Determination of N-n-alkyl-dimethylmorpholines and their metabolites by high resolution GC/MS

An analytical method is described to determine simultaneously cis/trans N-n-alkyl-dimethylmorpholines and their metabolites, the 4-(ω-carboxy-n-alkyl) cis/trans-2,6-dimethylmorpholines by pyrolytic alkylation and high resolution GC/MS in aqueous systems and sediments. The substances in the sediment phase were analyzed by GC/MS after extraction with methanol and water, substances in the water phase could be directly determined by GC/MS. The analytical procedure also allows the determination of further carboxylic acids in complex aqueous systems.     

Direct methylation at the surface of Carbopack B Part I: Determination of phenolic pesticides

 A procedure for the determination of phenolic pesticides, i.e. the hydroxybenzonitriles bromoxynil and ioxynil and the 2,4-dinitrophenol-derivatives dinoseb, dinosebacetate, dinoterb, dinoterbacetate, dinobuton, binapacryl and DNOC is presented. The herbicides with a free phenolic OH-group as well as the corresponding esters are very strongly adsorbed on Carbopack B, a special graphitized carbon black. In contrast to the esters, which can be removed almost quantitatively, the substances with a free phenolic OH-group cannot be eluted in any significant amount. This effect was used for the derivatization of the herbicides directly on Carbopack B, using diazomethane or TMSH as reagents. The derivatives were eluted with ethylacetate and identified and quantified by GC/MS. For recovery studies, water samples were spiked with the pesticides in concentrations within the range tolerated by the European Drinking Water Guideline. Received: 25 March 1996/Revised: 12 June 1996/Accepted: 17 June 1996     

Ultra trace determination of fluorinated aromatic carboxylic acids in aqueous reservoir fluids by solid phase extraction in combination with negative ion chemical ionisation mass spectrometry after derivatisation with pentafluorobenzyl bromide

A new GC/MS method for the ultra trace analysis of fluorinated aromatic carboxylic acids after solid phase extraction and derivatisation with pentafluorobenzyl bromide is described. The pentafluorobenzyl esters formed were determined by negative ion chemical ionisation GC/MS in aqueous reservoir samples in concentrations as low as 0.010 μg/L. Determination of selected fluorinated aromatic carboxylic acids in aqueous reservoir samples, already injected as water tracers in North Sea reservoirs, confirmed the applicability of the method. Received: 5 September 1997 / Revised: 21 January 1998 / Accepted: 26 January 1998     

Ultra trace determination of fluorinated aromatic carboxylic acids in aqueous reservoir fluids by solid phase extraction in combination with negative ion chemical ionisation mass spectrometry after derivatisation with pentafluorobenzyl bromide

A new GC/MS method for the ultra trace analysis of fluorinated aromatic carboxylic acids after solid phase extraction and derivatisation with pentafluorobenzyl bromide is described. The pentafluorobenzyl esters formed were determined by negative ion chemical ionisation GC/MS in aqueous reservoir samples in concentrations as low as 0.010 μg/L. Determination of selected fluorinated aromatic carboxylic acids in aqueous reservoir samples, already injected as water tracers in North Sea reservoirs, confirmed the applicability of the method. Received: 5 September 1997 / Revised: 21 January 1998 / Accepted: 26 January 1998     

Synthesis of Highly Fluorinated Chloroformates and Their Use as Derivatizing Agents for Hydrophilic Compounds and Drinking‐Water‐Disinfection By‐Products

A rapid, safe, and efficient procedure was developed to synthesize, on a small scale, fluorinated chloroformates often required to perform analytical derivatizations. This new family of agents allows straightforward derivatization of highly polar compounds (with multiple hydroxy, carboxy, and amino substituents) in the aqueous phase, compatible with GC and GC/MS analysis. A goal of this work was to develop a derivatization procedure that would enable the detection and identification of highly polar disinfection by‐products in drinking water.     

Dispersive liquid–liquid microextraction using extraction solvent lighter than water

For the first time a dispersive liquid–liquid microextraction method on the basis of an extraction solvent lighter than water was presented in this study. Three organophosphorus pesticides (OPPs) were selected as model compounds and the proposed method was carried out for their preconcentration from water samples. In this extraction method, a mixture of cyclohexane (extraction solvent) and acetone (disperser) is rapidly injected into the aqueous sample in a special vessel (see experimental section) by syringe. Thereby, a cloudy solution is formed. In this step, the OPPs are extracted into the fine droplets of cyclohexane dispersed into aqueous phase. After centrifuging the fine droplets of cyclohexane are collected on the upper of the extraction vessel. The upper phase (0.40 μL) is injected into the gas chromatograph (GC) for separation. Analytes were detected by a flame ionization detector (FID) (for high concentrations) or MS (for low concentrations). Some important parameters, such as the kind of extraction and dispersive solvents and volume of them, extraction time, temperature, and salt amount were investigated. Under the optimum conditions, the enrichment factors (EFs) ranged from 100 to 150 and extraction recoveries varied between 68 and 105%, both of which are relatively high over those of published methods. The linear ranges were wide (10–100 000 μg/L for GC‐FID and 0.01–1 μg/L for GC‐MS) and LODs were low (3–4 μg/L for GC‐FID and 0.003 μg/L for GC‐MS). The RSDs for 100.0 μg/L of each OPP in water were in the range of 5.3–7.8% (n = 5).     

Methods for the determination of neutral drugs as well as betablockers and β2-sympathomimetics in aqueous matrices using GC/MS and LC/MS/MS

An analytical method has been developed which allows the determination of 22 different neutral and weakly basic drugs belonging to several different medicinal classes like antiphlogistics, betablockers, β₂-sympathomimetics, lipid regulators, antiepileptic agents, psychiatric drugs and vasodilators in waste water as well as in river and drinking water. A method including solid phase extraction, derivatization by silylation and detection by GC/MS permits detection down to 5 ng/L. The recovery rates mostly exceeded 70%. However, the determination of phenazone, carbamazepine, cyclophosphamide, ifosfamide and pentoxiphylline is frequently disturbed by organic co-extractants in real samples of rivers and waste waters. Therefore, a time saving alternative method has been developed, combining solid phase extraction (as an enrichment step) together with detection by LC-electrospray/MS/MS allowing the measurement of 5 neutral drugs. Detection limits down to 10 ng/L have been achieved even for organically highly contaminated waters like sewage treatment plant effluents. Received: 18 November 1997 / Revised: 18 March 1998 / Accepted: 21 March 1998     

Aqueous vibromagnetic extraction of hydrophilic and hydrophobic biologically active substances from peloids of varied genesis

Aqueous vibromagnetic extraction of hydrophobic and hydrophilic biologically active substances from peloids of varied origin (sapropels, and sulfide-slime mud) was developed. Instrumental analytical techniques (GC/MS, TLS, IR spectroscopy), gravimetry, and other methods were used to determine polar and nonpolar lipids and saturated and unsaturated fatty carboxylic and humic acids in colloid systems.     

Drug impurity profiling strategies

A general scheme is set up for the estimation of the impurity profile of bulk drug substances by the complex use of chromatographic, spectroscopic and hyphenated techniques. Several examples are presented as illustrations to the scheme from the authors' laboratory involving the use of chromatographic methods such as thin-layer-(TLC), gas-(GC), analytical and preparative high-performance liquid chromatography (HPLC), spectroscopic methods such as mass spectrometry (MS) and NMR spectroscopy as well as hyphenated techniques (HPLC/diode-array UV, GC/MS and HPLC/MS). In addition to summarizing earlier work, new examples are also presented: identification of an impurity (propyl 4-[diethylcarbamoyl(methoxy)]-3-methoxy phenylglyoxylate, II) in propanidid (I) and two unsaturated impurities in allylstrenol (VII) by GC/MS and HPLC/diode-array UV as well as estimation of the impurity profile of mazipredone (III) by HPLC/MS and HPLC/diode-array UV.     

Selective and sensitive detection of organic contaminants in water samples by on-line trace enrichment–gas chromatography–mass spectrometry

Liquid chromatographic (LC) type trace enrichment is coupled online with capillary gas chromatography (GC) with mass spectrometric (MS) detection for the analysis of aqueous samples. A volume of 1–10 ml of an aqueous sample is preconcentrated on a trace-enrichment column packed with a polymeric stationary phase. After cleanup with HPLC-grade water the precolumn is dried with nitrogen and subsequently desorbed with ethyl acetate. A fraction of 60 μl is introduced on-line into a diphenyltetramethyldisilazane-deactivated retention gap under partially concurrent solvent evaporation conditions and using an early solvent vapor exit. The analytes are separated and detected by means of GC–MS. The potential of the LC–GC–MS system for monitoring organic pollutants in river and drinking water is studied. Target analysis is carried out with atrazine and simazine as model compounds; the detection limits achieved under full-scan and multiple ion detection conditions are 30 pg and 5 pg, respectively. Identification of unknown compounds (non-target analysis), is demonstrated using a river water sample spiked with 168 pollutants varying in polarity and volatility.     

Normal‐phase high‐performance counter‐current chromatography for the fractionation of dissolved organic matter from a freshwater source

Normal‐phase high‐performance counter‐current chromatography (HPCCC) is used to obtain a preliminary fractionation of components in dissolved organic matter (DOM) from a freshwater source. The HPCCC solvent system involved a normal‐phase approach with water/methanol (1:1) as the lower stationary phase and hexane/ethyl acetate (1:1) as the upper mobile phase. The critical experiment parameters were optimised: revolution speed 1800 rpm and flow rate 0.15 mL/min. Under these conditions 50 μL of a 0.50 mg/mL DOM solution was loaded. The detection wavelength was monitored at 330 nm in order to isolate the main portion of DOM, which includes substances such as carboxyl‐rich alicyclic molecules. By optimising this system it was possible to isolate materials that, according to GC–MS, can be related to molecules with an analogous structural background. Where fraction analysis was not suitable for GC–MS, RP‐HPLC with UV absorbance detection was used, showing unique chromatograms for each fraction at both 210 and 330 nm.     

Ultratraces analysis of organochlorine pesticides in drinking water by solid phase extraction coupled with large volume injection/gas chromatography/mass spectrometry

This study describes an SPE coupled with large volume injection (LVI) analytical method for the analysis of organochlorine pesticides, BHC (alpha, beta, delta), aldrin, endosulfan (alpha, beta), endrin, dieldrin, and DDT, from aqueous samples. Determination was carried out by GC with MS. The LODs of organochlorine pesticides were determined at 10 ng/L concentration levels, and the results show that SPE-LVI-GC/MS has the potential to accurately determine organochlorine pesticides in water, as it avoids analyte classes in the various steps of a typical extraction procedure.     

Analysis of cholesterol oxidation products by Fast gas chromatography/mass spectrometry

The aim of the present study was to set‐up a Fast gas chromatography/mass spectrometry method for the analysis of cholesterol oxidation products (COPs). A silylated mixture of seven oxysterol standards was injected into a Fast GC/MS system. A capillary GC column (10 m×0.1 mm internal diameter×0.1 μm film thickness) coated with 95% dimethyl‐ and 5% diphenyl‐polysiloxane, was used. The method gave a fast (total analysis time=3.5 min) and satisfactory resolution (R>1.2) of the COPs standards, with a good repeatability and sensitivity, similar to those of conventional GC/MS; recoveries were tested on mice liver. Fast GC/MS method suitability for COPs analysis in food was also tested on an oxidized sardine fillet, which had been previously saponified and purified by NH₂ solid‐phase extraction (SPE); a good repeatability and sensitivity was also obtained. The analytical performance of the Fast GC/MS method for the determination of COPs, together with the consequent significant reduction of the analysis time and consumables, demonstrates that Fast GC/MS represents a valid alternative to conventional GC/MS and evinces the great potential of such an analytical technique, which could be applied for both food and biological samples.     

Aqueous solubility data for pressurized hot water extraction for solid heterocyclic analogs of anthracene, phenanthrene and fluorene

We report the aqueous solubilities of phenanthrene and several solid three-ring aromatic heterocycles (phenanthridine, acridine, phenazine, thianthrene, phenothiazine, phenoxathiin, phenoxazine, carbazole, dibenzofuran, dibenzothiophene, and 4,6-dimethyldibenzothiophene) at temperatures ranging from 313K to the solute melting point and at a pressure of 5MPa. The data were measured by dynamic saturation method using an in-house-assembled apparatus for pressurized hot water extraction (PHWE). The solute from a known mass of the saturated aqueous solution was transferred to an organic solvent (hexane or toluene), and the organic phase was analyzed by GC/MS. In any of the solutes, the GC/MS records did not indicate any noticeable decomposition within the temperature range of the measurements. The resultant solubilities were converted to activity coefficients of the individual solutes in saturated aqueous solutions, and the results are discussed in terms of temperature and type/number of heteroatoms.     

In situ ethylation of organolead,organotin and organomercury species by bromomagnesium tetraethylborate prior to GC‐ICP‐MS analysis

An analytical method for simultaneous in situ ethylation, of organolead, organotin and organomercury compounds in aqueous samples was developed using a new derivatisation agent, bromomagnesium tetraethylborate (BrMgEt₄B). The determination of lead, tin and mercury compounds was done by species‐specific isotope dilution, derivatisation and GC–inductively coupled plasma MS (GC‐ICP‐MS) or by GC‐MS. The recovery and accuracy of the derivatisation were evaluated. The effect of pH and the relative quantity of derivatisation agent were studied.     

固相微萃取/气相色谱/质谱联用技术在农药残留物分析中的应用

综述了固相微萃取／气相色谱／质谱（SPME／GC／MS）在各种环境水、土壤等样品中农药残留分析中的应用和发展。SPME／GC／MS联用技术具有快速、简便、准确等优点。     

Determination of zinc O,O′-dialkyl dithiophosphate lubricant additives via the corresponding methyl and p-nitrobenzylic ester derivatives using GC-MS, GC-NPD and HPLC-MS

 A quantitative fingerprinting of automotive lubricants with respect to zinc dialkyl dithiophosphates (ZDP), major anti-wear/antioxidant additives, is presented. ZDPs in lubricant solutions are converted into the corresponding methyl and p-nitrobenzylic esters, respectively. After removal of the lubricant matrix the methyl esters are submitted to gas chromatography (GC). Mass spectrometric detection (MS) and comparison with reference methyl esters enable the characterisation of practical ZDP mixtures with respect to alkyl chain length and isomery of the single components. Overall recovery rates are higher than 90% and phosphorus-selective detection (NPD) allows a quantitative determination down to 0.1 pg/μl. The p-nitrobenzylic esters may be analysed by HPLC. Identification and quantification is performed by on-line HPLC-UV and HPLC-MS (APCI) with a determination limit of 20 pg/μl. The ZDP quantification via the methyl esters is applied to seven lubricants from the German market. The method is applicable to used oils allowing the monitoring of ZDP consumption during engine operation. Received: 22 March 1996/Revised: 19 June 1996/Accepted: 21 June 1996     

Separation and enrichment of traces of explosives and their by-products from water by multiple micro liquid extraction for their determination by capillary gas chromatography

A fast sample preparation method for the trace determination of some exploxives, by-products and degradation compounds in water by capillary gas chromatography is described. It is based on multiple extractions of the water sample with sub-milliliter amounts of solvent and subsequent concentration of the unified extracts by reducing its volume to a few microliters according to Dünges. The most suitable solvent was methyl-tert.-butylether. With electron caption detection and an aqueous sample volume of 25 to 100 ml, the determination level is in the pg/ml range. Received: 3 May 1996 / Revised: 28 June 1996 / Accepted: 5 July 1996     

Determination of pesticides in aqueous samples by solid-phase microextraction in-line coupled to gas chromatography—mass spectrometry

A multiresidue method was developed for the determination of nitrogen- and phosphorous-containing pesticides (amines, anilides, phosphorothioates, and triazines) by solid-phase microextraction (SPME) in-line coupled to gas chromatography—mass spectrometry (GC/MS). The 85-µm polyacrylate fiber was first dipped into the aqueous sample for a given time and then directly introduced into the heated injector of the gas chromatography—mass spectrometer, where the analytes are thermally desorbed. The method was evaluated with respect to the limit of detection, linearity, and precision. The limit of detection [selected ion monitoring (SIM) mode] depends on the compound and varies from 5 to 90 ng/L. The method is linear over at least 3 orders of magnitude with coefficients of correlation usually ≥0.996. In general, the coefficient of variation (precision) is <10%. The partitioning of the analyte between the aqueous phase and the polymeric phase depends on the hydrophobicity of the compound as expressed by the octanol—water partitioning coefficient P _ow. The addition of sodium chloride has a strong effect on the extraction efficiency. This effect increases with decreasing hydrophobicity (increasing polarity) of the compound. The triazines atrazine, simazine, and terbuthylazine were first identified and quantified in water samples from the effluent of sewage plants by SPME-gas chromatography—nitrogen—phosphorus detection (GC/NPD). For such a complex matrix GC/NPD is not sufficiently selective for an unambiguous identification at low levels (<1 ppb) of pesticides. Selectivity may be enhanced by using SMPE-GC/MS in the SIM mode with three characteristic ions for each pesticide. This method allows an unequivocal identification and quantification at low levels of pesticides in environmental samples. At a target limit of detection below 100 ng/L, SPME-GC/MS represents a very simple, fast, selective, and solvent-free multimethod for the extraction and determination of these nitrogen- and phosphorous-containing pesticides from aqueous samples.     

气相色谱—质谱法测定水中的二苯羟乙酸

本文报道用气相色谱－质谱法鉴定和定量测定水样中的二苯羟乙酸。对二苯羟乙酸及其甲基化产物的色谱行为进行了探讨。讨论了ＧＣ进样口污染对测定二苯羟乙酸甲酯的影响。应用本方法测定了国际实验室之间比较试验水样中的二苯羟乙酸，分析结果与ＨＰＬＣ方法相一致。