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PubMedDate not supplied

Quantitative amino acid analysis of feedstuff hydrolysates by reverse phase liquid chromatography and conventional ion-exchange chromatography.

Corn, soybean meal, and isolated soybean protein samples were acid-hydrolyzed and analyzed for amino acid content by reverse phase liquid chromatography (LC) and by conventional ion-exchange chromatography (IEC) using an amino acid analyzer. The former method employed pre-column derivatization with orthophthalaldehyde (OPTA)/ethanethiol and fluorescence detection. In the LC procedure, glycine and threonine were not resolved, and proline and cyst(e)ine were not detected. In general, amino acid values obtained by LC and IEC compared closely within and across feedstuffs, and both agreed well with published amino acid composition data. The notable exceptions were aspartic acid, glutamic acid, and alanine. Results of this study suggest that reverse phase LC with pre-column OPTA derivatization can be applied to accurately measure primary amino acids in individual feedstuffs.

Amino Acids↗
PubMed1984

Preparation of 40S ribosomal subunit proteins of rat liver by combination of ion exchange chromatography with reversed phase liquid chromatography.

Total protein of small subunits of rat liver ribosomes was fractionated by chromatography on carboxymethylcellulose. Aliquots (between 5 and 30 mg) of the protein material of each peak were further separated by reversed phase liquid chromatography on an octadecasilyl silica column. In this way 15 of the 32 proteins of the small ribosomal subunit of rat liver could be isolated in milligram amounts.

Animals↗
PubMedDate not supplied

Comparison of liquid chromatography and high performance thin layer chromatography for determination of aflatoxin in peanut products.

Recent research studies concerning aflatoxin in peanut products have involved the use of new instrumental methods for greater detection sensitivity. A comparison of 2 such techniques, liquid chromatography (LC) and high performance thin layer chromatography (HPTLC), is reported here. With respect to precision, accuracy, sensitivity, recovery, and linearity of response, HPTLC appears to be equivalent to LC. These points illustrate the viability of HPTLC as an alternative technique in the determination of aflatoxin.

Aflatoxins↗
PubMed1982

Characterization of uremic "middle molecular" fractions by gas chromatography, mass spectrometry, isotachophoresis, and liquid chromatography.

Uremic ultrafiltrates (and normal serum, for comparison) were fractionated by means of gel filtration. The collected fractions were further investigated by combined analytical techniques: "high-performance" liquid chromatography, gas chromatography, mass spectrometry, and isotachophoresis. Ultrafiltrate fractions in the so-called middle molecular mass region (Mr 500-2000) contained a considerable amount of substances of low molecular mass, such as carbohydrates, organic acids, amino acids, and ultraviolet absorbing solutes. Ultraviolet absorbance in the "middle molecular mass region" of the gel chromatogram is mainly due to the presence of these rather low-molecular-mass solutes. Therefore this signal is not a quantitative measure of molecules with a "middle" molecular mass.

Chemical Fractionation↗
PubMed1982

Molecular sieve chromatography of some plasma protein products by high performance liquid chromatography: comparison of quantitation by UV absorption and Lowry protein.

Commercially prepared fraction V products (5 and 25% albumin and 5% plasma protein fraction) and immune serum globulins were subjected to analytical molecular sieve chromatography by high performance liquid chromatography. Quantitation was performed by UV absorbance and by the Lowry protein assay. The proteins eluting in the void volume from the immune serum globulin samples yield equivalent results by UV absorbance and by Lowry assay. Proteins eluting in the void volume from fraction V products indicate approximately twice as much protein by UV absorbance when compared to Lowry protein assay.

Blood Proteins↗
PubMed1980

Measurement of verapamil concentrations in plasma by gas chromatography and high pressure liquid chromatography.

This study was carried out to compare gas chromatography (GC) and high-pressure liquid chromatography (HPLC) procedures in the measurement of plasma levels of verapamil. Other analytic methods previously reported are not widely available (mass fragmentography) or are subject to interference from drug metabolites (spectrophotofluorometry). A single extraction and derivatization procedure was developed to prepare samples for either GC or HPLC analysis. The GC procedure used a nitrogen-specific detector; the HPLC, a fluorescence detector. In a 1--500 ng/ml range of verapamil concentrations, both methods resulted in good separation of verapamil from a major metabolite, norverapamil, and from compound D517, used as an internal standard. Intraassay variation was similar for both procedures, with only slightly higher interassay variability found for the GC technique. Excellent correlation was found during analysis of the same unknown samples by both methods (r = 0.97; p less than 0.001). Either assay procedure appears satisfactory for use in measurement of verapamil levels in plasma.

Chromatography, Gas↗
PubMed1993

Automated sample preparation by on-line dialysis and trace enrichment. Analysis of morphine, 6-monoacetylmorphine, codeine, ethylmorphine and pholcodine in plasma and whole blood by capillary gas chromatography and capillary gas chromatography-mass spectrometry.

A fully automated sample preparation method for the determination of five opiates in human plasma and whole blood is described. The technique combines dialysis and trace enrichment prior to gas chromatography and gas chromatography-mass spectrometry. Dialysis and trace enrichment on a polymer column was shown to be a highly reliable method for sample preparation. The method can be used, after minor modification, to determine other basic drugs in plasma and whole blood. The method demonstrates the potential of the automated sequential trace enrichment of dialysate (ASTED) system for automated sample preparation.

Automation↗
PubMedDate not supplied

Simultaneous determination of linuron and trifluralin residues in carrots and their pulp by liquid chromatography and gas chromatography.

A simple method is described for determining trifluralin and linuron in carrots and their pulp. Samples are extracted with hexane-ethyl ether (1 + 1), cleaned up with a disposable Florisil cartridge, and eluted first with hexane-ethyl ether (99 + 1) (for trifluralin), and then with hexane-ethyl ether (3 + 7) (for linuron). Trifluralin is then analyzed by electron capture gas chromatography (GC/ECD), and linuron by GC/ECD and liquid chromatography with ultraviolet detection (LC/UV). Recoveries were determined by spiking untreated carrot and carrot pulp homogenates with trifluralin and linuron at 0.04, 0.16, and 0.32 micrograms/g. Six determinations were performed at each level for both compounds. GC/ECD average recoveries were 87.1% for trifluralin and 93.6% for linuron in carrots and 89.9% for trifluralin and 94.2% for linuron in carrot pulp. LC/UV recoveries for linuron were 91.5% for carrots and 92.8% for carrot pulp.

Chromatography, Gas↗
PubMed1977

[Determination of the urinary metabolites hydroxyindole-acetic acid, vanillyl mandelic acid and homovanillic acid by means of lipophilic gel chromatography and gas chromatography (author's transl)].

A specific and practicable method is described for the quantitative determination of urinary phenol- and indole-carboxylic acids. High specificity is achieved by a preliminary separation of the free acids (extracted from the urine sample) with the aid of organophilic gel chromatography on Sephadex LH 20, followed by gas chromatographic analysis of the silyl derivatives of the acids. The organophilic gel chromatography of the free acids shows a high recovery rate in the micro- and submicrogram range. The difficulties encountered in other techniques in the derivatisation and gas chromatographic separation of the individual components are avoided by using the preliminary separation, and by using N-methyl-N-trimethylsilyl-trifluoroacetamide for the derivatisation. Use of this preparation technique with a direct read-out gas chromatograph with automatic sample introduction, gives high accuracy and precision, and a facility for the determination of a wide range of aromatic acids in urine.

Chromatography, Gas↗
PubMedDate not supplied

Validated method for quantitation and identification of 4,4-desmethylsterols and triterpene diols in plant oils by thin-layer chromatography-high resolution gas chromatography-mass spectrometry.

Alkaline hydrolysis was performed on a series of different vegetable oils. The unsaponifiable lipid matter was extracted with ethyl ether, and the class of 4,4-desmethylsterols (sterols) plus the triterpene diols (diols) erythrodiol, uvaol, and betulinol were isolated by thin-layer chromatography. A validated method using the acetate derivatives of sterols instead of their silyl ethers is presented. The acetate derivatives were analyzed by high resolution gas chromatography (HRGC). Retention time, precision, recovery studies, and absolute response factors were calculated for these esters, and GC/mass spectrometric structure of the assigned retention times was confirmed for the sterols and triterpene diols.

Chromatography, Thin Layer↗
PubMedDate not supplied

Determination of the Fusarium mycotoxins nivalenol, deoxynivalenol, 3-acetyldeoxynivalenol, and 15-O-acetyl-4-deoxynivalenol in contaminated whole wheat flour by liquid chromatography with diode array detection and gas chromatography with electron capture detection.

A rapid and sensitive method was developed for simultaneous detection of nivalenol (NIV), deoxynivalenol (DON), 3-acetyldeoxynivalenol (3-A-DON), and 15-O-acetyl-4-deoxynivalenol (15-A-DON) in wheat flour. Samples were extracted with acetonitrile-water (84 + 16), and the extract was filtered and purified by a column containing a combination of charcoal, celite, and other adsorbents. For screening analysis, the column eluate was only extracted with ethyl acetate. After evaporation of the solvent, the dried residue was redissolved in acetonitrile-water (2 + 8) and then analyzed by reversed-phase liquid chromatography (LC) with diode array detection. Recoveries of NIV, DON, 3-A-DON, and 15-A-DON from whole wheat flour spiked at 2 levels were 49-55, 92-97, 98-100, and 100-105%, respectively. To quantitate mycotoxin amounts lower than 1 ppm, purified column extracts were evaporated to dryness, derivatized with heptafluorobutyric anhydride, and analyzed by gas chromatography with electron capture detection (GC-ECD). Average recoveries of NIV, DON, 3-A-DON, and 15-A-DON from whole wheat flour spiked at 2 levels, were 45-52, 91-103, 81-85, and 84-92%, respectively. GC-ECD detection limits for all mycotoxins tested at a signal-to-noise ratio of 4:1 were < 30 ng/g. Results of GC-ECD analysis for whole wheat flour samples spiked with mycotoxins at 3 and 10 ppm compared well with results (2.8 and 9.9 ppm) for the same samples analyzed by LC.

Chromatography, Gas↗
PubMed1998

Determination of free bile acids in pharmaceuticals by thin layer chromatography and high performance liquid chromatography.

High-performance liquid chromatography with evaporative light scattering detection (HPLC-ELSD) and thin layer chromatography with flame ionization detection (TLC-FID) have been applied to the separation of five main free bile acids present in humans: cholic (CA), chenodeoxycholic (CDCA), deoxycholic (DCA), lithocholic (LCA) and ursodeoxycholic (UDCA) acid. HPLC separation was performed on Biospher Si 100 column using a mixture of n-heptane, isopropanol, ethylacetate, methanol and glacial acetic acid as a mobile phase. All the compounds were separated in less than 12 minutes by using a gradient elution mode. TLC-FID separation was performed on S-II Chromarods with a mixture of isooctane, ethylacetate and glacial acetic acid as a mobile phase. HPLC-ELSD method was applied to the determination of CDCA and UDCA in pharmaceuticals and their purity control when LCA, DCA and CA were considered as impurities.

Bile Acids and Salts↗
PubMed2000

Trace determination of alpha- and beta-endosulfan and three metabolites in human serum by gas chromatography electron capture detection and gas chromatography tandem mass spectrometry.

Endosufan, alpha and beta, and three conversion products, sulphate, ether and lactone, were simultaneously determined in human serum by means of an analytical procedure which combines extraction with organic solvents, clean-up with H(2)SO(4) and by liquid column chromatography, and detection by gas chromatography (GC) using electron capture detection (ECD) and tandem mass spectrometry (MS/MS). The procedure was validated and the values of some merit figures, such as linear range, detection and quantitation limits, accuracy, precision and recovery, obtained with the GC/ECD and the GC/MS/MS methods, were compared. The lower limits of detection in GC/ECD and GC/MS/MS were 0.03 and 0.05 microg I(-1), respectively. The recovery of the pesticides at the 20 microg I(-1) concentration level was 60-65%, with the exception of endosufan alpha. Recovery studies at higher levels (100 and 200 microg I(-1)) were independent of pesticide concentration in serum samples. The application of the proposed analytical methodology to the determination of endosulfans and their metabolites in real samples was tested by analyzing serum samples from a population living in agricultural areas of Almeria (Spain). The results show the advantage of MS/MS over the ECD detector in the analysis of serum samples where matrix interferences can be confused with target pesticides.

Endosulfan↗
PubMed1977

Use of new silylating agents for identification of hydroxylated steroids by gas chromatography and gas chromatography mass spectrometry.

Differences in methylene unit values were used for the determination of the hydroxyl group number of a steroid by means of gas chromatography. This index is defined as the difference in the methylene unit value between trimethylsilyl and other dimethylalkylsilyl (DMAS) ether derivatives of hydroxylated steroids, namely dimethylethylsilyl (DMES) and dimethyl-n-propylsilyl (DMPS) ethers. The reactivities of DMES and DMPS imidazoles as silylating agents were nearly equal to that of TMS-I. Mass spectra of these derivatives were characterized by the molecular ion cluster, [M]+., [M-15]+ and [M-29]+ (or [M-43]+). The molecular ion cluster of these derivatives is most useful for estimating the molecular weight. Therefore, these DMAS ethers provide valuable information for structural elucidation of hydroxylated steroids by gas chromatography electron impact mass spectrometry.

Chromatography, Gas↗
PubMed1986

Separation of the components of commercial digitonin using high-performance liquid chromatography and centrifugal countercurrent chromatography. Identification of the products by californium-252 plasma desorption mass spectrometry.

Commercial digitonin has been separated into its components using high-performance liquid chromatography and centrifugal countercurrent chromatography. The individual glucosides have been identified by californium-252 plasma desorption mass spectrometry, occasionally supplemented by hydrolysis and analysis of the liberated sugars and aglycones. Mass spectra of commercial digitonin that have appeared in the literature are discussed in the light of their complex nature. A new glycoside of molecular weight 1035 is described and a structure proposed.

Californium↗
PubMed2005

Comparison of microemulsion electrokinetic chromatography and micellar electrokinetic chromatography methods for the analysis of phenolic compounds.

In this study, microemulsion electrokinetic chromatography (MEEKC) and micellar electrokinetic chromatography (MEKC) were compared for their abilities to separate and detect thirteen phenolic compounds (syringic acid, p-coumaric acid, vanillic acid, caffeic acid, gallic acid, 3,4-dihydroxybenzoic acid, 4-hydroxybenzoic acid, (+)-catechin, (-)-epigallocatechin, (-)-epicatechin gallate, (-)-epigallocatechin gallate, (-)-epicatechin, and (-)-gallocatechin), and two other ingredients (caffeine and theophylline) in teas and grapes. Separation of phenolic compounds was improved by changing the SDS concentration for MEEKC, but the SDS concentration rarely affected the resolution for MEKC. Organic modifier (acetonitrile or methanol) was found to markedly influence the resolution and selectivity for both MEEKC and MEKC systems. In addition, a higher voltage and a higher column temperature improved the separation efficiency without any noticeable reduction in resolution for MEEKC whereas they caused a poor resolution for the MEKC system. Although separations with baseline resolution were achieved by the optimized MEEKC and MEKC methods, the separation selectivity resulting from the proposed MEEKC method was completely different from that of MEKC.

Chromatography, Micellar Electrokinetic Capillary↗
PubMed2005

Analysis of flunarizine in the presence of some of its degradation products using micellar liquid chromatography (MLC) or microemulsion liquid chromatography (MELC)--application to dosage forms.

The separation of flunarizine hydrochloride (FLZ) and five of its degradation products--1-[bis(4-fluorophenyl)methyl]-4-(3-phenyl-2-propenyl)piperazine, 4-oxide (A), bis(4-fluorophenyl)methanone (B), bis(4-fluorophenyl)methanol (C), 1-(3-phenyl-2-propenyl)piperazine(D), and 1-[bis-4-fluorophenyl) methyl] piperazine (E)--could be accomplished by reversed phase liquid chromatography using either micellar or microemulsion mobile phases. Cyanopropyl-bonded stationary phase has been used with UV detection at 254 nm. Microemulsion mobile phase consisting of 0.15 M SDS, 10% n-propanol, 1% n-octanol, and 0.3% triethylamine in 0.02 M phosphoric acid of pH 7.0, has been used for the separation of FLZ and its degradation products (B, C, D, and E). Micellar mobile phases consisting of 0.15 M sodium dodecyl sulphate (SDS), 10% n-propanol, 0.3% triethylamine (TEA) in 0.02 M phosphoric acid of pH values either 4.0 or 6.8 have been used for the separation of FLZ from its degradation products, i.e. either from (B, C, D, and E) or from (A, B, C, and D), respectively. Micellar liquid chromatography (MLC) was applied to the determination of FLZ in pure form as well as in dosage forms; the calibration graph was linear over the concentration range of 0.15-50 microg/mL with detection limit of 0.02 microg/mL (4.19 x 10(-8)M).

1-Octanol↗
PubMed2005

Enantiomeric separation of chiral polychlorinated biphenyls on beta-cyclodextrin capillary columns by means of heart-cut multidimensional gas chromatography and comprehensive two-dimensional gas chromatography. Application to food samples.

Three commercially available chiral capillary columns, Chirasil-Dex, BGB-176SE, and BGB-172, have been evaluated for the separation into enantiomers of the 19 chiral polychlorinated biphenyls (PCB) congeners stable at room temperature. The enantiomers of 15 chiral PCBs were, at least to some extent, separated using these beta-cyclodextrin based columns. Multidimensional techniques, such as heart-cut multi-dimensional gas chromatography (heart-cut MDGC) and comprehensive two-dimensional gas chromatography (GC x GC), were investigated for their ability to solve coelution problems with other PCBs present in commercial mixtures and real-life samples. Heart-cut MDGC improved the separation as compared to one-dimensional GC, and enantiomeric fractions of the investigated chiral PCBs could be determined free from interferences. However, limitations on the number of target compounds that can be transferred to the second column in a single run and, therefore, the time consumption, have led to the evaluation of GC x GC as an alternative for this type of analysis. With GC x GC, two column set-ups were tested, both having a chiral column as first-dimension column, and two different polar stationary phase columns in the second dimension. On using both column combinations, congeners 84, 91, 95, 132, 135, 136, 149, 174, and 176 could be determined free from coelutions with other PCBs. Results on the application of heart-cut MDGC to food samples such as milk and cheese are given, as well as the first results on the application of GC x GC to this type of samples.

Animals↗