Preconcentration and solid phase extraction method for the determination of Co, Cu, Ni, Zn and Cd in environmental and biological samples using activated carbon by FAAS

2-{[1-(2-Hydroxynaphthyl) methylidene] amino} benzoic acid (HNMABA) was synthesized for solid phase extraction (SPE) to the determination of Co, Cu, Ni, Zn and Cd in environmental and biological samples by flame atomic absorption spectrophotometry (FAAS). These metals were sorbed as HNMABA complexes on activated carbon (AC) at the pH range of 5.0+/-0.2 and eluted with 6 ml of 1M HNO3 in acetone. The effects of sample volume, eluent volume and recovery have been investigated to enhance the sensitivity and selectivity of proposed method. The effect of interferences on the sorption of metal ions was studied. The concentration of the metal ions detected after preconcentration was in agreement with the added amount. The detection limits for the metals studied were in the range of 0.75-3.82 microg ml(-1). The proposed system produced satisfactory results for the determination of Co, Cu, Ni, Zn and Cd metals in environmental and biological samples.     

Spectrophotometric determination of aluminium and indium with 2,2',3,4-tetrahydroxy-3',5'-disulphoazobenzene

2,2',3,4-Tetrahydroxy-3',5'-disulphoazobenzene (tetrahydroxyazon 2S) has been synthesized for the first time. This reagent has been used for the spectrophotometric determination of aluminium and indium ions. The method is very sensitive and selective for the direct determination of aluminium and indium. The optimum pH and absorbance of complexes formed of tetrahydroxyazon 2S with aluminium and indium are 5; 500 nm and 495 nm for Al and In, respectively. The system obeys Beer's law at 0.05-1.6 microg mL(-1) of aluminium and 0.06-2.1 microg mL(-1) of indium concentration. The molar absorptivity is 6.42 x 10(4)L mol(-1)cm(-1) for aluminium and 7.70 x 10(4)L mol(-1)cm(-1) for indium. The molar compositions of the complexes are 1:1 at optimum conditions. Alkaline and alkaline earth elements, halogens, thiourea, ascorbic acid, Cd(II), Pb(II), Mn(II), Zn(II), Co(II), Ni(II), Cr(III), Bi(III), La(III), Si(IV) do not interfere this method. The method can be applied to the direct spectrophotometric determination of trace amounts of aluminium in steel, alloys, waste water, river waters, spring water and ground water. The method was also successfully applied to the indium determination in artificial mixture.     

Extractive spectrophotometric determination of trace amounts of cadmium(II) in medicinal leaves and environmental samples using benzildithiosemicarbazone (BDTSC)

A new thiosemicarbazone, benzildithiosemicarbazone (BDTSC), is proposed as a sensitive and selective analytical reagent for extractive spectrophotometric determination of Cd(II). BDTSC reacts with cadmium(II) to give a yellow-colored complex in ammonium chloride-ammonium hydroxide buffer of pH 10.5, which is easily extracted into isoamylalcohol with 1:1 composition having a maximum absorbance at wavelength 360 nm. The molar absorptivity and Sandell's sensitivity are found to be 0.196 x 10(4)dm3 mol(-1)cm(-1) and 0.008 microg cm(-2) of Cd(II), respectively. The instability constant of the method has been calculated by Asmus' method as 5.05 x 10(-5) (which is in close agreement with the value obtained by Edmonds and Birnbaum's method) at room temperature. The interfering effect of various cations and anions has also been studied. The method has been successfully applied for the determination of Cd(II) in several standard reference materials as well as environmental samples, medicinal leaves and leafy vegetables.     

Simultaneous determination of trace cadmium and arsenic in biological samples by hydride generation-double channel atomic fluorescence spectrometry

Hydride generation atomic fluorescence spectrometry (HG-AFS) has been used for determination of hydride-forming elements because of its high sensitivity, simplicity, and low costs, but most of such work has been concentrated on single element analysis, and reports dealing with multielement determination by HG-nondispersive (ND)AFS are rare. In this work, a sensitive HG-NDAFS method was developed for simultaneous determination of trace cadmium and arsenic in biological materials. The conditions for the generation of volatile cadmium and arsenic species from the reaction with KBH4 in aqueous solution were investigated using a double-channel AFS integrated with an intermittent flow reactor. Like thiourea and Co(II), ascorbic acid was found to significantly enhance the generation efficiency of volatile Cd and As species. The interferences of coexisting ions were evaluated. Under optimal conditions, the detection limits for Cd and As were determined to be 10 and 150 ng L(-1), respectively. The precision for 11 replicate determinations at the 1 microg L(-1) Cd level and the 10 microg L(-1) As level were 3.5 and 2.7% (RSD), respectively. The recoveries of spike analytes in the biological samples studied ranged from 94 to 109%. The proposed method was successfully applied to the simultaneous determination of Cd and As in a variety of biological samples.     

Simple, selective and sensitive spectrophotometric determination of fenitrothion using novel chromogenic reagent

A facile, rapid and sensitive spectrophotometric method was developed for the determination of fenitrothion in its formulations, water, food grain and agriculture soil samples with newly synthesised reagent. The method was based on the alkaline hydrolysis of fenitrothion pesticide and resultant hydrolysed product of fenitrothion was coupled with diazotised 4,4'-methylene-bis-(p-amino-3'-hydroxybenzanilide) in basic medium to give orange coloured product having lambdamax 480 nm. The formation of coloured derivatives with the coupling agent is instantaneous and stable for 48 h. Beer's law was obeyed in the concentration range of 0.1-19.0 microg ml(-1). The proposed method is sensitive, easy to operate and permitted the determination of fenitrothion with a detection limits of 0.085 microg ml(-1). The experimental results indicate that the procedure can eliminate the fundamental interferences caused by other pesticides and non-target ions, which made these methods more sensitive and selective. The method was applicable to the determination of fenitrothion residue in water, food grain and soil samples up to ng level.     

Spectrofluorimetric determination of tin in canned foods

A simple and sensitive spectrofluorimetric method for the determination of tin as its complex with 1-(2-pyridylazo)-2-naphtol (PAN) in a mixed micellar medium was developed. The mixture of a non-ionic surfactant, Triton X-100 and an anionic surfactant, bis(2-ethylhexyl) sulfosuccinate (AOT) was used as a suitable micellar medium for solubilizing of complex and ligand and also for enhancing the fluorescence intensity of complex. In the optimum experimental conditions the maximum excitation and emission wavelengths of Sn-PAN complex were 300 and 360 nm, respectively. The calibration graph was linear in the range of 0.01-0.8 microg ml(-1) with a correlation coefficient of 0.9991. The detection limit was found to be 2 ng ml(-1). The relative standard deviation of the method for the determination of 0.1 microg ml(-1) tin was calculated to be 0.74%. The interferences caused by the presence of a number of common cations and anions were studied. Finally, the method was successfully applied to the determination of tin in various canned products.     

Solid phase extraction method for selective determination of Pb(II) in water samples using 4-(4-methoxybenzylidenimine) thiophenole

A sensitive and selective extractive preconcentration procedure for the determination of traces of lead in water samples has been developed. An alumina-sodium dodecyl sulfate (SDS) coated modified with 4-(4-methoxybenzylidenimine) thiophenole (MBITP) was used for preconcentration and determination of Pb(II) by flame atomic absorption spectrometry. Lead was adsorbed quantitatively on modified column due to its complexation with MBITP and quantitatively eluted using 5 mL 1 mol L(-1) nitric acid in acetone. The effects of parameters such as pH, amount of solid phase, amount of MBITP, flow rate, type and concentration of eluting agent were examined. The effect of interfering ions on the determination of Pb(II) was also investigated. The response of proposed method is linear in the concentration range 0.05-1.2 microg mL(-1) of Pb(II). The limit of detections (3S.D.(b)/m, n=4) and relative standard deviations (n=11) are 1.6 ng mL(-1) and 0.9%, respectively. The presented procedure was successfully applied for determination of lead content in real samples such as river, spring, waste and drinking water.     

Removal of an iron matrix with polyoxyethylene-type surfactant-coated amberlite XAD-4 for the determination of trace impurities in high-purity iron

Admicellar sorbents for the removal of an iron matrix were prepared for the determination of trace impurities in high-purity iron. A 1.0-g amount of Amberlite XAD-4 (macroreticular styrene-divinylbenzene copolymer) was coated with 0.14-1.3 mmol of polyoxyethylene-type surfactants, including polyoxyethylene-4-tert-octylphenoxy ethers (Triton X series) and polyoxyethylene-4-isononylphenoxy ethers (PONPEs). The surfactant-coated XAD-4 was packed into a polypropylene column (7 mm i.d. x 50 mm high). A 5.0-cm(3) volume of sample solution was passed through the column at a flow rate of 0.5 cm(3) min(-1). Milligram amounts of iron(III) were effectively sorbed on the column from 8 mol dm(-3) hydrochloric acid solutions. Among the surfactants tested, polyoxyethylene(20)-4-isononylphenoxy ether (PONPE-20) showed the best performance: the iron leaked from the PONPE-20 column was 4 microg when 25 mg of iron(III) was introduced onto the column. Trace elements, such as Ti(IV), Cr(III), Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Ag(I), Cd(II), Pb(II), and Bi(III), were not retained on the column and thus quantitatively recovered in the column effluent. The effective separation of trace elements from an iron matrix allowed their accurate determinations by inductively coupled plasma-mass spectrometry or graphite furnace atomic absorption spectrometry. The detection limits (3sigma blank) were in the nanogram per gram range. The proposed method was successfully applied to the determination of trace impurities in high-purity iron samples.     

Solid phase extraction and determination of sub-ppb levels of hazardous Hg2+ ions

A simple, rapid and reliable method has been developed to selectively separate and concentrate ultra trace amounts of mercury(II) ions from aqueous samples for its highly sensitive measurement by cold vapor atomic absorption spectrometry (CV-AAS). The Hg(2+) ions were adsorbed selectively and quantitatively during the passage of aqueous samples through octadecyl silica membrane disks modified by isopropyl 2-[(isopropoxycarbothiolyl)disulfanyl]ethane thioate (IIDE). The retained Hg(2+) ions were then stripped from the disk with minimal amounts of 0.5 M hydrobromic acid (two 8 ml portions) as eluent, and determined by CV-AAS. The break-through volume of the method is greater than 3000 ml, which results in enrichment factors >150. Maximum capacity of the membrane disks modified with 10mg of the ligand was found to be 350+/-30 microg of mercury(II), and the limit of detection is 0.005 ng ml(-1). The effect of various cationic interferences on the recovery of mercury in binary mixtures was studied. The method was applied to the recovery of Hg(2+) ions from different synthetic and tap water samples, as well as the determination of mercury in human hair samples.     

Development and validation of a one-step immunoassay for determination of cadmium in human serum.

A sensitive and simple one-step immunoassay was developed and validated for quantitative determination of Cd(II) in human serum. In this method, a monoclonal antibody that recognizes Cd(II)-EDTA complexes was directly immobilized onto microwell plates. The serum sample containing metallothionein(MT)-bound and non-MT-bound Cd(II) was acidified to displace the Cd(II) from MT. The sample was then treated with metal-free EDTA to convert Cd(II) to Cd(II)-EDTA complexes. A mixture of Cd(II)-EDTA complexes derived from serum samples and Cd(II)-EDTA conjugated with peroxidase enzyme was incubated in the wells to compete for binding sites of the immobilized antibody. After addition of peroxidase substrate, the bound fraction of the enzyme conjugate was measured by a microplate reader, and the signal was inversely proportional to the concentration of the Cd(II) in the sample. The assay limit of detection was 0.24 microg/L, and the effective working range at coefficient of variation of < or = 10% was 0.24-100 microg/L. Analytical recovery of spiked Cd(II), in the concentration range between 0.8 and 50 microg/L, was 97.8 +/- 4.0%. The assay was selective for Cd(II); other metal ions (Mn, Co, Cu, Zn, Mg, Hg, Ca, Ni, Fe, and Pb), tested at concentrations considerably higher than those present in human serum, did not significantly interfere with the assay. The assay results correlated well with those obtained by graphite furnace atomic absorption spectrometry (r = 0.984).     

On-line preconcentration of copper as its pyrocatechol violet complex on Chromosorb 105 for flame atomic absorption spectrometric determinations

An on-line solid phase extraction method for the preconcentration and determination of Cu(II) by flame atomic absorption spectrometry (FAAS) has been described. It is based on the adsorption of copper(II) ion onto a home made mini column of Chromosorb 105 resin loaded with pyrocatechol violet at the pH range of 5.0-8.0, then eluted with 1 mol L(-1) HNO(3). Several parameters, such as pH of the sample solution, amount of Chromosorb 105 resin, volume of sample and eluent, type of eluent, flow rates of sample and eluent, governing the efficiency and throughput of the method were evaluated. The concentration of the copper ion detected after preconcentration was in agreement with the added amount. At optimized conditions, for 15 min of preconcentration time (30 mL of sample volume), the system achieved a detection limit of 0.02 microg L(-1), with relative standard deviation 1.1% at 0.03 microg mL(-1) copper. The present method was found to be applicable to the preconcentration of Cu(II) in natural water samples.     

Slurry sampling in serum blood for mercury determination by CV-AFS

The heavy metal mercury (Hg) is a neurotoxin known to have a serious health impact even at relatively low concentrations. A slurry method was developed for the sensitive and precise determination of mercury in human serum blood samples by cold vapor generation coupled to atomic fluorescence spectrometry (CV-AFS). All variables related to the slurry formation were studied. The optimal hydrochloric concentration and tin(II) chloride concentration for CV generation were evaluated. Calibration within the range 0.1-10 microg L(-1) Hg was performed with the standard addition method, and compared with an external calibration. Additionally, the reliability of the results obtained was evaluated by analyzing mercury in the same samples, but submitted to microwave-assisted digestion method. The limit of detection was calculated as 25 ng L(-1) and the relative standard deviation was 3.9% at levels around of 0.4 microg L(-1)Hg.     

Diaion SP-850 resin as a new solid phase extractor for preconcentration-separation of trace metal ions in environmental samples

A solid phase extraction method was developed for the preconcentration and separation of trace amounts of chromium, manganese, iron, cobalt, copper, cadmium and lead from environmental samples by complexation with alpha-benzoin oxime followed by adsorption onto Diaion SP-850-solid phase extraction column. One molar per liter HNO(3) was used as eluent. The recoveries of analytes at pH 8.0 with 700 mg of resin were greater than 95% without interference from alkaline, earth alkaline and some metal ions. The detection limits by three sigma for analyte ions were 0.65 microg l(-1) for Cr(III), 0.42 microg l(-1) for Mn(II), 0.28 microg l(-1) for Fe(III), 0.73 microg l(-1) for Co(II), 0.30 microg l(-1) for Cu(II), 0.47 microg l(-1) for Cd(II) and 0.50 microg l(-1) for Pb(II). The validation of the procedure was performed by the analysis of the certified standard reference materials. The presented procedure was applied to the determination of analytes in tap, river and sea waters, rice, wheat, canned tomato and coal samples with successfully results (recoveries greater than 95%, R.S.D.'s lower than 8%).     

Determination of Lead Ions by an Optical Sensor Based on 2-Amino-Cyclopentene-1-Dithiocarboxylic Acid

A new spectrophotometric sensor for the determination of lead at trace level was developed using chemically immobilized 2-amino-cyclopentene-l-dithiocarboxylic acid (ACDA) on a triacetylcellulose. The sensor provided a wide concentration range of 1.0 x 10^-6 to 5.0 x 10^-1 M Pb(II) with a limit of detection of 6.9 X 10^-7 M Pb(II). The method also showed a reproducible result with relative standard deviation of less than 3.5% and response time of the optode was 10 min. Interference studies showed that Co(II) and Ni(II) ions interfered during the determination. The interference of potential interfering ions could be eliminated using a simple extraction procedure. The method was successfully used to determination of Pb(II) ions in reference alloy, water, and waste water samples with satisfactory results.     

The facile flow-injection spectrophotometric detection of gold(III) in water and pharmaceutical samples using 3,5-dimethoxy-4-hydroxy-2-aminoacetophenone isonicotinoyl hydrazone (3,5-DMHAAINH)

A simple, sensitive and rapid flow-injection spectrophotometric method was developed for the determination of trace amounts of Au(III) in aqueous dimethylformamide (DMF). The method is based on formation of Au(III)-(3,5-DMHAAINH)3 complex. The optimum conditions for the chromogenic reaction of Au(III) with 3,5-DMHAAINH is studied and the colored (reddish brown) complex is selectively monitored at lambda(max) 490 nm at pH 6.0. The reaction and flow conditions of the full experimental design were optimized. The detection limit (2 s) of 0.1 microg l-1 Au(III) was obtained at a sampling rate of 15 samples h-1. Beer's law is obeyed over the range of 0.30-4.00 microg ml-1. The molar absorptivity and Sandell's sensitivity were 3.450x10(4) M and 0.0050 microg ml-1, respectively. Job's method of continuous variation and stability constants corresponding to these maxima was determined and found to be 9.3x10(15) (1:3, M:R) (M, metal; R, reagent). The detailed study of various interferences confirmed the high selectivity of the developed method. The method was successfully applied for the determination of trace amount of Au(III) in water and pharmaceutical samples. The results obtained were in agreement with the reported methods at the 95% confidence level.     

A biosorption system for metal ions on Penicillium italicum-loaded on Sepabeads SP 70 prior to flame atomic absorption spectrometric determinations

A solid phase extraction (SPE) preconcentration system, coupled to a flame atomic absorption spectrometer (FAAS), was developed for the determination of copper(II), cadmium(II), lead(II), manganese(II), iron(III), nickel(II) and cobalt(II) ions at the microg L(-1) levels on Penicillium italicum-loaded on Sepabeads SP 70. The analytes were adsorbed on biosorbent at the pH range of 8.5-9.5. The adsorbed metals were eluted with 1 mol L(-1) HCl. The influences of the various analytical parameters including pH of the aqueous solutions, sample volume, flow rates were investigated for the retentions of the analyte ions. The recovery values are ranged from 95-102%. The influences of alkaline, earth alkaline and some transition metal ions were also discussed. Under the optimized conditions, the detection limits (3s, n=21) for analytes were in the range of 0.41microg L(-1) (cadmium) and 1.60microg L(-1) (iron). The standard reference materials (IAEA 336 Lichen, NIST SRM 1573a Tomato leaves) were analyzed to verify the proposed method. The method was successfully applied for the determinations of analytes in natural water, cultivated mushroom, lichen (Bryum capilare Hedw), moss (Homalothecium sericeum) and refined table salt samples.     

Cyanuric acid trace analysis by extractive methylation via phase-transfer catalysis and capillary gas chromatography coupled with flame thermoionic and mass-selective detection. Process parameter studies and kinetics

A GC method using phase-transfer catalysis for the simultaneous derivatization, extraction, and preconcentration of the highly polar cyanuric acid (CYA) was developed. The method was based on the extractive N-methylation of the analyte of concern in two- and three-phase systems, whereby the 1,3,5-trimethyl-1,3,5-triazine-2,4,6-(1H,3H,5H)trione was formed. Subsequent detection was performed using flame thermoionic specific detection (FTD) and mass spectrometry (MS) selective-ion monitoring (SIM) using electron impact. The optimal experimental conditions related to pH, kind of catalyst and solvents, methyl iodide concentration, phase volumes, reaction time, temperature, and agitation were suitably established. Inter alia, the resulting method is highly sensitive, almost free from interferences, and was easily applied to the determination of cyanuric acid in swimming pool water, surface water, human urine, and simulated air filter samples. The minimal quantitable concentration was found to be less than 1 and 90 microg L(-1) using GC-MS-(SIM) and GC-FTD, respectively. The overall precision for the workup procedure did not exceed 3.6% (n = 6) for 5.0 microg L(-1) CYA-spiked urine and river water while the respective value for the same matrixes spiked at a concentration of 200 microg L(-1) was calculated to be in the range 1.9-4.0% (n = 6). The overall recovery from spiked samples was 98 +/- 5% for microgram per liter levels of CYA. A kinetic study conducted was helpful to get a better insight into the N-methylation reaction mechanism.     

Cloud point extraction of palladium in water samples and alloy mixtures using new synthesized reagent with flame atomic absorption spectrometry (FAAS)

The present paper outlines novel, simple and sensitive method for the determination of palladium by flame atomic absorption spectrometry (FAAS) after separation and preconcentration by cloud point extraction (CPE). The cloud point methodology was successfully applied for palladium determination by using new reagent 4-(2-naphthalenyl)thiozol-2yl azo chromotropic acid (NTACA) and hydrophobic ligand Triton X-114 as chelating agent and nonionic surfactant respectively in the water samples and alloys. The following parameters such as pH, concentration of the reagent and Triton X-114, equilibrating temperature and centrifuging time were evaluated and optimized to enhance the sensitivity and extraction efficiency of the proposed method. The preconcentration factor was found to be (50-fold) for 250 ml of water sample. Under optimum condition the detection limit was found as 0.067 ngml(-1) for palladium in various environmental matrices. The present method was applied for the determination of palladium in various water samples, alloys and the result shows good agreement with reported method and the recoveries are in the range of 96.7-99.4%.     

Celtek clay as sorbent for separation-preconcentration of metal ions from environmental samples

The sorption conditions including pH of the aqueous solution, sample volume, etc., on Celtek clay of copper(II), cadmium(II), lead(II), chromium(III), nickel(II) and cobalt(II) ions from environmental samples has been studied. The effects of electrolytes as matrix on the preconcentration were also investigated with the recoveries >95%. The 3 sigma detection limits for copper, cadmium, lead, chromium, nickel and cobalt ions were found to be 0.25, 0.32, 0.73, 0.45, 0.50 and 0.41 microg/l, respectively. The relative standard deviation was <10% for the determination of analytes. The procedure was validated by analysis of a NRCC-SLRS 4 Riverine Water, SRM 1573a Tomato leaves and IAEA 336 Lichen standard reference materials. The developed method was successively utilized for the determination of Cu(II), Cd(II), Pb(II), Cr(III), Ni(II) and Co(II) in various samples including natural waters, wheat and human hair by flame atomic absorption spectrometry (FAAS) with satisfactorily results (recoveries>95% and R.S.D.'s<10%).     

Solid-phase extraction of Mn(II), Co(II), Ni(II), Cu(II), Cd(II) and Pb(II) ions from environmental samples by flame atomic absorption spectrometry (FAAS)

A new method using a column packed with Amberlite XAD-2010 resin as a solid-phase extractant has been developed for the multi-element preconcentration of Mn(II), Co(II), Ni(II), Cu(II), Cd(II), and Pb(II) ions based on their complex formation with the sodium diethyldithiocarbamate (Na-DDTC) prior to flame atomic absorption spectrometric (FAAS) determinations. Metal complexes sorbed on the resin were eluted by 1 mol L(-1) HNO3 in acetone. Effects of the analytical conditions over the preconcentration yields of the metal ions, such as pH, quantity of Na-DDTC, eluent type, sample volume and flow rate, foreign ions etc. have been investigated. The limits of detection (LOD) of the analytes were found in the range 0.08-0.26 microg L(-1). The method was validated by analyzing three certified reference materials. The method has been applied for the determination of trace elements in some environmental samples.