Analysis of pesticide residues in fruit and vegetables with ethyl acetate extraction using gas and liquid chromatography with tandem mass spectrometric detection

A multiresidue method based on extraction with ethyl acetate has been used at the Swedish National Food Administration since 1989 to monitor pesticide residues in fruit and vegetables. The method has been continuously adjusted, resulting in simple and quick analyses of pesticide residues. To recover basic pesticides, the addition of an alkali is necessary. The addition of sodium hydrogen carbonate has been shown to recover all pesticides effectively without any degradation. The liquid chromatography (LC) with tandem mass spectrometry (MS/MS) technique has made it possible to analyse more polar pesticides and to replace many single methods. The latest development in the multiresidue method, comprising the use of gas chromatography (GC) with MS/MS, has further improved the analysis by replacing the conventional GC detectors. The need for cleanup has been reduced or eliminated entirely. Consequently, the method has been simplified in a way that makes it possible to recover all included analytes in many different matrices in one single extraction and to detect them either with GC-MS/MS or with LC-MS/MS.     

Simultaneous high-performance liquid chromatographic stability-indicating analysis of acetaminophen and codeine phosphate in tablets and capsules

A high-performance liquid chromatographic method has been developed for the simultaneous determination of acetaminophen and codeine phosphate for product stability studies, and release and dissolution testing of tablets and capsules. The reversed-phase method utilizes UV detection at 214 nm, a C18 column and requires a maximum of 10 min per analysis. The method has been validated for use with products containing as much as 500 mg of acetaminophen and as little as 7.5 mg of codeine phosphate. The known potential degradation products, p-aminophenol, codeine N-oxide, and codeinone are separated for quantitation simultaneous with the parent compounds. The method has been shown to be linear, reproducible, specific, sensitive and rugged.     

Preparation of several new polypeptides and proteins labelled with125I

Six¹²⁵I labelled polypeptides and proteins were prepared with high specific activity and good quality.The optimal iodination with Iodogen method has been studied and different Radio-HPLC methods for purification have been compared. In addition, the method of coating tube with Iodogen has been improved.     

热动力学特征对比参量法及其应用研究

基于简单级数反应的积分和微分热动力学方程，建立了热动力学特征对比参量 法的数学模型，提出了一种由特征时间参量计算特征对比参量的方法，通过几种不 同级数模型反应的热动力学研究证明了方法的正确性，并利用该法研究了过氧化氢 在磷酸盐缓冲液中氧化对苯醌反应的动力学特征，实验结果表明该反应动力学方程 可以表示为：dC(醌)/dt=kC(醌)C(H_2O_2)~0.5C(H~+)~(-0.5)     

Determination of tauromustine and its demethylated metabolites in plasma and urine

A sensitive, selective and precise high-performance liquid chromatographic method for simultaneous determination of tauromustine and its demethylated metabolites in plasma and urine has been developed. It is based on solid-phase extraction on C18 sorbent and separation on a semipolar column. The analytical procedure is described in detail. The method has been validated with respect to linearity, recovery, selectivity, precision and detection limit. The stability of the determined substances in various media has also been studied.     

Determination of magnesium by spectrofluorimetry and synchronous scanning first and second derivative spectrofluorimetry with 2-quinizarinsulphonate

Summary Determination of Magnesium by Spectrofluorimetry and Synchronous Scanning First and Second Derivative Spectrofluorimetry with 2-Quinizarinsulpbonate An analytical method has been developed for the fluorimetric determination of microgram amounts of magnesium in solution. The method is based on the reaction of magnesium with 2-quinizarinsulphonate. Synchronous scanned first and second derivative fluorimetry has been employed to increase the sensitivity of the method. The influence of reaction variables as well as instrumental parameters and the composition of the complex is discussed. The interference of various foreign cations and anions has also been examined and in some cases eliminated or reduced by addition of cyanide.     

Voltammetric determination of platinum in inorganic complexes and in water, geological and biological matrices using laboratory- and field-based instrumentation

The extremely sensitive catalytic hydrogen ion reduction wave observed after the formation of a platinum-formazone complex at a mercury electrode in a hydrazine-formaldehyde-H2SO4 medium has been utilised to determine platinum voltammetrically in well characterised platinum inorganic complexes (oxidation states O, II and IV) and in biological, geological and water samples. Experimental conditions have been optimised and sample-treatment procedures for various matrices have been critically evaluated for the quantification of platinum by the standard additions method. The determination of platinum in geological samples by this method has been compared with an inductively coupled plasma mass spectrometric method. Both conventional and portable field-based instrumentation have been used in the studies, and the possibility of developing a field-based method for the determination of platinum has been investigated. Despite the inherent sensitivity of the method, which enables concentrations down to 0.01 p.p.b. to be detected in simple matrices, natural levels in water and biological materials, where matrix effects suppress the voltammetric response, are often below the detection limit.     

Evaluation of some as-triazines and re-evaluation of PDT and ferrozine as reagents for spectrophotometric determination of ruthenium

A sensitive method for the spectrophotometric determination of ruthenium with the ferroinyielding as-triazines has been developed. This method has several advantages; complete reduction of ruthenium species to ruthenium(II) can be achieved by the recommended procedure, which shortens the colour development time, saves the unnecessary use of several-fold excess of the reagent and the molar absorptivity is increased significantly. A few of the new as-triazines together with the commercially available Ferene(R) have been evaluated as ruthenium(II) chromogens. 3-(2-Pyridyl)-5,6-diphenyl-as-triazine (PDT) and ferrozine, a sulphonated derivative of PDT, have been re-evaluated by the new method. It has been observed that the as-triazine acting as a bidentate ligand forms a tris-complex with ruthenium(II) similar to its reaction with iron(II).     

Radiochemical microdetermination of Manganese, strontium and barium by ion-exchange

A rapid radiochemical ion-exchange method has been developed for the quantitative separation of microamounts of Mn, Sr and Ba in the presence of other elements with atomic numbers below 84. The method proposed, combined with neutron-activation analysis, has been successfully applied to the simultaneous determination of Mn, Sr and Ba in plant and animal tissues. The method is simple and accurate.     

A revised method, and errors in the determination of thiosulphate by the Wollak method

The Wollak method for the determination of thiosulfate has been investigated. The experimental procedure has been revised in order to eliminate several problems associated with the method.     

A simple and rapid spectrophotometric method for determination of thiophanate-methyl in commercial formulations and its residues in foodstuffs

A new, simple, rapid, and sensitive spectrophotometric method for the determination of thiophanate-methyl, based on its reaction with cobalt(II) in the presence of triethylamine, has been developed. The yellowish green color that develops instantaneously on mixing the fungicide with the reagents in dimethylformamide is stable for at least 2 h and has maximum absorbance at 360 nm. The method has been successfully applied to the determination of thiophanate-methyl in its commercial formulations and residues on grains and apples. A photometric titration procedure for formulation analysis of the fungicide has also been developed.     

Isotope fraction of hydrogen in hydrogen dichloride anions of tetramethyl- and tetraethylammonium salts

The theory of the double dilution method is shortly described. Critical volume of the liquid specimen has been determined. Optimal specimen concentration ratios of the sample in a given diluent have been examined. The validity and precision of the method have also been investigated. The usefulness of the method has been confirmed by analyzing a typical coin of Thailand. Good agreement with atomic absorption spectrometry (AAS) is obtained.     

A clean and expedient synthesis of spirooxindoles in aqueous media catalyzed over nanocrystalline MgO

An efficient and eco-friendly method for the synthesis of spirooxindoles with fused tetrahydrochromenes has been demonstrated using basic nanocrystalline MgO catalyst in aqueous condition. The method has been applied for the synthesis of a range of compounds with variable functionalities in excellent yield and selectivity.     

CE Determination of Monosaccharides in Pulp Using Indirect Detection and Curve-Fitting

In the present work a capillary electrophoretic method for the analysis of monosaccharides utilizing indirect UV-detection has been developed. Different probes for indirect detection have been assessed using model carbohydrate samples. Background electrolytes with or without addition of cetyltrimethylammonium bromide have also been evaluated regarding the separation power. Furthermore, a curve-fitting algorithm has been introduced to increase the separation resolution. The optimized method has been used for analysis of monosaccharides from an acidically hydrolyzed pulp sample.     

食品及生物样品中痕量草酸的荧光动力学法测定

拟定了一个荧光动力学测定痕量草酸根的新方法。在硫酸介质中，草酸催化重铬酸钾氧化罗丹明６Ｇ使其荧光猝灭。方法线性范围为０．８－１４．０ｍｇ／Ｌ，直接用于菠菜，人尿中草酸根的测定，获得满意结果。     

Cyclic macromolecules. Synthesis and characterization of ring-shaped polystyrenes

A method has been developed to synthesize cyclic polystyrene molecules, by reacting bifunctional “living” polystyrene with α,α′ dibromo-p-xylene. The ability of the method to yield cyclic polymers over a molecular weight range from 7000 to 250,000 has been thoroughly investigated and discussed. Characterization of the cyclic macromolecules with respect to linear homologues of the same molecular weight has been performed by means of viscometry. The effect of cyclization tends to decrease as the molecular weight increases.     

Simple and highly efficient preparation and characterization of (−)-lupanine and (+)-sparteine

In a simple and convenient way, we have improved the non-chromatographic isolation of optically pure (−)-2-oxosparteine ((−)-lupanine) and (+)-sparteine. The fast and efficient method for the determination of the ee of bisquinolizidine alkaloids has been proposed. A relatively simple simple ¹H NMR method has been applied for evaluation of the % ee of enantiomers of the lupanines and sparteines with the chiral dibenzoyltartaric acids as the shift reagents. The ¹H NMR spectra of the bases and the new salts in polar solvents have been measured.The results are confirmed by chiral HPLC method. Additionally, for the first time X-ray analysis of the salt of (−)-lupanine has been performed. The improved method of purification of bisquinolizidine alkaloids will considerably facilitate the employment of these alkaloids as chiral ligands in asymmetric reactions and as pharmacological tools.     

A highly accurate and precise method for the assay of chromium metal and chromium(III) oxide

A method capable of a precision of 3 to 5 parts in ten thousand has been developed for the routine assay of high purity chromium metal and chromium trioxide. Use has been made of the favourable gravimetric factor of ferrous ammonium sulfate and of an amperometric end-point. Comparison with the arsenic trioxide method was made.     

High-pressure liquid chromatographic determination of propoxyphene hydrochloride in tablets and capsules.

The determination of propoxyphene hydrochloride by gas chromatography (GC) has been examined. Under a number of operating conditions significant on-column decomposition has occurred. The amounts of decomposition have been found to be dependent on sample size, flow-rate, column temperature, liquid phase loading, and solid support material. In view of this work a high-pressure liquid chromatographic procedure for quantitating propoxyphene hydrochloride has been developed. This method has been found to be specific for propoxyphene hydrochloride in the presence of its heat decomposition products formed with and without acetaminophen. This method does not suffer from problems associated with GC procedures.     

Quantitation of verapamil and norverapamil in postmortem and clinical samples using liquid-liquid extraction, solid phase extraction, and HPLC

Summary A sensitive micellar electrokinetic chromatography method for the determination of impurities in SB-209247, a novel LTB₄ antagonist, has been developed. Selectivity was optimised by systematic examination of the effects of the acetonitrile content in the separation buffer. Sensitivity and resolution was enhanced by focusing effects for both charged and neutral analytes achieved by a special sample buffer composition. Minor impurities well below 0.1% peak area ratio can be readily and reliably detected. The validity of the method has been successfully demonstrated with respect to reproducibility of peak area ratios and the linearity of a key impurity. A comparison with HPLC has shown the method has complementary selectivity and competitive sensitivity.