A kinetic determination of ultramicro quantities of manganese(II), molybdenum(VI) and tungsten(VI) on the basis of their catalytic action on the oxidation of Azorubin S by hydrogen peroxide

Summary A study has been made of the kinetics of catalytic oxidation of Azorubin S by hydrogen peroxide in the presence of Mn(II), Mo(VI) and W(VI) in order to find optimal conditions for the kinetic catalytic determination of these elements. Manganese(II), molybdenum(VI) and tungsten(VI) were determined in the concentration ranges 5.5–33.0×10^–3, 1.3–8.1 and 5.9–44.1g/ml, respectively. Standard deviations were less than 11%. The effect of some foreign ions on these determinations was also investigated.

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Zusammenfassung Die Kinetik der katalytischen Oxydation von Azorubin S mit Wasserstoffperoxid in Anwesenheit von Mn(II), Mo(VI) und W(VI) wurde untersucht, um die optimalen Bedingungen für deren kinetisch-katalytische Bestimmung zu finden. Mn(II) wurde im Konzentrationsbereich von 5,5–33,0×10^–3, Mo(VI) von 1,3–8,1 und W(VI) von 5,9–44,1g/ml mit Standardabweichungen <11% bestimmt. Außerdem wurden einige der möglichen Störungen untersucht.

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This work was presented in part at the 20th Annual Meeting of the Serbian Chemical Society, Belgrade, January 17, 1977.     

Spectrophotometric determination of 1-naphthylamine in urine with pentacyanonitrosylmanganate (II)

A new Spectrophotometric method is proposed for the determination of 1-naphthylamine (R), based on its reaction with Mn(CN)₅NO^2– to form Mn(CN)₅NH₂R^3– and measurement of the absorbance at 472 nm. In aqueous medium the molar absorptivity of the manganese complex is maximum ( = 8.0 × 10³1 · mole^–1 ·cm^–1) in the pH range 5.0–10.0, the colour develops more rapidly at pH 10.0. The absorptivity is increased by a factor of 3.5 if the complex is extracted as an ion-associate into chloroform. The extraction efficiency is 99.2% for a single-step extraction, and a concentration factor of 5 can also be achieved. Linearity of response extends over the range 0.04–1.4 gmg/ml 1-naphthylamine, the coefficient of variation being 1.4% at the 0.29 g/ml level (n = 6). The detection and determination limits are 0.005 and 0.018 g/ml, respectively. The method is selective enough to allow the determination of 1-naphthylamine in the presence of considerable amounts of other amines, such as aminophenols and phenylenediamines. Results obtained in the determination of 1-naphthylamine in human urine were very satisfactory.     

Catalytic determination of ultratrace amounts of Cu(II) by the oxidative coupling reaction of 3-methyl-2-benzothiazolinone hydrazone with N,N-dimethylaniline

Summary Copper (II) catalyzes the coupling reaction of 3-methyl-2-benzothiazolinone hydrazone (MBTH) with N,N-dimethylaniline (DMA) to form an intensely colored dye (_max=590 nm) in the presence of hydrogen peroxide and ammonia as an activator. On the basis of this reaction, a highly sensitive and selective catalytic method for Cu(II) has been developed. As little as 10^–9 M Cu(II) can be determined by measuring the absorbance of the reaction product at a fixed time (20 min at 40°C). Sandell's sensitivity calculated from the working curve is 1.3×10^–3 ng cm^–2. The method was applied to water analysis and some comments on the analysis of copper in river water were added.Presented at the 1st International Symposium on Kinetics in Analytical Chemistry, Córdoba, Spain, September 28th, 1983.     

3,3′,5,5′-Tetramethylbenzidme for the colorimetric determination of manganese in water

Manganese can be determined by colorimetry with previous oxidation of Mn(II) in a strong basic medium, using 3,3,5,5-tetramethylbenzidine as a chromogenic reagent. The molar absorptivity of the reaction product is 3.4 × 10⁴ mol^–1l cm^–1l, the detection limit 3 ng/ml, the RSD (0.5 mg/l,n = 8) 0.9% and the calibration range (1-cm cells) 0.02–0.8 mg/1 V(V), Cr(VI) and Co(II) are the most significant interferences. The new method was compared with an AAS procedure (air-acetylene flame) with previous solvent extraction and also with a colorimetric method for the determination of manganese in sea and drinking water.     

A sensitive and highly selective extractive spectrophotometric method for the determination of palladium

Summary A Sensitive and Highly Selective Extractive Spectrophotometric Method for the Determination of Palladium Palladium forms an anionic chelate with 4-(2-pyridylazo)resorcinol (PAR, H₂R) which is extractable with xylometazolonium cation (XMH) into chloroform in the pH range 7.2–7.8 giving an intensely pinkish red coloured solution. The coloured species exhibits maximum absorbance at 520 nm with molar absorptivity 3.34×10⁴1·mole^–1·cm^–1 and obeys Beer's law in the range 0.8–5.30g/ml of palladium. The composition of the extracting species is found to be 111 for Pd(II)PARXMH. Large concentrations of EDTA and oxalate have no interference in the spectrophotometric determination of palladium by this procedure. Based on this a highly selective and sensitive method for the determination of palladium in the presence of Zn(II), Cd(II), Hg(II), Fe(III), Mn(II), Co(III), Mo(VI), Ru(IV), Sb(III), Al(III) is described. The application of this method for the determination of palladium in synthetic mixtures corresponding to the composition of jewel alloy and stibiopalladinite mineral is also demonstrated.     

Flotation-spectrophotometric determination of ruthenium in the Ru(IV)-chloride-rhodamine 6G-toluene system

Summary Flotation-Spectrophotometric Determination of Ruthenium in the Ru(lV)-Chloride-Rhodamine 6G-Toluene System The reduction of RuO₄ in hydrochloric acid has been examined. A sensitive flotation-spectrophotometric method of the determination of ruthenium based on the ion associate formed by the anionic chloride complex of ruthenium RuCl₆ ^2– with the basic dye Rhodamine 6G (R6G) has been developed. The solution of the ion associate obeys Beer's law up to the concentration of 0.25g Ru/ml. The ion associate precipitates when the aqueous solution is shaken with toluene. The separated compound is dissolved in acetone. The molar absorptivity () at 530 nm is 5.1×10⁵ 1·mole^–1-cm^–1. The relative standard deviation is 3–7%. The mole ratio of RuR6G in the complex is 15. Osmium reacts similarly. The determination of ruthenium can be selective after the preliminary separation of osmium as OsO₄. The method was applied to the determination of microgram amounts of ruthenium in crucible platinum.     

Ion-pair adsorption film colorimetry — A new simple method for ppb level of aluminum ion in water sample

A new, highly sensitive and simple colorimetric method for trace aluminum(III) with 2,2-dihydroxyazobenzene, H₂L, is described, based on the ion-pair adsorption of the anionic Al chelate, [A1L₂ ^–, with crystal violet cation, CV⁺, on the surface of Polyvinylchloride film plasticized with dioctylphthalate. The blue violet species, CV⁺[A1L₂]^–, is enriched onto the transparent film, leading to a remarkable enhancement of the sensitivity, and the detection limits are 3 ng/ml by spectrophotometry and 5 ng/ml by visual colorimetry, respectively. Using spectrophotometer, a linear calibration curve is obtained over the concentration range of 0 to 50 ng/ml of Al. Further, the color system, consisting of red ([A1L₂]^–), yellow (H₂L), and blue violet (CV⁺), gave clear color changes suitable for visual determination of aluminum with an applicable range of 0 to above 3000 ng/ml. The four different color zones are khaki for 0–5 ng/ml, reddish-brown for 5–200 ng/ml, blue violet for 200 ng/ml-3g/ml, and colorless for more than 3g/ml. The proposed method has been successfully applied for the determination of aluminum in tap waters.     

Direct spectrophotometric method for the determination of cobalt with indane 1,2,3-trionetrioxime in aqueous medium

A simple, sensitive and selective Spectrophotometric method has been developed for the determination of cobalt using indane 1,2,3-trionetrioxime (ITT): The method is based on the colour reaction between ITT and cobalt(II) in sodium acetate-acetic acid buffer (pH 4.5–7.5) medium. The calibration graph for measurement at 320 nm is linear in the range 1.18–23.60g of cobalt per 25 ml, with molar absorptivity of 5.32×10⁴1mol^–1 cm^–1. The effect of interfering ions has been studied and the method was applied to the determination of cobalt in alloys, with good results.     

Analytical application of atomic emission and atomic absorption spectrometry for the determination of imidazoline derivatives based on formation of ion-associates with sodium cobaltinitrite and potassium ferricyanide

Ion-association complexes of Naphazoline HCl (I), Tolazoline HCl (II) and Xylometazoline HCl (III) with [Co(NO₂)₆]^3– and [Fe(CN)₆]^3– were precipitated and the excess of the unreacted iron or cobalt comples was determined. A new method using atomic emission and atomic absorption spectrometry for the determination of the above drags in pure solutions and in pharmaceutical preparations is given. The drugs have been determined in the ranges 0.98–14.76, 0.78–11.80 and 1.12–16.80 g/ml solutions of I, II and III. respectively, using [Co(NO₂)₆]^3–], with mean relative standard deviations of 0.4–1.5% and 1.92%–19.68, 1.52–5.68 and 2.24–22.4 g/ml solutions of I, II and III, respectively using [Fe(CN)₆]^3– with mean relative standard deviations of 0.6–1.6%. The recovery values of 98.12–101.26% indicate high precision and accuracy.     

Column preconcentration of gold by adsorbing AuCl<Stack><Subscript>4</Subscript><Superscript>−</Superscript></Stack> onto methyltrioctyl ammonium chloride–naphthalene and subsequent atomic absorption spectrometric determination

A sensitive, selective and simple preconcentration method for ultra-trace gold determination has been developed that uses naphthalene–methyltrioctyl ammonium chloride (Aliquat 336s) as an adsorbent. Gold, in the form of AuCl₄^–, was retained by the adsorbent in the column at a flow rate of 1 ml min^–1. After filtration, the solid mass consisting of the gold complex and naphthalene was dissolved out of the column with 5 ml of N,N-dimethylformamide (DMF), and the metal was then determined by atomic absorption spectrometry. In the initial solution, the calibration graph of absorbance versus gold concentration was found to be linear in the range 0.5–150 ng ml^–1 Au(III) with r=0.997 (n =9), and the 3 s detection limit was 0.428 ng ml^–1. The relative standard deviation for eight replicate measurements of 20 g of gold was 2.14%. Preconcentration factors of 390 and 650 were achieved using 5 ml and 3 ml of DMF, respectively. The proposed method was successfully applied to the determination of gold in wastewater, processed pool water, slurry pool water, and raw well-water from the Moteh gold mine, and synthetic samples.     

Thiazolylblue tetrazolium bromide — a new spectrophotometric reagent for determination of manganese

A method has been developed for the micro-determination of Mn(VII) by the selective extraction of the MnO₄ ^– anion with thiazolylblue tetrazolium bromide from acidic medium. The molar absorptivity of the complex is 1 × 10⁴lmol^–1cm^–1 at 250 nm and the system obeys Beer's law in the range 0.1–1.75 gml^–1 Mn(VII). The composition and stability of the complex are discussed. The characteristic values for the extraction equilibrium and the equilibrium in the aqueous phase are: extraction constantK _ex = 3.16 × 10⁴, distribution constantK _D = 21.85 and association constant =1.45 × 10³. Manganese(VII) was determined in soils and plants. The determination was carried out without preliminary separation of manganese.     

4(5)-D-Arabinotetrahydroxybutylimidazoline-2-thione (THBIT), a new reagent for the spectrophotometric determination of palladium

Summary 4(5)-D-Arabinotetrahydroxybutylimidazoline-2-thione, THBIT, is proposed as a new reagent for the spectrophotometric determination of Pd(II). Pd(II) forms 11, 12 and 14 complexes with THBIT. The system conforms to Beer's law up to 5g/ml palladium concentration in aqueous medium (molar absorptivity, 1.99×10⁴ l· mole^–1·cm^–1 at 338 nm). The most serious interference is from Hg(II), Os(VIII), Ru(IV), Cr(VI), V(V) and S₂O₃ ^2–. The method has been used successfully for the determination of palladium in catalysts and synthetic samples.     

Liquid-liquid extraction of cobalt(II) thiocyanate with hexamethyl phosphoramide: Direct spectrophotometric determination in the organic phase

Summary Use of HMPA in Co(II) thiocyanate colour system gives a simple, sensitive and selective method for the determination of Co(II). Maximum colour intensity is attained in the acidity range of 0.15–0.75M HCl and thiocyanate concentration of 0.5–1.0M. The colour is completely extractable into chloroform, when 2 to 4 ml HMPA is used. The colour system shows maximum absorption at 610 nm. The Beer's law range is 2 to 52g Co/ml with optimum concentration range of 6–48g Co/ml. The molar absorptivity and sensitivity are 1.24 x 10³ l·mole^–1·cm^–1 and 0.047g Co/cm² respectively. The method has been applied to the determination of cobalt in steel.

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Flüssig-flüssig-Extraktion von Kobalt(II)thiocyanat mit Hexamethylpbos-phoramid (HMPA) und spektrophotometrische Bestimmung in der organischen Phase

Zusammenfassung Auf der Grundlage der Farbreaktion von Kobalt(II)thiocyanat mit HMPA wurde eine einfache, empfindliche und selektive Methode zur Bestimmung von Co(II) entwickelt. Das Farbmaximum erhält man in 0,15–0,75M salzsaurer Lösung bei 0,5–1,0M Thiocyanat-Konzentration. Die Färbung ist mit Chloroform vollständig extrahierbar, wenn 2—4 ml HMPA verwendet werden. Die maximale Absorption liegt bei 610 nm. Der optimale Konzentrationsbereich liegt zwischen 6 und 48g Co/ml. Die molare Absorption beträgt 1,24 x l0³l·mole^–1·cm^–1, die Empfindlichkeit 0,047g Co/cm². Die Methode wurde zur Bestimmung von Kobalt in Stahl verwendet.

     

Electrochemical behaviour of persulphate on carbon paste electrodes modified with Prussian blue and analogous compounds

Summary Peroxodisulphate (persulphate) may be determined by direct current voltammetry (DCV) using carbon paste electrodes chemically modified with Prussian Blue, iron(III)-hexacyanoruthenate(II) or iron(III)-hexacyano-osmate(II). The determination is based on the exploitation of catalytic currents from the reduction of the modifiers. Best results are obtained for iron(III)-hexacyanoosmate(II) yielding a detection limit of 1 g O ₂ ^2– /ml (as persulphate) when using HCl (10^–2 mol/l) as supporting electrolyte and measuring in the DCV-mode. Electrodes doubly-modified with the osmium compound and a liquid anion-exchanger (Amberlite LA2) allow determinations of persulphate after preconcentration under open circuit conditions, in the presence of hydrogen peroxide and perborate, with a detection limit of 20 ng O ₂ ^2– /ml (as persulphate).     

Spectrophotometric determination of iron after separation of its 9,10-phenanthrenequinone monoximate on microcrystalline naphthalene

A sensitive and selective spectrophotometric method has been developed for the determination of iron as Fe(II) or Fe(III) using 9,10-phenanthrenequinone monoxime (PQM) as the complexing agent. Fe(II) and Fe(III) react with PQM to form coloured water insoluble complexes which can be adsorbed on microcrystalline naphthalene in the pH ranges 3.7–6.2 and 2.0–8.4, respectively. The solid mass consisting of the metal complex and naphthalene is dissolved in DMF and the metal determined spectrophotometrically by measuring the absorbances Fe(II) at 745 nm and Fe(III) at 425 nm. Beer's law is obeyed over the concentration range 0.5–20.0 g of iron(II) and 20–170.0 g of Fe(III) in 10 ml of DMF solution. The molar absorptivities are 1.333 × 10⁴ 1 · mole^–1 · cm^–1 for Fe(II) and 2.428 × 10³1· mole^–1 · cm^–1 for Fe(III). The precision of determination is better than 1%. The interference of various ions has been studied and the method has been employed for the determination of iron in various standard reference alloys, bears, wines, ferrous gluconate, human hair and environmental samples.     

An investigation of the chemiluminescence reaction in the sodium hypochlorite–folic acid–emicarbazide hydrochloride system

A chemiluminescence method for the determination of folic acid by the sodium hypochlorite–folic acid–semicarbazide hydrochloride system with a new flow injection technique has been established. The new method can perform simple, sensitive and rapid determinations of folic acid. The response to the concentration of folic acid, in the range of 1.0×10⁻⁷5.0×10⁻⁵ g/ml, is linear. The relative standard deviation of the method is 2.3% (C_s=4.0×10⁻⁶ g/ml, n=11). The detection limit is 2.7×10⁻⁸ g/ml. This method is suitable for automatic and continuous analysis, and has been successfully tested for the determination of folic acid in a folic acid tablet.     

Microdetermination of bromate ions with antipyrine

Summary A spectrophotometric method for the micro-determination of bromate ions has been described. A red colored complex is obtained when 3 ml of 5% antipyrine, 3 ml of 60% perchloric acid and 1 ml of 0.1M sodium nitrite solution are added in a solution containing bromate ions. The maximum absorbance occurs at 525 nm. Beer's law is obeyed for solutions containing 25.0–140.0/ml of bromate ions. Sensitivity has been found to be 0.029g BrO₃ ^–/cm² for logI ₀/I=0.04 with a molar absorptivity of 2·10³ moles^–1, cm^–1. liter. As(III), Ce(IV), Fe(III), CrO₄ ^2–, Cr₂O₇ ^2–, and Cl^– interfere in the determination.

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Zusammenfassung Eine spektrophotometrische Methode zur Mikrobestimmung von Bromationen wurde beschrieben. Nach dem Zusatz von 3 ml 5%iger Antipyrinlösung, 3 ml 60% iger Perchlorsäure und lml 0,1 ·m Natriumnitrit zu einer bromathaltigen Lösung erhält man eine rot gefärbte Komplexverbindung. Deren Absorptionsmaximum liegt bei 525 nm. Lösungen mit 25,0 bis 140,0g Bromat/ml entsprechen dem Beerschen Gesetz. Die Empfindlichkeit der Reaktion beträgt 0,029g BrO₃ ^–/cm₂ für logI ₀/I=0,04 mit einer molaren Absorption von 2 · 10³ m^–1 · cm^–1 · 1. As(III), Ce(IV), Fe(III), CrO₄ ^2–, Cr²O₇ ^2– und Cl^– stören die Bestimmung.

     

Semi-automatic catalytic titration of some aminopoly-carboxylic acids,copper(II), and cobalt(II)

Summary A semi-automatic potentiometric method is described for the catalytic titrimetric determination ofg amounts of some aminopolycarboxylic acids. The method is based on their inhibitory effect on the copper(II)-catalyzed periodate-thiosulfate reaction. Amounts of EDTA in the 0.7–600g range (10^–6–8×10^–5 M), of DCTA in the 7–7000g range (10^–6–10^–3 M), of EGTA in the 0.8–800g range (10^–7–10^–4 M), and of DTPA in the 4–800g range (5×10^–7–10^–4 M) were determined with average relative errors and coefficient of variation of about 0.4–1%. The method has also been used for the indirect catalytic titrimetric determination ofg amounts of Cu²⁺ and Co²⁺ ions with about the before mentioned accuracy and precision.

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Halbautomatische katalytische Titration einiger Aminopolycarbonsäuren sowie von Cu(II) und Co(II)

Zusammenfassung Eine halbautomatische potentiometrische Methode zur katalytischen Maßanalyse von Mikrogrammengen einiger Aminopolycarbonsäuren wurde angegeben. Sie beruht auf dem Hinderungseffekt gegenüber der Cu(II)katalysierten Perjodat-Thiosulfatreaktion. EDTA in Mengen von 0,7–600g, DCTA in Mengen von 7–7000g, EGTA in Mengen von 0,8–800g und DTPA in Mengen von 4–800g wurden mit einem mittleren relativen Fehler von etwa 0,4–1% bestimmt. Das Verfahren wurde auch zur Bestimmung von Cu(II) und Co(II) mit der angeführten Genauigkeit verwendet.

     

Flow Analysis of Transition Metals by Thermal Lensing

The conditions for the flow determination of Al(III), Bi(III), Cd(II), Co(II), Cr(III), Cu(II), Fe(III), Mn(II), Nd(III), Ni(II), Pb(II), Pr(III), and Zn(II) by reaction with Xylenol Orange in aqueous solutions at pH 4.5 and the determination of Cd(II), Co(II), Cu(II), Fe(II), Ni(II), Pb(II), and Zn(II) by reaction with 4-(2-thiazolylazo)resorcinol in water–ethanol mixtures (5 : 1) at pH 5.0 using an injected sample volume of 80 L were proposed. The limits of detection were n × 10^–8–n × 10^–7 mol/L; the linearity ranges in the calibration graphs were of about three orders of magnitude; the relative standard deviation was of 3–7%.