Abstract: Les limites de detection pour les alkylbenzenesulfonates lineaires (LAS) et les dialkyltetralinesulfonate (DATS) dans l'eau sont d'environ 0,001 mg/L; dans les sediments elles sont de 0,5 mg/kg pour LAS et de 0,2 mg/kg pour DTAS respectivement

Abstract: The hydroperoxides and secondary products formed from trilinoleoylglycerol autoxidized at 40°C were isolated and characterized to clarify their contribution to oxidative deterioration of vegetable oils. The products were purified by high performance liquid chromatography (HPLC) and identified, as intact triacylglycerols, by ultraviolet, infrared,1H NMR and13C NMR analyses, and after derivatization by lipolysis, gas chromatography, and gas chromatography-mass spectrometry. The main, primary products included mono-,bis- and tris-9-hydroperoxy-trans-10,cit-12-; 9-hydroperoxy-trans-10,trans-12; 13-hydroperoxy-cis-9,trans-11; and 13-hydroperoxy-trans-9,trans-11-linolenoyl glycerols. The structures of the minor secondary products analyzed after derivatization were consistent with known oxidative degradation products of linoleate hydroperoxides. HPLC analyses showed that thebis- and tris-hydroperoxides were formed from the mono-hydroperoxides during autoxidation at peroxide values above 18 and 28 meq/kg. Studies on the further oxidation of the mono-hydroperoxides support a mechanism for the consucutive formation ofbis- and tris-hydroperoxides from the monohydroperoxides. HPLC analyses showed that no preferential oxidation occurred between the 1(3)- and 2-triglyceride positions. Hydroperoxides of linoleate triacylglycerols may be important precursors of volatile compounds contributing to off-flavors of vegetable oils.

Abstract: A simple method to detect subnanomolar to micromolar levels of photochemically generated carbon-centered radicals in aqueous solutions has been developed and optimized. This method is based on the efficient trapping of radicals by a water-soluble amino nitroxide, followed by derivatization of the trapped products with fluorescamine to produce highly fluorescent adducts. These adducts can be separated by reversed-phase high-performance liquid chromatography and detected fluorometrically. The fluorescent derivatives are stable over a period of days. The detection limit, primarily determined by reagent interferences, ranged from 0.3 to 1 nM per analyte for a 500-{mu}L injection at a signal-to-noise ratio of two. The precision of the method for the determination of adduct concentrations in the 1-10 nM range varied from 2.4 to 8.4% relative standard deviation (n = 6). A direct comparison with electron paramagnetic resonance spectroscopy/spin trapping illustrates the advantages of our technique. One important feature of the method is that it permits the simultaneous detection of an array of radicals, as demonstrated through the study of the photochemical production of radicals in a variety of natural water samples and in Suwanee River fulvic acid.

Abstract: 1. Derivatization in Liquid Chromatography: Introduction 2. Derivatization Reactions and Kinetics in Liquid Chromatography 3. Sample Pretreatment Procedures 4. Postchromatographic Reaction Detection 5. Enantiomeric Derivatization 6. Enzymatic Derivatization 7. Ultraviolet-Visible Derivatization 8. Electrochemical Derivatization 9. Fluorescence Derivatization 10. Chemiluminescence Derivatization Reactions in Liquid Chromatography

Abstract: A method is described for the determination of amino acids in individual cells. The amino acids are derivatized with naphthalene-2,3-dicarboxaldehyde and then analyzed by open tubular liquid chromatography with amperometric detection. The total volume present after derivatization is approximately 25 nL. It was possible to quantitatively determine 17 amino acids in three different neurons of the land snail Helix aspersa. Quantitation was accomplished through the use of two internal standards and a calibration curve. Alanine was found to be the most abundant amino acid by about a factor of 2 over glutamine in all three types of neurons. This method has the advantages of sensitivity in the attomole range (5 X 10(-9) M) and selectivity for a specific class of compounds and is at least as reliable as other methods used for single-cell analysis.

Abstract: Dosage par chromatographie HPLC avec detection UV. Utilisation d'un agent de paire d'ions, le sulfate de tetrabutyl-ammonium, pour optimiser la separation sur une microcolonne en phase inverse (C18). Application de la methode a l'analyse d'echantillon d'eau de la Mer Noire

Abstract: Polymers tagged with pendant fluorescent groups are prepared by the (trans)amidation derivatization of pre-existing polymers having carbonyl-type pendant groups. Polymers having pendant amide groups wherein the amide nitrogen is substituted with fluorescent moieties, prepared by (trans)amidation derivatization, are provided. Polymers having pendant (sulfonated) napthalene moieties substituted to amide nitrogen are provided.

Abstract: Pentafluoropropionic anhydride (PFPA) and heptafluorobutyric anhydride (HFBA) derivatives of morphine and codeine demonstrated poor spectra due to low abundances of secondary and tertiary ions. Trifluoroacetamide (MBTFA) has been a widely used derivative; however, the internal standard, nalorphine, displayed very poor stability and this resulted in split peaks by gas chromatography making MBTFA unsuitable for quantitative methods. Quantitation of codeine and morphine using bis-trimethylsilyltrifluoroacetamide (BSTFA/1%TMS) revealed a significant gradual decrease (p less than 0.05) of peak area ratio (PAR) of codeine and morphine compared to the internal standard using selected ion monitoring (SIM). The acetic anhydride derivative showed no significant differences in the peak area ratios for codeine/IS over a period of 24 hours, although the coefficient of variation (CV) was higher for the acetyl derivative than for the TMS derivative of codeine. There was a significant difference associated with the acetyl derivative of morphine at 4 h post derivatization compared to the initial injection (p less than 0.05); however, the acetyl derivative was stable for 24 hours and had a CV of less than 10% at a cutoff of 300 ng/mL.

Abstract: A sensitive assay for quantitative determination of the vinyl chloride (VC)-induced cyclic DNA adduct N2,3-ethenoguanine (EG) was developed. The method is based on the detection of EG as its di-pentafluorobenzyl derivative (3,5-PFB2-EG). This compound exhibited good gas chromatographic properties and was detected with high sensitivity by gas chromatography with electron capture detection (limit of detection 300 amol/microliters injected solution) or with negative ion chemical ionization mass spectrometry monitoring the [M-181]-fragment ion at m/z 354 (GC-NICI-MS, limit of detection 190 amol/microliters injected solution). EG, its 13C-labeled analog [13C4]-EG and 3,5-PFB2-EG were synthesized and characterized by UV and fluorescence spectrophotometry, 1H- and 13C-NMR spectroscopy and mass spectrometry. The standards were used to optimize the isolation of EG and its derivatization with pentafluorobenzyl bromide (electrophore labeling) at fmol quantities. DNA solutions were spiked with EG, the DNA was depurinated by mild acid hydrolysis, and EG was isolated from the hydrolysates by low-pressure strong cation exchange chromatography with subsequent C18 solid-phase extraction. The extracted EG was electrophore labeled and 3,5-PFB2-EG was detected using GC-NICI-MS. [13C4]EG served as internal standard. 3,5-PFB2-EG was quantitated relative to its 13C-labeled analog by measuring the ion ratio m/z 354/358. The limit of detection for the complete method was 60 fmol EG/mumols guanine. The method was applied to liver DNA from young Sprague-Dawley rats exposed to 600 p.p.m. VC from day 10 through day 14 after birth. The EG concentration in these samples was 1.8 +/- 0.3 pmol/mumols guanine.

Abstract: Aromatic amino acids, sulfur-containing amino acids, peptides containing such constituents, and proteins can now be detected in high-performance liquid chromatography by the use of on-line, postcolumn, continuous photolytic derivatization with electrochemical (HPLC-hv-EC) detection. The overall approach is a very simple, reproducible, rapid, and fully automatable approach for the determination of certain amino acids, peptides, and proteins with excellent selectivity, sensitivity, and linearities of response. Dual-electrode response ratios, lamp-on/lamp-off behavior, and chromatographic capacity factors all contribute to the enhanced selectivity of the overall HPLC-hv-EC determination for these particular classes of bioorganics and biopolymers. The analytical figures of merit, chromatography detection, and method validation approaches have all been optimally derived and demonstrated reproducible. Applications of the basic methodology to real-world samples are demonstrated and validated.

Abstract: Corona discharge (CD) treated polyethylene films were examined using X-ray photoelectron spectroscopy (XPS) and a variety of chemical derivatization techniques. The composition of the CD-treated surfaces were found to be relatively unaffected by aging at temperatures between 70 and 80°F. Ink adhesion testing of films treated under progressively more serve conditions indicated the efficiency of adhesion varied directly with the severity of treatment. Derivatization of CDtreated polyethylene films with pentaflurophenylhydrazine (PFPH) resulted in the formation of a stable hydrazone complex. The PFPH complex extends the detection limit for enolizable carbonyl groups ca. eight-fold and provides relative quantitation of the number of these groups on variously treated polyethylenes. Formation of the hydrazone complex destroyed ink adhesion, indicating that the complex had blocked the site responsible for chemical bonding to the ink. Adhesion of water-soluble printing inks to CD-treated polyethylene is a direct consequence of hydrogen bonding between enolic hydroxyls on the polymer surface and carbonyl groups of the ink.

Abstract: A high performance liquid chromatographic (HPLC) method for analysis of 4 free and 8 conjugated bile acids in submicromolar quantities in serum is described using precolumn derivatization with 4-bromomethyl-7-methoxycoumarin (BMC) and fluorescence detection. Bile acids were extracted from serum with 0.4 M sodium bicarbonate, adsorbed onto a Sep-Pak C18 cartridge and eluted with methanol. The extract was derivatized with BMC in acetonitrile using 18-crown-6 crown ether as catalyst and the BMC labelled glycine conjugates and free bile acids were analysed using acetonitrile + methanol + water gradient elution and detection at 320/385 nm. Using a novel and simple approach, taurine conjugates were isolated by extracting the dried, derivatized material with water, in contrast to previous methods which required column chromatography cleanup to isolate the taurine conjugates prior to derivatization. The isolated taurine conjugates were then hydrolysed enzymatically, extracted, derivatized and analysed as free-bile acids. Recoveries of individual bile acids varied from 83-96% for free and glycine conjugates and 72-83% for taurine conjugates. Coefficients of variation were in the range of 5.1-12.5%. In addition to the simpler and shorter procedure for taurine conjugates, this method has increased sensitivity over most other procedures and improved HPLC separation for the various bile acids and conjugates with equivalent recovery and reproducibility compared with other published methods.

Abstract: We previously reported the usefulness of a fluorometric method to determine urinary delta-aminolevulinic acid (ALA) concentrations by using post-column derivatization to monitor the effect of lead exposure. We have further improved the method by introducing pre-column derivatization by using reaction of ALA with acetylacetone and formaldehyde. Response of the hematopoietic system to lead exposure can now be easily detected at blood lead concentrations as low as 162 micrograms/L. The fluorescent ALA derivative, a new aromatic product, 2-methylideneamino-3,5-diacetyl-4,6-dimethylphenylpropionic acid, is separated on octadecyl silica column by high-performance liquid chromatography and the fluorescence intensity is detected with a fluorophotometer. Sample recoveries for 12 urine samples from workers exposed to lead and unexposed controls were 91.9-110.2%. The results obtained by the pre-column derivatization method agreed with those by the post-column derivatization method. The new method increases the sensitivity to a detection limit to 10 micrograms of delta-aminolevulinic acid per milliliter of urine and is simple enough to be used for routine monitoring of the biological effect of exposure to low concentrations of lead.