, pH and reagent concentration is studied and optimum operating conditions are established. Beer's law is applicable in the concentration range 2.0-22.8 mug/ml chromium(VI). The resin beads act as a catalyst and as little as 1.6 mug of chromium(VI) is detected in the resin phase as compared to 4.1 mug in the solution phase. The standard deviation in the determinations is +/-0.40 mug/ml for a 10.35 mug/ml solution.     

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.     

Iodnitrotetrazolium chloride-A new analytical reagent for determination of chromium

The extraction of chromium (VI) with iodnitrotetrazolium chloride (INT) was studied spectrophotometrically. The basic spectrophotometric characteristics of the ion associated formed were determined. Using different methods it was found that the ratio between chromium and INT was 1:1. The molar absorptivity of the associate is (250) = (3.70 +/- 0.08) x 10(4) 1.mole(-1).cm(-1). Performing the reaction in acid medium (0.1-1.1M hydrochloric acid) allowed the determination of chromium in the presence of large amounts of W(VI), Mo(VI), Fe(III) and V(V). Hence INT is suggested as a sensitive and selective reagent for extractive-spectrophotometric determination of microquantities of chromium(VI).     

The simple and rapid spectrophotometric determination of trace chromium(VI) after preconcentration as its colored complex on chitin

Preconcentration method with collection of metal complexes on a chitin has been applied to the spectrophotometric determination of chromium(VI) in water. The chromium(VI) is collected as its 1,5-diphenylcarbazide(DPC) complex on a column of chitin in the presence of dodecyl sulfate as counter-ion. The Cr-DPC complex retained on the chitin is eluted with a methanol-1 M acetic acid mixture (7:3, v/v), and the absorbance of the eluent is measured at 541 nm. Beer's law is obeyed over the concentration range of 0.05-0.6 mug of chromium(VI) in 1 ml of the eluent. The apparent molar absorptivity is 3.5x10(4) dm(3) mol(-1) cm(-1). The tolerance limits for Fe(III) is low, i.e. ten times that of chromium(VI), but some metal ions and common inorganic anions do not interfere in concentration range of 100-10 000 times that of chromium(VI). The present method can be applied to the determination of chromium(VI) in natural water samples.     

Spectrophtometric determination of tungsten(VI) with rutin and cetyltrimethylammonium bromide

Tungsten-(VI) reacts with rutin in the presence of cetyltrimethylammonium bromide to form a soluble yellow complex having maximum absorbance at 416 nm. The molar ratio of tungsten to rutin in the complex is 1:2. The molar absorptivity is 5.01 x 10(4) 1.mole(-1).cm(-1). Beer's law is obeyed over the range 1 x 10(-7)(-1) x 10(-5)M tungsten (VI). Optimum solution conditions for the determination of tungsten in various sample matrices have been found and the interference of diverse ions has been examined.     

Spectrophotometric determination of chromium in waste water and soil

The reaction of Cr(VI) with o-nitrophenylfluorone (NPF) in presence of cetyltrimethyl-ammonium bromide (CTMAB) to form a purplish red complex at pH 4.7-6.6 by heating at 50 degrees for 10 min has been investigated. The composition of the complex is 1:2:2 [Cr(VI):NPF:CTMAB], the wavelength of maximum absorbance is 582 nm. The molar absorptivity is 1.11 x 10(5)1.mole(-1).cm(-1). Beer's law is obeyed up to 0.2 microg ml Cr(VI) concentration. The interference of several ions, including Cu(2+), Fe(3+) and Al(3+), is eliminated by addition of a masking mixture containing KF, DCTA and tartrate. A new sensitive method for determination of chromium in waste water and soil is presented.     

A highly sensitive spectrophotometric determination of gallium with Pontachrome Azure Blue B and cetyltrimethylammonium chloride

A new spectrophotometric method for the determination of gallium with Pontachrome Azure Blue B and cetyltrimethylammonium chloride is described. The sensitivity of the colour reaction between gallium and Pontachrome Azure Blue B is greatly increased in the presence of cetyltrimethylammonium chloride. The gallium complex has maximal absorbance at 680 nm and pH 6.0-6.6. Beer's law is obeyed over the range 0.08-0.6 ppm of gallium; the molar absorptivity is 1.39 x 10(5) 1.mole(-1). cm(-1) and sensitivity 4.9 x 10(-4) mu/cm(2). The mole ratio of the complex, the formation constant and effect of interfering ions are described.     

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.     

Analytical properties of 5,5-dimetyl 1,3-cyclohexanedione dithiosemicarbazone monohydrochloride; spectrophotometric determination of chromium(VI) in alloy steels and industrial effluents

The analytical properties of 5,5-dimethyl 1,3-cyclohexanedione dithiosemicarbazone monohydrochloride (5,5-DiMe-1,3-CHDT.HCl) are described. The reagent gives pink coloured solutions with chromium(VI) in acetic medium. The maximum colour intensity is observed in 0.5-2.5 pH range. This colour reaction (molar absorptivity, 1.63 x 10(4) 1 mol(-1) cm(-1) at 360 nm) has been used for the spectrophotometric determination of total chromium in alloy steels and industrial effluents.     

Spectrophotometric determination of micro amounts of nitrite in water and soil

A spectrophotometric method for determination of micro amounts of nitrite in water and soil with p-aminoacetophenone and resorcinol is described. The interference of foreign ions can be eliminated by masking with complexing agents. Beer's law is obeyed up to 20 mug of NO(2)(-) in 60 ml of solution and the molar absorptivity at 435 nm is 5.27 x 10(4) l.mole(-1).cm(-1). The colour is stable for 10 hr. Results obtained by using the proposed method for water and soil samples agree well with those obtained by the Saltzman standard method.     

The spectrophotometric determination of trace molybdenum (VI) after collection and elution as molybdate ion on protonated chitin

Collection and elution method for inorganic anion on protonated chitin has been applied to the spectrophotometric determination of molybdenum (VI). The molybdenum (VI) is collected as molybdate ion on a column of chitin in weak acidic medium which is easily eluted with a small volume of 0.1 M ammonia buffer solution (pH 10). The molybdenum (VI) in the eluent is determined by bromopyrogallol red-Zephiramine method spectrophotometrically. Beer's law is obeyed over the concentration range of 0.1-0.8 mug of molybdenum (VI) in 1 ml of eluent at 634 nm. The apparent molar absorptivity is 6x10(4) dm(3) mol(-1) cm(-1). The tolerance limits for WO(4)(2-), VO(3)(-), CrO(4)(2-) and Fe (III) is low, that is, 1-100 times that of molybdenum (VI), but some metal ions and common inorganic anions do not interfere in concentration range of 1000-5000 times that of molybdenum (VI). The present method can be applied to the determination of molybdenum (VI) in natural water samples.     

Spectrophotometric determination of paraquat with BiI(-)(4) in the presence of gum arabic

A spectrophotometric method for determination of Paraquat, based on its reaction with BiI(-)(4) ion in the presence of gum arabic, is described. The apparent molar absorptivity of the product is 1.64 x 10(4) 1.mole(-1).cm(-1) at 515 nm. Results for the analysis of commercial herbicides are in good agreement with those obtained by the dithionite method.     

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.     

Spectrophotometric determination of vanadium with 1,10-phenanthroline

A simple and sensitive spectrophotometric method for the determination of vanadium based upon the reaction of vanadate with 1,10-phenanthroline in the presence of sodium dithionite in ammoniacal solution is described. The absorbance of the complex measured at 645 nm follows Beer's law for solutions containing 30-400 microg of vanadium in 100 ml of solution. A 10-fold excess of molybdenum, tungsten, phosphorus or chromium does not interfere. The molar absorptivity is 8.0 x 10(3) 1 mole(-1) cm(-1). The complex is shown to be tris-1,10-phenanthroline vanadium(II). The method has been applied successfully to the determination of vanadium in bauxite.     

Spectrophotometric study of the complexation and extraction of chromium(VI) with cyanine dyes

Solvent extraction of chromium(VI) ion associates with symmetric cyanine dyes including the heterocyclic radicals of 1,3,3-trimethyl-3N-indoline, benzooxazol, benzothiazol and quinoline has been studied by means of spectrophotometric method. In the acidic medium in the presence of chloride ions, extractable by aromatic hydrocarbons and esters of acetic acids, chromium(VI) ion associates are formed. The molar absorptivities of ion associates are 2.5-3.6x10(5) l mol(-1) cm(-1) in dependence on extractant and dye. The absorbance of the coloured extracts obeys the Beer's law in the range 0.01-2.1 mg l(-1). The extraction of chromium is the highest during extraction from the sulphuric acid medium in the range 0.05-03 M H(2)SO(4). It was found that the Cr(VI):Cl:R molar ratio is 1:1:1. A novel procedure of chromium(VI) extraction and spectrophotometric determination in various types of soils and sewage doped with chromium(VI) was examined.     

Simultaneous spectrophotometric determination of nickel and iron in copper-base alloy with bromo-PADAP

The reaction of nickel (II) with Br-PADAP, in the presence of tergitol NPX surfactant, forms a complex with absorption peaks at 520 and 560 nm. The iron(II)-Br-PADAP system at the same conditions forms a chelate with absorption peaks at 560 and 748 nm. This allows the simultaneous spectrophotometric determination of nickel and iron by measuring the absorbance at 560 and 748 nm. The proposed method, at ph 4.0-5.7, shows a molar absorptivity of 1.22 x 10(5)l . mole(-1) . cm(-1) for nickel at 560 nm and 8.20 x 10(4)l . mole(-1) . cm(-1) at 560 nm and 3.35 x 10(4)l . mole(-1) . cm(-1) at 748 nm for iron(II). Beer's law is obeyed up to 0.40 mu/ml of nickel(II) and up to 0.65 mu/ml of iron(II). Thiosulphate as masking agent allows the simultaneous determination of iron and nickel in the presence of high concentrations of copper. The ethylene glycol 2-(2-amino-ethyl) tetracetic acid provides the elimination of many other interferences. The method has been applied successfully to the simultaneous determination of nickel and iron in reference samples.