Determination of Cr(VI) in welding fumes by anion-exchange fast protein liquid chromatography with electrothermal atomic absorption spectrometric detection

The applicability of an anion-exchange fast protein liquid chromatographic-electrothermal atomic absorption spectrometric procedure (FPLC-ETAAS) was investigated for the determination of Cr(VI) in welding fumes after alkaline extraction of aerosols loaded on filters. Gas tungsten arc welding (GTAW) of stainless steel was applied. Samples of welding fumes were collected during regular welding on polycarbonate membrane filters of 8 microm and 0.4 microm pore size (inhalable and respirable aerosols). Alkaline extraction (2% NaOH-3% Na2CO3) of filters in a heated ultrasonic bath was applied to leach Cr from the airborne particulate matter. 0.5 cm3 of sample extract was then injected onto an anion-exchange FPLC column. Tris-HCl buffer (0.005 mol dm(-3), pH 8.0) and the same buffer with NaCl (0.5 mol dm(-3)) were employed in gradient elution (15 min, flow rate 1 cm3 min(-1)). The separated Cr species were determined "off line" by ETAAS in 0.5 cm3 fractions. Cr(VI) was reproducibly and quantitatively eluted from 12.0 to 13.0 min with a maximum peak at 12.5 min. Good repeatability of measurement (+/-3.0%) of alkaline extracts was obtained for Cr(VI). The LOD (3s) was found to be 0.035 microg m(-3) Cr(VI), when 2 m3 of aerosols were collected on the filter. Validation of the procedure was performed by spiking alkaline extracts and by the analysis of standard reference material CRM 545, Cr(VI) in welding dust loaded on a filter. The technique was successfully applied for the determination of Cr(VI) in welding fumes.     

Extraction and determination of hexavalent chromium in soil samples

A procedure for the extraction of Cr(VI) from solid soil-like samples was presented in which the complexing properties of diethylenetriaminepentaacetic acid (DTPA) were exploited to extract insoluble compounds of Cr(VI). A concentration of DTPA in an ammonium sulphate/ammonium hydroxide buffer equal to 0.02 mol l⁻¹ was chosen. The conditions of extraction of insoluble Cr(VI) from solid samples were optimised using soil certified reference material spiked with known concentration of insoluble Cr(VI) added as PbCrO₄. The extracts were analysed by adsorptive stripping voltammetry. Validation of the proposed procedure of extraction was carried out by analysis of certified reference material (CRM) 545 and comparison of the results obtained using the proposed and other methods of extraction in the course of analysis of natural soil samples.     

Speciation of chromium by in-capillary reaction and capillary electrophoresis with chemiluminescence detection

A sensitive method for the simultaneous determination of chromium(III) (Cr3+) and chromium(VI) (CrO4(2-)) using in-capillary reaction, capillary electrophoresis (CE) separation and chemiluminescence (CL) detection was developed. The chemiluminescence reaction was based on luminol oxidation by hydrogen peroxide in basic aqueous solution catalyzed by Cr3+ ion followed by capillary electrophoresis separation. Based on in-capillary reduction, chromium(VI) can be reduced by acidic sodium hydrogensulfite to form chromium(III) while the sample is running through the capillary. Before the electrophoresis procedure, the sample (Cr3+ and CrO4(2-)), buffer and acidic sodium hydrogensulfite solution segments were injected in that order into the capillary, followed by application of an appropriate running voltage between both ends. As both chromium species have opposite charges, Cr3+ ions migrate to the cathode, while CrO4(2-) ions, moving in the opposite direction toward the anode, react with acidic sodium hydrogensulfite which results in the formation of Cr3+ ions. Because of the migration time difference of both Cr3+ ions, Cr(III) and Cr(VI) could be separated. The running buffer was composed of 0.02 mol l(-1) acetate buffer (pH 4.7) with 1 x 10(-3) mol l(-1) EDTA. Parameters affecting CE-CL separation and detection, such as reductant (sodium hydrogensulfite) concentration, mixing mode of the analytes with CL reagent, CL reaction reagent pH and concentration, were optimized. The limits of detection (LODs) of Cr(III) and Cr(VI) were 6 x 10(-13) and 8 x 10(-12) mol l(-1) (S/N=3), respectively. The mass LODs for Cr(III) and Cr(VI) were 1.2 x 10(-20) mol (12 zmol) and 3.8 x 10(-19) mol (380 zmol), respectively.     

Multielemental determination of arsenic, selenium and chromium(VI) species in water by high-performance liquid chromatography-inductively coupled plasma mass spectrometry

A new method for the simultaneous chromatographic separation and determination of arsenite, arsenate, mono-methylarsonic acid, dimethylarsinic acid, selenite, selenate and hexavalent chromium in water is presented. Speciation was achieved by on-line coupling of anion-exchange LC and inductively coupled plasma mass spectrometry (ICP-MS). Optimisation of the chromatographic conditions led to baseline separation of the seven species in 14 min using gradient elution with NH4NO3 20 mM, pH 8.7-NH4NO3 60 mM, pH 8.7 as mobile phase. Detection limits are in the range 40-60 ng l(-1) for arsenic species, around 130 ng l(-1) for Cr(VI), and higher for Se(IV) and Se(VI) (1.2 and 1.4 microg l(-1) respectively). The method showed good accuracy and repeatability, and no interference of chloride on 75As, 77Se or 53Cr was observed. The developed method was applied to the analysis of several environmental surface water samples.     

Simultaneous determination of arsenic species and chromium(VI) by high-performance liquid chromatography-inductively coupled plasma-mass spectrometry

The simultaneous determination of As(III), As(V), monomethylarsenic acid (MMA), dimethylarsinic acid (DMA) and Cr(VI) in fresh water has been carried out by coupling an anion-exchange column to an inductively coupled plasma-mass spectrometer. Optimisation of chromatographic conditions led to baseline separation of signals from the five species in approximately 9 min using gradient elution. Detection limits were 0.02-0.05 microg As l(-1) and 5.5 microg Cr l(-1). Repeatability was 2-3% for arsenic species and higher, i.e., 8%, for Cr(VI) due to the higher background for this species. Arsenic species and hexavalent chromium stability in surface water samples was evaluated, and storage conditions were set to 1 day at 4 degrees C in polyethylene flasks (without acidification) in order to avoid As(III)-As(V) conversions. The method was applied to the analysis of surface water.     

Potential for the speciation of Zn using fast protein liquid chromatography (FPLC) and convective interaction media (CIM) fast monolithic chromatography with FAAS and electrospray (ES)-MS-MS detection

Analytical procedures were developed for the speciation of Zn using fast protein liquid chromatography (FPLC), flame atomic absorption spectrometry (FAAS) and convective interaction media (CIM) fast monolithic chromatography with FAAS and electrospray (ES)-MS-MS detection. The investigation was performed on synthetic solutions (2 microg cm-3 Zn) of hydrated Zn2+ species and Zn complexes with citrate, oxalate and EDTA (ligand-to-Zn molar ratio 100:1) over a pH range from 5.4 to 7.4. It was found that Zn interacts with various buffers and the careful adjustment of the pH with diluted solutions of KOH is, therefore, required. FPLC separations were carried out on a Mono Q HR 5/5 strong anion-exchange column, applying an aqueous 1 mol dm(-3) NH4NO3 linear gradient elution over 15 min, at a flow rate of 1.0 cm3 min(-1). The separated Zn species were determined in 1.0 cm3 eluate fractions "off line" by FAAS. Speciation of Zn was also performed on a weak anion-exchange CIM DEAE fast monolithic disc by applying an aqueous 0.4 mol dm(-3) NH4NO3 linear gradient elution over 7.5 min, at a flow rate of 2.0 cm3 min(-1) and determination of the separated Zn species in 1.0 cm3 eluate fractions "off line" by FAAS. Zn-binding ligands in separated fractions were also characterized by electrospray (ES)-MS-MS analysis. The CIM DEAE disc was found to be more efficient in the separation of negatively charged Zn complexes than the Mono Q FPLC column. On the CIM DEAE disc Zn-citrate was separated from both Zn-oxalate and from Zn-EDTA. All these species were also separated from hydrated Zn2+, which was eluted with the solvent front. This method has an advantage over commonly used analytical techniques for the speciation of Zn which are only able to distinguish between labile and strong Zn complexes. Good repeatability of the measurements (RSD 2-4%), tested for six parallel determinations (2 microg cm(-3) Zn) of Zn-EDTA, Zn-citrate and Zn-oxalate was found at a pH of 6.4 on a CIM DAEA disc. The limit of detection (3s) for the separated Zn species was 10 ng cm(-3). The proposed analytical procedure was applied to the speciation of Zn in aqueous soil extracts and industrial waste water from a lead and zinc mining area.     

Retention of Cr(III) by high-performance chelation ion chromatography interfaced to inductively-coupled plasma mass spectrometric detection with collision cell

High-performance chelation ion chromatography (HPCIC) was employed to retain cationic Cr(III) on an anion-exchange column and hence allow the separation of the two most prevalent forms of chromium, Cr(II) and Cr(VI). A mobile phase of nitric acid was utilized at pH = 1.5; additionally, 2,6-pyridinedicarboxylic acid was used at a concentration of 6 mM. Additives with different structural characteristics were used in an effort to elucidate retention mechanisms. Inductively-coupled plasma mass spectrometry was used for chromium detection. A collision cell was utilized to reduce chloride-based polyatomic ions that may interfere with the detection of Cr(III), and a detection limit study yielded levels in the low part-per-billion range. The newly developed method was applied to the chromatographic analysis of samples of an incubation medium containing Cr(VI) incubated with cell nuclei.     

Speciation of chromium in wastewater and sludge by extraction with liquid anion exchanger Amberlite LA-2 and electrothermal atomic absorption spectrometry

A simple, integrated method for the speciation of chromium in wastewater and sewage sludge was developed, utilising liquid anion exchange by Amberlite LA-2 (LAES) and final determination by electrothermal atomic absorption spectrometry (ETAAS). Samples were filtered through a 0.45 μm membrane filter and chromium species were determined in filtered water samples and in sludge on the filters. In the former case (filtrate), total Cr was determined directly by ETAAS, while for the determination of Cr(VI) the filtrate was buffered to pH 6.4, extracted with LAES and Cr(VI) was determined in the organic extract. Cr(III) was determined by the difference. In the latter case (filter), the filters were leached with an alkaline buffer solution (pH 12.7) and the supernatant was subjected to the same extraction procedure. For the determination of total leachable Cr, the filters were subjected to acid leaching with dilute HNO₃ (pH 1) and the supernatant was subjected to ETAAS, after appropriate dilution with water. Then, Cr(III) was determined by the difference. The limits of detection (LOD) were 0.39 and 0.45 μg l⁻¹ for total Cr and Cr(VI), respectively, in the dissolved phase and 2.10 and 0.87 ng g⁻¹ for total Cr and Cr(VI) in the suspended solids. The recoveries of total Cr and Cr(VI) in filtrated wastewater samples and filters were quantitative, ranged from 93 to 106%. The effect of time and temperature of sonication and suspended solids concentration on total Cr and Cr(VI) recovery was studied. No significant difference in recoveries was obtained for sonication temperatures between 30 and 70 °C. However, sonication time equal to or higher than 30 min and concentration of suspended solids equal to or less than 30 mg significantly improved Cr recovery. The ETAAS program for the determination of Cr(VI) in Amberlite/MIBK extract was carefully optimised in the absence of a chemical modifier to avoid memory effects. The developed analytical method was applied for the determination of chromium species in wastewater and suspended solids of a municipal and a lab-scale wastewater treatment plant.     

Analytical speciation of chromium in in-vitro cultures of chromate-resistant filamentous fungi

In this work, different analytical speciation schemes have been used to study the reduction of Cr(VI) by a chromate-resistant strain of filamentous fungi Ed8 (Aspergillus sp), indigenous to contaminated industrial wastes. As demonstrated previously, this strain has the capability to reduce chromate present in the growth medium without its accumulation in the biomass, yet the reduced chromium end-products have not been characterized. Liquid growth medium, initially containing 50 mg L(-1) Cr(VI), was analyzed for Cr(III)/Cr(VI) and for total Cr at different time intervals (0-24 h) after inoculation with fungi. Three hyphenated procedures, based on the Cr(III)-EDTA formation and species separation by anion-exchange or ion-pairing reversed-phase chromatography with ICP-MS or DAD detection were used. The results obtained for Cr(VI) in each case were consistent, demonstrating efficient reduction of chromate during 24 h of Ed8 growth. However, pre-column complexation with EDTA did not ensure complete recovery of the reduced forms of chromium in the above procedures. An alternative speciation scheme, based on extraction of Cr(VI)-benzyltributylammonium bromide (BTAB) ion pairs into chloroform and subsequent determination of residual chromium by ICP-MS has provided evidence on the effective conversion of chromate into reduced chromium species in the growth medium. The results indicate the feasibility of using Ed8 strain for chromate bioremediation purposes. Analytically it can be concluded that speciation of chromium in biological systems should not be limited to its two most common oxidation states, because the actual reduced chromium species are not converted quantitatively to Cr(III)-EDTA.     

Development of analytical procedures for determination of total chromium by quadrupole ICP–MS and high-resolution ICP–MS,and hexavalent chromium by HPLC–ICP–MS,in different materials used in the automotive industry

A European directive was recently adopted limiting the use of hazardous substances such as Pb, Hg, Cd, and Cr(VI) in vehicle manufacturing. From July 2003 a maximum of 2 g Cr(VI) will be authorised per vehicle in corrosion-preventing coatings of key components. As no standardised procedures are available to check if produced vehicles are in agreement with this directive, the objective of this work was to develop analytical procedures for total chromium and Cr(VI) determination in these materials. The first step of this study was to optimise digestion procedures for total chromium determination in plastic and metallic materials by inductively coupled plasma mass spectrometry (ICP–MS). High resolution (HR) ICP–MS was used to examine the influence of polyatomic interferences on the detection of the ⁵²Cr⁺ and ⁵³Cr⁺ isotopes. If there was strong interference with m/z 52 for plastic materials, it was possible to use quadrupole ICP–MS for m/z 53 if digestions were performed with HNO₃+H₂O₂. This mixture was also necessary for digestion of chromium from metallic materials. Extraction procedures in alkaline medium (NH₄⁺/NH₃ buffer solution at pH 8.9) assisted by sonication were developed for determining Cr(VI) in four different corrosion-preventing coatings by HPLC–ICP–MS. After optimisation and validation with the only solid reference material certified for its Cr(VI) content (BCR 545; welding dusts), the efficiency of this extraction procedure for screw coatings was compared with that described in the EN ISO 3613 standard generally used in routine laboratories. For coatings comprising zinc and aluminium passivated in depth with chromium oxides the extraction procedure developed herein enabled determination of higher Cr(VI) concentrations. This was also observed for the screw covered with a chromium passivant layer on zinc–nickel. For coating comprising a chromium passivant layer on alkaline zinc the standardized extraction procedure was more efficient. In the case of painted metallic plate, because of a reactive matrix towards Cr(VI), its extraction without degradation was difficult to perform.     

Thermal lens spectrometric determination of hexavalent chromium

The applicability of thermal lens spectrometry (TLS) for quantification and routine determination of hexavalent chromium was investigated by using a collinear dual beam thermal lens spectrometer. In aqueous solutions the LOD of 0.1 μg l⁻¹ was obtained for Cr(VI) by using 160 mW laser power. The performance of the technique was verified by the determination of hexavalent chromium in standard reference water samples (NIST SRM 1643a and NIST SRM 1643c) and comparing the results for Cr(VI) in CCA (Cr, Cu, As)-treated timber extracts to concentrations obtained by atomic absorption spectrometry (AAS). Good agreement between the TLS results and reported values for Cr(VI) in SRMs as well as AAS results for Cr(VI) in CCA-treated timbers confirmed that TLS is a reliable and accurate analytical technique applicable for the determination of Cr(VI) in aqueous solutions at concentration levels 0.5–100 μg l⁻¹.     

Electrophoretic separations with polyether ether ketone capillaries and capacitively coupled contactless conductivity detection

The Raipore R1030 membrane, an anion-exchange membrane containing ammonium groups as ionogenic groups, was evaluated as the interface of an optical sensor for Cr(VI), and the effect of chemical parameters affecting Cr(VI) transport were studied. Good transport features were obtained, demonstrating the suitability of the Raipore R1030 membrane for this application. Thus, an optical sensor for chromium(VI) monitoring in industrial process waters was developed. The sensor is based on the renewable reagent approach and uses the Raipore R1030 membrane as the interface between the sample and the sensor head, which contains 1,5-diphenylcarbazide as spectrophotometric reagent for chromium. Chromium(VI) crosses the membrane and reacts with the reagent inside the sensor head, resulting in changes in the absorption of light. These changes are monitored in situ through a system of optical fibers. The sensor performance was tested by analysing samples from a waste water treatment plant for effluents from electroplating industries.     

Single-column ion-chromatographic determination of chromium(VI) in aqueous soil and sludge extracts

Single-column ion-chromatography (SCIC) was investigated as a routine, rapid, precise and selective analytical method for the determination of chromium(VI) in aqueous extracts of soil and sewage sludge. Chromatographic parameters were optimized for determination of Cr(VI), NO(-)(3) and SO(2-)(4). A low-capacity resin-based column was used for the separation and the anions were determined by conductometric detection. p-Hydroxybenzoic acid (5mM) at pH 8.5 was used as the eluent. The limit of detection, defined as S/N = 3, was 92 mug/l. The resolution between Cr(VI) and SO(2-)(4) was 2.8, the precision ranged from 0.9% for NO(-)(3) to 2.0% for Cr(VI) with a 500-mul injection. The SCIC results for Cr(VI) agreed closely with those obtained by inductively coupled argon-plasma emission and spectrophotometry.     

Speciation of Cr(III) and Cr(VI) in Environmental Samples after Solid Phase Extraction on Amberlite XAD–2000

A method for speciation of Cr(III) and Cr(VI) in real samples has been developed. Cr(VI) has been separated from Cr(III) and preconcentrated as its pyrrolidinedithiocarbamate (APDC) complex by using a column containing Amberlite XAD–2000 resin and determined by FAAS. Total chromium has also been determined by FAAS after conversion of Cr(III) to Cr(VI) by oxidation with KMnO₄. Cr(III) has been calculated by subtracting Cr(VI) from the total. The effect of pH, flow‐rate, adsorption and batch capacity and effect of various metal cations and salt anions on the sorption onto the resin were investigated. The adsorption is quantitative in the pH range of 1.5–2.5, and Cr(VI) ion was desorbed by using H₂SO₄ in acetone. The recovery of Cr(VI) was 97 ± 4 at a 95% confidence level. The highest preconcentration factor was 80 for a 200 mL sample volume. The adsorption and batch capacity of sorbent were 7.4 and 8.0 mg g^?1 Cr(VI), respectively, and loading half time was 5.0 min. The detection limit of Cr(VI) is 0.6 μg/L. The procedure has been applied to the determination and speciation of chromium in stream water, tap water, mineral spring water and spring water. Also, the proposed method was applied to total chromium preconcentration in microwave digested moss and rock samples with satisfactory results. The developed method was validated with CRM‐TMDW‐500 (Certified Reference Material Trace Metals in Drinking Water) and BCR‐CRM 144R s (Certified Reference Material Sewage Sludge, Domestic Origin) and the results obtained were in good agreement with the certified values. The relative standard deviations were below 6%.     

Speciation of Chromium in Natural Waters,Tea, and Soil with Membrane Filtration Flame Atomic Absorption Spectrometry

A sensitive and selective method was developed for the speciation of chromium(III) and chromium(VI) in environmental samples based on membrane filtration and determination by flame atomic absorption spectrometry. Chromium(III) reacts with cochineal red A, yielding a complex that is adsorbed on a cellulose acetate membrane filter, whereas chromium(VI) remains in aqueous solution, permitting separation. After reduction of chromium(VI) to chromium(III) with hydroxylamine hydrochloride, the total concentration of chromium was determined, and the concentration of chromium(VI) was calculated by subtraction. The pH, amount of cochineal red A, and sample volume were optimized on the basis of the recovery of Cr(III). The influence of matrix ions was also investigated. The preconcentration factor was 94. The detection limit (3 sigma) for Cr(III) was 1.4 micrograms per liter. The method was validated using environmental certified reference materials. The method was successfully employed for the speciation of chromium in wastewater and lake water.     

Quantitative analysis of manganese, chromium and molybdenum by ion-pair reversed-phase high-performance liquid chromatography with pre-column derivatization and UV-visible detection.

An ion-pair reversed-phase high-performance liquid chromatographic method with UV-visible spectrophotometric detection is proposed for the simultaneous determination of manganese, chromium and molybdenum. By using a C18-bonded silica column, 4-(2-pyridylazo)resorcinol (PAR) chelates of Mn(II), Cr(VI) and Mo(VI) were successfully separated and accurately determined at 480 nm. Tetrabutylammonium bromide (TBAB) was used as the ion-pair reagent. Effects of pH, the buffer system, the concentration of buffer, the color developing time, the concentration of chelating reagent and the ion-pair reagent on the resolution were investigated. PAR chelates were eluted within 20 min at a flow-rate of 1.0 ml min(-1) with a methanol aqueous mobile phase, CH3OH-water (20:80, v/v), containing 1.0 x 10(-3) mol l(-1) acetate buffer (pH 6.5), 1.8 x 10(-2) mol l(-1) TBAB and 2.0 x 10(-4) mol l(-1) PAR. The feasibility of the proposed method was verified with the standard reference materials of nickel-based alloys. The nickel-based alloys were analyzed chromatographically after ammonium pretreatment. Under the optimum conditions, the detection limits for the chelates of Mn(II), Cr(VI) and Mo(VI) were 0.31, 4.2 and 4.6 ng with 100 microl injection, respectively. The accuracy of the proposed chromatographic method was verified by good agreement between the values obtained by this method and certified values.     

Possibilities for speciation of Al-citrate and other negatively charged Al complexes by anion-exchange FPLC-ICP-AES

An anion-exchange fast protein liquid chromatographic-inductively coupled plasma atomic emission spectrometric procedure (FPLC-ICP-AES) was developed for speciation of Al-citrate and other negatively charged Al complexes. FPLC separations were carried out on a Mono Q HR 5/5 strong anion-exchange FPLC column over a pH range from 3.5 to 11.0. An aqueous-NaNO(3) (4 mol dm(-3)) linear gradient elution was applied over 10 min for separation of a particular Al species. The separated Al species were determined in 0.5 cm(3) eluate fractions ;off line' by ICP-AES. Under optimal analytical procedures Al-citrate was separated from Al-oxalate and Al-EDTA in a neutral pH range. Good reproducibility of the FPLC-ICP-AES procedure was obtained for determination of a particular Al species at optimal measurement conditions (RSD +/-2%). Al(3+) and neutral Al-citrate species were strongly adsorbed on the column resin and did not interfere with the separation of negatively charged Al complexes. Al(OH)(4)(-) species were separated from Al-citrate in an alkaline pH region, but quantitatively determined only at a pH of 11.0. The distribution of Al species over a pH range from 3.5 to 11.0 agreed with the reported calculated data. The limit of detection (3sigma basis) for separated Al species was 0.1 mug cm(-3).     

Note on the use of reciprocity of chiral recognition in designing liquid chromatographic chiral stationary phases

The effect of methanol, acetone and acetonitrile on the sensitivity, selectivity and the detection limits (LODs) of the determination of chromium species by ion chromatography was investigated. A collinear dual-beam thermal lens spectrometer was used for the direct detection of chromium complexes [pre-column derivatized Cr(III)–pyridine-2,6-dicarboxylic acid, and post-column derivatized Cr(VI)–1,5-diphenylcarbazide] following the ion chromatographic separation on a Dionex HPIC-CS5A solvent compatible column. Different amounts of organic solvents were added directly to the eluent (up to 30%) and to the post-column reagent (up to 60%) to improve the thermooptical properties of the solvents. Consequently, the sensitivity of the technique was increased by a factor of 2–3 and LODs of 0.1 and 10 μg dm⁻³ were achieved for Cr(VI) and Cr(III), respectively, when the eluent reaching the detector contained 30% of acetonitrile. The addition of organic solvents also resulted in significant changes in retention times, which improved the Cr(III)/Cr(VI) separation.     

Separation of Cr(III) and Cr(VI) in river and reservoir water with 8-hydroxyquinoline immobilized polyacrylonitrile fiber for determination by inductively coupled plasma mass spectrometry

A rapid and simple method has been developed for the separation of chromium (III) and Cr(VI) species in river and reservoir water. Chromium (III) can be chelated with 8-hydroxyquinoline immobilized polyacrylonitrile (PAN) fiber, whereas Cr(VI) cannot. Chelated Cr(III) can be eluted with 2 mol l(-1) HCl-0.1 mol l(-1) HNO(3). Cr(VI) in the filtrate and Cr(III) in the eluant were determined by inductively coupled plasma mass spectrometry. The effect of pH, sample flow rate, eluant type and its volume on the concentration effectiveness of Cr(III) was investigated. The recommended method has been applied for the separation and determination of Cr(III) and Cr(VI) in river and reservoir water. The results indicated that the recovery of each individual Cr species ranged from 96 to 107% and the R.S.D. were found to be <10% at the level of ng ml(-1). The effect of HNO(3) added in the sampling procedure was also evaluated.     

Spectrophotometric study of the complexation and extraction of chromium(VI) with cyanine dyes

Solvent extraction of chromium(VI) ion associates with symmetric cyanine dyes including the heterocyclic radicals of 1,3,3-trimethyl-3N-indoline, benzooxazol, benzothiazol and quinoline has been studied by means of spectrophotometric method. In the acidic medium in the presence of chloride ions, extractable by aromatic hydrocarbons and esters of acetic acids, chromium(VI) ion associates are formed. The molar absorptivities of ion associates are 2.5-3.6x10(5) l mol(-1) cm(-1) in dependence on extractant and dye. The absorbance of the coloured extracts obeys the Beer's law in the range 0.01-2.1 mg l(-1). The extraction of chromium is the highest during extraction from the sulphuric acid medium in the range 0.05-03 M H(2)SO(4). It was found that the Cr(VI):Cl:R molar ratio is 1:1:1. A novel procedure of chromium(VI) extraction and spectrophotometric determination in various types of soils and sewage doped with chromium(VI) was examined.