Combination of three analytical techniques for speciation of Al in environmental samples

An analytical scheme is proposed which combines three speciation techniques for determination of particular Al species in soil extracts and percolating waters. A cation-exchange fast protein liquid chromatography — inductively coupled plasma atomic emission spectrometry (FPLC-ICP-AES) procedure, a microcolumn chelating ion-exchange chromatography- atomic absorption spectrometry (MCC-ETAAS) technique and the 8-hydroxyquinoline spectrophotometric method (8HQ-spectrophotometry) were employed. The FPLC-ICP-AES procedure offers determination of Al³⁺ (retention time 4.5 min) and Al(OH)²⁺ species (retention time 4.0 min) which are separated from Al(OH)⁺ ₂ (retention time 1.5min). AlF²⁺ coelutes with Al(OH)²⁺ species, while Al(SO₄)⁺, AlF⁺ ₂ and negatively charged Al organic complexes coelute with Al(OH)⁺ ₂ species. The MCC-ETAAS technique enables determination of the sum of positively charged monomeric aqua- and hydroxy-Al species plus sulphate- and fluoro-Al complexes. Employing the 8HQ-spectrophotometry the sum of positively charged monomeric aqua- and hydroxy-Al species plus sulphato- and most of the labile organic Al species are determined. The sensitivities of these selected techniques were adequate for speciation of Al in the samples analyzed. On the basis of the specific selectivity of a particular technique various groups of Al species may be determined. Thus, the comparison of analytical data from complementary procedures provides more comprehensive information on Al species present in soil extracts and percolating waters.     

Electron microprobe analysis of micro amount powder samples: A case study on high purity coal

For the major, minor and trace element analysis of the inorganic compounds of a Ruhr-Saar coal different preparation techniques are investigated with X-ray fluorescence analysis, electron microprobe and classical wet chemical methods minimizing sample weight at standard preparation times and analytical accuracies. Considering accuracy as well as preparation efforts, determinations by electron microprobe on small sample amounts (<50 mg) proved to be superior to the other methods.Abbreviations AAS atomic absorbtion spectrometry - EMA electron microprobe analysis - IC ion chromatography - ISE ion sensitive electrode - PHOT photometry - WCA wet chemical analysis - XRF X-ray fluorescence analysis - LTA low temperature plasma ashing - HTA high temperature ashing - l.o.i. loss on ignition     

Flow-injection spectrofluorometric determination of trace amounts of formaldehyde in water after derivatization with acetoacetanilide

A novel fluorophotometric method for formaldehyde determination in environmental waters was developed: the method does not require any enrichment procedures. A flow-injection analysis method for the spectrofluorometric determination of formaldehyde in waters, which is based on the reaction of formaldehyde with acetoacetanilide and ammonia, is proposed. The proposed method shows a good linearity from 0.50 to 40 × 10⁻⁷ M, and the limit of detection (LOD) of 3 × 10⁻⁹ M (0.09 ppb) is achievable. The sample throughput is 15 h⁻¹. One of the main advantages in the proposed method is that the reaction can be carried out at room temperature without any heating system. The effect of various interferences possibly present in the real water samples was investigated. Most cations and anions, as well as organic compounds, do not interfere with the determination of formaldehyde in environmental water samples. The proposed method is very simple, rapid, less expensive, and highly sensitive, and can be applied to the environmental water samples, such as rain, tap water and river water, at low concentration levels without any enrichment procedure.     

Trace Spectrophotometric Determination of Dichlorvos using Diphenyl Semicarbazide (DPC) in Environmental and Agricultural Samples

A new and highly sensitive spectrophotometric method is developed for the determination of sub ppm levels of the widely used organophosphorus insecticide dichlorvos. The method is based on alkaline hydrolysis of dichlorvos to dichloroacetaldehyde followed by coupling with diphenyl semicarbazide (DPC) in alkaline medium. The absorption maxima of the wine red dye compound formed is measured at 490 nm. Beer's law is obeyed over the concentration range of 4.3 to 34 μg in a final solution volume of 25 mL (0.18–1.36 ppm). The molar absorptivity, Sandell's sensitivity and correlation coefficient were found to be 2.9 × 10⁵ l mole^?1 cm^?1, 0.013 μg cm^?2 and 0.9999, respectively. The standard deviation and relative standard deviation were found to be ± 0.007 and 1.90%, respectively. The lower limit of detection is 0.04 μg. The method is simple, sensitive and free from interferences of other pesticides and diverse ions. Other organophosphorous pesticides do not interfere with the proposed method. The method has been satisfactorily applied to the determination of dichlorvos in environmental and agricultural samples.     

An integrated coupled column liquid chromatography system for the determination of leukotriene metabolites in biological samples

Summary A fully integrated chromatographic system was developed for the determination of leukotrienes in biological samples using photodiode-array detection (PDAD), which eliminates time consuming manual sample handling steps. A special solid phase extraction, (SPE) methodology for leucotriene metabolite stability was developed which increased the recoveries and eliminates the contamination risk of biological samples. The inherent instability (autooxidation) of many of the leukotriene mediators, and the adsorption effects onto exposed surfaces in vials and in the chromatographic system were found to be very important parameters to control in order to circumvent high loss of sample analytes. By binding the cell supernatants to the functionalities of the SPE support stabilised these mediators. Cell culture samples were eluted through a disposable C₁₈ SPE column. The SPE columns were allowed to thaw and deposited in an automated sample handling unit (ASPEC XL). Desorption of the analytes was followed by a second on-line SPE step, to eliminate remaining interfering matrix compounds. Typical recoveries when stored at −70°C were in-between 55–97% except for (LTE₄) which was found to be around 40% after 72 days of storage. Seven reversed-phase packings were studied. Selectivity factors, as well as the separation efficiencies, were found to differ for the various C₁₈ bonded silica stationary phases. This integrated on-line column liquid chromatographic system was applied to the determination of leukotriene B₄, leukotriene C₄, leukotriene D₄, leukotriene and E₄ in human cell extracts using prostaglandin B₂ as the internal standard. More than 1500 biological samples were analysed. Some validation data are presented for unattended operations.     

Simultaneous Determination of Various Classes of Pesticides Using Micellar Electrokinetic Capillary Chromatographyin Combination with Solid-Phase Extraction

The potential of micellar electrokinetic capillary chromatography (MEKC) with UV-detection for the simultaneous determination of various selected pesticides in water samples was investigated. The developed method using solid-phase extraction showed high efficiency and good resolution with detection limits in the 0.2 to 0.5 ppm range. Comparison of several SPE cartridges demonstrates their suitability for the extraction of pesticides with different hydrophobicity achieving 5000-fold enrichment. The described method involving SPE procedure and MEKC separation enables the successful determination of a wide spectrum of pesticides in water in the range of maximum residue limits (MRLs).     

Determination of fungicide residues in fruits by coupled-column liquid chromatography

Coupled-column liquid chromatography with fluorescence detection was applied to the determination of o-phenylphenol and bitertanol residues in orange and banana fruits. After extraction with a mixture of acetone, dichloromethane-petroleum ether, and ethyl acetate, an extract aliquot of 100 microL was injected directly without any additional clean-up into the chromatographic system using two reversed phase C18 coupled columns. The LC-LC approach allowed automated sample clean up of the vegetal extracts, leading to a simple and rapid analytical procedure, with limits of quantification between 0.01 and 0.05 mg kg(-1). Recovery experiments performed on orange and banana samples fortified at different concentrations (0.01 - 4 mg kg(-1)) gave average recoveries between 70 and 113% with relative standard deviations lower than 15%. The procedure developed was finally applied to orange and banana samples from different geographical locations and the results were confirmed by GC-MS.     

Isolation of new quinidine metabolites and simultaneous determination of quinidine and its metabolites in blood and urine by direct injection HPLC analysis

Summary New quinidine metabolites, including 10,11-dihydrodiol quinidine N-oxide, 10,11-dihydrodiol quinidine and their glucuronides, were found in human urine. A quinidine monitoring HPLC method including these metabolites, is proposed by the direct injection of body fluid samples onto the precolumn for deproteinization followed by reverse phase separation in the analytical column with a column switching technique. The recovery of spiked quinidine and its metabolites in plasma was quantitative (98–102%) with good reproducibility (C.V.: 1.6–4.0%). Several clinical samples such as whole blood and urine were analyzed by the present method.     

Sample preparation in analysis of pharmaceuticals

Sample preparation is a very important and essential step in environmental analysis. This article presents an overview of extraction methods for environmental samples, focusing especially on pharmaceuticals as there is great concern about them as pollutants.     

倒数示波计时电位法在合金样品测定中的应用

应用倒数示波计时电位法，在含有吸附络合物的溶液中，采用桂汞电极作为极化电极，测定了Ｃｕ＾２＋、Ｎｉ＾２＋、Ｃｄ＾２＋、Ｐｂ＾２＋等几种金属离子的检测下限，并通过沿（ｄＥ／ｄｔ）－１￣Ｅ曲线上的峰高对合金样品进行定量分析，得到满意结果。实现了示波分析由常量到微量的飞跃。