Indirect spectrophotometric determination of fluoride using the ternary system: Thorium-chrome azurol S-cetyltrimethylammonium

Summary The conditions for the reactions of fluoride with the ternary Th-CAS-CTA/CP/zeph and Th-ECR-CTA complexes have been examined, and a new, sensitive and precise method based on the Th-CAS-CTA-F^– system developed for the indirect determination of fluoride. The molar absorptivity of the method is extremely high —10.0× 10⁴l·mole^–1·cm^–1 at 635 nm (in the others, frequently used, spectrophotometric methods for determining fluoride, does not exceed 2.7×10⁴, e. g. for the method with Alizarin Complexone —1.4×10⁴ and with zirconium and Eriochrome Cyanine R— 2.7×10⁴). Beer's law is obeyed up to a fluoride concentration up to 0.08g per ml. The precision and accuracy of the method were tested in analysis of tap water.

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Indirekte spektrophotometrische Bestimmung von Fluorid mit Hilfe des Systems Thorium-Chromazurol S-Cetyltrimethylammonium

Zusammenfassung Die Bedingungen für die Umsetzung von Fluorid mit den ternären Komplexen Th-CAS-CTA(CP)zeph und Th-ECR-CTA wurden geprüft und eine neue, empfindliche und genaue Methode für die indirekte Fluoridbestimmung ausgearbeitet, die auf dem System Th-CAS-CTA-F^– beruht. Dessen molare Absorptivität ist sehr groß: 10,0×10⁴l·mol^–1·cm^–1 bei 635 nm. (Bei den üblichen spektrophotometrischen Methoden zur Fluoridbestimmung ist nicht größer als 2,7×10⁴ bei der Methode mit Zr und Eriochromcyanin bzw. 1,4×10⁴ bei der Methode mit Alizarin-Komplexon). Das Beersche Gesetz gilt bis zu 0,08g Fluorid/ml. Die Genauigkeit des Verfahrens wurde mit Analysen von Leitungswasser geprüft.

     

The spectrophotometric determination of thallium(iii)by ternary complex formation

If thallium(III) is added to an aqueous solution of potassium thiocyanate containing a large amount of pyridine in the pH range 5.2–5.5, a yellow solution which is stable in diffuse light is obtained. The yellow colour can be measured at 405 nm for the colorimetric determination of thallium(III) in the range 20–300 μg Tl ml^-1. The complex is a mixed ligand complex with a metal-ligand ratio of 1:2:2. Thallium(I) does not interfere. The interference of various other metal ions and anions is discussed.     

Analytical applications of ternary complexes-V Indirect spectrophotometric determination of cyanide

An indirect spectrophotometric method is proposed for the determination of cyanide down to 0.2 ppm. It is based on the fact that cyanide prevents the formation of the strongly absorbing ternary complex between silver(I), 1,10-phenanthroline and Bromopyrogallol Red in nearly neutral aqueous solution. Among 17 cations examined, only mercury(II) could not be tolerated. Zinc, cadmium and cobalt interfered only when present in large amounts. A 1000-fold molar excess (over cyanide) of 14 anions can also be tolerated. Bromide, iodide and thiocyanate interference is overcome by addition of lead nitrate, ammonium sulphate and barium nitrate, followed by centrifugation.     

Indirect spectrophotometric determination of cerium(IV)

A simple and very fast photometric method for the determination of trace levels of cerium(IV) has been developed. Use has been made of the reaction in which iron (II), on oxidation with cerium(IV), gives iron(III) which is complexed with tiron, in acidic medium, to form a stable blue color, the intensity of which is in direct proportion to the amount of cerium(IV) originally present in the sample solution. In addition, the method has a wide range of determination and reasonable sensitivity, and it avoids both temperature control and the tedious extraction step.     

Indirect spectrophotometric determination of chromium(VI)

A new simple and sensitive spectrophotometric method for the determination of chromium(VI) is established. It relies upon the oxidation of iron(II) with the titled ion, in acidic medium, to form iron(III) which is complexed with tiron to form a stable blue color with maximum absorption at 650 nm. Adherence to Beer's law is observed in the range 10–100 μg of chromium(VI) per 25 ml, with a molar absorptivity of 5.6 × 10³ liters mol^?1 cm^?1, sensitivity index of 0.0093 μg cm^?1, relative error of ?5.0 to +0.3%, and relative standard deviation of 0.3–4.0%, depending on the concentration level. Furthermore, the reaction needs neither temperature control nor an extraction step.     

Indirect spectrophotometric determination of sulfur dioxide (sulfite)

Sodium sulfite/sulfur dioxide reacts with iron(III) in acidic range (pH 2–3.5) to form iron(II) which is complexed with 1,10-phenanthroline to form a stable orange-red complex with maximum absorption at 510 nm. Beer's Law is obeyed over the concentration range of 0.5–10 ppm of sulfur dioxide.     

Indirect spectrophotometric determination of silicate

An indirect spectrophotometric method has been developed for trace determination of silicate in aqueous samples. The silicate is converted into silicomolybdic acid and extracted into a mixture of 1-butanol and butyl acetate. The silicomolybdic acid is then decomposed with sodium hydroxide and the molybdenum(VI) reduced to molybdenum(III) with a Jones reductor, followed by reoxidation to molybdenum(VI) with iron(III). The resulting iron(II) is complexed with ferrozine, and the absorbance of the complex measured at 562 run. In this manner, submicroamounts of silicate can be determined.     

Indirect spectrophotometric determination of cyanide

A spectrophotometric method for cyanide based on its inhibition of the colour formation reaction between nickel(II) and 3-(4,5-dimethyl-2-thiazolylazo)-2,6-dihydroxybenzoic acid has been developed, and allows the determination of down to 0.1 g of cyanide. Most of the interferences can be avoided by displacement of the hydrogen cyanide using an arsine generator.     

Indirect potentiometric determination of sulphide with an iodide-selective electrode

Summary An indirect potentiometric method for the determination of sulphide is based on oxidation by an ethanolic solution of iodine and the measurement of the resulting iodide with an iodide-selective electrode. The limit of determination is 0.2g. If interferents are present the sulphide is separated by precipitation and then H₂S is evolved from it, absorbed and measured. The reproducibility is about 8% (relative).

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Zusammenfassung Eine indirekte potentiometrische Methode zur Bestimmung von Sulfid beruht auf der Oxydation mit alkoholischer Jodlösung und Messung des Jodids mit einer jodid-selektiven Elektrode. Die untere Grenze der Bestimmung beträgt 0,2g. Bei Anwesenheit störender Substanzen wird das Sulfid gefällt, filtriert, daraus Schwefelwasserstoff freigesetzt und dieser absorbiert und gemessen. Die Reproduzierbarkeit beträgt etwa 8% relativ.

     

Indirect spectrophotometric determination of thiocyanate by extraction as bisthiocyanatobisquinolinemercury(II) complex and its ligand substitution reaction with dithizone

Thiocyanate forms with mercury(II) in the presence of quinoline a mixed-ligand mercury(II) complex, bisthiocyanatobisquinolinemercury(II), and is extracted into chloroform. This mixed-ligand complex is treated with dithizone and forms the bisdithizonatomercury(II) complex. Maximum and constant absorbance of the dithizone complex is obtained when thiocyanate is extracted at pH 5.1-6.5, and Beer's law is obeyed at 498 nm, where the difference in absorbance between the dithizone complex and dithizone is largest. Chloride, bromide, iodide, cyanide and large amounts of ammonium and copper(II) ions interfere.     

Copper(II)-cetyltrimethylammonium chloride-chromal blue G ternary complex and its application to the spectrophotometric determination of copper(II)

A sensitive spectrophotometric method for the determination of copper(II) based on a ternary complex with chromal blue G, a triphenylmethane reagent in the presence of cetyltrimethylammonium chloride, is described. The sensitivity of color reaction between copper and chromal blue G has been greatly increased by the sensitizing action of cetyltrimethylammonium chloride, a cationic surfactant. The color development of the ternary complex can be utilized in the highly sensitive spectrophotometric determination of copper. The molar absorptivity of the binary complex between copper and chromal blue G ε_630nm = 9.56 × 10³liters · mol⁻¹ · cm⁻¹ is enchanced on ternary complex formation to ε_{542 nm} = 4.78 × 10⁴liters · mol⁻¹ · cm⁻¹. The ternary complex gave a maximal absorbance at 542 nm in the pH range 9.8–11. Beer's law is obeyed up to at least 1.2 ppm of copper. The maximal absorbance of the ternary complex was found to develop within 5 min and then it remains constant for several hours. The formation constant of the ternary complex is calculated to be 8.6 × 10¹⁰ under these conditions.     

水解还原铜磷钼酸光度法间接测定丙酮肟

利用丙酮肟在酸性条件下经加热水解生成具有还原性的羟胺,将铜磷钼黄定量还原为铜磷钼蓝的现象,建立了光度法间接测定丙酮肟的方法。结果表明,测定的线性范围为0～24mg/L,相关系数r=0.9996,检出限为0.06mg/L,丙铜肟质量浓度为12.0mg/L时,RSD为0.37%(n=7)。已用于合成水样中丙酮肟的测定。     

Third-order derivative spectrophotometric determination of phosphate as ternary complex with molybdate and rhodamine 6G

This paper describes a third-order derivative Spectrophotometric procedure for the determination of traces of phosphate, based on the formation of a ternary ion-association complex by reaction of phosphate with rhodamine 6G in the presence of molybdate. The pink complex is readily formed in 0.08–0.16M H₂SO₄ medium and remained stable for 2 h. The influence of various instrumental parameters and reaction conditions for maximum colour development are discussed. The few interfering ions can be masked by the addition of appropriate reagents. The procedure is simple, rapid and reliable and allows the determination of 1.5 g l^–1 of phosphate. The relative standard deviation for the determination of 0.08 mg l^–1 of phosphate was 1.1%. The method is applicable to the determination of phosphate in river water, sea water, drinking water, milk powder and standard reference materials.     

Use of the molybdenum-thiocyanate-rhodamine 6G ternary complex for spectrophotometric molybdenum determination without extraction

A modified thiocyanate method without extraction by using rhodamine 6G as a secondary ligand was developed. Molybdenum in 1.0×10⁻² M HCl, after the addition of ascorbic acid, was heated for 10 min in a 90 °C water bath for reduction. Suitable amounts of glycerine, Triton X-100, rhodamine 6G solutions and 2+1 (v/v) 9 M H₂SO₄+3 M KHSO₄ were added in this order. This solution was allowed to cool to room temperature and the absorbance at 570 nm was measured against a reagent blank 45 min after the addition of thiocyanate solution and the second aliquot of Triton X-100 solution. The complex was stable for at least 4 h, the order of reagent addition was important, and thiocyanate should be in large excess. Beer’s law was obeyed over the range 0.9×10⁻⁶ to 1.1×10⁻⁵ M Mo with the molar absorptivity being 1.1×10⁵ l mol⁻¹ cm⁻¹. The R.S.D. for the determination of 0.7 mg Mo l⁻¹ was 1.83% (n=8). Possible interferences of various cations and anions on molybdenum determination were studied. The proposed method was applied to the determination of molybdenum in a dental alloy, Wiron 99.     

Indirect spectrophotometric determination of trace cyanide with cationic porphyrins

Three highly sensitive methods for the determination of cyanide have been developed, based on the fact that the complexation of silver ions with three cationic porphyrins, 5,10,15,20-tetrakis-(1-methyl-2-pyridinio)porphine [T(2-MPy)P], 5,10,15,20-tetrakis(1-methyl-3-pyridinio)porphine [T(3-MPy)P] and 5,10,15,20-tetrakis(1-methyl-4-pyridinio)porphine [T(4-MPy)P], in alkaline media is inhibited by cyanide and the decrease in absorbance of the silver(II) complex is proportional to the cyanide concentration. Sensitivities of the procedures developed are 0.133, 0.126 and 0.234 ng/cm(2), respectively for an absorbance of 0.001. Cadmium(II), copper(II), mercury(II), zinc(II), iodide and sulfide interfere with the cyanide determination. One of the proposed methods was applied to the determination of cyanide in waste-water samples, with satisfactory results.     

Indirect atomic absorption spectrophotometric determination of arsenic

Arsenic has been determined indirectly by atomic absorption spectroscopy by estimating molybdenum in a solution of arsenomolybdic acid in methyl isobutyl ketone. Interference from other ions has been eliminated by prior extraction of arsenic as the diethyldithiocarbamate in diethyl ether. Arsenic has been determined in the presence of phosphate, silicate and germanium (IV). The method has also been used for the determination of arsenic in organic material.     

Catalytic spectrophotometric determination of molybdenum (VI) with the hydrazine-metanil yellow system

A new catalytic Spectrophotometric method for the determination of trace amounts of molybdenum (VI) has been proposed. The method is based on the catalytic effect of Mo(VI) on the reduction of metanil yellow by hydrazine dihydrochloride. Under experiment condition, the linear range of determination is 20–160 ng/mL for molybdenum and the detection limit is 11.2ng/mL. The method has been used to determine trace molybdenum in bean samples with the recovery of 96.0–99.0%, with relative standard deviations of 1.50–2.53%.     

Indirect atomic-absorption spectrophotometric determination of phosphorus in steel by use of the bismuth phosphomolybdate complex

An indirect method for determination of phosphorus by atomic-absorption spectrophotometry has been developed, based on formation of the bismuthophosphomolybdate complex and its extraction by methyl isobutyl ketone. Bismuth is determined in the extract and correlated with the phosphorus content. The method is applicable to different kinds of steel.