Comparison of four chromogenic reagents for the flow-injection determination of aluminum in water

Pyrocatechol violet (PCV), aluminon, eriochrome cyanine R (ECR) and eriochrome cyanine R with cetyltrimethylammonium bromide (ECR/CTA) are compared as chromogenic reagents for the flow-injection determination of aluminium in water. The detection limit of the ECR/CTA method is 1 μg Al 1^?1. The detection limits of the PCV and ECR methods are 5 μg Al 1^?1. The aluminon method is the least sensitive, with a detection limit of 50 μg Al l^?1. Interference from iron, fluoride, phosphate and the acidity of the sample were investigated. The interference from iron is suppressed by hydroxylammonium chloride/1,10-phenanthroline in the PCV and ECR/CTA methods at concentrations less than 5 mg Fe l^?1. In the ECR and aluminon methods, iron <5 mg l^?1) is masked by ascorbic acid. Fluoride at <0.2 mg l^?1 can be tolerated in all methods. The aluminon method can tolerate up to about 500 mg l^?1 in the three other methods. All methods are sensitive to changes in acidity of the samples; the acidity should be 0.08–0.12 M HCl.     

Detection and semiquantitative determination of bismuth(III) in water on immobilized and plasticized polyurethane foams with some chromogenic reagents

Polyurethane foams immobilizing 1,2-di-(2-fluorophenyl)-3-mercaptoformazan (F(2)H(2)Dz) and dithizone (H(2)Dz) have been used for the detection of bismuth(III) in water via batch, dynamic and pulsated column modes of extraction. The detection limits of bismuth(III) with the F(2)H(2)Dz- and H(2)Dz-immobilized foams were found to be 0.01 and 0.02 mug ml(-1) respectively. Lower concentrations (相似文献   

A comparison of three absorptiometric methods for the determination of copper in biological materials

Absorptiometric methods for traces of copper based on dithizone, 2,9-dimethyl-1,10-phenanthroline (neocuproine) and bis-cyclohexanone-oxalyldihydrazone (BCOD) were compared by carrying out replicate analyses on specimens of liver; the amount of sample taken was varied so as to provide a means of detecting systematic errors. Agreement between the results by the different methods was poor, the neocuproine method giving higher and more variable results than the other two. A systematic error, inconsistent with the sample size, was detected in the BCOD method. The dithizone method showed no systematic error and possessed better precision and sensitivity.     

Spectrophotometric determination of copper in alkaline solutions and evaluation of some hydroxy-substituted 1,10-phenanthrolines as chromogenic reagents

Seven new hydroxy-substituted 1,10-phenanthroline derivatives have been evaluated as chromogenic reagents for the determination of copper in strongly alkaline solution. The most sensitive of these, 2,9-dimethyl-4,7-dihydroxy-1,10-phenanthroline, has proven to be highly effective in a simple, rapid procedure for determining trace amounts of copper in sodium hydroxide, potassium carbonate, sodium phosphate or ammonium hydroxide.     

An automatic absorptiometric method for the determination of nitrate

A method has been developed for the determination of nitrate with the Technicon Autoanalyser in the range 2–10 p.p.m. The method depends on the reduction of nitrate to nitrite by hydrazine in alkaline solution, with copper as a catalyst. The nitrite produced diazotises sulphanilamide and the product is coupled with N-(1-naphthyl) ethylenediamine, to give a red dye, the absorbance of which is measured at 550 mμ. A relative standard deviation of 3–4% is obtained.     

Synthesis and evaluation of some pyridyl-substituted pyrimidines as copper-specific chromogenic reagents

Preparation and metal-ion chromogenic properties of five new 2,4,6-trisubstituted pyrimidines containing pyridyl and methyl or phenyl groups are described. All five exhibit specific chromogenic reactions with copper(I), and two possess suitable characteristics for use as sensitive spectrophotometric copper reagents. The results obtained are also of interest in designing related chromogenic reagents.     

Fluorimetric and absorptiometric determination of dissociation constants and chromogenic reactions of benzyl 2-pyridyl ketone 2-quinolylhydrazone

The dissociation constants in the ground state of benzyl 2-pyridyl ketone 2-quinolylhydrazone (BPKQH) have been determined fluorimetrically and spectrophotometrically in aqueous ethanol medium. The pK(a) values of this compound in the excited state have also been established. The analytical properties of the reagent and its chromogenic reactions with some metal ions were studied.     

Dithizone derivatives as sensitive water soluble chromogenic reagents for the ion chromatographic determination of inorganic and organo-mercury in aqueous matrices

Water-soluble sulfonate and the novel carboxylate analogues of dithizone, combined with ion interaction chromatography on a Dionex Acclaim 120 C18 silica column (250 x 4.6 mm id) with an eluent consisting of 10 mM tetrabutylammonium bromide and 60:40 methanol:water, have been developed as highly sensitive chromogenic ligands for the quantitative isocratic determination of inorganic and organo-mercury compounds in aqueous matrices in under 12 min. Using an optimised post column reagent system containing 0.65 mM dye, 0.5% Triton X-100 and 50 mM sodium hydroxide, good linearity (0-7.5 mg L(-1) R2 > 0.999), reproducibility using peak area measurements (RSD 0.69-1.38%, n = 8), and limits of detection (4-12 microg L(-1)) were achieved for methyl mercury, inorganic mercury and phenyl mercury.     

A flow-injection system using immobilized peroxidase and chromogenic reagents for possible determination of hydrogen peroxide

Summary A flow injection system with a reactor containing peroxidase immobilized on porous glass was used for the determination of hydrogen peroxide. A number of chromogenic reagents were studied in combination with different immobilization methods, in particular with regard to adsorption of the coloured product on the enzyme support. A f. i. a. manifold had a throughout of 210 samples h^–1 and a detection limit of 0.1 M H₂O₂ and could be used for at least 17000 determinations with the same enzyme reactor. Systems with higher sensitivity or higher sample throughput are also described.     

Spectrofluorimetric determination of aluminium in silicon and in electronic grade reagents

Summary A sensitive spectrofluorimetric method is based on the complexation of Al with the dye Mordant Black 17 or Calcon (CI 15705). The complex solution in n-propyl alcohol (1.5×10^–4 mol/l) is mixed (5:20) with 1 mol/l acetic acid — sodium acetate buffer (pH 4.8) and maintained at 40°C for 60 min. The fluorescence intensity is measured at Ex=565 nm, Em=610 nm: The calibration curve for Al was found to be linear in the range 0 to 60 ng×ml^–1 with a standard deviation of =1.5 and an Al detection limit of 3 ng×ml^–1. The interferences due to more than 40 ions were investigated; the presence of Fe³⁺, Cr³⁺, Co²⁺, Cu²⁺, Ti⁴⁺, VO²⁺, ZrO²⁺, WO ₄ ^2– , MoO ₄ ^2– , CrO ₄ ^2– and particularly F^–, must be avoided or masked during the determination of Al. The sample of silicon/silicon dioxide was treated with a mixture of conc. HF and HNO₃ (2:1), followed by digestion and distillation at 90°C to eliminate the matrix as fluorosilicic acid. A small residue of AlF₃ was decomposed with HClO₄. In SiO₂ anodized layers (25–250 g) the minimum detection of Al was estimated to be 10¹⁸ At×cm^–3, in monocrystalline silicon (25–250 mg) 10¹⁶ At×cm^–3. The method can also be employed to determine the presence of Al in the residues by distillation of a small quantity (5–10g) of many solvents or reagent solutions. Presented at: IX. Congresso Nazionale — Div Chim Anal (S.C.I.) Ferrara 1990     

An improved, automated xylenol orange method for the colorimetric determination of aluminium

An automated colorimetrie procedure is described for the determination of aluminium, based on its complex with Xylenol Orange. Ethanol is used to accelerate the reaction and EDTA to mask iron. The procedure has been applied successfully to natural waters, soil extracts and plant digests.     

A comparison of some pyridyl-substituted pyrazines as analytical reagents

A comparative study of six 2-pyridyl and 2-(6-methyl-pyridyl) derivatives of pyrazine as chromogenic reagents of the ferroin and cuproin types has established 2,3,5,6-tetrakis(2'-pyridyl)pyrazine as a highly sensitive reagent for iron(II); 2,3-bis(2'-pyridyl)-5,6-dihydropyrazine and 2,3-bis[2'-(6'-methyl pyridyl)]-5,6-dihydropyazine both show high sensitivity and characteristic high selectivity in their reactions with iron(II) and copper(I) respectively-the reaction with copper(I) being almost as sensitive as that given by bathocuproine. The ease with which the highly coloured metal chelates can be extracted into immiscible solvents to give stable solutions makes these reagents useful for the determination of traces of iron and copper.     

A field aluminium speciation method to study the aluminium hazard in water

The toxicity of aluminium is governed by its bioavailability. Therefore, the speciation of aluminium in drinking water becomes of prime importance to understand its fate and the population exposure, and to develop guidelines for the concentration levels. At Health Canada, a field speciation method has been developed to perform on-site speciation followed by measurement of Al in the laboratory. The following species are generated: 1) total recoverable; 2) total acid-leacheable; 3) total dissolved; 4) dissolved extracted; and 5) dissolved non extracted. The field extractions are performed by percolation through chelation columns, which are later processed in the laboratory. Aluminium determinations can then be performed by numerous methods, such as by Inductively Coupled Plasma Mass Spectrometry (ICPMS), Graphite Furnace Atomic Absorption Spectrometry (GFAAS) or Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). Examples of results for raw or treated/ distributed surface waters, as well as for groundwaters, are used to illustrate the validity of the method, and the importance of considering aluminium speciation in characterizing the aluminium hazard in water.     

An improved rapid method for the determination of actinides in water

A new rapid method has been developed for the determination of Th, Pu, Np, U, Am and Cm isotopes in water samples of about 1 L. Actinides are pre-concentrated by co-precipitation with Ca phosphate, sequentially separated on stacked TEVA and TK221 cartridges and measured by alpha spectrometry. The TK221 extraction chromatographic resin contains i.e. CMPO and DGA extractants. It has been characterized by measuring the weight distribution ratios (D_w) of actinides which are higher than 1000 for all actinides in 3 M HNO₃. The method has been optimized, applied for the analysis of tap and seawater samples and validated by participating in an IAEA proficiency test. Chemical recoveries for all actinides are better than 50%. The method can be performed within one day.

     

A study of some pyridylazo dyestuffs as chromogenic reagents and the elucidation of the nature of their metal complex spectra

A series of dyestuffs having the same basic structure as 2-(2-pyridylazo)-5-diethyl-aminophenol (PADAP) but varying in their substituents on the 5-positions of both rings has been prepared. Dissociation constants for three such dialkylaminophenol derivatives have been determined, the pK(OH) values being of the same order as that reported for 4-(2-pyridylazo)resorcinol (PAR), while the pK(NH) values are lower. Two different 5-bromo-PADAP complexes are formed with the uranyl ion, one between pH 2 and 5 which is a neutral complex and probably a dimer, and the other an unstable neutral complex which forms between pH 5.5 and 8 and is a 1:1:1 ternary hydroxo-complex. A stable 1:1:1 ternary fluoro-complex is also formed between pH and 6 and 8. Double maxima occur in the spectra of all the metal complexes of these dyes. Evidence given shows the double peaks to originate from the one moiety and to be directly related to the presence of a substituent on the benzene ring para to the azo linkage. A tautomeric equilibrium with two imine tautomers in addition to the azo form of the complex is postulated and it is suggested that they correspond to the three composite bands given by computer analysis of the spectrum.     

Improved method for the simultaneous absorptiometric determination of cobalt and nickel with quinoxaline-2,3-dithiol

A new, more stable reagent, S-2-(3-mercaptoquinoxalinyl)thiuronium chloride (MQT), is proposed for the simultaneous absorptiometric determination of cobalt and nickel. It is hydrolysed rapidly to quinoxaline-2,3-dithiol (QDT) in ammonia buffer at pH 10. In the presence of zinc(II), QDT is stabilized by complex formation and the reagent blanks are reduced. Samples containing cobalt(II) and nickel(II) react with the mixture on warming to give 1:3 cobalt and 1:2 nickel complexes, with maximum absorbances at 472 and 520 mmu respectively. The sensitivity of the method is high, 0.0017 and 0.0028 mug cm (2) for cobalt and nickel respectively, and there is a significant improvement in accuracy and precision, which is about +/-1 % over a 15-fold change in cobalt to nickel ratio. The selectivity is moderate; Ag(I), Cu(II), Pd(II), Cd(II), Hg(II), Sn(II), Pb(II), Bi(III) and Pt(IV) cause significant interference but most other common cations and anions can be tolerated.     

The quality of our drinking water: aluminium determination with an acoustic wave sensor

A new methodology based on an inexpensive aluminium acoustic wave sensor is presented. Although the aluminium sensor has already been reported, and the composition of the selective membrane is known, the low detection limits required for the analysis of drinking water, demanded the inclusion of a preconcentration stage, as well as an optimization of the sensor. The necessary coating amount was established, as well as the best preconcentration protocol, in terms of oxidation of organic matter and aluminium elution from the Chelex-100. The methodology developed with the acoustic wave sensor allowed aluminium quantitation above 0.07 mg L(-1). Several water samples from Portugal were analysed using the acoustic wave sensor, as well as by UV-vis spectrophotometry. Results obtained with both methodologies were not statistically different (alpha=0.05), both in terms of accuracy and precision. This new methodology proved to be adequate for aluminium quantitation in drinking water and showed to be faster and less reagent consuming than the UV spectrophotometric methodology.     

A new water-soluble chromogenic indicator: an application to the determination of chlorine in aqueous solutions.

A novel compound, N,N'-bis(2,4-di-sulfobenzyl)tolidine tetrasodium salt (SBT), was synthesized for use as a chromogenic indicator for oxidizing substances, and its applicability to the colorimetric determination of chlorine in water was examined.