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A highly sensitive and selective quantitative assay for unchanged veralipride has been developed. The compound is extracted from alkalized samples (plasma or urine) with dichloromethane and converted to its trimethylated derivative by reaction with trimethylanilinium hydroxide. The reaction mixture is then chromatographed on a 3% OV-1 column. Trimethylated derivatives of plasma samples were assayed by selected-ion monitoring in the chemical-ionization mode and quantified by comparing the intensity of the quasi-molecular ion m/z 426 (M + H) with the intensity of the corresponding ion from trideuterated internal standard, m/z 429 (M + H). Flame-ionization detection was used for the assay of urine samples. The peak height ratio of trimethylated veralipride over trimethylated sulpiride, the internal standard, was used for quantitation of urine samples. A relative standard deviation of less than 10% was found when quantifying 10 ng/ml veralipride in plasma or 1 microgram/ml in urine.
Steam distillation (SD) extraction-solid-phase microextraction coupled to GC-MS was developed for the determination of terpenes and Bligh-Dyer extraction-derivatization coupled with GC for the determination of fatty acids such as ethyl esters were used. It was found that the three different Agave species have the same profile of fatty acids; the quantity of these compounds is different in each Agave variety. On the other hand, different terpenes were identified in the three Agave plants studied: nine in A. salmiana, eight in A. angustifolia and 32 in A. tequilana Weber var. azul.
Two GC-MS methods, based on the application of N,O-bis(trimethylsilyl)trifluoroacetamide-derivatization-GC-MS (selected-ion monitoring) and GC-MS-MS without derivatization, respectively, were optimised and applied to the determination of a group of five selected endocrine disrupting compounds (EDCs) in wastewaters. Both methods included solid-phase extraction with Oasis HLB cartridges allowing an enrichment factor for wastewater samples of 100-fold. The investigated EDCs were estrone, 17beta-estradiol, 17alpha-ethynylestradiol, 4-tert-octylphenol and bisphenol A. Results obtained from the validation studies yielded comparable results in both cases. Recoveries in spiked wastewaters at 50 ng/l were higher than 90% for all the compounds, except for 4-tert-octylphenol (75%). Repeatability and reproducibility were adequate, varying from 1.6 to 14%, except for estrone which reproducibility was 28% when the derivatization-GC-MS method was applied. Limits of detection calculated ranged from 2.5 to 27.5 ng/l with differences between both methods from 1.1 (estrone) to 10.4 (bisphenol A) times. Both methods were successfully applied to the analysis of the target compounds in sewage treatment plant influents and effluents. Traces of bisphenol A, 4-tert-octylphenol, estrone and 17beta-estradiol were detected at concentration levels ranging from 13.3 to 1105.2 ng/l.
In the present work, a study attempting to characterize the Manila elemi and Mexican copal resins from the Burseraceae family, which are used as components of varnishes and binding media of artworks, has been carried out. A new GC-MS method involving the use of methyl chloroformate as derivatisation reagent has been proposed. A second method which uses pyrolysis-GC-MS and hexamethyldisilazane as derivatization reagent has also been applied. Characterization of the main components of the mono-, sesqui- and triterpenoid fractions occurring in the raw materials has been achieved. Both alpha- and beta-amyrin have been established as the major triterpenoid compounds occurring in these resins together with hop-22(29)-en-3beta-ol, found only in the Mexican copal. Artificially aged samples of Manila elemi and Mexican copal have also been analysed in order to study the stability of the triterpenoid components of the resins and their possible use as marker molecules. The results obtained indicate that these molecules, in particular, alpha- and beta-amyrin undergo oxidation processes during both artificial and natural ageing. Nevertheless, hop-22(29)-en-3beta-ol could be selected as marker compound for Mexican copal. The proposed methods of analysis have been applied to real paint samples extracted from paintings in which Mexican copal was present as the main component of an "oleoresin" binding medium to assess their ability for identifying this product when used in artworks. Satisfactory identification of this resin is obtained by means of GC-MS whereas Py-GC-MS provides, in general, weaker signals for the components of the resin. Additionally, the influence of the pigments present in real samples on the resin ageing process has been considered.
A new technique for sample preparation on-line with LC and GC-MS assays was developed. Microextraction in a packed syringe (MEPS) is a new miniaturised, solid-phase extraction technique that can be connected on-line to GC or LC without any modifications. In MEPS approximately 1mg of the solid packing material is inserted into a syringe (100-250 microl) as a plug. Sample preparation takes place on the packed bed. The bed can be coated to provide selective and suitable sampling conditions. The new method is very promising. It is very easy to use, fully automated, of low cost and rapid in comparison with previously used methods. This paper presents the development and validation of a method for microextraction in packed syringe MEPS on-line with GC-MS. Local anaesthetics in plasma samples were used as model substances. The method was validated and the standard curves were evaluated by the means of quadratic regression and weighted by inverse of the concentration: 1/x for the calibration range 5-2000 nM. The applied polymer could be used more than 100 times before the syringe was discarded. The extraction recovery was between 60 and 90%. The results showed close correlation coefficients (R>0.99) for all analytes in the calibration range studied. The accuracy of MEPS-GC-MS was between 99 and 115% and the inter-day precision (n=3 days), expressed as the relative standard deviation (R.S.D.%), was 3-10%.
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