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J A Hurlbut

Publications and source records attributed to J A Hurlbut.

At least 19 recordsLinked to original sources
PubMed1999

Confirmation of avermectin residues in food matrices with negative-ion atmospheric pressure chemical ionization liquid chromatography/mass spectrometry.

A multi-residue LC/MS method has been developed to confirm avermectin drug residues in several food matrices. Ivermectin (IVR), doramectin (DOR), eprinomectin (EPR) and moxidectin (MOX) are confirmed using atmospheric pressure chemical ionization (APCI) with negative ion detection and selected ion monitoring of three to four ions for each compound. The drug residues are extracted from tissue or milk using previously published procedures. IVR and DOR are confirmed at 20 ppb levels in fortified salmon muscle; IVR is also confirmed in tissue from salmon dosed with the drug. Residues of DOR, IVR, and EPR are confirmed in fortified milk at the 20 ppb level and in fortified beef liver at 40 ppb. Residues of MOX can also be confirmed in these matrices, but at slightly higher levels (40-80 ppb).

Animals↗
PubMed1995

Particle beam liquid chromatography-mass spectrometry of triphenylmethane dyes: application to confirmation of malachite green in incurred catfish tissue.

Eight triphenylmethane dyes (malachite green, leucomalachite green, gentian violet, leucogentian violet, brilliant green, pentamethyl gentian violet, N',N'-tetramethyl gentian violet and N',N"-tetramethyl gentian violet) have been characterized by particle beam liquid chromatography-mass spectrometry. The electron ionization spectra obtained of these dyes by this technique exhibit similar fragmentation, with the formation of phenyl and substituted phenyl radicals, and loss of alkyl groups from the amines. It was observed that the six cationic dyes are reduced in the mass spectrometer source to form the corresponding leuco compounds. This technique was evaluated for the confirmation of malachite green and leucomalachite green in incurred catfish (Ictalurus punctatus) muscle tissue.

Animals↗
PubMed1989

High-performance liquid chromatography of gentian violet, its demethylated metabolites, leucogentian violet and methylene blue with electrochemical detection.

High-performance liquid chromatographic conditions are reported for the electrochemical detection (ED) of Gentian Violet, its demethylated metabolites, Leucogentian Violet and Methylene Blue. Gentian Violet, its demethylated metabolites and Leucogentian Violet were separated within 14 min on a cyano column eluted isocratically with methanol-buffer (60:40) as the mobile phase. ED responses for Gentian Violet, Leucogentian Violet and Methylene Blue were linear over the ranges 0.54-6.75, 0.50-25.2, and 5.7-285 ng, respectively. Under these conditions, the compounds were eluted in the following order: Leucogentian Violet, N"-2-tetra-methylparaosaniline chloride, N'-1-tetramethylpararosaniline chloride, pentamethylpararosaniline chloride and Gentian Violet. Methylene Blue and Gentian Violet had essentially the same retention time under these parameters. The detection limit for Gentian Violet, its demethylated metabolites and Leucogentian Violet was determined to be 0.1 pmol. A detection limit of 3 pmol was established for Methylene Blue. Detector response, elution, separation, linearity and sensitivity of detection are discussed.

Chemical Phenomena↗
PubMed1988

1-(4-Hydroxyphenyl)-, 1-(2,4-dihydroxyphenyl)- and 1-(2,5-dihydroxyphenyl)-2-bromoethanones: new labels for determination of carboxylic acids by high-performance liquid chromatography with electrochemical and ultraviolet detection.

A method is presented for the derivatization and determination of carboxylic acids by high-performance liquid chromatography with electrochemical and ultraviolet detection. The derivatizing reagents used in this study were synthesized, and their suitability was investigated for determination of drugs and metabolites with carboxylic acid groups. Quinoxaline-2-carboxylic, benzoic and salicylic acids each labeled with 1-(4-hydroxyphenyl)-, 1-(2,4-dihydroxyphenyl)- and 1-(2,5-dihydroxyphenyl)-2-bromoethanone were the principal esters studied; in addition, some antibiotics and their salts were also esterified. Conditions of derivatization are relatively mild at 60 degrees C for 60 min or less, and the reaction is 76% complete. The detection limits are as low as 1 pmol for some acids. Clean-up steps are not required to remove excess derivatizing reagent.

Acetophenones↗
PubMedDate not supplied

Determination of residues of azamethiphos in salmon tissue by liquid chromatography with fluorescence detection.

A liquid chromatographic (LC) method with fluorescence detection (FLD) is described for determining residues of the pesticide azamethiphos (AZA) in salmon tissue. The sample is extracted with ethyl acetate, centrifuged, dehydrated with anhydrous sodium sulfate, evaporated, reconstituted in water, and defatted with hexane. The aqueous phase is passed through a C18 solid-phase extraction (SPE) column. The SPE column is eluted with methanol, and the eluate is evaporated to dryness and then taken up in 10% acetonitrile (ACN) in water. The analyte is determined by LC using a C18 column, ACN-H2O (32 + 68) mobile phase, and FLD with excitation at 230 nm and emission at 345 nm. Composited salmon tissues were fortified with AZA at 5, 10, 21, 42, and 83 ng/g or ppb (target level, X = 10 ng/g). Overall recoveries were 86%, with between-day variability of 5.3%. The method detection limit was calculated as 1.2 ppb AZA based on a 5 g sample. The limit of quantitation as determined empirically by this method is the lower limit of the standard curve, approximately 5 ppb.

Animals↗
PubMedDate not supplied

Rapid method for determination of leucogentian violet in chicken fat by liquid chromatography with electrochemical detection.

The metabolite leucogentian violet (LGV) was found in chicken fat obtained from chickens dosed with gentian violet (GV); however, no residues of the parent compound, GV, and its oxidized metabolites were found. Therefore, a rapid method was developed for the specific determination of LGV in chicken fat. Chicken fat containing LGV is separated from the cellular protein with methylene chloride. LGV is then separated from the fat by partition extraction with an aqueous acid phase in which LGV is protonated, and the fat is discarded with the methylene chloride layer. The aqueous solution is neutralized, LGV is re-extracted into methylene chloride, and the methylene chloride is evaporated. An acetonitrile-water solution containing LGV is filtered before liquid chromatography using a cyano column, an acetate buffer-acetonitrile mobile phase, and an electrochemical detector set at a potential of +1.000 V. Average recoveries of LGV from chicken fat were 83.9% with a coefficient of variation (CV) of 12.9% for the 5 ppb level; 82.8% with a CV of 13.5% for the 10 ppb level; and 77.7% with a CV of 2.56% for the 20 ppb level. Levels of incurred LGV in chicken fat averaged 49.3 ppb with a CV of 2.43%.

Animals↗