Fast gas chromatography with solid phase extraction clean-up for ultratrace analysis of pesticide residues in baby food.

A sample preparation method based on single solvent phase extraction and solid-phase extraction (SPE-NH2) clean-up is studied in combination with fast capillary gas chromatography (GC) to determine 18 selected pesticides belonging to various chemical classes in apples, the common raw material for baby food production and baby food, at the concentration level < or = 10 microg/kg maximum residual limit (MRL). Possibilities of mass spectrometry (MS) detector and electron capture detector (ECD) in fast gas chromatography (GC) of samples with complex matrice at ultra trace levels of pesticide residues were studied and compared. MS detection in single ion monitoring (SIM) mode provided higher selectivity compared to ECD. Optimisation of extraction as well as the simplifying of the whole process of sample preparation was carried out. Recoveries obtained at concentration level of 5 microg/kg (the required value for limit of quantification (LOQ) in baby food) were >90%, except of dimethoate (77.7%) and captan (46.4%) with MS detection. The obtained LOQs were at least 1 order lower than 5 microg/kg for the majority of compounds. The repeatability of gas chromatography-mass spectrometry (GC-MS) measurements of the matrix matched standards expressed as relative standard deviation was <11% except of captan and cypermethrin.

Application of porous carbon for solid-phase extraction of dicarboxyimide fungicide residues from wines in combination with high-resolution capillary gas chromatography and gas chromatography-mass spectrometry.

Solid-phase extraction with a novel porous carbon sorbent CARB GR was used for the clean-up step of dicarboxyimide fungicides residues from variety of Slovak grape wines with subsequent capillary gas chromatography-flame ionization detection, -electron-capture detection (ECD) and -mass spectrometry-ion-trap detection (MS-ITD) analysis. Recovery was tested at various concentration levels of vinclozolin and iprodione in standard solutions (R = 80-97%, R.S.D. < or = 5). The value of recovery in spiked wines is dependent on concentration level (studied in the range of 5.9 micrograms/1-1.96 mg/l) and on the variety of wine (R = 80-96%; R.S.D. = 3-5%). Limits of quantitation (for sample volume 50 ml) were determined to be with GC-ECD for both fungicides in ppt range and with GC-MS-ITD in the multiple ion detection mode monitoring in ptt range for vinclozolin and ppb range for iprodione. Concentration levels of vinclozolin residues were determined in treated wines (with 0.1% Ronilan 50 WP) as well as iprodione residues (with 0.15% Rovral 50 WP) and a strong dependence on the protective term before the harvest is shown.

Analysis of metalaxyl residues in wines by SPE in combination with HRCGC and GC/MS.

Solid phase extraction (SPE) with the porous carbon sorbent CARB GR was used for the preconcentration of metalaxyl residues from a variety of Slovak grape wines with subsequent capillary GC and GC/MS analysis. Recovery was tested at various concentrations of metalaxyl in standard solutions (recovery, R > or = 92%, relative standard deviation RSD < or = 4.3%) and in wines. The value of recovery in spiked wines was dependent on the concentration (studied in the range 0.02-1.96 mg/l) and on the variety of wine (R = 80-99%; RSD = 2-7%). Limits of quantitation (for a sample volume of 50 ml) were determined to be 0.75 microgram/l with GC-FID and 0.50 microgram/l with GC/MSITD. Concentration levels of metalaxyl residues were determined in treated wines (with 0.25% Ridomil plus 48 WP) and a strong dependence on the protective term before the harvest was shown.

Stability study of novel zinc complexes of pharmaceutical relevance by CE.

CE was used as a stability-indicating assay for zinc mixed-ligand complexes with promised biological activity. CE measurements indicated that Zn(RCOO)2Ln compounds (where R = H, CH3, C2H5, or C3H7; L = caffeine, nicotinic acid, thiourea, or phenazone; and n = 1 or 2) in water tend to decompose at room temperature. For thiourea and phenazone compounds, the degradation products (free zinc ion, carboxylate anion, and the corresponding neutral ligand) were found to increase within a few hours of storage in water. More stable complexes of caffeine and nicotinic acid showed no appreciable changes in CE behavior during the same period of time and only decomposed notably after 10 hr. The stability differences of zinc complexes were characterized in terms of apparent half-life values and rate constants of decomposition reaction. Relationships between the stability and structure of the complexes are discussed, and theoretical interpretation is presented.

Determination of tetracycline antibiotics in animal tissues of food-producing animals by high-performance liquid chromatography using solid-phase extraction.

A high-performance liquid chromatographic (HPLC) method was developed for the determination of oxytetracycline (OTC), tetracycline (TC) and chlortetracycline (CTC) residues in bovine and porcine muscles. The method involved the homogenization of the sample in EDTA-McIlvaine buffer with added n-hexane and dichloromethane, centrifugation, precipitation of the supernatant using trichloroacetic acid and filtration. Preconcentration on Separcol SI C18 cartridges improved the clean-up and the recovery of tetracyclines that were separated by HPLC using the optimized mobile phase of 0.01 M oxalic acid-acetonitrile-methanol (45:35:20) on a Spherisorb ODS 2 column (250 x 4 mm I.D.). UV detection at 360 nm was applied with a detection limit of about 50 ng/g. The diode-array spectra confirmed the applicability of this method to the study of tetracycline residues in carcasses.

Determination of ethylenethiourea in grapes and wine.

Residues of ethylenethiourea (ETU) in grapes and wine were determined by capillary gas chromatography and paper chromatography, without a cleanup step, and after derivatization to S-benzyl-ETU. The detection limit was 0.0002 mg/kg for flame ionization detection, 0.008 mg/kg for paper chromatography with photodensitometric evaluation of the detected spot. Results were compared with a generally used GC method specifying electron capture detection of trifluoroacetylated S-benzyl-ETU. The recoveries of ETU in grapes and wine at different concentration levels were determined. ETU residues were determined in treated grapes but no residues were detected in wine.

Some properties of the adenosine triphosphatase associated with herpes simplex virus and nuclear membrane of host cells.

An enzyme capable to split adenosine triphosphate (ATP) was shown to be firmly associated with mature herpes simplex virus particles purified from infected rabbit lung (ZP) cells. The enzyme localized in the viral envelope was markedly activated by bivalent cations, to the largest degree by Mg2+ at a pH optimum of 7.8--8.0. Na+ and K+ ions neither separately nor together showed any activating effect. Enzyme activity was not sensitive to the action of ouabain. No adenosine diphosphatase (ADPase) and adenosine monophosphatase (AMPase) activities were observed. ATPase activity was competitively inhibited by ADP. AMP and inorganic phosphate were without effect. The ATPase of nuclear membranes isolated from ZP cells exhibited similar properties but behaved differently to the action of sodium dithionite, dinitrophenol, oligomycin and gramicidin, as well as on heat inactivation. The origin of the virus enzyme is discussed.

Capillary gas chromatography of s-triazines.

In order to achieve better resolution and lower detection limits for s-triazines, glass capillary columns made of soft soda-lime glass and etched with gaseous hydrogen chloride have been introduced. Columns with non-polar (OV-101, SE-30) mixed (Carbowax 20M + SE-30) and polar stationary liquids (Carbowax 20M) were used. The thickness of the ultra-thin film columns was determined by weighing the capillaries before and after coating of the capillary with stationary phase and conditioning, and varied from 0.05 to 0.5 mum. From the capacity ratios of s-triazines and n-alkanes measured in sections of an originally long dynamically coated column after it had been cut into several equal parts, the constancy of the film thickness along the whole column was judged. The film thickness was not uniform and increased along the whole column. It was found that glass capillary columns with non-polar stationary phase are not very suitable for the analysis of s-triazine herbicides, as tailing occurs with some of them. Symmetrical peaks and the separation of 17 from 18 analysed s-triazines were achieved on glass capillary columns coated with Carbowax 20M.

Purification and separation of enveloped and unenveloped herpes simplex virus particles.

Enveloped and unenveloped forms of herpes simplex virus (HSV) occurring in infected rabbit lung (ZP line) cells were purified by differential and discontinuous Ficoll density gradient centrifugation. Then the viral particles were separated in a sucrose-D2O density gradient. In the course of the procedures, both virus preparations were freed of Mg2+-dependent Na+ plus K+-stimulated adenosine triphosphatase (ATPase), 5'-nucleotidase, and glucose-6-phosphatase activities. However, Mg2+ -activated ATPase was shown to be firmly associated with purified virions. The recovery of infectious virus was 50-60 percent. The specific infectivities (TCID50/mg protein) of the purified enveloped and unenveloped viral particles were 1-2 times 10(10) and 2-5 times 10(6), respectively. The infectivity of the unenveloped viral particles was discussed.