Simultaneous Determination of Carbamate and Organophosphorus Pesticides in Honeybees by Liquid Chromatography-Mass Spectrometry

Summary The potential of liquid chromatography-mass spectrometry (LC-MS) has been studied for the simultaneous determination of sixteen carbamate and organophosphorus pesticides in honeybees using a traditional sample preparation protocol based on acetone extraction and dichloromethane partitioning. The performances of both atmospheric pressure chemical ionization (APCI) and electrospray (ES) interfaces were compared. APCI offered better sensitivity and specificity for a higher range of pesticides. Limits of quantification were from 0.01 to 0.17 mg kg^–1, at which recoveries obtained were between 64 and 93%, except for pirimicarb that was at 13%, with relative standard deviations ranging from 7 to 20%. Fenitrothion, fenoxycarb, methiocarb and phoxim were found in bees from Valencian Community beehives at concentrations between 0.03 and 3.75 mg kg^–1.     

溶膜预富集-石墨炉原子吸收法测定痕量钯

强酸性条件下 ,钯 (Ⅱ )与 5 [( 5 氯 2 吡啶 )偶氮 ] 2 ,4 二氨基甲苯 ( 5 Cl PADAT)生成紫红色螯合物 ,该螯合物可与十二烷基苯磺酸钠 (SDBS)生成离子缔合物 ,离子缔合物经 0 .3μm孔径的硝化纤维微孔滤膜富集后 ,于小体积 ( 0 .5mL)的浓硫酸中溶膜 ,用石墨炉原子吸收法 (GFAAS)测定 ,富集倍数可达 2 0 0倍 ,钯含量在 4.69× 1 0 - 1 2 ～ 7.0 9× 1 0 - 9mol/L范围内线性良好 ,检出限为 1 .78×1 0 - 1 2 mol/L。方法用于海水中痕量钯的测定。     

流动注射原子吸收光谱法测定富硒天麻、葡萄及大米中的硒

建立了流动注射氢化物发生-原子吸收光谱法测定富硒天麻、葡萄及大米中硒的方法。测定硒的线性范围为0．33μg/L-50μg/L，相对标准偏差小于3％，加标回收率为93％-106％。方法已广泛应用于实际样品中微量硒的测定。     

Determination of styrene in olive oil by an automatic purge-and-trap system coupled to gas chromatography-mass spectrometry

Summary A new gas chromatographic method using an automatic purge-and-trap system coupled to a GC with mass selective detection to analyze styrene at the parts-per-trillions (ng kg^–1) level is described. The method shows a good sensitivity and the detection limit is 10 ng kg^–1 with a relative standard deviation (RSD) of 4.7% for 164 ng kg^–1 styrene in olive oil. This analytical method has been successfully applied to the analysis of styrene in extra-virgin olive oil from the European market.     

Mechanism of the thermal decomposition of nitrates from graphite furnace mass spectrometry studies

A basically new mechanism of the thermal decomposition of solids is proposed to explain the mass spectral observations of gaseous molecules of CoO, CuO, Cu₂O, NiO, PbO and Mg(OH)₂ during the low-temperature decomposition of the anhydrous and hydrated nitrates of these metals. The mechanism consists of two stages: congruent gasification of all reaction products irrespective of their saturated vapor pressure and subsequent condensation of the low-volatility species (oxides and hydroxides). The partial pressures of these species at the appearance temperatures calculated from this theory for the first stage of the process (1–50 mPa) are in agreement with the detection limits of the quadrupole mass spectrometers used in these experiments. The proposed mechanism is supported by other available data obtained by thermal analysis.     

Chemical imaging in biology and medicine using ion microscopy

The ability to quantitatively map the distribution of elements on the micrometer scale and smaller with high sensitivity and isotopic discrimination is unique to ion microscopy. The information contained in ion images can be crucial to the study of the solid state, where chemical heterogeneity is often directly related to observed behavior. The tools of digital image processing allow the extraction of quantitative information from the image data. These techniques coupled with improved instrumentation for the detection of ion images drastically increase the problem solving capabilities of the ion microscope. The use of such methods and instrumentation in the ion microscopic analyses of cell cultures and tissues of biological and biomedical relevance will be discussed.     

Radio-Frequency Hexamethyldisiloxane Plasma Deposition: A Comparison of Plasma- and Deposit-Chemistry

This study reports on the effect of input power to hexamethyldisiloxane (HMDSO) plasmas. The power dependence of the plasma-phase species and of the surface chemistry (of the deposits) has been investigated. Neutral and positive molecular species were detected within the plasma using mass spectrometry (MS). Secondary ion mass spectrometry (SIMS) was used to probe the molecular structure of the deposits. The elemental composition of the surface was determined by XPS and the deposition rate was monitored using a vibrating quartz crystal microbalance. Neutral and cationic molecules of mass greater than HMDSO were detected in the plasma. Their formation through ion-molecule reactions is proposed. Changes in the relative concentration of plasma-phase species follow those seen in molecular species detected at the deposit surface. Thus, we believe that the molecular structure of the deposits can be related to the species present in the plasma. While traditionally the dominant mechanism in deposit formation is assumed to be free radical combinations, we propose other possibilities involving cations with the aim of putting forward a new perspective on plasma polymerization mechanisms and thereby stimulating discussion.     

Sample preparation procedure for the determination of sulphur and trace metals in oil products by the ICP with a minitorch using emulsions

A quick sample preparation method was used for the determination of sulphur and trace metals in oil and oily products by the ICP with a minitorch. Stable aqueous emulsions of oils and oil products were made by using two kinds of emulsifiers (one with low sulphur content, the other sulfonated). Aqueous standard solutions can be used for the preparation of calibration solutions. The contents of S, Al, Cr, Cu, Fe, Mg, Ni and Pb in aqueous emulsions were determined and the results were in good agreement with the composition of oil standard solutions used for control analysis procedure.     

Pyrolysis chemical ionization mass spectrometry of cellulose ethers

Pyrolysis ammonia chemical ionization (PyCI) mass spectrometry was performed on hy-droxyethyl-, hydroxypropyl-,methyl-, hydroxypropylmethyl-, and ethylhydroxyethyl cel-luloses. The mass peaks in the PyCI mass spectra of these cellulose ethers could be assigned to the ions of pyrolytic dissociation products which form via the [2 + 2 + 2] cycloreversion and the E_i elimination pyrolysis pathway. Structural information about the residual amount of nonderivatized cellulose, the relative chain length distributions of the substituents in hydroxyalkyl celluloses, and the end-capping of hydroxyalkyl substituents by alkyl groups in the mixed cellulose ethers is obtained. Interference of secondary pyrolysis products in the PyCI mass spectra is found to be of minor importance, especially in the lower mass regions. © 1995 John Wiley & Sons, Inc.