Characterization and analytical application of the ion-association complex crystal violet-cadmium bromopyrogallol red

In the presence of polyvinylalcohol (PVA-124) and polyethylene glycol monooctylphenyl ether (emulsifier OP), cadmium ions(II) can form a colour ion-association complex with both Bromopyrogallol Red (BPR) and Crystal Violet (CV). In the NH(3)NH(4)Cl medium, the ion-association complex has a composition of Cd:BPR:CV = 1:1:2, and its corresponding molecular formula is [CV](2)[Cd(BPR)]. The maximum absorption of the colour complex is located at 654 nm with an apparent molar absorptivity of 1.79 x 10(5) l.mole(-1).cm(-1). Beer's law is obeyed for cadmium over the range 0-10 mug/25 ml. A highly sensitive spectrophotometric method for trace cadmium in water and zinc was developed with good precision and accuracy. The mechanism of the reaction is also discussed.     

Spectrophotometric determination of micro amounts of cadmium in waste water with cadion and triton X-100

A spectrophotometric method for determination of micro amounts of cadmium in waste water with Cadion and Triton X-100 is described. The interference of foreign ions can be eliminated by masking with an ascorbic acid-Rochelle salt-potassium cyanide-potassium fluoride mixture. After demasking with formalin, cadmium is determined directly in aqueous solution without separation. Beer's law is obeyed for 0-8 mug of Cd in 25 ml of solution. The method is more sensitive than the dithizone method, its apparent molar absorptivity at 480 nm being 1.19 x 10(5) 1. mole(-1). cm(-1). Results obtained by using the proposed method on waste water samples agree well with those obtained by atomic-absorption spectrophotometry.     

Extraction and photometric determination of lead with diazacrown ether dye

N,N'-Bis(2-hydroxy-5-nitrobenzyl)cryptand-22 (22-Koshland) forms yellow complexes with bivalent metal ions, and these are extractable into 1,2-dichloroethane. The overall extraction constants have been estimated for lead (10(-5.4)), copper (10(-5.6)), mercury (10(-5.8)) and cadmium (10(-8.4)). The result obtained has been applied to extraction and photometric determination of lead. The molar absorptivity at the absorption maximum (406 nm) is 4.47 x 10(4) l.mole(-1).cm(-1). The interferences from copper and mercury can be eliminated by the addition of sodium thiosulphate and the interference from cadmium can be eliminated by calculation from the absorbances at 406 and 391 nm (the cadmium complex with 22-Koshland has its absorption maximum at 391 nm). The method has been successfully applied to the determination of lead in zinc powder.     

Manual and fia methods for the determination of cadmium with malachite green and iodide

A sensitive and rapid spectrophotometric method for the determination of cadmium is described, based on the formation of a blue complex at pH 4 between the anionic iodide complex of cadmium(II) and Malachite Green; the colour is stabilized with poly(vinyl alcohol). The calibration graph for measurement at 685 nm is linear over the range 1-50 mug of cadmium per 25 ml of final solution, with a relative standard deviation of +/-1.7% for 1 mug/ml cadmium. The molar absorptivity is 6.1 x 10(4) 1.mole(-1).cm(-1). The method can be successfully adapted for FIA, the peak height being proportional to the cadmium concentration over the range 0.1-3 mug/ml; a two-channel manifold is used and an improvement in selectivity is obtained. The use of a gradient tube is demonstrated to give a good calibration for Cd(II) over the range 2 x 10(-2) -2 x 10(-6)M.     

Spectrophotometric and spectrofluorometric determination of zinc and cadmium with 2,2'-pyridil bis(2-quinolylhydrazone)

The chelating ligand, 2,2'-pyridil bis(2-quinolylhydrazone), has been used for the spectrophotometric determination of zinc and cadmium in synthetic samples. The molar absorptivities of these metal complexes in 80% ethanol-water solution at pH 8 were found to be 4.60 x 10(4) and 5.10 x 10(4) 1.mole(-1).cm(-1) for zinc and cadmium respectively. Beer's law was obeyed for metal-ion concentrations between 1.0 x 10(-6) and 2.5 x 10(-5)M. The limits of detection were found to be 52 and 79 ng ml for zinc and cadmium respectively. The complexes fluoresced in 80% ethanol-water at pH 8 for zinc and at pH 10 for cadmium. The linear range for fluorescence as a function of metal-ion concentration was found to be 5 x 10(-7)-5 x 10(-6)M for both zinc and cadmium. Transition-metal ions interfere severely with both the spectrophotometric and fluorimetric determinations, and must be removed beforehand. An ion-exchange procedure is suitable for this.     

Dual-wavelength spectrophotometric determination of trace sulphide in domestic water through its ligand-exchange reaction with silver-Cadion 2B-triton X-100

Trace amounts of S(2-) can be determined by means of the exchange reaction with the Ag(+)-Cadion 2B complex in presence of Triton X-100 and Na(2)B(4)O(7) solution, by dual-wavelength spectrophotometry. Beer's law is obeyed for the sulphide range 0-2.0 microg/25 ml . The apparent molar absorptivity is 2.65 x 10(5) l.mole(-1).cm(-1). The effect of diverse ions in the presence of EDTA has been studied. The interferences produced by some anions in water samples can be eliminated by precipitation with zinc acetate.     

A highly sensitive spectrophotometric determination of cadmium with alpha,beta,gamma,delta-Tetrakis(4-N-trimethylaminophenyl)-porphine

A new and highly sensitive reagent is proposed for spectrophotometric determination of cadmium. alpha,beta,gamma,delta-Tetrakis (4-N-trimethylaminophenyl) porphine forms a chelate with cadmium in alkaline solution with a molar absorptivity of 5.77 x 10(5)l. mole(-1).cm(t1), the largest value reported to date for a cadmium complex. An extraction method is described for selective separation of cadmium.     

Spectrophotometric determination of zinc with hydrazidazol in the presence of Triton X-100 and its application in metal analysis

A new spectrophotometric method for the determination of zinc is proposed. The chromogenic agent Hydrazidazol forms a 1:1 chelate with zinc in the presence of Triton X-100 in a medium containing 20-40% ethanol. The molar absorptivity and conditional formation constant have been found to be 2.7 x 1O(4) l.mole(-1).cm(-1) (at 640 nm) and 10(5.32) respectively. Beer's law is obeyed for zinc over the range of 0.2-0.8 mug/ml with a standard deviation of 0.024 mug/ml. The method can be applied to the determination of zinc in cadmium metal and its oxide after preconcentration by selective extraction of zinc thiocyanate into ethyl acetate in the presence of EDTA and thiosulphate as masking agents.     

Spectrophotometric studies on the simultaneous determination of cadmium and mercury with 4-(2-pyridylazo)-resorcinol

A new method for direct spectrophotometric determination of cadmium with 4-(2-pyridylazo)-resorcinol is reported. Absorption maximum, molar absorptivity and Sandell's sensitivity of the 1:1 (M:L) complex are 510 nm, 2.5 x 10(5) l mol(-1) cm(-1) and 3.55 ng cm(-2), respectively. A linear calibration graph is obtained up to 4.49 microg ml(-1). The zero-crossing measurement technique is found suitable for the direct measurement of the first-derivative value at the specified wavelengths. Cadmium(II) (0.42-9.2 microg ml(-1)) and mercury(II) (0.35-7.4 microg ml(-1)) in different ratios have been determined simultaneously. A critical evaluation of the proposed method is performed by statistical analysis of the experimental data. The developed method was applied to the simultaneous spectrophotometric determination of Cd and Hg in some synthetic mixtures and was found to give satisfactory results.     

A sensitive spectrophotometric method for the determination of hydroxylamine by use of p-nitroaniline and N-(1-naphthyl)-ethylenediamine

A sensitive method for the spectrophotometric determination of hydroxylamine is described, based on known diazotization and coupling reactions. Hydroxylamine is oxidized by iodine in acetic acid medium to nitrite which then diazotizes p-nitroaniline to form a diazonium salt which is later coupled with N-(1-naphthyl)ethylenediamine to give a purple dye which has an absorption maximum at 545 nm, with a molar absorptivity of 6.6 x 10(4) l.mole(-1).cm(-1). Beer's law is obeyed over the hydroxylamine concentration range 0-8(microg/25 ml) (0.0-0.32 ppm) in the final solution.     

Some azo-dye reagents for the spectrophotometric determination of cadmium

2-[2-(5-Bromopyridyl)azol-4,5-dimethylphenol (BrPDMP) and 2-[2-benzothiazolylazo)-5-dimethylaminophenol (BTADAP) have been synthesised and compared, as reagents for cadmium, with the related dyes BrPADAP and BTDMP. The new dyes both form stable highly coloured 2:1 complexes with cadmium, with molar absorptivities (in o-xylene solution) of 3.8 x 10(4) 1.mole(-1).cm(-1) at 590 nm (BrPDMP) and 4.5 x 10(4) 1.mole(-1).cm(-1) at 600 nm (BTADAP). Cadmium can be determined by extraction under alkaline conditions with a solution of BTADAP in xylene. Beer's law is obeyed up to at least 16 mug of cadmium. A limit of detection of 0.15 mug has been estimated and a coefficient of variation of 3.3% at the 5 mug level was found. The only species which interfere seriously are Co(2+), Ni(2+), and Ca(2+). A 200-fold excess of zinc may be tolerated. The method has been applied to the determination of cadmium in water samples, plant materials and hair. Interferences were overcome by preliminary extraction into Aliquat/carbon tetrachloride. The acid dissociation constant of BTADAP (pK = 9.5) and formation constant of the cadmium-BTADAP complex (log beta = 15.1) have been determined.     

Zincsulphate induced metallothionein in pancreatic islets and protected against the diabetogenic toxin streptozotocin

A new azoamino reagent amido black diazoaminoazobenzene (ABDAB) has been synthesized, and found to be a good chromogenic reagent for cadmium. In pH 10.4 Na(2)B(4)O(7)NaOH buffer solution cadmium reacts with ABDAB to form an orange-red chelate (1:2), exhibiting an absorption maximum at 520 nm. The apparent molar absorptivity is 1.62x10(5) l mol(-1) cm(-1). Beer's law is obeyed in the range 0-8 mug/25 ml Cd. The method is simple and rapid, with high sensitivity and good selectivity and is applied to the determination of trace amounts of cadmium in waste water and metal materials with satisfactory results.     

Extraction and photometric determination of microamounts of Zn2+, Cd2+ and Hg2+ with 1-(2-quinolylazo)-2-acenaphthylenol

1-(2-Quinolylazo)-2-acenaphthylenol (QAAc) combines with Zn(II), Cd(II) and Hg(II), giving deep red 1:2 complexes which are extractable in CCl(4)and other organic solvents. Spectrophotometric methods based on the reactions are sensitive and fairly selective, the Sandell's sensitivities being 8.8 x 10(-4), 2.4 x 10(-3) and 3.3 x 10(-3) microg/cm(2) for Zn(II), Cd(II) and Hg(II) respectively.     

Spectrophotometric determination of zinc with 2-(3,5-dibromo-2-pyridylazo)-5-diethylaminophenol in the presence of anionic surfactant

A sensitive spectrophotometric method for zinc has been established by reacting zinc with 2-(3,5-dibromo-2-pyridylazo)-5-diethylaminophenol (3,5-diBr-PADAP) in the presence of an anionic surfactant, sodium lauryl sulphate. The molar absorptivity is 1.3 x 10(5) l.mole(-1).cm(-1) at 570 nm. The molar ratio of zinc to 3,5-diBr-PADAP is 1:2. Beer's law is obeyed up to 0.7 ppm of zinc. With preseparation of zinc by extraction of its thiocyanate complex, the method has been applied to the determination of zinc in waste water.     

Preconcentration and determination of trace elements with 2,6-diacetylpyridine functionalized Amberlite XAD-4 by flow injection and atomic spectroscopy

An on-line flow injection method for the direct determination of trace elements in environmental samples is described. A mini-column packed with 2,6-diacetylpyridine functionalized Amberlite XAD-4 was used to preconcentrate and separate 8 trace metals (Cd, Co, Cu, Mn, Ni, Pb, U and Zn) from water and extracts from solid samples. The metals were eluted with 0.1 M HNO(3) directly to the detection system (either inductively coupled plasma-mass spectrometry (ICP-MS) or flame atomic absorption spectrometry (FAAS)). As well as demonstrating that the resin could be used to preconcentrate ultra-trace analytes from natural waters, it was also shown to work well at a pH of 5.5. Therefore, after treatment of sample digests with sodium fluoride, samples that contain extremely large concentrations of iron may be analysed for trace analytes without the excess iron overloading the capacity of the resin. To this end, the analytes Cd, Co, Cu and Ni were preconcentrated from acid extracts of certified soil/sediment samples and then eluted with nitric acid to be determined on-line. Limits of detection (3sigma) of Cd = 0.33 microg l(-1), Co = 0.094 microg l(-1), Cu = 0.34 microg l(-1), Mn = 0.32 microg l(-1), Ni = 0.30 microg l(-1), Pb = 0.43 microg l(-1), U = 0.067 microg l(-1) and Zn = 0.20 microg l(-1) for the FI-ICP-MS system and Cd = 22 microg l(-1), Co = 60 microg l(-1), Cu = 10 microg l(-1) and Ni = 4.8 microg l(-1) for the FI-FAAS system were obtained. Analysis of certified reference materials showed good agreement with the certified values using the two methods.     

A rapid spectrophotometric method for determination of zinc in milk

1-(2',3'-Dihydroxypyridyl-4'-azo)benzene-4-sulphonic acid and the corresponding 5'-chloro-substituted acid are proposed as sensitive reagents for zinc. Cyanide masking and selective demasking of zinc can be used to deal with the interference of many metal ions, cadmium can be masked with semithiocarbazide, and thiosulphate can be used for masking Hg(II), Pd(II) and Os(VIII). The molar absorptivities are about 1.3 x 10(5) 1.mole(-1).cm(-1). The method has been used for determinating zinc in milk.     

Extractive-spectrophotometric determination of molybdenum as mixed-ligand complexes with thiocyanate and amidopyridines

A fairly selective and sensitive method is described for the determination of microgram amounts of molybdenum(V) by means of its reaction with thiocyanate and the enolic form of various amidopyridines and extraction into benzene. The molar absorptivity of the complexes is in the range 1.5-1.9 x 10(4) l.mole(-1).cm(-1) at lambda(max) 470 nm. The method is applicable in 1.5-7M hydrochloric acid or 1.2-6(M) sulphuric acid media. Cu(+), Co(2+), Mn(2+), Zn(2+), Ni(2+), Cd(2+), Fe(3+), Al(3+), Cr(3+), Ti(4+), Zr(4+), V(V), Nb(5+), Ta(5+), W(VI) and U(VI) do not interfere.     

Determination of 0.1 to 1000 μ g/ml cadmium in a hydrometallurgical zinc refining process stream by a flow injection technique with computer controlled injection method

A computer-controlled flow injection system was developed for the determination of cadmium in a hydrometallurgical zinc refining process stream. An anion-exchange method in acidic potassium iodide medium was used for the on-line separation of cadmium from the matrix zinc. 1-(4-Nitrophenyl)-3-(4-phenylazophenyl)triazene (Cadion) was used as the chromogenic reagent for the spectrophotometric detection of cadmium. In order to expand the dynamic range of the flow injection - spectrophotometry, a computer-aided time-based variable-volume injection method has been employed for the introduction of the sample into the flow injection system. Samples ranging from 0.56 to 350 microl can be delivered by controlling the time period of the sample introduction valve and the flow rate of the carrier solution. The system permits a throughput of 5 samples per hour. The reproducibility has been proven to be satisfactory with a relative standard deviation of less than 6.2% (sample injected: 0.56 microl of 850 microg Cd/ml; n=100) and 5.0% (350 microl of 0.14 microg Cd/ml; n=5). The determination limit was 20 microg Cd/ml with 0.56 microl sample injection and 0.05 microg Cd/ml with 350 microl sample injection (the absolute amount of cadmium injected into the system was 11 ng and 17.5 ng, respectively).     

Evaluation of new high-frequency discharge lamps for atomic absorption and atomic fluorescence spectrometry of cadmium,lead and zinc

High-frequency discharge lamps with a hollow electrode are successfully utilized as the spectral line sources for atomic absorption and atomic fluorescence spectrometry of cadmium, lead and zinc. The sensitivities for atomic absorption spectrometry are superior to those obtained with commercially available hollow-cathode lamps by factors of 1.5 (Cd), 1.4 (Pb) and l.6 (Zn). Detection limits for non-dispersive atomic fluorescence spectrometry with graphite furnace atomization are 1 × 10^-13 g (Cd), 3 × 10^-11 g (Pb) and 2 × 10^-13 g (Zn). The linear analytical range covers over four (Cd, Zn) and three (Pb) decades of concentration above the detection limits.     

Spectrophotometric determination of saccharin in different materials by a solvent extraction method using Nile Blue as reagent

In a slightly acidic medium (sodium acetate-acetic acid buffer, pH 4) saccharin and Nile Blue form an ion-association compound which is extractable into methyl isobutyl ketone and allows the spectrophotometric determination of saccharin. At 630 nm Beer's law is obeyed over the saccharin concentration range 0.1-3.5 microg/ml in the aqueous phase and the apparent molar absorptivity is 5.8 x 10(4) l.mole(-1).cm(-1). The method shows good selectivity and can be applied to the determination of saccharin in artificial sweeteners, soft drinks and toothpastes.