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PubMed2001

Analysis of fatty acid isomers in ruminant tissues by silver thin layer chromatography followed by gas chromatography.

A method for the analysis of trans fatty acids is described in this paper. Separation of trans isomers from the corresponding cis was based on the different facility with which the double bonds in the alkyl chains of both types of fatty acids form polar complexes with silver, and it was carried out by Thin Layer Chromatography (TLC), using silver nitrate impregnated plates. Further separation, identification and quantification of the individual C18:1 isomers, analysed as methyl esters, was carried out by Gas Chromatography (GC). The determination of the content of the isomer t11-C18:1 in ruminant tissues can contribute to try to elucidate the metabolic pathway formation of conjugated linoleic acid (CLA), shown as a fatty acid of beneficial health effects. Furthermore, the analysis of trans fatty acids in other dietary foods seems to be interesting due to their influence on the modification of the serum lipids profile and the role of this type of compounds in human health.

Animals↗
PubMedDate not supplied

Thin-layer chromatography-densitometry and liquid chromatography analysis of alkaloids in leaves of Papaver somniferum under stress conditions.

The effect of stress conditions on the concentrations of secondary metabolites were examined during various developmental stages of Papaver somniferum plants. P. somniferum plants were grown in laboratory conditions (Budakalász). The experiment consisted of 22 treatments. Significantly different alkaloid contents can be observed under different stress conditions. In general, the alkaloid contents of plants are very low; therefore, a highly sensitive and reliable method has to be developed for analysis. The amount of alkaloids was measured by 2 separation and detection techniques. Accuracy of the thin-layer chromatography method for quantitative analysis is limited. Without purification of samples the background is too noisy. Column liquid chromatography is a sensitive and relatively inexpensive method that allows precise quantitative determination of the alkaloid content.

Alkaloids↗
PubMedDate not supplied

Determination of spinosad in vegetables and fruits by high-performance liquid chromatography with UV and mass spectrometric detection after gel permeation chromatography and solid-phase extraction cleanup on a 2-layered column.

A simple and reliable method was developed for the determination of spinosyns A and D, the active ingredients of spinosad, in vegetables and fruits, by high-performance liquid chromatography with UV detection (HPLC-UV) and confirmation by mass spectrometry (MS); the method uses selected gel permeation chromatography (GPC) and a 2-layered column for solid-phase extraction system. An aliquot of the crude sample extract obtained by acetonitrile extraction is loaded into the GPC system. The fraction containing spinosyns A and D is selectively collected and loaded directly onto a 2-layered column consisting of graphitized carbon (upper layer) and cyclohexyl-bonded silica gel (lower layer). After the column is washed with the GPC mobile phase acetone-cyclohexane (3 + 7), the column is eluted with acetonitrile containing 2% triethylamine. The eluate is used for HPLC-UV/MS analysis. Average recoveries from fortified cabbage, green perilla, fig, and strawberry at analyte concentrations of 0.05 and 0.25 microg/g were >85%, and the relative standard deviations were <9%. The detection limits for spinosyns A and D in green perilla were 0.005 microg/g by UV detection and 0.001 microg/g by MS detection.

Chromatography, Gel↗
PubMed1990

Determination of molecular species of enantiomeric diacylglycerols by chiral phase high performance liquid chromatography and polar capillary gas-liquid chromatography.

A simple method is described for the determination of molecular species of enantiomeric sn-1,2- and sn-2,3-diacylglycerols derived from natural triacylglycerols by Grignard degradation. The method is based on a preparative separation of the enantiomeric diacylglycerols as 3,5-dinitrophenylurethane (DNPU) derivatives by high performance liquid chromatography (HPLC) on a chiral column (25 cm x 4.6 mm ID) containing R-(+)-1-(1-naphthyl)ethylamine as a stationary phase. This is followed by polar capillary gas-liquid chromatography (GLC) of the trimethylsilyl (TMS) ether derivatives of the enantiomeric diacylglycerols derived from the DNPU derivatives using trichlorosilane, which does not cause acyl migration and racemization during the reaction. The cleavage is better than 94% complete. The method was standardized with synthetic sn-1,2- and sn-2,3-dipalmitoyl- and rac-1,2-dioleoylglycerols and was applied to the identification and quantitation of individual molecular species of enantiomeric diacylglycerols generated by Grignard degradation of the triacylglycerols from corn oil, cocoa butter, and lard.

Chromatography, Gas↗
PubMedDate not supplied

Comparison of postcolumn derivatization-liquid chromatography with thin-layer chromatography for determination of aflatoxins in naturally contaminated corn.

Quantitation of aflatoxins by liquid chromatography with postcolumn iodine derivatization (LC-PCD) and fluorescence detection was compared with quantitation by the AOAC CB method, 968.22. Thirty-seven naturally contaminated corn samples were ground and then divided. One portion was extracted, and the extract was cleaned up and analyzed by thin-layer chromatography according to the CB method. The second portion was extracted and cleaned up in a similar fashion, but quantitation was by the LC-PCD method. For aflatoxin B1 concentrations ranging from 0 to 150 ng/g, results obtained by the 2 methods were fitted to a linear equation with the LC-PCD results as the dependent variable. The correlation coefficient was 0.99, the intercept was near 0, and the slope was near 1. For aflatoxin B2, the correlation coefficient was 0.97, and the intercept was near 0. However, the slope of the equation relating LC-PCD concentration to TLC concentration was only 0.5. We believe that this lack of equivalence between the methods for determination of aflatoxin B2 is due to overestimation by the TLC method because the low levels present are near the TLC detection limit for B2.

Aflatoxin B1↗
PubMed1989

Analysis of beechwood creosote by gas chromatography-mass spectrometry and high-performance liquid chromatography.

Compounds in beechwood creosote were analyzed by gas chromatography-mass spectrometry, and 22 major constituents were identified. Of these, 19 were phenolic compounds, i. e., guaiacol, phenol, two cresol isomers, four methylguaiacol (creosol) isomers, six xylenol isomers, two trimethylphenol isomers, 4-ethylguaiacol, 4-ethyl-5-methylguaiacol, and 4-propylguaiacol. The remaining three were hitherto unpredicted five-membered ring compounds, i. e., 3-methyl-2-hydroxy-2-cyclopenten-1-one, 3,5-dimethyl-2-hydroxy-2-cyclopenten-1-one, and 3-ethyl-2-hydroxy-2-cyclopenten-1-one. The relative quantities of these compounds were also compared with those obtained by high-resolution high-performance liquid chromatography. This report probably represents the first extensive analysis of beechwood creosote.

Carcinogens↗
PubMedDate not supplied

Determination of polysorbates in foods by colorimetry with confirmation by infrared spectrophotometry, thin-layer chromatography, and gas chromatography.

A method is presented for the detection of polysorbates (PSs) in 8 kinds of processed foods by colorimetric and thin-layer chromatographic (TLC) techniques. The PSs are extracted from processed foods with a mixture of methylene chloride and ethanol by using an Extrelut column. The extract is further purified by using a silica gel column. The PS extract is complexed with cobalt-thiocyanate (Cothiocyanate) reagent and is determined spectrophotometrically at 620 nm. The recoveries and coefficients of variation for 8 kinds of processed foods fortified with 0.1% PS 80 were 67.9-94.6% and 4.0-11.3%, respectively. The detection limit of TLC corresponded to 50 mg PS 80/kg. PS identity was confirmed by infrared spectrophotometry of PS extract, and gas chromatography of fatty acids and thin layer chromatography of POE-sorbitan residues after saponification.

Chromatography, Gas↗
PubMed1986

Screening and quantification of hypnotic sedatives in serum by capillary gas chromatography with a nitrogen-phosphorus detector, and confirmation by capillary gas chromatography-mass spectrometry.

We describe a quantitative screen for hypnotic-sedative drugs in which we use capillary gas chromatography with a nitrogen-phosphorus detector (GC/NPD) as the primary method and capillary gas chromatography-mass spectrometry (GC-MS) for confirmation. GC retention times of the acid-extracted underivatized drugs were stable (CVs less than 1%), and the detector response varied linearly over a 20-fold concentration range with a mean correlation coefficient for 11 drugs of 0.989. The limits of detection were satisfactory (0.5 mg/L in a 0.5-mL serum sample and 1-microL injection volume), as were precision (average CV 5.2% within day, 6.4% between day). The complementary use of capillary GC-MS not only unambiguously confirms presumptive peaks identified by GC, but also prevents reports of false positives and identifies compounds not included in the quantitative GC screen that may be listed in the GC-MS library.

Amobarbital↗
PubMed1986

Detection of measles-specific IgM antibodies: comparison of 2-mercaptoethanol treatment, density gradient centrifugation, protein A-sepharose affinity chromatography, ion-exchange chromatography and haemadsorption techniques.

The sensitivity, specificity and effectivity of 5 methods for detection of measles-specific IgM antibodies were compared. A total of 371 sera from non-immunized as well as immunized measles patients was included into the study. The highest positive rate was achieved by the haemadsorption-immunosorbent (HIST) test. The density gradient (DG) centrifugation and the ion-exchange chromatography (IERCR) were 10-15% less effective. Protein A-Sepharose affinity chromatography (ACR) and 2-mercaptoethanol (2-ME) treatment showed positive results in the half of samples which had been positive in the HIST. The titres were in significant correlation (r = 0.90 to r = 0.8793 at P = 0.01). Specificity and reproducibility of the tests were good. Rheumatoid factor did not influence the results. In general, HIST was found as most sensitive and effective.

Antibodies, Viral↗
PubMed1989

Preparation of fecal samples for assay of volatile fatty acids by gas-liquid chromatography and high-performance liquid chromatography.

We describe a procedure for preparing fecal samples for determination of volatile fatty acids (VFAs) by gas-liquid chromatography (GLC) and "high-performance" liquid chromatography (HPLC). The simple, one-step procedure involves only ultrafiltration through a membrane with a molecular-mass cutoff of 3000 Da. As revealed by the GLC chromatograms, ultrafiltration appears to be as effective as steam distillation in sample clean-up. It also enables higher, more reproducible analytical recoveries of long-chain VFAs. The VFA content of the filtrate can also be measured by HPLC. Use of the ion-exclusion mechanism completely resolves isobutyric acid and butyric acid on a cation-exchange column. The mean (+/- SD) percentage distribution values of VFAs (measured by GLC) from five healthy subjects were 56.0 +/- 3.5 (acetic acid), 17.0 +/- 5.3 (propionic acid), 2.9 +/- 1.5 (isobutyric acid), 18.8 +/- 5.8 (butyric acid), 2.3 +/- 1.2 (isovaleric acid), and 2.9 +/- 0.8 (valeric acid).

Acetates↗
PubMedDate not supplied

Quantitation of ochratoxin A: use of reverse phase thin-layer chromatography for sample cleanup followed by liquid chromatography or direct fluorescence measurement.

An improved procedure for sample preparation and quantitation of ochratoxin A in moldy grain was developed. Grain samples were acidified and extracted, and extracts were subjected to reverse phase thin-layer chromatography (RPTLC). The separated spots, which were identified under UV light, were scraped and collected into recovery devices. Ochratoxin A was eluted from the adsorbent and analyzed by either liquid chromatography with fluorescence detection or direct spectrofluorometric measurement. The method yielded values that were proportional to the concentrations of toxin in the sample, had relatively high levels of recovery (94%), and required considerably less volume of solvents and preparation time than a standard packed column method.

Chromatography, Liquid↗
PubMedDate not supplied

[Study of middle molecular weight fraction in the plasma of patients with uremia using high performance liquid chromatography and thin layer chromatography].

Detection and quantitative estimation of peptides were carried out in the middle molecular fraction of blood plasma from patients with uremia using high performance liquid chromatography and thin-layer chromatography. The middle molecular fraction was separated into four fractions after ultrafiltration through a column of Protein Pak i-60. As low as 40-60 mcg/ml of the peptides were detected in the first and second fractions.

Blood Proteins↗
PubMed1977

High-pressure liquid chromatography and enzyme immunoassay compared with gas chromatography for determing phenytoin.

We compared a gas-chromatographic method for determination of phenytoin with a high-pressure liquid chromatographic technique and with enzyme immunoassay by three instrumental procedures. More than 100 sera from patients being treated with this drug were assayed by all these techniques. The coefficient of variation was the lowest (4.0%) with liquid chromatography, but all methods gave a CV of less than 10%. The correlation coefficients for all methods exceeded 0.97 when compared to gas chromatography. Operation costs varied with the number of tests per batch, reagent costs, and operator labor costs. All assays gave comparable values for the therapeutic range, so it would be plausible to use more than one method in a situation where (e.g.) satellite laboratories handle different quantities of assays. In any of these techniques, interferences from carbamazepine, mephenytoin, phenobarbital, and primidone were negligible.

Chromatography, Gas↗
PubMed1987

A preparative high performance liquid chromatography method for separation of lecithin: comparison to thin-layer chromatography.

We have developed a high performance liquid chromatography (HPLC) method to separate lecithin from other phospholipid classes and to obtain lecithin from biologic materials. The separation was performed on a preparative 10-micron Spherisorb column with an optimized solvent system consisting of the following components: acetonitrile, isopropanol, methanol, water, and trifluoroacetic acid. The advantages of this method are the use of an isocratic solvent system limited to about 30 min and the very good separation of the phosphatidyl-choline fraction from the sphingomyelin fraction. Furthermore, the HPLC method has a better recovery rate than the thin-layer chromatography method, and it can be run under automatic control.

Animals↗
PubMed1986

Determination of benzarone in human plasma and urine by high-performance liquid chromatography and gas chromatography-mass spectrometry. Identification of the conjugates.

Benzarone (the debrominated metabolite of the uricosuric drug benzbromarone) has been proposed for treatment of vascular disorders. An assay was developed for the quantitation of total benzarone (conjugated and unconjugated) in plasma and urine, following oral intake of benzarone. Enzymatic hydrolysis of the samples with beta-glucuronidase/arylsulphatase, extraction, gradient elution high-performance liquid chromatography with reversed-phase columns and UV detection were used for the assay. The concentration ranges, precision and sensitivities were: 0.01-2 micrograms/ml, 3-5% and 0.01 microgram/ml, respectively, for both plasma and urine. These results were validated by gas chromatography-mass spectrometry after methylated derivatives were prepared. Enzymatic hydrolysis of plasma with pure beta-glucuronidase or arylsulphatase showed that the relative amounts of unconjugated, glucuronidated, and sulphated benzarone were 6, 12 and 82% respectively, for both plasma and urine.

Adult↗
PubMed1985

Thin layer chromatography and high pressure liquid chromatography of musk ambrette and other nitromusk compounds including photopatch studies.

For qualitative and quantitative analysis of musk ambrette and 4 other nitromusk compounds (musk ketone, moskene, musk tibetine, musk xylene) thin layer chromatography (TLC) and high pressure liquid chromatography (HPLC) techniques were developed. By TLC a reasonable separation was obtained and the limit of detection was 2-5 x 10(-7) g. By HPLC the separation was even better and the limit of detection for musk ambrette was 2 x 10(-9) g. The correlation between the amount of musk ambrette/ketone and the HPLC peak was linear. The TLC and HPLC techniques were used to demonstrate the presence of nitromusks in several commercial products, mainly aftershave lotions and eau-de-toilettes preparations. By ultraviolet spectrophotometry, absorption spectra were studied for the nitromusk compounds. The absorption maximum for musk ambrette was at 264 nm, that for moskene at 253 nm. Photopatch testing was carried out in 13 patients photoallergic to musk ambrette. Only 3 patients also reacted to other nitromusks. Photoallergey to musk ketone and musk tibetine is reported for the first time.

Chromatography, High Pressure Liquid↗
PubMed1981

Determination of aflatoxins, ochratoxin a, and zearalenone in mixed feeds, with detection by thin layer chromatography or high performance liquid chromatography.

A sensitive, reliable, and economical method for the determination of 6 mycotoxins in mixed feeds is described. The feed is extracted with chloroform-water and the extract is cleaned up by using a disposable Sep-Pak silica cartridge. The procedure requires less time (15 min from sample extraction to extract preparation) and less solvent (approximately one-tenth) compared with conventional methods and is suitable for a fast, economical screen. Additional cleanup procedures, involving dialysis or extraction into base, are described for samples containing high levels of interfering compounds. Thin layer chromatography (TLC) and high performance liquid chromatography (HPLC) with fluorescence detection are described for identification and estimation of mycotoxins. The method has been applied to a wide range of mixed feeds, including laboratory animal diets, and raw materials. The limit of detection is 1 microgram/kg for all mycotoxins measured by HPLC.

Aflatoxins↗