Spectrophotometric and atomic absorption determination of Ni(II) in fresh and sea waters after preconcentration by flotation

A highly selective and sensitive procedure for flotation separation followed by spectrophotometric determination, confirmed by AAS, of Ni(II) traces is proposed. The maximum flotation separation (100%) is achieved at approximately 25 degrees C in the pH range of 1-3 using sodium diethyldithiocarbamate (as a collector) and oleic acid surfactant. The floated (1 : 2) colored complex is measured spectrophotometrically at 430 nm over a concentration range of 0.5-4.0 microg/g with a molar absorptivity of 0.44 x 10(4) L mol(-1) cm(-1). The procedure was successfully applied for the separation and determination of Ni(II) in fresh and sea waters.     

Selective flotation-spectrophotometric determination of trace copper(II) in natural waters, human blood and drug samples using phenanthraquinone monophenylthiosemicarbazone.

Copper(II) forms 1:1 and 1:2 intense red complexes with phenanthraquinone monophenylthiosemicarbazone (PPT) at pH 3-3.5 and > or =6.5, respectively. These complexes exhibit maximal absorbance at 545 and 517 nm, the molar absorptivity being 2.3 x 10(4) and 4.8 x 10(4) l mol(-1) cm(-1), respectively. However, the 1:1 complex was quantitatively floated with oleic acid (HOL) surfactant in the pH range 4.5-5.5, providing a highly selective and sensitive procedure for the spectrophotometric determination of CuII. The molar absorptivity of the floated Cu-PPT complex was 1.5 x 10(5) l mol)(-1) cm(-1). Beer's law was obeyed over the range 3-400 ppb at 545 nm. The analytical parameters affecting the flotation process and hence the determination of copper traces were reported. Also, the structure of the isolated solid complex and the mechanism of flotation were suggested. Moreover, the procedure was successfully applied to the analysis of CuII in natural waters, serum blood and some drug samples.     

Separation via flotation, spectrophotometric speciation, and determination of vanadium(IV) in wastes of power stations.

1-(2-Hydroxy-4-methoxybenzophenone)-4-phenylthiosemicarbazone (HMBPT) was investigated as a new reagent for the flotation of vanadium(IV). At pH approximately 1.5, vanadium(IV) forms a 1:1 pale-violet complex with HMBPT in aqueous solution. An intense clear violet layer was formed after flotation, by adding an oleic acid (HOL) surfactant. The composition of the float was 1:1 [V(IV)]:[HMBPT]. A highly selective and sensitive spectrophotometric procedure was proposed for the determination of microamounts of V(IV) as its floated complex. The molar absorptivities of the V(IV)-HMBPT and V(IV)-HMBPT-HOL systems were 0.4 x 10(4) and 0.12 x 10(5) L mol(-1) cm(-1) at 560 nm, respectively. The formation constants of the species formed in the presence and absence of HOL were 4.6 x 10(7) and 8.7 x 10(5) L mol(-1), respectively. Beer's law was obeyed up to 1 x 10(-4) mol L(-1) in the aqueous layer as well as in the oleic acid layer. The HMBPT-V(IV) complexes formed in the aqueous solution and scum layer were characterized by elemental analysis, infrared and UV spectrophotometric studies. The mode of chelation between V(IV) and HMBPT is proposed to be due to a reaction between the protonated bidentate HMBPT ligand and V(IV) through the S=C and N=C groups. Interferences from various foreign ions were avoided by adding excess HMBPT and/or Na2S2O3 as a masking agent. The proposed flotation method was successfully applied to the analysis of V(IV) in synthetic mixtures, wastes of power stations, simulated samples and in real ores. The separation mechanism is discussed.     

Highly sensitive extractive spectrophotometric determination of palladium(II) in synthetic mixtures and hydrogenation catalysts using benzildithiosemicarbazone.

A simple and highly sensitive method was developed for the extractive-spectrophotometric determination of palladium with benzilidithiosemicarbazone. The metal ion formed a reddish brown complex with benzildithiosemicarbazone in a potassium chloride-hydrochloric acid buffer of pH 2.5, which was easily extractable into methyl isobutyl ketone. The 1:1 complex showed the maximum absorbance at 395 nm with a Beer's law range of 0.25-3.5 ppm. The molar absorptivity and Sandell's sensitivity were found to be 3.018 x 10(4) dm3 mol(-1) cm(-1) and 0.0035 microg cm(-2), respectively. The correlation coefficient of the Pd(II)-BDTSC complex was 0.998, which indicated an excellent linearity between the two variables. The repeatability of the method was checked by finding the relative standard deviation (RSD) (n = 10), which was 0.46%. The instability constant of the complex calculated from Edmond and Birnbaum's method was 2.41 x 10(-5), that of Asmus' method is 2.53 x 10(-5) at room temperature. The interfering effects of various cations and anions were studied. The proposed method was successfully applied to the determination of palladium(II) in synthetic mixtures and hydrogenation catalysts. The validity of the method was tested by comparing the results with those obtained using an atomic absorption spectrophotometer.     

Flotation-spectrophotometric determination of mercury in water samples using iodide and ferroin.

This paper describes a simple and highly selective method for separation, preconcentration and spectrophotometric determination of trace amounts of mercury. The method is based on the flotation of an ion-associate of HgI4(2-) and ferroin between aqueous and n-heptane interface at pH 5. The ion-associate was then separated and dissolved in acetonitrile to measure its absorbance. Quantitative flotation of the ion-associate was achieved when the volume of the water sample containing Hg(II) was varied over 50 - 800 ml. Beer's law was obeyed over the concentration range of 3.2 x 10(-8) - 9.5 x 10(-7) mol l(-1) with an apparent molar absorptivity of 1 x 10(6) l mol(-1) cm(-1) for a 500 ml aliquot of the water sample. The detection limit (n = 25) was 6.2 x 10(-9) mol l(-1), and the RSD (n = 5) for 3.19 x 10(-7) mol l(-1) of Hg(II) was 1.9%. A notable advantage of the method is that the determination of Hg(II) is free from the interference of the almost all cations and anions found in the environmental and waste water samples. The determination of Hg(II) in tap, synthetic waste, and seawater samples was carried out by the present method and a well-established method of extraction with dithizone. The results were satisfactorily comparable so that the applicability of the proposed method was confirmed in encountering with real samples.     

Determination of platinum(IV) by UV spectrophotometry

A simple, rapid and sensitive spectrophotometric procedure for the determination of platinum has been elaborated. Pt traces were determined in the form of the PtCl(6)(2-) complex in hydrochloric acid solution whose concentration varies from 0.01 to 2 mol L(-1) by measuring the absorbance at 260 nm. The detection limit is 4.7 x 10(-7) mol L(-1), the linearity range from 2 x 10(-6) mol L(-1) to 7 x 10(-6) mol L(-1), and the correlation coefficient is r=0.9990. No significant interferences were observed from a majority of the investigated ions, such as Zn(II), Pb(II), Mn(II), Cd(II), Co(II) and Ni(II) with the exception of Cu(II), Sb(III), Fe(III), Pd(II), Sn(II) and I(-) ions. The method was successfully applied for the determination of Pt traces in different solid samples and the recovery from inorganic materials was studied.     

Selective determination of cobalt using polyurethane foam and 2-(2-benzothiazolylazo)-2-p-cresol as a spectrophotometric reagent

The present work describes a selective, rapid and economical method for the determination of cobalt using the 2-(2-benzothiazolylazo)-p-cresol (BTAC) as a spectrophotometric reagent associated with a solid extraction on polyurethane foam. The BTAC reacts with Co(II) in the presence of Triton-X100 surfactant forming a green complex with maximum absorption at 615 nm. The reaction is used for cobalt determination within a pH range of 6.50-7.50, with an apparent molar absorptivity of 1.62 x 10(4) L mol(-1) cm(-1). Beer's Law is obeyed for a concentration of at least 1.60 microg ml(-1). A selective procedure is proposed for cobalt determination in the presence of Fe(II), Hg(II), Zn(II) and Cu(II) up to milligram levels using masking agents. Polyurethane foam is used for the preconcentration and separation of cobalt from thiocyanate media and this procedure is applied to its determination in nickel salts and steel alloys.     

Extraction-spectrophotometric determination of iron(II) by ternary complex formation with pyrocatechol violet and cetyltrimethylammonium bromide

A method for iron(II) determination based on reaction with Pyrocatechol Violet to form a 1:2 binary complex at pH 5-7 is described and has been extended to an extraction-spectrophotometric procedure for the determination of iron(II) by formation of the 1:2:2 iron(II)-Pyrocatechol Violet-cetyltrimethylammonium bromide ternary complex. The molar absorptivities of the binary and ternary complexes at 595 and 605 nm are 6.55 x 10(4) and 1.35 x 10(5)1.mole(-1).cm(-1), respectively. The method has been successfully applied to the determination of iron in felspar, Portland cement and sodium hydroxide.     

Selective determination of cadmium(II) from divalent metal ions in environmental samples by capillary electrophoresis using in-capillary complexation with a lacunary Keggin-type [PW11O39]7- complex.

A novel capillary electrophoretic (CE) method, based on in-capillary complexation with [PW(11)O(39)](7-), was developed for the determination of cadmium(II) in natural water samples. When a sample solution is injected into a capillary containing 0.20 mM [PW(11)O(39)](7-) and 0.10 M malonate buffer (pH 3.0), the ternary Keggin-type complex, [P(Cd(II)W(11))O(39)](5-), which possesses high molar absorbtivities in the UV region, is formed in the capillary, and its migration toward the anode gives a well-defined migration peak in the electropherogram. An advantage of this method is that many divalent metal ions do not interfere. The proposed method was successfully applied to the determination of Cd(II) in environmental samples. The detection limits were 1 x 10(-7) and 5 x 10(-7) M for river-water and seawater samples, respectively (signal-to-noise ratio = 3).     

A rapid and sensitive extractive spectrophotometric determination of copper(II) in pharmaceutical and environmental samples using benzildithiosemicarbazone.

Benzildithiosemicarbazone (BDTSC) is proposed as a sensitive and selective analytical reagent for the extractive spectrophotometric determination of copper(II). BDTSC reacts with copper(II) in the pH range 1.0-7.0 to form a yellowish complex. Beer's law is obeyed in the concentration range 0.5-0.4 microg cm(-3). The yellowish Cu(II)-BDTSC complex in chloroform shows a maximum absorbance at 380 nm, with molar absorptivity and Sandell's sensitivity values of 1.63 x 10(4) dm3 mol(-1) cm(-1) and 0.00389 microg cm(-2), respectively. A repetition of the method is checked by finding the relative standard deviation (RSD) (n = 10), which is 0.6%. The composition of the Cu(II)-BDTSC complex is established as 1:1 by slope analysis, molar ratio and Asmus' methods. An excellent linearity with a correlation coefficient value of 0.98 is obtained for the Cu(II)-BDTSC complex. The instability constant of the complex calculated from Edmond and Birnbaum's method is 7.70 x 10(-4) and that of Asmus' method is 7.66 x 10(-4), at room temperature. The method is successfully employed for the determination copper(II) in pharmaceutical and environmental samples. The reliability of the method is assured by analyzing the standard alloys (BCS 5g, 10g, 19e, 78, 32a, 207 and 179) and by inter-comparison of experimental values, using an atomic absorption spectrometer.     

Use of 1-(2-thiazolylazo) 2-naphthol in rapid determination of iron in geological matrices

The present work describes the use of 1-(2-thiazolylazo)-2-naphthol (TAN) as a spectrophotomeric reagent for iron determination. TAN reacts with iron(II) forming a brown complex with absorption maximum at 575 and 787 nm. The following parameters were studied: complex stability, pH effect, amount of the TAN, buffer selection, amount of acetate buffer, reductor effect, order of addition of reagents and adherence to Beer's Law. The results demonstrated that iron can be determined with TAN in a pH range of 4.0-6.2 with an apparent molar absorptivity of 1.83 x 10(4) 1 . mol(-1) . cm(-1) (at 787 nm) and 1.41 x 10(4) 1 . mol(-1) . cm(-1) (at 575 nm). Beer's Law is obeyed for at least 3.00 microg/ml. The TAN reacts with other cations, but at 787 nm only the iron(II)-TAN complex absorbs. So, iron can be determined selectively in the presence of several cations. A procedure based on the direct mixture of the sample and a chromogenic solution is proposed, where iron can be determined rapidly and easily. Such procedures were used for the determination of iron in several geological matrices. No significant differences were obtained for TAN method and certificate results.     

Determination of trace metals by capillary electrophoresis

A new analytical procedure is developed using a strong complexing agent, 1,10-phenanthroline (Phen), for direct UV detection of Zn, Mn, Cu, Co, Cd, and Fe at microg/L concentrations in environmental water samples. The metal chelates formed showed different electrophoretic mobilities and solved the comigration problem for capillary electrophoresis (CE) separation of free metal ions. To obtain stable metal-Phen chelates during the capillary zone electrophoresis (CZE) run, both pre-column and on-column complexation are required and threefold excess of Phen over metal ions should be added to the sample. The optimized background electrolyte (BGE) consists of 30 mM hydroxylamine hydrochloride and 0.1% methanol at pH 3.6. Under hydrodynamic sampling, CE run at + 20 kV in 65 cm x 0.05 mm ID fused-silica column with detection at 265 nm, baseline separation, satisfactory working ranges (10 microg/L to 5.5 mg/L), sensitive detection limits (1-3 microg/L), good repeatability for migration times (relative standard deviation, RSD 0.36-0.81%, n = 5), peak area (RSD 3.2-4.2%, n = 5) and peak height (RSD 3.2-4.5%, n = 5) were obtained for the metal cations investigated. The reliability of the method was established by parallel determination using the inductively coupled plasma-atomic emission spectrometry (ICP-AES) method giving results within statistical variation. The procedure developed is shown to provide a quick, sensitive, precise, and economic method for simultaneous determination of metal cations that can form stable chelates with Phen.     

Determination of thallium(I) by flotation-spectrophotometric method using iodide and rhodamine B.

A method for the trace amount determination of Tl(I), via its preconcentration, is proposed. The method is based on the reaction of iodide, Tl(I) and Rhodamine B in a weakly acidic medium. In this process an ion-associated complex is formed, which is floated at the interface of aqueous-cyclohexane layers. Various amounts of Tl(I) by a subsequent separation and dissolution of the floated complex in methanol could be determined, spectrophotometrically. Beer's law was obeyed for the Tl(I) content in the range of (0.8-8.0) x 10(-7) mol l(-1) with a correlation coefficient of 0.9974. The conditional molar absorptivity was found to be 1.0 x 10(6) l mol(-1) cm(-1) at 560 nm, which indicated the considerable sensitivity of the procedure. The detection limit (DL) was 4.7 x 10(-8) mol l(-1) and the RSD (n = 5) for 4 x 10(-7) mol l(-1) of Tl(I) was 3.34%. None of the alkaline cations was interfered, and the interference of many other metal ions was eliminated via ion-exchange separation using a cation-exchanger resin, Amberlite IR-120, before the flotation step. The reliability of the procedure was confirmed by determining the Tl(I) contents of synthetic laboratory waste water by both flotation spectrophotometry and graphite furnace atomic absorption spectrometry (GFAAS). The recovery was 92.3-95.4% for 1 x 10(-7) and 4 x 10(-7) mol l(-1), respectively. The precision and accuracy of the results were comparable via F and t tests at the 95% confidence level.     

4-(N,N-diethylamino) benzaldehyde thiosemicarbazone in the spectrophotometric determination of palladium

4-(N,N-diethylamino)benzaldehyde thiosemicarbazone(DEABT) is proposed as a sensitive and selective analytical reagent for the spectrophotometric determination of palladium(II). The reagent reacts with palladium (II) in a potassium hydrogen phthalate-hydrochloric acid buffer of pH 3.0, to form a yellow complex. Beer's law is obeyed in the concentration range up to 3.60 microgmL(-1). The optimum concentration range for minimum photometric error as determined by Ringbom plot method is 0.36 - 3.24 microg mL(-1). The yellow Pd(II)-DEABT complex shows a maximum absorbance at 408 nm, with molar absorptivity of 3.33 x 10(4) dm3 mol(-1) cm(-1) and Sandell's sensitivity of the complex from Beer's data, for D = 0.001, is 0.0032 microg cm(-2). The composition of the Pd(II)-DEABT complex is found to be 1:2 (M:L). The interference of various cations and anions in the method were studied. The proposed method was successfully used for the determination of Pd(II) in alloys, catalysts, complexes and model mixtures with a fair degree of accuracy.     

Determination of proteins using the p-acetylchlorophosphonazo-barium(II) complex as a spectroprobe.

A novel spectrophotometric method has been developed for the determination of proteins using the p-acetychlorophosphonazo (CPA-pA)-barium(II) complex as a spectroprobe. In the pH range of 2.0-2.8, the absorbance of the CPA-pA-barium(II) complex at 649 nm is greatly decreased by protein. The absorbance decrease is in proportion to the concentration of protein in the range of 0-20 mg/L. The apparent molar absorptivities are 1.56 x 10(6), 1.70 x 10(6) and 6.04 x 10(5) L mol(-1) cm(-1) for bovine serum albumin (BSA), human serum albumin (HAS) and ovalbumin (OVA), respectively. The method is reproducible and simple, and has been used to determine total protein in human sera. The results are in agreement with those obtained by the pyrocatechol violet (PV)-Mo(VI) method, with relative standard deviations of 2.5-3.5% (n=6).     

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.     

Sequential extraction and determination of copper and nickel with 2,4-dihydroxyacetophenone thiosemicarbazone

2,4-Dihydroxyacetophenone thiosemicarbazone (DAPT) forms a 1:1 complex with copper(II) which can be extracted into n-butanol or ethyl acetate from acetic acid-sodium acetate (pH 5.0) buffer, and a 1:1 nickel(II) complex which can be extracted into n-butanol from ammonium chloride-ammonia (pH 7.5) buffer. The difference between the pH(1 2 ) values for extraction of the two complexes is 3.4 and this has been exploited for their sequential extraction and determination. The molar absorptivities for the copper and nickel complexes are 1.5 x 10(4)l.mole(-1).cm(-1) at 390 nm and 8.2 x 10(3)l.mole(-1).cm(-1) at 385 nm respectively. The procedure has been applied to the analysis of cupronickel.     

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.     

Interaction of nickel with 4-(2'-benzothiazolylazo) salicylic acid (BTAS) and simultaneous first-derivative spectrophotometric determination of nickel(II) and iron(III)

The solution properties of nickel complex with 4-(2'-benzo-thiazolylazo) salicylic acid (BTAS) have been studied by zero-order absorption spectrophotometry in 40% (v/v) ethanol at 20 degrees C and an ionic strength of 0.1 mol dm(-3) (KNO(3)). The equilibria that exist in solution were established and the basic characteristics of complexes formed were determined. A new direct spectrophotometric method for the determination of trace amounts of the nickel is proposed based on the formation of the Ni (BTAS) complex at pH 7.0. The absorption maximum, molar absorbtivity, and Sandell's sensitivity of 1:1 (M:L) complex are 525 nm, 0.6 x 10(4) l mol(-1) cm(-1) and 2.824 x 10(-9) microg cm(-2), respectively. The use of first-derivative spectrophotometry eliminates the interference of iron and enables the simultaneous determination of nickel and iron using BTAS. Quantitative determination of Ni(II) and Fe(III) is possible in the range (0.59-7.08) and (2.1-8.4) microg ml(-1), respectively with a relative standard deviation of 0.5%. The proposed method has been successfully applied to the simultaneous spectrophotometric determination of nickel and iron in steel alloys and aluminum alloys.     

Flow injection spectrophotometric analysis of lead in human saliva for monitoring environmental pollution

A new highly sensitive, simple and low-cost methodology for the direct determination of Pb (II) with 2-(5-bromo-2-pyridylazo)-5-dimethylaminophenol in ethanolic medium has been developed. The absorption spectroscopy of the complex has been examined in detail, and the chemical variables affecting the sensitivity of procedure studied, optimized and applied to the determination of trace amounts of lead in human saliva. Under the optimal experimental conditions, a precision of 1.61x10(-4) mug cm(-2) was achieved, the molar absorptivity being (epsilon) 5.6x10(4) l mol(-1) cm(-1). An FI technique is proposed, and it is possible to determine trace levels of lead by injection into a steam buffered at pH 7.15, containing 70% ethanol: 30% Tris buffer 3.5x10(-3) mol l(-1) (pH=7.2), 1x10(-4) mol l(-1) 5-BrDMPAP. The FIA configuration allows the analysis of 45 samples per hour. The lower limit of detection (LOD) was 1x10(-7) mol l(-1). The calibration plot was linear at least within two orders of magnitude of lead concentration. The use of an HPLC pump for the FI analysis led to a substantial improvement in the analytical performance of the method, which clearly satisfies the typical requirements for control processes.