Bulk acoustic wave sensor for the ion chromatographic determination of copper in human plasma

By using ion chromatography with series bulk acoustic wave detection, a method for the determination of copper in human blood plasma has been developed. The advantages of the good selectivity of ion chromatography and the highly sensitive response of SBAW have been combined to improve detection limit, accuracy and reproducibility. The detection limit (3) of the method to copper is 0.3 g/ml. The relative standard deviation for the determination of 1.0 g/ml of copper is 2.1% (n=7). For the IC analysis, the analytical column is a Shim-pack IC C1 column, and the mobile phase is 4.0 mM tartaric acid/2.0 mM ethylenediamine solution with pH 4.2. This system has been applied to the determination of Cu in blood plasma from healthy people or patients with renal failure.     

Determination of selenite,selenate and selenomethionine by ion chromatography,microwave digestion and HGAAS

An on-line system for the simultaneous determination of Se(IV), Se(VI) and selenomethionine (Se-Met) in aqueous samples was developed, consisting of separation by ion chromatography, microwave digestion and detection by hydride generation atomic absorption spectrometry. 8.3 mmol/l Na₂HPO₄ (pH 9.2) was used as mobile phase for the ion chromatography, with a flow-rate of 1.5 ml/min. After the separation the sample was mixed with concentrated KBr-HCl solution and heated with microwave energy to digest Se-Met and reduce Se(VI) to Se(IV). The detection limits were 15 g/l, 12 g/l and 103 g/l for Se(IV), Se(VI) and Se-Met, respectively.     

Multi-element analysis of biological material by RNAA using HPLC with on-line yield determination

The idea to use high performance liquid chromatography with continuous UV detection for multi-element radiochemical separation and simultaneous multi-element on-line yield determination is introduced. The validity of the concept was evaluated by demonstrating the constancy of the ratio of the signals for a main isotope (⁶⁰Co) and a carrier (⁵⁹Co) as a function of the elemental mass processed in the separation. The suitability of the method for practical purposes is demonstrated by its application to the RNAA determination of cobalt in biological materials. It is concluded that the method, although not yet completely developed, bears the potential of improving both accuracy and precision of multi-element RNAA.     

Small-scale method for the determination of selected organochlorine pesticides in soil

A small-scale method was developed for the simultaneous determination of -HCH, heptachlor, aldrin, dicofol, mirex, endosulfan I, endosulfan II and endosulfan sulphate in soil. The extraction and clean-up steps were combined into one step by transferring soil samples to chromatographic columns prepacked with neutral alumina. The pesticides elution was processed with n-hexane : dichloromethane (7:3) and the concentrated eluate was analysed using gas-liquid chromatography with electron capture detection. Analyses of the in vitro fortified samples with the selected pesticides were performed at three different levels. Mean recoveries for aldrin, -HCH and heptachlor, at levels of 2, 10 and 20 ng/g, ranged from 71 to 87%; for dicofol, at levels of 8, 40 and 80 ng/g, ranged from 97 to 103%; for endosulfan I and II, at levels of 5, 25 and 50 ng/g, ranged from 88 to 96%; for mirex, at levels of 6, 30 and 60 ng/g, ranged from 86 to 110%; and for endosulfan sulphate, at levels of 15, 75 and 150 ng/g, ranged from 93 to 104%. The method can be used for rapid determination of these pesticides in soil.     

Analysis and behaviour of organophosphorus pesticides in a rice crop field

Summary A comprehensive analytical protocol for the determination of organophosphorus pesticides in the biotic and abiotic compartments of a rice crop field (Ebro delta, Spain) is described. This include two alternative clean-up procedures (Florisil column chromatography and Bio Beads SX-3 gel permeation chromatography) and gas chromatographic analysis with nitrogen-phosphorus and mass spectrometric detection. Among the pesticides identified, Fenitrothion was the most abundant with residue levels in sediment samples varying from 1–3 g/g in the first day of application to 0.5 g/g two days after, whereas in the water canals the concentrations were of 3–10 g/l, after aircraft application, with a rapid decrease several hours later. Half lives of Fenitrothion in water and sediment samples under natural conditions have been estimated to be lower than 1 day and between 1–1.5 days, respectively, with volatilization and microbial degradation accounting for this decay. The bivalves analysed in the coastal bays (Tapes semidecussatus, Ostrea edulis and Mytilus galloprovincialis) exhibited residue levels between 20–90 ng/g of organophosphorus pesticides, Fenitrothion being the most abundant organophosphorus pesticide. These levels are likely in the safe range for bivalves but not for other organisms such as crustacea, which are sensitive to water concentrations of 0.1 g/l.     

Determination of methylmercury in biological samples by capillary gas chromatography with electron capture detection

A precise and accurate method has been developed for the determination of methylmercury in biological material using capillary gas chromatography with electron-capture detection. Homogenized fish or mussel samples were digested with acid, spiked with ethylmercury chloride as an internal standard and extracted with toluene. After treatment of the solvent extract with sodium thiosulphate and cupric bromide the alkylmercurials were extracted into benzene as their bromide derivatives and analyzed using an OV-275 coated glass capillary column. The detection limit of the method for methylmercury was 5 g/kg tissue.     

Determination of Polysaccharides and Lipopolysaccharides by Spectrophotometry and Thermal-Lens Spectrometry

A procedure for the photometric determination of polysaccharides with phenol in a sulfuric acid solution was optimized to reduce the blank signal. The procedure was used for the thermal-lens determination of polysaccharides (heparin, dextran, plantaglucide) qualitatively reproducing the chemical properties of pyrogenic lipopolysaccharides under experimental conditions. The detection limits were found to be 2–5 g/mL. With the use of thermal-lens spectrometry, lipopolysaccharides can be determined in water (in a model sample, pharmaceutical preparation pyrogenal) with a detection limit of 0.3 g/mL, which is ten times lower than the minimal injected concentration of the preparation.     

Determination of210Pb in sediments by extraction chromatography

A selective method is described for the determination of²¹⁰Pb in sediments, based on the separation of the daughter²¹⁰Bi by extraction chromatography with Microthene 710-tri-n-octylphosphine oxide (TOPO) and on a final source counting with a low background -counter. The average chemical yield is 92.0%. The detection limit for 2 g samples is 19 Bq kg^–1. An IAEA reference sediment sample was analyzed to check the reliability of the method.     

Flow Injection Spectrophotometric Determination of Trace Amounts of Hydrazine by the Inhibition of the Pyrogallol Red-Iodate Reaction

A simple and sensitive flow injection method is described for the determination of trace amounts of hydrazine, based on its inhibitory effect on the reaction between pyrogallol red and iodate in hydrochloric acid media. The reaction was monitored spectrophotometrically by measuring the change in absorbance of pyrogallol red at 470 nm. The calibration graph was linear over the range of 0.050–1.20 g/mL, with a limit of detection of 0.03 g/mL. The relative standard deviation for ten replicate measurements of 0.060 and 0.70 g/mL was 2.2 and 0.50%, respectively. Potential interfering substances were studied in the presence of hydrazine. The proposed method was applied to the determination of hydrazine in water samples.     

Multi-residue procedure for the analysis of pesticides in groundwater: Application to samples from the comunidad Valenciana,Spain

Summary A simple multi-residue procedure has been developed and applied to the analysis of pesticides in groundwater samples from the Comunidad Valenciana, a predominantly agricultural area on the Mediterranean coast of Spain. The procedure includes a liquid-liquid extraction, after addition of NaCl on the samples, and a subsequent analysis by capillary gas chromatography using a dual detection system with electron capture and nitrogen-phosphorous detectors. This allows the determination of more than 30 compounds (organophosphorous, organochlorine and pyrethroid pesticides) at the low ppb (g l^–1) levels. Detection limits obtained varied between 0.01 g l^–1 (lindane, fonofos) and 0.5 g l^–1 (cypermethrin). An additional injection of the sample extracts into a gas chromatograph equipped with a column of different polarity and electron capture detector is used for the confirmation of chromatographic peaks. The recommended procedure has been applied to 66 ground water samples. Pesticides, including organophosphorus and organochlorine compounds were detected in 31 of them, in levels ranging from 0.02 to 0.7 g l^–1.     

Spectrophotometric method for phosphine residue determination in coriander

Spectrophotometric method for the determination of phosphine (PH₃) residues in coriander has been developed based on the reaction of phosphine with silver nitrate in 2% aqueous isopropanol. The yellow chromophore formed has an absorption maximum at 430 nm and the linear relation between the absorbances at 430 nm and the concentration of PH₃ is obeyed in the range of 0.02 to 0.17 g. The method is sensitive with a detection limit of 0.008 g and can be applied for determination of 0.02 g/g residue in coriander. Recovery of added PH₃ from a closed system ranges from 96 to 101%.     

Trace analysis of cationic surfactants in water using HPLC with conductometric detection

Summary A simple and fast determination of trace amounts of commercially used cationic surfactants is described. After extraction from water cationic surfactants are separated by HPLC and detected by conductometry. The detection limit is 3 g/l for distearyldimethylammonium chloride, 16 g/l for ditallowimidazolinium methosulphate, and 6 g/l for dodecylpyridinium chloride.     

HPLC with electrode array detection

Summary A fast method for the determination of amitrole in drinking and ground water is described. Amitrole is separated from other substances by HPLC. For the determination a highly sensitive coulometric electrode array detector is applied. Tap and well water with concentrations down to 0.1 g amitrole/L can be determined without any enrichment steps. The detection limit of amitrole added to Viennese tap water is 0.05 g/L.     

Determination of chromium in liquid fertilizers by ICP/OES using spectra accumulation

Summary Spectrum accumulation was used for the determination of small quantities of chromium near the detection limit in liquid fertilizers using a sequential ICP spectrometer. The results were compared with those obtained by the commonly used technique based on peak height measurement for the emission spectral line Cr 267.716 nm in the concentration range 2–100 ng/g. Spectrum accumulation with 5 accumulations yields about two times more precise results compared with the classical technique with 5 replications.     

Determination of netilmicin in serum by thin-layer densitometry and fluorescence polarization immunoassay

Summary A newly developed thin-layer chromatographic method (TLC) for the quantitative determination of netilmicin in serum is described and compared with fluorescence polarization immunoassay (FPIA). The TLC procedure involves solid-phase extraction of the aminoglycoside from serum and chromatography on reversed-phase thin layer. Post-chromatographic derivatization is carried out using 2,2-diphenyl-1-oxa-3-oxonia-2-boratanaphthalene (DOOB) as fluorescence reagent. The calibration curve for netilmicin in serum is linear in the range 1.0–5.0 g/ml and the detection limit is about 0.2 g/ml (correlation coefficient r=0.9963, mean coefficient of variation V_XO=±5.3 %). A total of 25 serum samples from patients treated with netilmicin was measured by TLC and the results were compared with those of FPIA (Abbott TDx). There is no statistically significant difference between the two procedures (y=–0.35+1.094·x, Passing/Bablok). Thus the TLC-procedure is an alternative for the determination of netilmicin in serum, that possesses the necessary sensitivity of other comparable methods.Dedicated to Professor Dr. Wilhelm Fresenius on the occasion of his 80th birthday.     

Voltammetric Determination of Trace Amounts of Fenitrothion on a Novel Nano-TiO2 Polymer Film Electrode

A novel nano-TiO₂ polymer modified glassy carbon (GC) electrode was developed for the determination of an organophosphorous pesticide, fenitrothion (-NO₂), in citrate buffer solution. The electrochemical behavior of fenitrothion was characterized by using cyclic voltammetry. An irreversible form, -NO₂, was transformed into a reversible redox couple (-NHOH/-NO), and it can be used to determine trace fenitrothion by square wave voltammetry. The experimental parameters, such as film thickness, pH value, accumulation potential and time were optimized. Interestingly, a cyclic voltammetric scan was observed to be more effective than a constant potential for the accumulation of fenitrothion. A linear response over a fenitrothion concentration of 2.5×10^–8 to 1.0×10^–5M was exhibited, with a detection limit of 1.0×10^–8M (S/N=3). The high sensitivity and selectivity of this film electrode was demonstrated by its practical application to the determination of trace amounts of fenitrothion in lake water and apple samples.     

Determination of phosphorus,sulfur and chlorine in high-purity aluminium

Multi-step procedures for the determination of phosphorus, sulfur and chlorine are described and tested against established methods and on reference materials. Phosphorus is separated as hydrogen phosphide, extracted as phosphomolybdic acid, reduced to molydenum blue and measured photometrically (detection limit 0.05 g/g). Sulfur is separated after reduction as hydrogen sulfide or by means of pyrohydrolysis and measured by ICP-OES (detection limit 0.1 g/g). Chloride can be measured by ion chromatography after pyrohydrolytic separation (detection limit 0.1 g/g). The determination of sulfur was also successfully tested on copper and steel samples.Dedicated to Professor Günther Tölg on the occasion of his 60th birthday     

Phthalates in surface water — a method for routine trace level analysis

Summary A routine method for the determination of phthalates in water is presented. It is suitable for all kinds of water like surface water, waste water, landfill leachate, rain water and ground water. Unfiltered water samples including all suspended particulate matter are extracted by solid-phase extraction in an all-glass apparatus using RPC-18. The extracts are measured by GC/MSD in the SIM mode. Due to an easy but efficient decontamination technique, method blanks could be decreased below 0.02 g/l for all phthalates. The detection limits are 0.01 to 0.02 g/l, the determination limits are 0.02 to 0.05 g/l. Recovery for all phthalates is about 98% (±5%). Phthalates were measured in about 400 samples of water of the river Rhine and its main affluents in Northrhine-Westfalia.     

Determination of neptunium in plutonium and mixed uranium-plutonium samples by isotope dilution gamma-spectrometry with243Am as a spike

A method was developed for isolating neptunium from Pu, U or mixed oxide (MOX) samples and its determination by isotope dilution -spectrometry (IDGS) using²³⁹Np (²⁴³Am) as a spike. Extraction chromatography with trilaurylamine fixed on a SGX-C18 support was used for the isolation of Np. The decontamination factors for U, Pu, Am and Pa vary between 1000–2000 and 100, respectively. The average separation yield of Np is (95±3)%. The amount of²⁴³Am required for spiking is about 0.2–0.3 g. It is recommended to use the pair of -rays 86.53 keV (²³⁷Np)-106.13 keV (²³⁹Np) for the assay of neptunium. A relative uncertainty of 4% or better is achievable in the analysis of plutonium samples, containing 0.4–80 g neptunium. The detection limit, under the proposed experimental conditions, is about 0.05 g Np. The results were compared with the results obtained by using high resolution -spectrometry (HRGS).     

Gas-chromatographic determination of trace amounts of vinyl chloride in water and air after derivatization to 1,2-dibromochloroethane

Summary A quantitative method for the determination of trace amounts of vinyl chloride in water and air is presented. Analysis of water is performed by stripping it with 250 ml/min helium from a 1-l sample at 20°C for 30 min to transfer the vinyl chloride into the gas phase. The vinyl chloride is concentrated on an ice-cooled adsorption tube, which is filled with 550 mg of silica gel and 300 mg of activated charcoal. Air samples are taken by drawing a known volume directly through the ice-cooled adsorption tube. The tubes are eluted with carbon disulfide and the vinyl chloride is derivatizised with bromine water to form 1,2-dibromochloroethane. The derivative is determined by capillary gas chromatography with an electron capture detector. The method was tested using water samples over a range from 0.4 ng/l to 1.25 g/l. The detection limits are 0.4 ng/l for 1-l water samples or 50 ng/m³ for 7.5 l air.