电感耦合等离子体原子发射光谱法同时测定植物样品中多种元素

本文为环境样品分析建立了准确、灵敏、快速的分析方法,探讨了酸类及酸度对谱线强度的影响,同时对基体元素的谱线干扰进行了校正和背景扣除,测定了环境背景值样品树干和树叶中15种元素,经标样测定结果满意。     

Determination of ultra trace amounts of bismuth in biological and water samples by electrothermal atomic absorption spectrometry (ET-AAS) after cloud point extraction

A new approach for a cloud point extraction electrothermal atomic absorption spectrometric method was used for determining bismuth. The aqueous analyte was acidified with sulfuric acid (pH 3.0-3.5). Triton X-114 was added as a surfactant and dithizone was used as a complexing agent.After phase separation at 50 °C based on the cloud point separation of the mixture, the surfactant-rich phase was diluted using tetrahydrofuran (THF). Twenty microliters of the enriched solution and 10 μl of 0.1% (w/v) Pd(NO₃)₂ as chemical modifier were dispersed into the graphite tube and the analyte determined by electrothermal atomic absorption spectrometry. After optimizing extraction conditions and instrumental parameters, a preconcentration factor of 196 was obtained for a sample of only 10 ml. The detection limit was 0.02 ng ml⁻¹ and the analytical curve was linear for the concentration range of 0.04-0.60 ng ml⁻¹. Relative standard deviations were <5%.The method was successfully applied for the extraction and determination of bismuth in tap water and biological samples (urine and hair).     

On-line electrochemical preconcentration and flame atomic absorption spectrometric determination of manganese in urine samples

A sensitive and selective method was developed for the determination of traces of manganese in urine using on-line electrochemical preconcentration followed by flame atomic absorption spectrometry detection. A home made flow-through polypropylene cell (4.5 cm long × 0.8 cm diameter filled with glass marbles) with an effective inner volume of 0.5 ml containing a working and a counter electrode, both of glassy carbon and a Pt pseudo reference electrode was located in a flow injection manifold specially designed for the purpose of this work. The manganese was deposited from buffer solution of NH₃/NH₄Cl at pH 9.00 through an oxidizing process at a current of 400 mA during 7 min. A flow of HCl 0.1 mol l⁻¹ at 4 ml min⁻¹ through the cell, chemically dissolved the deposit. A small portion (15 μl) of the concentrate was introduced in a continuously flowing system by means of a timing device and was then carried to the detector for the manganese quantification. All electrochemical and spectroscopic variables as well as possible interferences in both systems were systematically studied. The relative standard deviations for ten consecutive measurements of manganese solutions of 2.0 and 20 μg l⁻¹ were of 2.3 and 1.5%, respectively, while for a sample processed five times was less then 5%. The accuracy of the developed procedure was evaluated by adding known amounts of manganese standard to urine samples and following the whole procedure. Recoveries within the range 97.2-102.8% were obtained. To further prove the accuracy, a Seronorm Trace Elements in Urine, Batch 403125 sample with a reported concentration of 13 μg Mn l⁻¹ was also analyzed. The experimental value obtained was of 12.7 ± 0.1 μg l⁻¹, which does not differ significantly from the reported amount (p < 0.05). A preconcentration factor of 40, a linear range between 0.015 and 60 μg l⁻¹ and a limit of detection of 15 ng l⁻¹ permitted the determination of manganese in real urine samples from non-exposed subjects in the range 0.5-2.8 μg l⁻¹.     

Pressurized liquid extraction in determination of polychlorinated biphenyls and organochlorine pesticides in fish samples

Pressurized liquid extraction (PLE) is a relatively new technique applicable for the extraction of persistent organic pollutants from various matrices. The main advantages of this method are short time and low consumption of extraction solvent. The effects of various operational parameters (i.e. temperature of extraction, number of static cycles and extraction solvent mixtures) on the PLE efficiency were investigated in this study. Fish muscle tissue containing 3.2% (w/w) lipids and native polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs) and other related compounds was used for testing. Purification of crude extracts was carried out by gel permeation chromatography employing Bio-Beads S-X3. Identification and quantitation of target indicator PCBs and OCPs was performed by high-resolution gas chromatography (HRGC) with two parallel electron-capture detectors (ECDs). Results obtained by the optimized PLE procedure were compared with conventional Soxhlet extraction (the same extraction solvent mixtures hexane–dichloromethane (1:1 v/v) and hexane–acetone (4:1 v/v) were used). The recoveries obtained by PLE operated at 90–120 °C were either comparable to “classic” Soxhlet extraction (for higher-chlorinated PCB congeners and DDT group) or even better (for lower chlorinated analytes). The highest recoveries were obtained for three static 5 min extraction cycles.     

Concentration levels of total and methylmercury in mussel samples collected along the coasts of Sardinia Island (Italy)

This paper reports the assessment of the total mercury (T-Hg) and methylmercury (MeHg) contamination of mussel samples collected by two sampling campaigns from along the coastline of Sardinia (Italy). T-Hg has been determined by a direct mercury analyser (DMA) whereas MeHg has been determined by gas chromatography-mass spectrometry (GC-MS) after acid extraction, and employs a novel NaBPh₄ derivatization method. The evaluation of the quality of measurements was carried out by analysing candidate certified reference material (CRM) BCR 710, for MeHg and T-Hg, and CRM IAEA-350 for T-Hg. In the analysed samples, the T-Hg concentrations range from 35 to 115 μg kg⁻¹ and from 40 to 830 μg kg⁻¹, for the two sampling campaigns, respectively, whereas the MeHg concentrations range from l5 to 51 μg kg⁻¹ and from 17 to 116 μg kg⁻¹. Consequently, the MeHg/T-Hg ratios range from 0.33 to 0.91 and from 0.14 to 0.98, respectively. Despite the increasing trend of Hg concentration from the first to the second sampling campaign, the T-Hg concentration of all the samples was much below the 0.5 μg g⁻¹ WHO limit, and the MeHg values ranged between 2.2 and 17.2 μg kg⁻¹, not exceeding the 43.5 μg kg⁻¹ tolerable daily residue level calculated for Italy.     

On-line preconcentration and determination of cobalt by DPTH-gel chelating microcolumn and flow injection inductively coupled plasma atomic emission spectrometry

This paper reports the development of a new methodology for the determination of cobalt in biological samples by using a flow injection system with loaded DPTH-gel as solid phase to preconcentrate analytes. The procedure is based on the on-line preconcentration of cobalt on a microcolumn of 1,5-bis(di-2-pyridyl)methylene thiocarbohydrazide immobilized on silica gel (DPTH-gel). The trapped cobalt is then eluted with 1% tartaric acid and 1% citric acid (7.1 mL) and determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). The analytical figures of merit for the determination of cobalt are as follows: detection limit (3S), 8.5 ng mL^–1; precision (RSD), 5.8% for 100 ng mL^–1 of cobalt; enrichment factor, 13 (using 7.3 mL of sample); sampling frequency, 40 h^–1 using a 60-s preconcentration time. For a 120-s preconcentration time (14.6 mL of sample volume) a detection limit of 5.7 ng mL^–1, an RSD under 5% at 50 ng mL^–1, an enrichment factor of 25, and a sampling frequency of 24 h^–1 were reported. The precision and accuracy of the method were checked by analysis of biological certified reference materials.     

Coupled SFE/SFC/GC for the trace analysis of pesticide residues in fatty food samples

An on-line SFE-chromatographic system, where SFE has been coupled with SFC and GC, was developed and utilized for trace analyses of organochlorine and organophosphorus pesticide residues from gram-sized complex sample matrices, such as chicken fat, ground beef, and lard. The SFE process and chromatographic techniques were instrumentally integrated for efficient and automated on-line analysis, having minimal sample handling between the sample preparation and separation steps. A cleanup step, incorporating packed column SFC, allowed the fractionation of relatively small-sized, non-polar pesticides from the co-extracted fatty materials. This permitted final high-resolution separation of analytes on a capillary GC column. Detection of pesticides was accomplished using selective electron-capture and nitrogen-phosphorus detectors. Pesticide concentrations determined with the on-line system were accurate and reproducible, for fatty samples containing both fortified and incurred pesticides. This method, utilizing supercritical carbon dioxide, was considerably faster and less laborious than the conventional analytical procedures based on liquid extraction.     

Liquid chromatographic trace enrichment with on-line capillary gas chromatography for the determination of organic pollutants in aqueous samples

Trace enrichment for the GC analysis of a series of chlorinated pesticides and polychlorinated biphenyls (PCBs) in aqueous samples has been achieved through a simple on-line technique involving sorption on an LC micro-precolumn followed by direct elution into a gas chromatograph with hexane. A 5-m retention gap coupled to the capillary GC column served as the recipient of a relatively large sample volume (ca. 100 μl) introduced into the GC. Partially concurrent solvent evaporation during sample introduction allowed a large sample capacity. Recoveries of more than 95% were observed for the majority of the compounds studied. Using 1.0 ml aqueous samples, detection limits of less than 1 ppt were found. The applicability of the developed method was demonstrated for a river water sample.     

Determination of organic acids by capillary electrophoresis with simultaneous addition of Ca and Mg as complexing agents

Summary A capillary electrophoretic method, with divalent cations as complexing agents in the electrolyte, has been developed for separation and determination of the low molecular weight organic acids most commonly found in wine, viz. formic, fumaric, succinic, oxalic, malic, tartaric, acetic, lactic, and citric acids. The separation conditions optimized were electrolyte concentration, organic flow modifier concentration, type and concentration of complexing agents in the electrolyte, and injection time. The best resolution of some of the acids studied was achieved by use of an electrolyte containing tetraborate buffer (10mm) at pH 9.3, an organic flow modifier (tetradecyltrimethylammonium hydroxide), and Ca²⁺ (10 ppm) and Mg²⁺ (10 ppm) as complexing agents. Other conditions used in the method were hydrostatic injection (10 cm height for 30 s), detection at 185 nm, and temperature 20°C. For all the acids studied detector response was linear for the concentration ranges considered. The repeatability of each point on the calibration plot for standards (n=4) was generally better than 1% the method was applied to samples of must, wine, brandy, and vinegar from the Jerez region.     

Determination of Antimony in Environmental Samples by ETAAS Using Different Permanent Modifiers

Single noble metal permanent modifiers such as, Rh, Ir, and Ru, as well as mixed tungsten plus noble metal (W–Rh, W–Ru, W–Ir) permanent modifiers thermally deposited on the integrated platform of a transversally heated graphite atomizer (TGA) were employed for the determination of antimony in sludge, soil, sediment, coal, ash and water samples by electrothermal atomic absorption spectrometry (ETAAS).Microwave digests of solid samples and water samples were directly introduced into different pre-treated platforms of graphite tubes. The performance of the modifiers for accurate antimony determination in real samples depended strongly on the type of permanent modifier chosen. The single noble metal (Rh, Ir and Ru) permanent modifiers were suitable for analyte determinations in simpler matrices, such as waters (recoveries of certified values 95–105%), but the analyte recoveries of certified values in sludge, soil, sediment, coal, and ash samples were always lower than 90%. On the other hand, for the determination of antimony, using W–Rh, W–Ru, and W–Ir permanent modifiers presented recoveries of certified values within 95–105% for all the samples.Long-term stability curves obtained for the determination of antimony in environmental samples with different permanent modifiers (Rh, Ir, Ru, W–Rh, W–Ir, W–Ru) showed that the improvement in tube lifetime depends on the tungsten deposit onto the platform. The tungsten plus noble metal permanent modifier presents a tube lifetime of at least 40% longer compared to a single permanent modifier.