Preconcentration of inorganic selenium species (Se (IV) and Se (VI)) in an alumina filled microcolumn and on-line determination by hydride generation atomic absorption spectrometry

A flow injection system has been developed consisting of on-line preconcentration of selenium species in a microcolumn filled with activated alumina, reduction of Se(VI) to Se(IV) and determination by HG-AAS. When 0.01 mol/L HNO₃ is used both as carrier and activation reagent for the alumina microcolumn, up to 150 ng of Se(IV) and Se(VI) can be preconcentrated and quantitatively eluted by 500 L of 2 mol/L NH₃. The preconcentration factor is 50 when 25 mL of sample is used. The detection limit is about 6 ng/L, the precision is 5% for low concentrations such as 150 ng/L and 3% at high concentrations such as 120 ng/mL. The proposed method is suitable for natural water samples and inorganic Se speciation can be performed by determining Se(IV) and total selenium [Se(VI) is evaluated from the difference].     

Cr(III) and Cr(VI) on-line preconcentration and determination with high performance flow flame emission spectrometry in natural samples

Methods for the on-line chromatographic preconcentration of Cr(III) and Cr(VI) have been developed. Cr(VI) has been preconcentrated on an RP C18 silica based column with tetrabutylammonium-bromide (TBABr) as ion-pairing agent. Specially for Cr(III) a new and effective preconcentration technique based on the sorption of Cr(III)-ions in a C18 column in presence of KH-phthalate has been developed. The efficiency of sample introduction into the atomic emission spectrometer could be improved by hydraulic high pressure nebulization. For the detection of chromium the acetylene/N₂O flame has been used as a powerful emission spectrometric source. Applying these steps the detection limit (3) could be improved to 25 pg/mL for Cr(III) and to 20 pg/mL for Cr(VI). The method has been applied for the chromium speciation in natural water samples.     

Analysis of high-purity reagents using automatic on-line column preconcentration-separation and electrothermal atomic absorption spectrometry

Summary A fully automatic flow-injection on-line column preconcentration and separation procedure for electrothermal atomic absorption spectrometry is described for the determination of cadmium and lead in high-purity reagents. A microcolumn with 9 L of solid sorbent, introduction of air prior to elution, and use of methanol as the eluent made it possible to elute the sorbed analyte quantitatively with only 80 L of solvent. The total eluate volume was transferred into the graphite tube which was pre-heated to 80°C using a flow rate of 0.08 mL min^–1 which allowed the solvent to evaporate in part during eluate introduction. The efficiency of the total procedure was 0.63 and 0.65, and the enrichment factor was 62 and 64 for cadmium and lead, respectively, compared with the direct introduction of 30 L of an aqueous solution. The sample throughput was 13 h^–1 for a sample loading time of 60 s and the detection limits (3 ) were 0.7 and 4.5 ng L^–1 for cadmium and lead, respectively. The relative standard deviation of the entire procedure in the optimum working range was typically around 3% (n=6). A number of high purity (suprapure) and analytical grade (pro analysi) reagents were analyzed, and spiking experiments resulted in recoveries of 97–104%.Dedicated to Professor Dr. Wilhelm Fresenius on the occasion of his 80th birthdayOn leave from Jiangsu Institute of Petrochemical Technology, Changzhou, Jiangsu, China     

Kinetic Spectrophotometric Determination of Total Iron in Natural Water by Flow Injection Analysis Using On-Line Preconcentration

A new flow injection catalytic spectrophotometric method for on-line preconcentration and determination of total iron in natural water is described. The method is based on a combination of iron-catalyzed oxidation of diaminoditolyl by potassium bromate and the use of on-line preconcentration of iron onto 8-hydroxy-quinoline immobilized on silica gel. The corresponding calibration graph is linear over the range of 2.0–110ngmL^–1 for Fe(III) using a time-based technique for 5min preconcentration. The relative standard deviation of 11 measurements of 60ngmL^–1 Fe(III) was 0.67%. The method was applied to the determination of iron in natural water. The results obtained by the proposed method were compared with those obtained by ICP-AES. The t-test showed no significant differences between the two methods at a confidence level of 95%.     

碳纳米管分离富集-原子荧光光谱法测定化妆品中的痕量汞

建立了多壁碳纳米管分离富集-原子荧光光谱法测定化妆品中痕量汞(Hg2+)的新方法,考察了Hg2+在碳纳米管填充固相萃取柱上的吸附行为,优化出了最佳吸附和洗脱条件。优化后的实验条件：pH4,流速2.0 mL/min,络合剂1gL吡咯烷二硫代氨基甲酸铵(APDC)溶液用量1.0 mL;洗脱剂采用6 mol/LHNO3,流速...     

Flow Injection Semi-online Preconcentration Graphite Furnace Atomic Absorption Spectrometry for Determination of Cadmium, Copper and Manganese

IntroductionGraphite furnace atomic absorption spectrome-try (GFAAS) is one of the most sensitive tech-niques for the determination of various elementswith detection limits in the range ofμg/ L to ng/ L.Despite the impressive detection power of the tech-nique,GFAAS can tbe routinely used to make di-rect analysis of some real samples with complexcomposition[1] . This is due to the matrix interfer-ence and/ or insufficient detection power. Conse-quently,separation and preconcentration proc…     

Determination of La,Eu and Yb in Water Samples by Inductively Coupled Plasma Atomic Emission Spectrometry After Solid Phase Extraction of Their 1-Phenyl-3-Methyl-4-Benzoylpyrazol-5-one Complexes on Silica Gel Column

A simple preconcentration method has been developed for the determination of trace amounts of rare earth elements (La, Eu, and Yb) in natural water samples by inductively coupled plasma atomic emission spectrometry (ICP-AES). Preconcentration of La, Eu, and Yb was achieved by sorption of their 1-phenyl-3-methyl-4-benzoylpyrazol-5-one (PMBP) complexes on a silica gel column at pH 5 and then eluting with 1.0molL^–1 HNO₃. For the preconcentration of 100mL of aqueous solution, an enrichment of 100 was obtained for all analytes, and the detection limits for La, Eu and Yb were 82, 34 and 45ngL^–1, respectively. The accuracy of this method was demonstrated by analyzing a standard reference material. The method has been successfully applied to the determination of La, Eu and Yb in lake water and synthetic seawater.     

Comparative characterization of two techniques for selenium(IV) preconcentration on a film mercury electrode with the use of an automated solution replacement system without circuit disconnection

Two versions of selenium(IV) preconcentration and determination on a mercury film electrode (MFE) by cathode stripping voltammetry with an automated solution replacement system without circuit disconnection are compared. In one version, selenium(IV) is preconcentrated together with copper(II); in the other, selenium is preconcentrated on a copper-modified MFE. Under optimum conditions (against the 0.1 M HCl background at selenium electrolysis potentials from ?350 to ?400 mV and electrolysis times of 180–300 s), calibration curves for both selenium preconcentration versions are linear over the concentration ranges from 2.5 to 20 μg/L and from 50 to 250 mg/L. The selenium peak heights are well reproduced in both cases (in the range of the concentrations studied, S _r lie in the range from 0.02 to 0.05). Sequential copper and selenium preconcentration is more convenient: there is no need to add copper to each analyzed solution, and it is possible to optimize selenium preconcentration parameters (solution composition, electrolysis potential, and electrolysis time) regardless of the copper preconcentration parameters.     

Surface modification by calcium ions—Effect on chromatographic properties of silica

Summary A liquid chromatographic method incorporating column-switching and fluorimetric detection for the determination of triamterene in untreated urine, is described. The urine samples (5 L) were directly introduced onto an Hypersil ODS-C18, 30 m (20 mm×2.1 mm I.D.) pre-column. Polar urinary compounds were removed by flushing the pre-column with water for 1 min, and the analyte was then switched onto an HP-LiChrospher RP C18,5 m (125 mm×4mm ID) analytical column using an acetonitrile/phosphate buffer gradient elution. Fluorescence detection was performed at 230 nm excitation and 430 nm emission wavelengths. The recovery of drug was 102±2% in the 0.10–20.0 g/mL concentration range, the limit of detection being 5 ng/mL. A validation of the usefulness of this procedure was accomplished by analysing urine extracts obtained from real samples.Hypersil ODS is not a product of Merck, Germany. Please give supplier (p. 5).     

Flow Injection Semi-online Sorbent Extraction Preconcentration for Graphite Furnace Atomic Absorption Spectrometry

A micro-flow injection sorbent extraction preconcentration system was combined with a graphite furnace atomic absorption spectrometer. The combination results in an integrated system for the determination of trace amounts of heavy metals. Silica bonded with octadecyl functional groups (C₁₈) was used as a sorbent in a 15-μL conical microcolumn. The metals to be determined were preconcentrated as diethyl dithiocarbamate chelates onto the column for 60 s and then rinsed with deionized water and eluted with 40 μL of ethanol. Compared with direct injection of 40 μL of aqueous sample solution, enrichment factors of 30, 32, and 29 and detection limits (3ς) of 7.8, 12.8, and 3.9 ng/L for cobalt, nickel, and lead, respectively, were obtained with 60-s sample loading at 3.0 mL/min for sorbent extraction, 40 μL of eluate injection, and peak area measurement. The results obtained for trace amounts of cobalt, nickel, and lead in reference materials showed that there were no significant differences between the certified and determined values.     

Preconcentration technique for nonylphenol using cellulose cotton with homogenous liquid–liquid extraction for liquid chromatographic analysis

A powerful preconcentration method for nonylphenol (NP) has been developed for liquid-chromatography by combining the use of cellulose cotton (solid-phase extraction) with homogeneous liquid–liquid extraction. A 100 ml of sample solution was preconcentrated using cotton, and the eluate obtained (acetonitrile; 5 ml) was further preconcentrated to 50 l within 10 min using a homogeneous liquid–liquid extraction method (volume ratio, 2,000-fold; 100 ml 50 l). The sample concentration increases from preconcentration was 1,599-fold, and NP was extracted into the sedimented phase at 80%. The proposed method was applied to high performance liquid chromatography with fluorescence detection (FL/HPLC); the lowest determination limit obtained was 1.0×10^–9 mol l^–1.     

Multi-element preconcentration from technical alkali silicates

Summary After evaporation of the matrix SiO₂ as SiF₄ traces of Ag, Au, Bi, Cd, Co, Cu, Fe, Mn, Mo, Ni, Pb, Pd, Sn, Tl, V and Zn can be preconcentrated from water glasses with recoveries R_s 95% by collector precipitation with hexamethyleneammonium - hexamethylenedithiocarbamate and indium as collector element (Se and Te with varying recoveries between 90 and 95%). The relative standard deviation of the combined method of sample decomposition, preconcentration and AAS-determination is generally about 5% (n=17); the detection limits were found to be between 0.01 and 2 g·g^–1 (3s, n=24). The accuracy of the determination step was verified by analysing the trace concentrates by AAS, ICP-OES and TR-XFS.     

Solid-Phase Extraction and Spectrophotometric Determination of Molybdenum(VI) in Soil and Plant Samples as a Mo(V)-Thiocyanate Complex

A method for the preconcentration and determination of molybdenum(VI) in soil and plant samples using Amberlite XAD-7 resin and spectrophotometry is proposed. Molybdenum was preconcentrated as its Mo(V)-thiocyanate complex using a column containing Amberlite XAD-7 resin and determined spectrophotometrically at 461.0nm in acetone after elution. We investigated several parameters that affect the recovery of molybdenum, such as acidity, amount of reducing and complexing agents, flow rates, volume of sample solution, type and amount of eluent, and the presence of diverse ions. The limit of detection of the proposed method was 38µgL^–1 of molybdenum. The recovery of molybdenum was 98.25±0.05 at 95% confidence level. The highest preconcentration factor was 100 for 250mL of sample volume. The proposed method was applied to soil and plant samples, and molybdenum was determined with a relative error of <3.5%.     

Filters for the Preconcentration of Elements from Solutions

The main techniques for the preconcentration of elements on thin-layer filters are considered: sorption on filters with noncovalently immobilized reagents, bonded groups, and mechanically fixed sorbents and the extraction of elements on filters as poorly soluble and polymeric forms previously formed in solution. The matrix of the filters is cellulose, synthetic polymers of the linear and branched structures, synthetic fibers, reversed-phase silica gels, foamed polyurethanes, etc. The variation of the nature of the bonded group or the reagent introduced into the solution, the matrix material, and the technique for the immobilization of groups provides the preconcentration of elements with regard to the peculiarities of test materials and the method for the subsequent determination of elements. Methods for the determination of elements in different samples including preconcentration on filters are considered.     

Carbon Paste Electrode Bulk-Modified with the Conducting Polymer Poly(1,8-Diaminonaphthalene): Application to Lead Determination

Carbon paste electrodes modified with conducting polymers for sensitive and selective determination of lead are presented. A novel method for generating a reproducible polymer-coated electrode surface is developed. We prove that 1,8-diaminonaphthalene (1,8-DAN) mixed with a carbon paste electrode leads to a conducting polymer in acidic medium while, in the same medium, this polymer is known to be non-conducting on platinum electrode. The electrode behaviour of poly(1,8-DAN), electropolymerised into carbon paste, was investigated by cyclic voltammetry in the presence of the ferri-ferrocyanide couple.A carbon paste electrode modified with poly(1,8-DAN) was used to determine Pb²⁺ in aqueous solutions. Pb²⁺ ions were firstly complexed and then electrochemically deposited by a potential step to –0.9V. The accumulated lead after reduction was anodically stripped by differential pulse voltammetry. Different parameters, such as pH of the solution, preconcentration time, and electropolymerisation procedures were studied.For a preconcentration time of ten minutes, the calibration graph was linear from 40 to 2070ngmL^–1 with r²=0.998. The detection limit was found to be 30ngmL^–1, and the relative standard deviation was 6%.     

Effect of organized media on the chromatographic and electrophoretic determination of pharmaceutical preparations in biological samples

Procedures were developed for the simultaneous determination of endogenous and exogenous steroids in biological fluids by reversed-phase high-performance liquid chromatography (RP HPLC), capillary zone electrophoresis, and micellar electrokinetic chromatography (MEKC) using components of organized media (micelles of sodium dodecyl sulfate, β-cyclodextrin, sulfo-β-cyclodextrin, and carbamide). The detection limits were 50 and 500 ng/mL without preconcentration and 3–5 and 5–10 ng/mL with preconcentration for RP HPLC and MEKC, respectively. The time of separation was 30 and 10 min, and the total time of analysis (including preconcentration and the conditioning of a column or a capillary) was 80 and 90 min for RP HPLC and MEKC, respectively.     

微波浓缩/离子色谱法测定印刷电路板表面的7种痕量无机阴离子

建立了印刷电路板上7种痕量无机阴离子(F-、NO-2、Cl-、Br-、NO-3、PO3-4、SO2-4)的微波浓缩/离子色谱测定方法.印刷电路板样品经纯水提取,微波浓缩后,在Ionpac AS23分析柱上,以4.5 mmol/LNa2 CO3+0.8 mmol/L NaHCO3为淋洗液,流速为1.0 mL/min.结果...     

Determination of Cd, Co, Cr, Cu, Fe, Mn, Ni and Pb in natural waters, alkali and alkaline earth salts by electrothermal atomic absorption spectrometry after preconcentration by column solid phase extraction

Methods are described for the determination of trace and ultra trace amounts of Cd, Co, Cr, Cu, Fe, Mn, Ni and Pb in natural waters, alkali and alkaline earth salts. Separation and preconcentration of trace metals is achieved by a column solid phase extraction procedure using silica gel modified with derivatives of dithiocarbamates — Na-DDTC (sodium diethyldithio-carbamate and HMDTC (ammonium hexamethylene-dithiocarbamate) as column packing material. The influence of the sorbent preparation procedure on the degree of sorption of the trace analytes is examined for different pH values of the sample solution. Isobutylmethyl ketone (IBMK) is proposed as an effective eluent for quantitative elution of retained metal ions. Optimal instrumental parameters for ETAAS determination of preconcentrated elements in organic eluate are presented. Practical application of sorbents in analysis of natural waters and alkali and alkaline earth salts is demonstrated. Proposed preconcentration procedure combined with ETAAS determination of trace analytes allows the determination of 0.04 g l^–1 Cd, 0.1 g l^–1 Cr, Cu, and Mn and 0.3 g l^–1 Co, Fe, Ni and Pb in natural waters and 1.10^–7% Cd, 3.10^–7% Cr and Mn, 7.10^–7% Co, Ni and Pb and 2.10^–6% Cu and Fe in alkali and alkaline earth salts.     

Use of Hypercrosslinked Polystyrene for the Determination of Pyrocatechol, Resorcinol, and Hydroquinone by Reversed-Phase HPLC with Dynamic On-line Preconcentration

Adsorption isotherms of pyrocatechol, resorcinol, and hydroquinone on hypercrosslinked polystyrene MN-200 are described by the Langmuir equation; distribution coefficients of these compounds are 1500, 550, and 370 mL/g, respectively; breakthrough capacities are 15.3, 11.2, and 11.3 mg/g, respectively. The comparison of hypercrosslinked polystyrene with other sorbents in the efficiency of the dynamic preconcentration of hydroxyphenols demonstrated its advantages. A procedure is proposed for the determination of pyrocatechol, resorcinol, and hydroquinone in water by high-performance liquid chromatography with dynamic on-line preconcentration on a concentrating column instead of the injector loop, which provides the determination of these compounds at concentrations down to 2–3 g/L. The accuracy of the procedure was verified by the added–found method with a water sample.     

Determination of five priority haloacetic acids by capillary electrophoresis with contactless conductivity detection and solid phase extraction preconcentration

A sensitive capillary electrophoretic separation method with contactless conductivity detection (C4D) for analysis of five priority haloacetic acids (HAA5) is presented. The analytes were baseline separated in an electrolyte composed of 20 mM 2-(N-Morpholino) ethanesulfonic acid (MES), 20 mM L-histidine (HIS), and 30 μM cetyltrimethylammonium bromide (CTAB) at pH 6.0 in less than 4 min. A simplified solid-phase extraction (SPE) preconcentration procedure on highly cross-linked polystyrene-divinylbenzene (PS-DVB) type sorbent was developed and optimized with respect to short preconcentration time. HAA5 from a 25-mL sample aliquot of tap and swimming pool water could be preconcentrated in less than 5 min using an in-house made SPE column with recoveries ranging from 23 to 98%. Combining the SPE preconcentration procedure with capillary electrophoretic analysis, the attained limits of detection were between 6.1 and 12.2 μg/L with total analysis time of less than 10 min.