Determination of tin and titanium in soils, sediments and sludges using electrothermal atomic absorption spectrometry with slurry sample introduction

Fast-heating programmes for determining titanium and tin in soils, sediments and sludges using electrothermal atomic absorption spectrometry (ETAAS) with slurry sampling are developed. For titanium determination, suspensions are prepared by weighing 5-40 mg of sample and adding 25 ml of a solution containing 50% (v/v) concentrated hydrofluoric acid. For tin determination, suspensions are prepared by weighing up to 300 mg of sample and then adding 1 ml of a solution containing 25% (v/v) concentrated hydrofluoric acid. Palladium (30 μg) and ammonium dihydrogen phosphate (7% w/v) are used as matrix modifiers for titanium and tin, respectively. Prior mild heating in a microwave oven is recommended for titanium determination. Calibration is carried out using aqueous standards. The tin and titanium contents of a number of samples obtained by using the slurry approach agree with those obtained by means of a procedure based on the total dissolution of the samples using microwave oven digestion. The reliability of the procedures is also confirmed by analysing several certified reference materials.     

Determination of molybdenum, chromium and aluminium in human urine by electrothermal atomic absorption spectrometry using fast-programme methodology

Rapid and direct procedures for the determination of molybdenum, chromium and aluminium in human urine samples are developed. Fast-programme methodology is used to simplify the heating cycles. Hydrogen peroxide, nitric acid and Triton X-100 are added to the urine samples which are directly introduced into the furnace. For molybdenum, two successive injection steps are required due to the low level of this element in the samples analyzed. Calibration is carried out using aqueous standards for aluminium and the standard additions method for both molybdenum and chromium. The reliability of the procedures is checked by analyzing two certified reference materials.     

Development of certified reference samples of solutions of trihalomethanes

A method for the metrological certification of reference samples (RS) of solutions of organic compounds was proposed. The method is based on a procedure of sample preparation that uses both calculated and experimental data and involves the evaluation of the purity of the reagents employed. Impurity components were identified. Procedures for the determination of impurity components in source materials by gas chromatography with flame-ionization detection were developed. Calibration coefficients for halogen-containing impurity components in reference to an internal standard were determined experimentally or calculated. Certified reference samples of solutions of trichloromethane, bromodichloromethane, dibromochloromethane, and tribromomethane were designed for the quality control of drinking water     

Potentialities of Quantitative Analysis by High-Performance Liquid Chromatography without Reference Standards of Analytes: Use of Reference Data on UV Spectra for Calculating Calibration Coefficients

It was shown by the examples of simple organic compounds and some medicinal substances that, in the quantitative analysis by the internal standard method in high-performance liquid chromatography (HPLC) with UV detection, one can use calibration coefficients calculated from reference data on UV spectra. Determinations should be performed at several constant wavelengths (for example, 220, 254, 280, and 320 nm) using at least two internal standards (a set of eight samples was proposed) rather than one standard. As can be judged from the estimates obtained, the systematic component of the determination error under these conditions does not exceed the contributions of random errors. The developed approach opens up new opportunities for quantitative determinations by HPLC without reference samples of analytes, instead of which reference data on molar absorptivities are used.     

Slurry sampling for the rapid determination of cobalt, nickel and copper in soils and sediments by electrothermal atomic absorption spectrometry

Electrothermal atomic absorption procedures for the rapid determination of cobalt, nickel and copper in soil and sediment samples are presented. The samples are suspended in a hydrofluoric acid solution before being injected into the electrothermal atomizer. Prior mild heating in a microwave oven is recommended for nickel and copper determination. No modifier other than hydrofluoric acid is required. The conventional ashing step is unnecessary since the fast-heating programmes lead to well defined atomization profiles with low background levels that can be corrected using a common deuterium device. Calibration is performed directly using aqueous standards. The results obtained for six certified reference materials confirm the reliability of the procedures.     

Comparison of partial digestion procedures for determination of Ca, Cr, Cu, Fe, K, Mg, Mn, Na, P, and Zn in milk by inductively coupled plasma-optical emission spectrometry

A fast procedure was developed for determination of Ca, Cr, Cu, Fe, K, Mg, Mn, Na, P, and Zn in milk samples. This procedure consisted of a partial digestion with hydrochloric acid on a hot plate. The results obtained were compared with 3 other digestion procedures (dry ashing and 2 microwave digestions). All the procedures showed similar precision levels, with coefficients of variation <10% for most analyzed elements. Accuracy was evaluated by using certified reference materials, and the values obtained were within the confidence intervals for these products. The results obtained were not considered statistically different. The partial digestion on a hot plate with HCl can be very practical for laboratories with relatively large numbers of sample analyses.     

Determination of Fe, Ni and V in asphaltene by ICP OES after extraction into aqueous solutions using sonication or vortex agitation

A simple procedure for the extraction of Fe, Ni and V from asphaltene into acid solutions prior to the ICP OES determination is proposed. Either sonication or vortex agitation was used to disperse the organic sample into concentrated nitric acid, achieving efficient analyte extraction into the aqueous acid solution. Both procedures were compared and the advantage of the ultrasound-assisted procedure was evaluated. In both cases, pre-heating of sample–acid mixtures was necessary to enable quantitative extractions. Optimized conditions for the ultrasonic bath were established: 1 L of water at room-temperature, 20 min of sonication and tubes (maximum of eight) in vertical position. By using the vortex, 50 min of vigorous mechanical agitation was needed for each one of the tubes containing samples. The acid solution obtained after extraction was directly aspirated into the ICP in order to perform quantification by optical emission. Calibration was made with aqueous analyte standards containing Sc as internal standard. The procedures were tested using certified fuel oil (SRM NIST 1634c) and the method was applied for the determination of Fe, V and Ni in one asphaltene sample obtained by the fractionation of the SRM NIST 1634c. Recoveries above 90% were achieved and limits of quantification in the asphaltene sample were 1.5, 15 and 1.0 μg g^− 1 estimated for Fe, Ni and V, respectively.     

Slurry-electrothermal atomic absorption spectrometric determination of aluminium and chromium in vegetables using hydrogen peroxide as a matrix modifier

Fast heating programmes for determining aluminium and chromium in vegetables using electrothermal atomic absorption spectrometry with slurry sampling are developed using wall atomization. The build-up of carbonaceous residues inside the atomizer is avoided by adding 4% hydrogen peroxide and 1% nitric acid to the slurries instead of using an air-ashing stage. In accordance with fast-programme methodology, the conventional drying and charring steps are replaced by a modified drying stage. simplifying the heating programmes. For suspensions containing 0.1% m/V of ground vegetables, the relative standard deviation (RSD) is about +/-5% for aluminium. For chromium determination, the use of 0.5-1% m/V suspensions leads to RSDs close to +/-4%. Calibration is carried out using aqueous standards. The aluminium and chromium contents of a number of vegetable samples obtained by using the slurry approach agree with those obtained by means of a conventional procedure based on the total dissolution of the samples. The reliability of the procedures is also confirmed by analysing two certified reference materials.     

Application of tandem calibration for the direct analysis of copper by inductively coupled plasma atomic emission spectrometry (ICP-AES)

A procedure has been proposed for the direct ICP-AES analysis of solid copper samples using spark sampling. Calibration curves have been obtained using multi-element reference solutions of analytes (MES). The internal standards are spectral lines of copper with the energy parameters (excitation and ionization potentials) similar to those of analytes. Standard Reference Material (SRM) of copper have been used for the estimation of performance characteristics. The absence of significant differences between the found and certified concentrations of analytes has been shown. The developed procedure of ICP-AES analysis of solid copper samples with spark sampling and calibration using MES provides the determination of up to 14 elements: Ag, As, Au, Cd, Fe, Mn, Ni, P, Pb, Pt, Sb, Se, Sn, Te, and Zn in the concentration range from n × 10^?3 to n × 10^?1 wt %.     

Direct inductively coupled plasma-atomic emission spectrometry analysis of trace elements in muscle tissues of hairtail using electrothermal vaporization with slurry sampling

A procedure for direct determination of trace elements in muscle tissue of hairtail was developed using inductively coupled plasma-atomic emission spectrometry and electrothermal vaporization with slurry sampling. Due to use of polytetrafluoroethylene as the chemical modifier, the vaporization behaviors of analytes from the slurry and the aqueous standard solutions were very similar. In this case, the aqueous standards could be used for the calibration of slurry samples. The main factors influencing this method were studied systematically. The detection limits for Cr, Ni, Zn, Cd, and Pb were 3.1, 10.5, 176, 6.9, and 83 ng/mL, respectively, and the relative standard deviations were less than 10%. The proposed method was applied to the determination of trace Cr, Ni, Zn, Cd, and Pb in hairtail samples with satisfactory accuracy and precision. A certified reference material of mussel (GBW 08571) was analyzed, and good agreement was obtained between the results from the proposed method and certificate values.     

X-ray fluorescence analysis of polymetallic ores

An analytical procedure for determination of Fe, Ti, V, Ni, Co and Cu, the most important constituents of the polymetallic ore has been developed. Twenty four powdered samples were prepared from the material taken in various places of the ore deposit. The samples were analyzed by wavelength dispersive (WD) and energy dispersive (ED) XRF method. The EDXRF method was applied using radioisotope source as well as a low power X-ray tube (Rh-anode) for excitation of the characteristic K-line radiation of the elements. A Si(Li) detector was used for the detection of radiation. The detection limits and precision of the analytical procedures, using reference materials, were estimated. The accuracy of the different XRF techniques is discussed. The developed analytical procedures based on the XRF method are rapid and quite simple. They can be useful for exploration data accumulation.     

Direct determination of calcium,copper, iron,magnesium, manganese and zinc in amniotic fluid samples using inductively coupled plasma-atomic emission spectrometry

An inductively coupled plasma-atomic emission spectrometric method is reported for the determination of calcium, copper, iron, manganese, magnesium and zinc. Samples are introduced directly when a sheath gas device is used. An external calibration procedure is used. The standards are prepared in a matrix composed of 0.5% (w/v) albumin and 0.76% (w/v) sodium chloride. The procedure was evaluated with a standard reference material (NBS SRM 909 Human Serum); all the values obtained are in agreement with the certified values. Results obtained for the determination of zinc, calcium, magnesium, copper, iron and manganese in amniotic fluid samples are reported.     

Simultaneous determination of chromium, selenium, and molybdenum in nutritional products by inductively coupled plasma/mass spectrometry: single-laboratory validation

An inductively coupled plasma/MS method was developed for the simultaneous determination of Cr, Se, and Mo in infant formulas and other nutritional products. All samples were digested using a closed vessel microwave oven system, together with Ni and Te internal standards. The practical quantitation limits for Cr, Se, and Mo were 0.4, 0.2, and 0.4 ng/mL, respectively; dilution factors were 250 for powders and 50 for liquids. The Cr, Se, and Mo concentrations in 10 nutritional products were within specification limits, and within-day and day-to-day (6 independent days) precision values were <5% RSD. For two control samples, the observed precision was < or = 2% RSD over 10 independent days. In three National Institute of Standards and Technology standard reference materials, Cr, Se, and Mo results were within the certified limits. The average sample spike recoveries for 10 nutritional products ranged from 93 to 107%. Robustness studies showed a minimal effect from concomitant easily ionized element concentrations. However, the choice of internal standard and matrix matching carbon content were critical to obtaining accurate Se results. All indications are that this method would be a suitable candidate as a global reference method for the determination of these trace elements in nutritional products.     

Dosage de la silice des silicates,apres distillation,par gravimetrie du molybdosilicate de quinoleineThe determination of silica in silicates by distillation and gravimetry as quinoline 12-molybdosilicate

The determination of silica in silicates by distillation and gravimetry as quinoline 12-molybdosilicateQuantitative distillation of silica as hexafluorosilicic acid is followed by gravimetric determination of the silicate as quinoline 12-molybdosilicate. Precise results are obtained even when the samples contain phosphorus and fluorine. Compared to classical insolubilization procedures with strong acids, the proposed method is quicker and more sensitive, being applicable down to ca. 1 mg SiO₂. Its application is limited to silicates decomposed by hot sulphuric acid—hydrofluoric acid mixtures. The accuracy of the procedure is confirmed by the results for numerous reference standards.     

Development and supply system of reference materials based on the Measurement Law in Japan

 Analytical instruments used for measurements of air and water pollution are calibrated by using reference materials such as standard gases and standard solutions. In Japan, since the middle of the 1970s, those reference materials which are traceable to the national standards maintained at national research institutes have been supplied to users by reference material producers. In order to establish the primary standards and to secure the traceability from the working standards to the national ones, various analytical methods such as coulometric, titrimetric and gravimetric analyses for purity determination and highly sensitive atomic spectrometry for trace analysis have been developed as the primary methods and reference methods. The Japanese Measurement Law, revised in 1992, has introduced a new traceability system in which a public organization, a "designated calibration body", can also prepare and maintain the national standards under the advice and instruction of national research institutes. The designated calibration body can provide calibration services to reference material producers (accredited calibration bodies) by using the national standards. The reference materials supplied in conformity with the traceability system include standard gases, pH standard solutions, metal standard solutions and non-metal ion standard solutions. Received: 4 October 1996 Accepted: 2 December 1996     

Flow injection flame atomic absorption analysis of Fe and Mn in cement samples

Summary A new procedure has been developed for the determination of Fe and Mn in cements. It consists in dispersing 50 mg of the solid sample in 25 ml of 0.15 mol/l HNO₃ and 0.12 mol/l HCl solution. Acid slurries are heated at 50°C for 10 min and then different volumes of the slurry are injected into a water carrier stream. This previous acid treatment leaches the elements to be determined and permits the use of acid solutions as standards. For the Mn determination, the use of a single line flow injection manifold provides a limit of detection of 0.03 mgl^–1 and a dynamic range up to 6 mgl^–1. For the determination of Fe, the on-line dispersion of samples, using a well stirred mixing chamber, increases the dynamic range up to a concentration of 125 mgl^–1 and provides a limit of detection of 1 mgl^–1. The procedure has been applied to the analysis of real cement samples and a certified reference material. Results were in agreement with those obtained by a reference procedure involving the alkaline fusion of samples and batch analysis by flame atomic absorption spectrometry.     

A Comparison of the Efficiency of Nucleotide Extraction by Several Procedures and the Analysis of Nucleotides from Extracts of Liver and Isolated Hepatocytes by HPLC

Abstract

A high pressure liquid chromatography (HPLC) system was developed, capable of resolving most 5′-nucleotides and nucleotide-sugars present in liver tissue. Using three different extraction procedures, the recovery of the twelve major 5′-ribonucleotides from solutions of nucleotide standards, or liver samples, or isolated hepatocytes was compared. Nucleotides were obtained from acid extracts for HPLC analysis by adsorbing the nucleotides on charcoal, or precipitating the acid (perchloric acid) by KOH, or extracting the acid with alamine/ freon. The last two procedures were found to be superior to the charcoal adsorption procedure for recovering nucleotides from acid extracts. The recovery of nucleotides from either liver samples or isolated hepatocytes by these two procedures was similar; however, the recovery of nucleotides from standard solutions was slightly higher for the alamine/freon procedure than the KOH precipitation procedure.     

Determination of calcium, iron and manganese in moss by automated discrete sampling flame atomic absorption spectrometry as an alternative to the ICP-MS analysis

An automated, fast and reliable procedure has been developed for flame atomic absorption analysis of Ca, Fe and Mn in moss. The method is suitable for routine analysis of a large number of moss samples and allows sequential determination of all three elements in the same solution. In order to inhibit the matrix interference on Ca and to level the diverse analytical behaviour of the moss matrix, approximately 1% La was added to both samples and standard solutions as well. An integrated system of ‘sandwich-type’ air segmented discrete sample introduction and flame atomic absorption detection (ASDI-FAAS) was successfully applied. It works at ‘solvent-air-sample-air-solvent’ mode, which tolerates the introduction of high salt content solutions, reduces reagent and sample consumption and allows the application of data treatment models to pseudo-steady state signals for bettering the repeatability. For moss samples containing high Ca and Fe concentrations, equivalent procedure was used by turned on 45° burner head without worsening the analytical characteristics. Concerning these three elements, the method is suggested as a cheaper, easier and more trustworthy alternative with a better precision to the inductively coupled plasma-mass spectrometry (ICP-MS) one. The ASDI-FAAS results were used for selection of appropriate isotopes and correction procedures for ICP-MS determination. Both methods show good agreement of the Ca, Fe and Mn results that correspond to the moss reference materials tested.     

Comparison of Microwave-Assisted Digestion Methods and Selection of Internal Standards for the Determination of Rh, Pd and Pt in Dust Samples by ICP-MS

Different temperature-pressure controlled microwave-assisted digestion methods were compared for the digestion of dust samples prior to the determination of rhodium and platinum by inductively coupled plasma mass spectrometry (ICP-MS). The results obtained for platinum and rhodium in the digested reference material (BCR-723, road dust) were generally in good agreement with the certified values. However, the determination of matrix elements (Zn, Rb, Sr, Y, Hf and Pb) showed clear differences between the digestion methods. In addition, different internal standards were compared in the determination rhodium, palladium and platinum by ICP-MS. According to the results, even serious non-spectral interferences can be corrected by choosing a suitable internal standard or combination of internal standards.     

Application of inductively coupled plasma/mass spectrometry for the measurement of chromium, selenium, and molybdenum in infant formula and adult nutritional products: First Action 2011.19

An inductively coupled plasma/MS method was developed for the simultaneous determination of Cr, Se, and Mo in infant formula and other nutritional products. All samples were digested using a closed vessel microwave oven system, together with Ni and Te internal standards. The practical quantitation limits for Cr, Se, and Mo were 0.4, 0.2, and 0.4 ng/mL, respectively; dilution factors were 250 for powders and 50 for liquids. The Cr, Se, and Mo concentrations in 10 nutritional products were within specification limits; within-day and day-to-day (6 independent days) precision values were <5% RSD. For two control samples, the observed precision was < or = 2% RSD over 10 independent days. Cr, Se, and Mo results were within the certified limits in three National Institute of Standards and Technology standard reference materials. The average sample spike recoveries for 10 nutritional products ranged from 93 to 107%. Robustness studies showed a minimal effect from concomitant easily ionized element concentrations. However, the choice of internal standard and matrix-matching carbon content were critical to obtaining accurate Se results. All indications are that this method would be a suitable candidate as a global reference method for the determination of these trace elements in infant formula, adult nutritionals, and other nutritional