Spectrophotometric determination of lithium ion with the chromogenic crown ether, 2″,4″-dinitro-6″-trifluoromethylphenyl-4′-aminobenzo-14-crown-4

A spectrophotometric method of determining alkali metal ions with a chromogenice crown ether reagent was found to be more selective and sensitive than an ion-pairing method based on the same size of crown ether cavity. It is shown that in the ion-pairing method, the sensitivity toward lithium ion was 5.685 × 10^?4 absorbance/mg l^?1, with sodium interfering at 300 mg l^?1. The chromogenic crown ether, 2″,4″-dinitro-6″-trifluoromeethylphenyl-4′-aminobenzo-14-crown-4, was much superior to benzo-14-crown-4. The sensitivity of the chromogenic crown ether was 1.69 × 10^?3 absorbance/mg l^?1. This represents a three-fold increase in sensitivity and less reagent is needed (2 × 10^?4 M for the chromogenic method versus 1.4 × 10^?3 M for ion-pairing). Interference from sodium decreased to 3000 mg l^?1. The reagent was used to determine lithium ion in treated blood serum samples in both a batch and flow injection method and results were compared with data obtained with atomic absorption; excellent agreement was obtained in all cases.     

Sample preconcentration by continuous flow extraction with a flow injection atomic absorption detection system

The flow manifold described allows automatic extraction of metal ions in aqueous samples into 4-methyl-2-penthanone with ammonium pyrrolidinedithiocarbamate as an extracting agent. The organic extract is led into the loop of an injector situated in an integrated feed system of an atomic absorption spectrometer. No dispersion of the injected organic extract plug, 110 μl, occurs in the aqueous feed stream and the resulting signal from the spectrometer is a peak. An increase in sensitivity of 15–20 is achieved for copper, nickel, lead and zinc in comparison with direct aspiration of the aqueous samples. The sampling frequency is 40 h^?1 and the consumption of 4-methyl-2-pentanone is typically 0.3 ml min^?1. The detection limit for copper is about 1 μ l^?1.     

Sequential flow-injection determinations of calcium and magnesium in waters

A tubular PVC membrane electrode for calcium without inner reference solution and a device for location of the reference electrode are described. In the flow-injection system, calcium is determined potentiometrically and then magnesium is determined by atomic absorption spectrometry. The electrode provides linear response to calcium in the range 5 × 10^?5/2-10^?1 M. On-line dilution of the sample allows magnesium determination in the range 0/2-10 mg l^?. Flow rates between 3 and 6 ml min^?1 are possible. The sampling frequency is 60/2-90 h^?1.     

Determination of lead in whole blood with a simple flow-injection system and computerized stripping potentiometry

An automated (24 samples/hour) procedure is described for the determination of lead (0–1000 μg l^?1) in human blood based on flow-injection stripping potentiometry. The samples are diluted 20-fold with 0.5 M hydrochloric acid containing 100 mg l^?1 mercury and 40 μg l^?1 cadmium (II), and a 1.1 ml aliquot is injected into the flow system. With a mercury-coated carbon fibre as working electrode, lead (II) is determined by using cadmium (II) as internal standard and a calibration graph prepared from bovine blood. Analyses of two human blood reference samples yielded results of 335±37 and 691±24 μg l^?1 lead, the certified values being 332 and 663 μg l^?1, respectively.     

An atomic absorption spectrometric method for the determination of non-ionic surfactants

A method is described for the determination of non-ionic surfactants in the concentration range 0.05–2 mg l^-1.Surfactant molecules are extracted into 1,2-dichlorobenzene as a neutral adduct with potassium tetrathiocyanatozincate(II) and the determination is completed by atomic absorption spectrometry. With a 150-ml water sample, the limit of detection is 0.03 mg l^-1(as Triton X-100).The method requires a single phase separation step, is applicable, without modification, to fresh, estuarine and sea-water samples and is relatively free from interference by anionic surfactants; the presence of up to 5 mg l^-1 of anionic surfactant (as LAS) introduces an error of no more than 0.07 mg l^-1 (as Triton X-100) in the apparent non-ionic surfactant concentration.     

Rapid determination of copper,nickel, lead and cadmium in small samples of estuarine and coastal waters by liquid/liquid extraction and electrothermal atomic absorption spectrometry

A rapid liquid/liquid extraction of 1.25-ml samples is used with graphite-furnace atomic absorption spectrometry for the determination of dissolved trace metals in saline waters. The metals are chelated with ammonium pyrrolidine dithiocarbamate and extracted into 1,1,1-trichloroethane; 20–40 μl of extract is injected into the furnace. Sample manipulation and overall time are greatly decreased compared to other similar large-scale extraction methods; all the chemical steps are done in the sample cups of an auto-sampler for graphite-furnace a.a.s. Detection limits (Cu 0.3 μg l^?1, Cd 0.02 μg l^?1, Pb 0.7 μg l^?1, Ni 0.5 μg l^?1 are low enough for applications in routine monitoring of filterable trace metal concentrations in coastal and estuarine waters to check for compliance with Environmental Quality Standards that apply in the European Community.     

Determination of cadmium,copper and lead in urine by flame atomic absorption spectrometry after extraction of the iodide complexes as ion-pairs with tri-n-octylamine

A simple, rapid sensitive atomic absorption spectrometric method is described for the determination of cadmium, copper and lead in urine. The metals are extracted as their iodide complexes with tri-n-octylamine in n-butyl acetate, without elaborate pretreatment, and measured by direct nebulization of the extract into an air/ acetylene flame. Detection limits for cadmium, copper and lead in urine were 0.008, 0.05 and 0.02 × 10^?6 mol l^?1, respectively.     

Application of the iron(III)/3,4-dihydroxybenzaldehyde 4-nitrophenylhydrazone complex for the analysis of sulphide/fluoride/phosphate mixtures by spectrophotometry or atomic absorption spectrometry

3,4-Dihydroxybenzaldehyde 4-nitrophenylhydrazone reacts with iron(III) to form a red complex extractable into methyl isobutyl ketone. Sulphide, fluoride and phosphate inhibit the formation of the complex. Sulphide and fluoride are masked with Cu(II) and Al(III), respectively. These properties are used to determine sulphide (0.15–4 mg l^?1), fluoride (0.3–9 mg l^?1) and phosphate (0.3–8 mg l^?1) in mixtures by spectrophotometry or atomic absorption spectrometry.     

The direct determination of cadmium in urine by electrochemical atomic absorption spectrometry with the L'vov platform

A simple, direct procedure for the measurement of cadmium in urine is described. Graphite-furnace atomic absorption spectrometry is used in conjunction with selective atomisation at 800°C from a L'vov platform. Urine samples are diluted with an equal volume of deionised water and 20-μl aliquots are injected. Calibration is done by standard additions. The sensitivity is 0.016 μg Cd l^?1 for 1% absorption for a 20-μl sample. Within-run precision is 4.9% at 0.84 μg l^?1. The detection limit is 0.06 μg l^?1, which allows normal unexposed levels of cadmium in urine to be determined. The method is applicable to the determination of urinary cadmium levels of both occupationally non-exposed and exposed populations.     

Spectrophotometric determination of copper(II) in natural waters, vitamins and certified steel scrap samples using acetophenone-p-chlorophenylthiosemicarbazone

A very simple, highly sensitive and selective spectrophotometric procedure was developed for the determination of copper(II). It is based on the reaction at pH 4–9 between the synthesized acetophenone-p-chlorophenylthiosemicarbazone (A-p-ClPT) and Cu(II) forming a green complex, Cu(II):A-p-ClPT (1:2), that floats quantitatively with oleic acid (HOL) surfactant. It exhibits a constant and maximum absorbance at 600 nm in both aqueous and surfactant layers. Beer’s law is obeyed over the concentration range 0.25–6.35 mg l^?1 with a detection limit of 0.021 mg l^?1 for a standard aqueous solution of Cu(II) with a concentration of 3.82 mg l^?1 (calculated on the basis of 3σ) and molar absorptivities of 5.5 × 10³ and 1.3 × 10⁴ mol l^?1 cm^?1 in aqueous and surfactant layers, respectively. Sandell’s sensitivity was calculated to be 0.244 μg cm^?2 and the relative standard deviation (n = 9) was 0.19%. The different analytical parameters affecting the flotation and determination processes were examined. The proposed procedure has been successfully applied to the analysis of Cu(II) in natural waters, certified scrap steel samples and vitamin samples. The results obtained agree well with those samples analyzed by atomic absorption spectrometry (AAS). Moreover, the flotation mechanism is suggested based on some physical and chemical studies on the solid complexes isolated from aqueous and surfactant layers.     

The masking effect of iron(III) on the interference from nickel and copper in the determination of tellurium by hydride generation/atomic absorption spectrometry

Iron(III) can minimize the serious interferences from copper(II) and nickel(Il) on the determination of tellurium by hydride generation/atomic absorption spectrometry. The optimal concentrations were found to be 1 g l^?1 and 2 g l^?1 Fe (III) in 4.0 mol l^?1 HCl in presence of nickel (II) and copper (II), respectively. The signals were only 25 % lower in a solution of 1.6 g 1^?1 Ni(II) than for a nickel-free solution. For copper (II), reasonable sensitivity was retained in the presence of 100 mg l^?1 Cu(II).     

A microcomputer-based peak-width method of extended calibration for flow-injection atomic absorption spectrometry

In the proposed method of extended calibration based on peak widths, all data collection and reduction are done by a microcomputer interfaced to the spectrometer. The method produces an estimate of concentration without dilution of the off-range samples. Calibrations covering the ranges 40/2-1000 mg l^?1, 1.0/2-50 mg l^?1 and 20/2-1000 mg l^?1 were obtained for chromium, magnesium and nickel, respectively.     

Lead Extraction from Natural Waters—A Simple and Rapid Technique

Abstract

A technique is described for the concentration of lead from fresh and saline waters before analysis by atomic absorption spectrophotometry. The lead is adsorbed on managanese dioxide supported on glass fibre filters. Quantitative adsorption of up to 75 mg Pb/g MnO₂ was achieved, with a maximum adsorption of 190 mg Pb g^?1. The technique, which allows rapid processing of large samples, is suited to field use.     

Simultaneous determination of copper and lead by graphite-furnace atomic absorption spectrometry after liquid-liquid extraction of the ion pair with zephiramine

A procedure for the simultaneous determination of copper and lead by graphite-furnace atomic absorption spectrometry was investigated by means of a two-channel atomic absorption spectrometer. Both copper(II) and lead(II) are converted into their iodo complex anions and extracted quantitatively into diisobutyl ketone as their ion pairs with tetradecyldimethylbenzylammonium (zephiramine) in a 10-ml centrifuge tube. An aliquot of the organic extract is directly pipetted from the upper layer in the centrifuge tube and injected into the graphite furnace. The detection limits (S/N = 3) are 2.6 ng ml^?1 of copper and 1.0 ng ml^?1 of lead. The relative standard deviations for 10 replicate determinations are 2.9% for 20 ng ml^?1 of copper and 2.7% for 10 ng ml^?1 of lead. Results of analyses of some practical samples are given.     

Determination of cobalt in plant digests by adsorption stripping voltammetry

The procedure involves adsorption of cobalt onto a static mercury drop as its dimethylgloximate complex (pH 9.3, adsorption potential ?0.70 V, adsorption time 2 min), followed by a d.c. cathodic scan, effecting reduction at ?1.15 V (SCE). Of the dominant electroactive trace elements in plants (Mn, Fe, Zn), only zinc interfered; it was masked by nitrolotriacetic acid (2 × 10^?4 M). The detection limit is 0.01 μg l^?1 cobalt in the digest; the relative standard deviation is 2.5% at 0.75 μg l^?1. Calibration is linear in the range 0–6.0 μg l^?1 cobalt. Results obtained by the voltammetric method, by electrothermal atomic absorption spectrometry and neutron activation analysis are compared for seven pasture samples containing 0.1–0.2 mg kg ^?1 cobalt. The activation method provides validation for the same preparation and voltammetric results.     

Determination of heavy metals in real samples by anodic stripping voltammetry with mercury microelectrodes : Part 2. Application to Rain and Sea Waters

Differential-pulse anodic stripping voltammetry at a mercury microelectrode is applied to determine labile and total zinc, cadmium, lead and copper in samples of rain and sea water. The low ohmic drop associated with microelectrodes permits reliable measurements in rain water without addition of supporting electrolyte. The values found in a typical sample were 0.95 μg l^?1 Cu, 0.38 μg l^?1 Pb, 0.01 μg l^?1 Cd and 0.95 μg l^?1 Zn, with relative standard deviations in the range 4–18%. The small effects of organic matter at microelectrodes, compared with those at a hanging mercury drop electrode, allow sensitive and reliable measurements of labile metals in surface sea water. Total metal concentrations are determined after acidification to pH 1.5 with hydrochloric acid. The results are compared with those obtained with atomic absorption spectrometry and with differential-pulse anodic stripping voltammetry at conventional mercury electrodes. Satisfactory results were obtained for a reference sea water.     

Determination of sulphur(II) compounds by flow injection analysis with application of the induced iodine/azide reaction

Sulphur(II) compounds that rapidly induce the iodine/azide reaction are determined by injection of 10-μl samples into an iodine/azide solution at a flow rate of 1.4 ml min^?1. Iodine consumption in the induced reaction is detected by biamperometry with platinum electrodes. The linear calibration ranges depend on the concentration of iodine in the iodine/azide solution pumped. The detection limit for thiosulphate, 2-mercapto-pyrimidine, 2-thiouracil, 2-thiobarbituric acid or 6-mercaptopurine is 0.1 mg l^?1 and for sulphide, cysteine, thiourea or glutathione is 0.2 mg l^?1 in the injected sample.     

Determination of Mo and V in multiphase gasoline emulsions by electrothermal atomic absorption spectrometry

This paper proposes an alternative analytical method using electrothermal atomic absorption spectrometry to determine Mo and V in multiphase gasoline emulsions. Samples were prepared by mixing gasoline with a nitric acid solution (0.1% v/v) and two cationic surfactants. The mixture was sonicated, resulting in an emulsive system. Calibration was done by using the aforementioned solutions with added analyte. The detection limits (3σ) of Mo and V were 0.9 μg l^− 1 and 4.7 μg l^− 1, respectively. The accuracy and precision of the proposed method were evaluated by the analysis of samples spiked with metallo-organic standard and the relative standard deviation obtained ranged from 1.2% to 4.4% in samples spiked with 2 μg l^− 1 of each metal. The recovery rates varied from 91.2% to 101.6%. The proposed method was applied to determine Mo and V in samples of gasoline from different gas stations.     

Determination of very low levels of inorganic and organic mercury in natural waters by cold-vapor atomic absorption spectrometry after preconcentration on a chelating resin

Inorganic and organic mercury at ng l^?1 levels in fresh waters are collected simultaneously on a column of a dithiocarbamate-treated resin and quantitatively eluted with slightly acidic aqueous thiourea solution. Mercury vapor is generated from inorganic mercury by reduction with alkaline SnCl₂ solution, and from inorganic and organic mercury with a CdCl₂SnCl₂ solution, for determination by cold-vapor atomic absorption spectrometry. The range of determination is 0.2–5,000 ppt (ng l^?1) for 20-l water samples.     

Automated direct determination of chromium in blood and urine by electrothermal atomic absorption spectrometry

A simple direct procedure for the determination of chromium in whole blood and urine by graphite-furnace atomic absorption spectrometry is described. Whole blood samples are diluted with 0.1% Triton-X solution before injection, whereas urine samples are injected directly. Calibration is done by direct comparison against matrix-matched standards. Between-run precision is 5.4% at 154 nmol l^?1 for urine and 3.6% at 142 nmol l^?1 for blood. The detection limits are 3.8 nmol l^?1 for urine and 11.5 nmol l^?1 for blood, each for a 20μl sample. The calibration range extends up to 770 nmol l^?1 for both blood and urine. This allows the determination of chromium in both occupationally exposed and unexposed groups. The graphite-furnace conditions for each matrix are similar. Elimination fo sample pretreatment minimizes the risk of contamination and allows a rapid sample throughput of 50–60 samples per day. The methods described are particularly suited for the screening and surveying of populations occupationally exposed to chromium.