Trace analysis of bromate and bromide with ion chromatography on coated reversed phase materials

 The ion-chromatographic method for trace analysis of bromate and bromide presented in this paper is based on coating of reversed phase (RP) material with an ionogenic agent, tetrakisdecylammonium bromide, to obtain a pseudo ion-exchange column. The analysis is carried out with usual HPLC pump and UV-detection near 200 nm. Some commercially available RP materials were tested for the coating procedure. The differences between the reversed phases are not significant. All HETP values are calculated between 0.02 and 0.14 mm. The calibration, the sensitivity of the method and the long-time stability of the coated column were tested with one selected RP material. It is shown that the simultaneous trace analysis of bromate and bromide in surface and drinking waters with chloride concentrations up to 50 mg/L is possible without any clean-up on Ag precolumns. A comparison of performance data with a determination method for bromate and bromide employing a commercially available equipment demonstrates the efficiency of the new technique. Received: 23 February 1996/Received: 10 May 1996/Accepted: 14 May 1996     

Bromide/bromate speciation by NTI-IDMS and ICP-MS coupled with ion exchange chromatography

 Two different mass spectrometric methods, negative thermal ionization isotope dilution mass spectrometry (NTI-IDMS) and inductively coupled plasma mass spectrometry (ICP-MS), off-line and on-line coupled with anion exchange chromatography, have been developed for simultaneous bromide and bromate determinations in water samples. The detection limits of these methods are in the range of 0.03–0.09 μg/L using a 50 mL sample.The results are independent of the content of other anions, which could be demonstrated by the analyses of six mineral waters containing chloride and sulfate of up to 160 mg/L and 1500 mg/L, respectively. Bromide has been analyzed by the NTI-IDMS method in the range of 10–500 μg/L and bromate in the range of 1–50 μg/L with relative standard deviations of 0.3–1.2% and 0.4–6%. Quantification for the ICP-MS method was carried out by the standard addition technique, which resulted in relative standard deviations of 5.5% for bromide at the 500 μg/L level and of 13% for bromate at the level of about 3 μg/L. These results are compared with those described in the literature for ion chromatographic (IC) and other methods and those obtained in this work by IC using UV detection, which allows high concentrations of chloride in the bromate fraction. The detection limits of this IC method are 6 μg/L for bromide and 30 μg/L for bromate. NTI-IDMS and ICP-MS therefore fit the recommendations of the European Union (detection limit<2.5 μg/L; precision and accuracy better than 25% at the 10 μg/L level) for methods analyzing the carcinogenic bromate much better than IC and other methods applied up to now. As a definitive but time consuming method, NTI-IDMS is preferably applicable as a calibration technique, whereas ICP-MS, with relatively short analysis times, due to on-line coupling with chromatography, can be used as a sensitive and powerful routine method for trace bromide and bromate species in water samples. Received: 5 July 1996/Accepted: 7 August 1996     

Bromide/bromate speciation by NTI-IDMS and ICP-MS coupled with ion exchange chromatography

 Two different mass spectrometric methods, negative thermal ionization isotope dilution mass spectrometry (NTI-IDMS) and inductively coupled plasma mass spectrometry (ICP-MS), off-line and on-line coupled with anion exchange chromatography, have been developed for simultaneous bromide and bromate determinations in water samples. The detection limits of these methods are in the range of 0.03–0.09 μg/L using a 50 mL sample.The results are independent of the content of other anions, which could be demonstrated by the analyses of six mineral waters containing chloride and sulfate of up to 160 mg/L and 1500 mg/L, respectively. Bromide has been analyzed by the NTI-IDMS method in the range of 10–500 μg/L and bromate in the range of 1–50 μg/L with relative standard deviations of 0.3–1.2% and 0.4–6%. Quantification for the ICP-MS method was carried out by the standard addition technique, which resulted in relative standard deviations of 5.5% for bromide at the 500 μg/L level and of 13% for bromate at the level of about 3 μg/L. These results are compared with those described in the literature for ion chromatographic (IC) and other methods and those obtained in this work by IC using UV detection, which allows high concentrations of chloride in the bromate fraction. The detection limits of this IC method are 6 μg/L for bromide and 30 μg/L for bromate. NTI-IDMS and ICP-MS therefore fit the recommendations of the European Union (detection limit<2.5 μg/L; precision and accuracy better than 25% at the 10 μg/L level) for methods analyzing the carcinogenic bromate much better than IC and other methods applied up to now. As a definitive but time consuming method, NTI-IDMS is preferably applicable as a calibration technique, whereas ICP-MS, with relatively short analysis times, due to on-line coupling with chromatography, can be used as a sensitive and powerful routine method for trace bromide and bromate species in water samples. Received: 5 July 1996/Accepted: 7 August 1996     

Determination of copper by anodic stripping voltammetry on a glassy carbon electrode using a continuous flow system

 A successful flow-through system was developed for trace analysis of copper using DPASV with a glassy-carbon electrode. Periodical chemical regeneration of the electrode with a 1 mol/L NaOH solution increased sensitivity and precision. The method was shown to be applicable with a detection limit of 0.56 μg/L, with a determination time of less than 7 min per measurement (without deaeration time). The drawback of the system is the 10 min deaeration time. The system gave an accuracy of 0.090±0.005% for a certified reference material of low alloy steel containing 0.090±0.004% Cu. Applicability to various fresh water samples with a Cu content between 1.57 and 13.11 μg/L with an RSD<2.36% is illustrated. Received: 11 March 1996/Revised: 1 July 1996/Accepted: 4 July 1996     

Determination of copper by anodic stripping voltammetry on a glassy carbon electrode using a continuous flow system

 A successful flow-through system was developed for trace analysis of copper using DPASV with a glassy-carbon electrode. Periodical chemical regeneration of the electrode with a 1 mol/L NaOH solution increased sensitivity and precision. The method was shown to be applicable with a detection limit of 0.56 μg/L, with a determination time of less than 7 min per measurement (without deaeration time). The drawback of the system is the 10 min deaeration time. The system gave an accuracy of 0.090±0.005% for a certified reference material of low alloy steel containing 0.090±0.004% Cu. Applicability to various fresh water samples with a Cu content between 1.57 and 13.11 μg/L with an RSD<2.36% is illustrated. Received: 11 March 1996/Revised: 1 July 1996/Accepted: 4 July 1996     

Distillation, on-line RP C18 preconcentration and HPLC-UV-PCO-CVAAS as a new combination for the determination of methylmercury in sediments and fish tissue

 Distillation as a way of sample digestion has been combined with on-line RP C18 preconcentration and HPLC-UV-PCO-CVAAS (high performance liquid chromatography – ultra violet – post column oxidation – cold vapour atomic absorption spectrometry) for the determination of methylmercury at background levels in sediments, soils and fish tissue. To prove the accuracy of this method, it was applied to sediment and fish tissue reference materials. The results correspond with the reference values within their error ranges. Excellent recoveries (92–95%) were obtained for the sediment samples by means of the standard addition method. The standard deviations of the sediment samples were within an acceptable range (7.2–12.5%), those of the fish samples were substantially lower (3.4–5.0%). The detection limit is 0.04 ng/g for 1 g sample weight. Received: 23 November 1995/Revised: 16 April 1996/Accepted: 20 April 1996     

Determination of Fe-55 and Ni-63 using semi-preparative ion chromatography – a feasibility study

 The feasibility of semi-preparative high-performance ion chromatography (HPIC) for the analysis of the activation products Fe-55 and Ni-63 in samples of different sources was studied. A mixed anion/cation exchanger column was applied to the separation of Fe(III), Ni(II) and Co(II) using 1 mmol/L PDCA-solution as an eluent. After fractionation of the eluate, Fe(III)- and Ni(II)-fractions were analysed by low-level liquid scintillation counting (LSC). The method was applied to the analysis of corrosion products originating from the primary circuit of a shut-down nuclear power plant. The limits of detection are dependent on the loading of metal ions on the column and are therefore given in terms of specific activities. For a typical sample composition they were found to be 0.011 Bq per mg Fe for Fe-55 and 0.054 Bq per mg Ni for Ni-63. An assessment of semi-preparative HPIC connected to off-line and on-line LSC as compared with standard radiochemical procedures is given. Received: 10 May 1996 / Revised: 2 July 1996 / Accepted: 6 July 1996     

An optosensor for tryptophan with C18 silica gel as a substrate

 A flow-through optosensor for tryptophan with C18 silica gel as a substrate is proposed. It has been developed in conjunction with a flow-injection analysis system and is based on the retention of tryptophan on the C18 column and the enhancement of its fluorescence. The detection limit is 25 ng mL^-1 with a relative standard deviation of 2.9% for 7 determinations of 10 μg mL^-1 of tryptophan. Most of the common species do not interfere. The method has been successfully applied to a pharmaceutical preparation. Received: 8 July 1996/Revised: 26 September 1996/Accepted: 30 September 1996     

HPLC determination of collectors used for the flotation of heavy metal minerals

 A reversed-phase HPLC-method for the separation of mixtures of collectors for the flotation of heavy metal minerals is described. It is based on a Nucleosil 5C18 column, isocratic elution and UV-detection at 238 nm. The mobile phase is methanol-water-5% phosphoric acid (40:60:4, v/v). The method is applied to the determination of six collectors in aqueous solutions from flotation processes. The relative standard deviations are 1.6–3.2% in the concentration range 2–10 mg/L. The detection limits are 1 μg/L for 8-hydroxyquinoline, dimethylglyoxime and salicylic acid, 2 μg/L for salicylhydroxamic acid and 5 μg/L for benzenetriazol and salicylaldoxime, respectively. Received: 19 April 1996/Revised: 14 August 1996/Accepted: 23 August 1996     

Cyclodextrin-based optosensor for the determination of quinine

 A flow-through optosensor for quinine is described. It has been developed in conjunction with a flow-injection analysis system and uses immobilized β-cyclodextrin as the sensing agent. The detection limit for quinine was 0.20 ng ml^-1 with a relative standard deviation of 2.1% for the determination of 0.05 μg ml^-1 (n=7) of quinine. The method has been successfully tested for the determination of quinine in some pharmaceutical preparations. Received: 4 June 1996 / Revised: 23 August 1996 / Accepted: 24 August 1996     

Cyclodextrin-based optosensor for the determination of quinine

 A flow-through optosensor for quinine is described. It has been developed in conjunction with a flow-injection analysis system and uses immobilized β-cyclodextrin as the sensing agent. The detection limit for quinine was 0.20 ng ml^-1 with a relative standard deviation of 2.1% for the determination of 0.05 μg ml^-1 (n=7) of quinine. The method has been successfully tested for the determination of quinine in some pharmaceutical preparations. Received: 4 June 1996 / Revised: 23 August 1996 / Accepted: 24 August 1996     

PLS-UV spectrophotometric method for the simultaneous determination of paracetamol, acetylsalicylic acid and caffeine in pharmaceutical formulations

 A simple and fast analytical procedure is proposed for the simultaneous determination of paracetamol, acetylsalicylic acid and caffeine in pharmaceuticals by means the partial least square treatment of the spectrophotometric absorbance data between 216 and 300 nm, taken at 5 nm intervals. The method involves the use of 8 standard mixtures of the three compounds assayed, considered at two concentration levels, and the measurement of the absorbance of samples in a 20% (v/v) ethanol in water solution previously filtered. In the analysis of real and synthetic samples precise and accurate values were obtained by the aforementioned procedure, providing in all cases variation coefficients and accuracy errors lower than 5% which agree with the tolerance level established by the pharmacopoeia for this kind of samples which is ±10%. Received: 10 May 1996 / Revised: 8 July 1996 / Accepted: 12 July 1996     

Solvent extraction of rare-earth metals with bis(2-ethylhexyl)phosphinic acid

 The extraction behavior of tervalent rare-earth metals (Ln) using a heptane solution containing bis(2-ethylhexyl)phosphinic acid (PIA-8, HR) from 0.1 mol/dm³ sodium perchlorate media was studied. The pH_0.5 values and separation factors obtained were compared among the metals. The stoichiometry of the extracted species and the extraction constants for the present aqueous/heptane system were determined by slope analysis. It is demonstrated that the rare-earth metals were extracted as monomers LnR₃⋅mHR (m=3, 4, 5 or 6), and the extracted species could be stripped into a relatively low concentrated hydrochloric acid. PIA-8 was found to be the most selective extractant for the mutual separation of rare-earth metals among the other phosphinic acids reported. Received: 27 February 1996/Revised: 13 May 1996/Accepted: 21 May 1996     

Anionic cartridge preconcentrators for inorganic arsenic, monomethylarsonate and dimethylarsinate determination by on-line HPLC-HG-AAS

 Preconcentration anionic cartridges in combination with hyphenated FI-HG-AAS and HPLC-HG-AAS have been evaluated for the preconcentration and quantification of total toxic arsenic and of inorganic arsenic, monomethylarsonate and dimethylarsinate species, respectively. Optimum retention and elution parameters of the species on the anionic cartridges are evaluated and the quality parameters of the analysis are reported. The detection limits for the arsenic species under study range from 0.1 μg L^-1 to 0.6 μg L^-1. The proposed method was successfully applied to the determination of arsenic species in spiked fresh water. Received: 2 April 1996/Revised: 22 July 1996/Accepted: 25 July 1996     

Separation of ADAM derivatives of carnitine and acyl-carnitines by capillary electrophoresis

 The separation of carnitine, acetylcarnitine and palmitoylcarnitine as ADAM (9-anthryldiazo-methane) derivatives was performed using capillary electrophoresis. A buffer system with 90% methanol and various amounts of phosphoric acid and micelle forming SDS was optimized with respect to the best resolution of the carnitine derivatives. A detection limit of 10 μmol/l or 32 ng carnitine was determined by laser induced fluorescence detection. Under optimized conditions low carnitine contents in acylcarnitine standards have been determined. Received: 30 May 1996/Accepted: 17 June 1996     

Separation of trace heavy metals from silver matrix by solid – liquid extraction for graphite-furnace atomic absorption spectrometry

 A silver sample (50–300 mg) was dissolved in 6 mol/l nitric acid and mixed with 6 mol/l hydrochloric acid to form silver chloride. The solution was evaporated to dryness and the residue was treated ultrasonically in 0.1 mol/l nitric acid for the extraction of trace impurities from the silver chloride. Traces of iron, copper, lead and bismuth were recovered in greater than 94% yields, though considerable amounts of cadmium were not extracted due to the strong occlusion in the silver chloride. The separation factor for the silver was about 10^-4; hence the trace heavy metals were immediately determined by graphite-furnace atomic absorption spectrometry without any interference. The validity of the method was confirmed by the analysis of certified reference material. The proposed method is simple and allows the detection of as little as 10 ng/g levels in silver samples. Received: 13 January 1995/Accepted: 29 March 1995     

Use of microwave plasma torch atomic emission spectrometry for the determination of silicon

 A method for the elimination of matrix effects was developed for the determination of trace amounts of silicon by microwave plasma torch atomic emission spectrometry (MPT-AES). The sample solution was introduced into the MPT with a pneumatic nebulizer (PN). When Ar was used as both carrier and support gas, a detection limit of 10.8 ng/ml was obtained. The precision was 4.2% (RSD). The characteristics of the emission spectrum of silicon in MPT was studied in detail. The interference of some concomitant cations with the silicon emission was eliminated by incorporation of a cation-exchange column into the flow injection system. The method has been applied to analyze some practical samples and the results obtained are satisfactory. Received: 23 October 1995/Revised: 16 April 1996/Accepted: 20 April 1996     

Separation of ADAM derivatives of carnitine and acyl-carnitines by capillary electrophoresis

 The separation of carnitine, acetylcarnitine and palmitoylcarnitine as ADAM (9-anthryldiazo-methane) derivatives was performed using capillary electrophoresis. A buffer system with 90% methanol and various amounts of phosphoric acid and micelle forming SDS was optimized with respect to the best resolution of the carnitine derivatives. A detection limit of 10 μmol/l or 32 ng carnitine was determined by laser induced fluorescence detection. Under optimized conditions low carnitine contents in acylcarnitine standards have been determined. Received: 30 May 1996/Accepted: 17 June 1996     

Rapid determination of lead, cadmium and thallium in cements using electrothermal atomic absorption spectrometry with slurry sample introduction

 A method is proposed for the determination of Pb, Cd and Tl in cements by ETAAS. The samples are suspended in a medium containing 10% v/v ethanol and 1% v/v both conc. nitric and hydrofluoric acids and are directly introduced into the electrothermal atomizer. The drying stage is performed by programming a 400 °C temperature, a ramp time of 5 s and a hold time of 30 s on the power supply to the atomizer. No ashing step is used. Atomization is carried out at 2100, 1800 and 1700 °C for Pb, Cd and Tl, respectively. For Cd determination, ammonium dihydrogen phosphate is added to the suspension medium. No modifier other than hydrofluoric acid is required for the Pb and Tl determination. It is shown that the results obtained by using direct calibration with aqueous standards for five commercial samples agree with those found by means of the standard additions method. Received: 29 March 1996/Revised: 24 May 1996/Accepted: 30 May 1996     

Solid-phase spectrophotometric microdetermination of iron with ascorbic acid and ferrozine

 A very sensitive and selective method for the determination of trace amounts of iron has been developed, based on the reduction of Fe(III) to Fe(II) by ascorbic acid, followed by chromogenic chelation of Fe(II) with ferrozine. The complex Fe(II)-ferrozine is easily sorbed on a dextran-type anion-exchange gel packed in a 1 mm cell, and the absorbance of the gel is measured directly at 569 and 800 nm. The extended linear range of the determination is 0.5–10 ng ml^-1 of iron (apparent molar absorptivity=4.4×10⁷ l mol^-1 cm^-1) and the precision (RSD) 1.3% for a concentration of 5 ng ml^-1 of iron (n=10). The detection limit for a sample volume of 1000 ml, using 0.040 g of anion-exchanger, corresponds to 0.12 ng ml^-1. The method has been successfully applied to the determination of iron in natural and waste waters, wine, soil extract and previously digested vegetal tissues, drugs and human hair. Received: 20 November 1995/Revised: 23 January 1996/Accepted: 26 January 1996