Full scan confirmation of tetrahydrophthalimide in whole milk using gas chromatography/ion trap mass spectrometry.

The determination of tetrahydrophthalimide (THPI) in whole milk extracts by gas chromatography/ion trap mass spectrometry (GC/ITMS) in the full-scan, electron impact (EI) mode is presented. THPI is first isolated from whole milk by a procedure including protein precipitation, liquid-liquid partitioning, and 2 solid-phase extraction (SPE) cleanup steps. GC/ITMS in the EI mode is used for the determinative step. The average recovery of THPI at fortification levels ranging from 5 to 54 ppb was 85.6% (n = 16, coefficient of variation = 9.13%). Full-scan mass spectral confirmation of THPI in milk extracts was obtained at the 5 ppb fortification level. The limit of detection was estimated to be 0.5 ppb. Chemical ionization also was used for THPI determination in whole milk extracts. The simultaneous isolation and determination of captan and captofol in whole milk are also discussed.

Determination of paraquat and diquat in low-moisture food crops using silica column cleanup and liquid chromatography with UV detection.

A sample cleanup method was developed for the determination of paraquat (PQ) and diquat (DQ) in low-moisture food crops. Low-moisture commodities, such as milled dry navy beans, are digested in acid. PQ and DQ are isolated from the digestates by using a 4 g column of preconditioned silica gel. The analytes are concentrated and then determined by liquid chromatography with a silica analytical column, sodium chloride as an ion-pairing re-agent, and acetonitrile as an organic modifier. PD and DQ are determined simultaneously with a diode array UV absorbance detector. Recoveries for PQ and DQ were determined on 3 different fortified low-moisture crops. Fortification levels ranged from 0.01 to 0.30 ppm; average recoveries ranged from 47.5% (DQ) to 95.3% (PQ).

Liquid chromatographic determination of paraquat and diquat in crops using a silica column with aqueous ionic mobile phase.

A method was developed for the determination of paraquat (PQ) and diquat (DQ) in high moisture food crops. Samples were digested with 6M HCl, and the herbicides were isolated from the digest using pH-controlled silica solid phase extraction. The analytes were then determined by ion-pairing liquid chromatography with a silica analytical column, sodium chloride as the ion-pairing reagent, and acetonitrile as the organic modifier. A diode array UV absorbance detector was used to simultaneously quantify PQ and DQ at their respective maximum absorbance wavelengths, 257 and 310 nm. Average recoveries of PQ and DQ standards from 4 different crops fortified at 0.01-0.50 ppm levels ranged from 79.3 to 104.8%.

Determination of melengestrol acetate in bovine tissues by automated coupled-column normal-phase high-performance liquid chromatography.

A method has been developed for the determination of melengestrol acetate in bovine tissues at lower levels than previously reported. Liquid-liquid extraction of tissue homogenates provided crude clean-up while final isolation, screening, and quantification was done on-line with an automated, normal-phase, coupled-column high-performance liquid chromatographic system. The chromatographic system included phenyl and silica analytical columns for the purposes of isolation and final separation, respectively. These columns provided a large difference in selectivity when operated under normal-phase conditions which allowed for the efficient isolation of melengestrol acetate from the complex tissue extracts. Mobile phases were composed of hexane and dichloromethane modified with methanol and water. Transfer and enrichment of the analyte from the primary phenyl column to the silica column was via a short (12 mm x 4 mm I.D.) silica column. Regeneration and equilibration of the phenyl column was performed after the injection of each tissue extract and was accomplished simultaneously while analytical separation occurred on the final silica column. Routing of the mobile phases and regeneration solvent was performed with automated switching valves. The total time required for each analysis was 12 min. Quantification is demonstrated using external standards with UV detection at 287 nm. The overall recovery of the method was 86% with a coefficient of variation of 9.84% at the 10 ppb [the American billion (10(9] is used in this article] level in bovine liver extracts.

Screening, confirmation and quantification of boldenone sulfate in equine urine after administration of boldenone undecylenate (Equipoise).

Methods for screening by thin-layer chromatography, quantification by high-performance liquid chromatography with ultraviolet detection and confirmation by gas chromatography-mass spectrometry of boldenone sulfate in equine urine after administration of boldenone undecylenate (Equipoise) are presented. Sample work-up was done with C18 liquid-solid extraction followed by solvolytic cleavage of the sulfate ester. Confirmatory evidence of boldenone sulfate in equine urine was obtained from 2 h to 42 days following a therapeutic intramuscular dose of Equipoise. The use of 19-nortestosterone sulfate as the internal standard for quantification of boldenone sulfate is discussed.

Distribution of zeranol in bovine tissues determined by selected ion monitoring capillary gas chromatography/mass spectrometry.

Bovine tissues, including liver, muscle, kidney, bile, serum, and urine, have been quantified by selected ion monitoring capillary gas chromatography/mass spectrometry to establish the distribution of the anabolic drug, zeranol, and its metabolites, taleranol and zearalanone, after administration of zeranol to 9 bovine animals. The method used to isolate, confirm, and quantify zeranol is undergoing validation by the United States Department of Agriculture, Food Safety Inspection Service (FSIS). Application of this method demonstrates utility in determining residue levels of zeranol in a variety of tissues with levels ranging over 4 orders of magnitude (i.e., 100 parts per trillion (ppt) to 1 part per million (ppm]. The analyte levels determined in this study complement previously reported pharmacokinetic data on the distribution of zeranol in addition to providing more specific information for taleranol and zearalanone. In this quantitative study it is shown that the liver is the main organ of deposition for zeranol, taleranol, and zearalanone, that taleranol is the main metabolite in the bovine, and that zeranol is efficiently eliminated.