Gas chromatography analysis of organophosphorous pesticides in plant samples

Summary The work presents a GC method for the determination of six organophosphorous pesticide residues in cabbage. Chopped cabbage was blended with acetone, then extracted with the mixture of n-hexane:methylene chloride (1:1). The extract was purified on a GPC column packed with BioBeads SX-3 gel. The pesticides were eluted with the mixture of methylene chloride:cyclohexane (1:1) at the flow rate of 0.5 mL min⁻¹. After concentrating the extract was analysed by GC. Nearly 100 samples of cabbage were analysed; trace residues of dimethoate (about 0.05 ppm) were found in 10 samples. The average recoveries of the pesticides were above 80% with a relative standard deviation mostly less than 10%. Presented at: Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, September 3–5, 1997.     

Ti (IV) modified vinyl phosphate magnetic nanoparticles for simultaneous preconcentration of multiple arsenic species from chicken samples followed by HPLC-ICP-MS analysis

Ti (IV)-modified vinyl phosphate magnetic nanoparticles (Fe₃O₄@SiO₂@KH570-PO₄-Ti (IV)) was prepared for simultaneous extraction of multiple arsenic species, followed by high performance liquid chromatography (HPLC)– inductively coupled plasma mass spectrometry (ICP-MS) analysis. Inorganic arsenic (iAs), dimethyl arsenic acid (DMA), monomethyl arsenic acid (MMA), p-amino phenyl arsenic acid (p-ASA), 4-hdroxyphenylarsenic acid (4-OH), phenyl arsenic acid (PAA), and 3-nitro-4-hydroxyphenylarsenic acid (ROX) were investigated as interest analytes. It was found that they were quantitatively adsorbed on Fe₃O₄@SiO₂@KH570-PO₄-Ti (IV) at pH 5, and desorbed completely with 0.1 mol/L sodium hydroxide solution. Enrichment factor of 100-fold was obtained by consuming 100 mL sample solution. Under the optimal conditions, the method combining MSPE with HPLC-ICP-MS presented a linear range of 1–5000 ng/L for seven arsenic species. The limits of detection were 0.39, 0.60, 0.23, 1.85, 0.54, 0.48, and 0.84 ng/L for DMA, MMA, p-ASA, iAs, 4-OH, PAA, ROX, with the relative standard deviations (c = 10 ng/L, n = 7) of 3.6, 3.9, 5.5, 12.4, 6.1, 5.8, 5.0, respectively. The accuracy of the method was validated by analyzing BCR 627 Tuna fish. The application potential of the method was further evaluated by chicken muscle and liver samples. No target arsenic species were detected in these samples, and good recoveries (80.6–123%) were obtained for the spiked samples at low, medium, and high concentration levels.     

原子荧光光谱法测定化探样品中砷锑铋汞

研究用传统方法在其他条件基本不变的情况下,用自来水代替酒石酸,测定化探样品中砷,锑,铋和汞,方法简便,快速,结果准确可靠。     

二苯硫脲纤维分离富集原子吸收法测定地质样品中痕量金

采用自行研究合成的二苯硫脲纤维素分离富集，并用火焰原子吸收法测定了地质样品中痕量金，系统研究了题示方法的各种条件，该法简便快速，测定准确，经济实用，具有推广价值。     

A column-switching method for quantification of the enantiomers of omeprazole in native matrices of waste and estuarine water samples

This work reports the use of a two-dimensional liquid chromatography (2D-LC) system for quantification of the enantiomers of omeprazole in distinct native aqueous matrices. An octyl restricted-access media bovine serum albumin column (RAM-BSA C₈) was used in the first dimension, while a polysaccharide-based chiral column was used in the second dimension with either ultraviolet (UV-vis) or ion-trap tandem mass spectrometry (IT-MS/MS) detection. An in-line configuration was employed to assess the exclusion capacity of the RAM-BSA columns to humic substances. The excluded macromolecules had a molecular mass in the order of 18 kDa. Good selectivity, extraction efficiency, accuracy, and precision were achieved employing a very small amount (500 μL or 1.00 mL) of native water sample per injection, with detection limits of 5.00 μg L⁻¹, using UV-vis, and 0.0250 μg L⁻¹, using IT-MS/MS. The total analysis time was only 35 min, with no time spent on sample preparation. The methods were successfully applied to analyze a series of waste and estuarine water samples. The enantiomers were detected in an estuarine water sample collected from the Douro River estuary (Portugal) and in an influent sample from the wastewater treatment plant (WWTP) of São Carlos (Brazil). As far as we are concerned, this is the first report of the occurrence of (+)-omeprazole and (−)-omeprazole in native aqueous matrices.     

Comparison between cocoa and chocolate: characterisation and fatty acid content

The connection between chocolate and cocoa is studied. As cocoa is produced in different countries, samples coming from the same geographical region are analysed. The analyses focus on the characterisation of the considered samples for different aspects of quality and to individuate the original locations of production, also connecting this with the nutritional aspects. For this purpose, qualitative and quantitative traditional analysis and determination of fatty acid content are performed. The obtained experimental data show interesting correlations. The percentages of fatty acids computed allow for distinctions to be made among cocoa and chocolate samples. Furthermore, a relation can be assumed among the data obtained for primary matters and final products corresponding to countries being positioned on the same latitude, even if they are situated in different continents.     

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.     

Simultaneous extraction of acidic and basic drugs via on-chip electromembrane extraction

In the present work, a on-chip electromembrane extraction (CEME) was designed and employed for simultaneous extraction of mefenamic acid (MEF) and diclofenac (DIC), as acidic model analytes, and betaxolol (BET), as a basic model analyte, followed by HPLC-UV. The CEME consists of two polymethyl methacrylate (PMMA) parts which each part consists of two separated microfluidic channels. A polypropylene sheet membrane impregnated with an organic solvent was sandwiched between the parts. One of the parts was used as the flow path for the sample solution and the other one as holder for the acceptor phases. The separated microfluidic channels of the sample solution part were connected to each other using a small piece of a capillary tube and the sample solution was pumped through them by means of a micro-syringe pump. However, the acceptor phases of the acidic and basic analytes were separately kept stagnant in the two microfluidic channels during the extraction process. A d.c. potential was applied for migration of the analytes from sample solution through the organic membrane into the acceptor phases. All effective variables on the extraction efficiency of the analytes were optimized. Under the optimized conditions, preconcentration factors higher than 15 were achieved and the calibration curves were linear in the range of 10–500 μg L⁻¹ (r² > 0.9982). RSD% values (n = 4) and LODs were less than 7.1% and 5.0 μg L⁻¹. The results demonstrated that CEME could efficiently be used for the simultaneous analysis of acidic and basic analytes in biological samples.     

Preconcentration of Nicotinamide Using Molecularly Imprinted Microspheres for Solid-phase Extraction with Determination by High-performance Liquid Chromatography

The determination of target molecules in complicated matrices such as biological samples is largely dependent on sample pretreatment. Molecularly imprinted solid-phase extraction (SPE), using molecularly imprinted polymers as the adsorbent, has been demonstrated to be effective for the selective enrichment of target molecules in biological samples. In this study, molecularly imprinted polymeric microspheres were fabricated by two-step swelling polymerization using polystyrene particles as seeds, nicotinamide as the template, methacrylic acid as a functional monomer, and ethylene glycol dimethacrylate as a cross-linker. The molecularly imprinted polymeric microspheres were packed into empty SPE cartridges, and the spiked urine and serum samples were loaded separately. After an initial washing and elution step, the effluents were analyzed by high-performance liquid chromatography (HPLC) using 1:9 methanol/0.05% phosphoric acid. The obtained molecularly imprinted polymeric microspheres were uniform, and the spherical particles were well distributed. The established method was validated, and the results showed that the method was linear from 0.499 to 19.96?µg?mL^?1. The limits of detection and quantification for nicotinamide were 0.3 and 0.9?µg?mL^?1, respectively. The relative standard deviations were 1.55 and 2.86% in urine and serum, respectively. The spiked recoveries of nicotinamide were 86.0–98.8% and 87.0–96.8% in urine and serum, respectively. The molecularly imprinted SPE and HPLC methods in this study are useful for the pretreatment and determination of the target compounds in these matrices.     

Qualitative and quantitative analysis of pathological and non-pathological human bone using radioisotope X-ray fluorescence technique

Pathological and non-pathological human elbow bone samples were collected from one male human patient and one female human patient who were undergoing treatment in our University Research Hospital. Pathological and non-pathological human elbow bone samples were analyzed by means of energy-dispersive X-ray fluorescence spectrometry by using standard additions method. Experimental results are presented and discussed in this work.