Determination of norflurazon residues in mixed crop matrices.

A method for determining norflurazon residues in mixed crop matrices is described. The method included methanol Soxhlet extraction, hexane wash, addition of 10% saline, methylene chloride extraction, concentration, preparative thin layer chromatography of 10% sample aliquot, and resuspension of sample zone for gas-liquid chromatographic analysis. The lower level of electron capture detection is 0.01 ppm. Recoveries for 0.08 ppm spiked samples of cottonseed; soybean seed and foliage; peanut seed plus hulls and foliage; orange and tangerine; lemon; apple and peach; and soil are generally greater than 80%.

Analysis of tissue progesterone residues by gas chromatography - mass spectral and radioimmunological detection methods.

Methods for the extraction, isolation and analysis of tissue concentrations of progesterone suitable for studying residue levels from livestock treated with this steroid for the control and synchronization of estrus are presented. The system employs biphasic partitioning for the extraction and silica gel chromatography for the isolation and demonstrates 80 to 90% recovery of 14C-labeled progesterone added as an internal standard. Residue analysis of fat, kidney, liver and muscle tissue samples from ovariectomized non-treated and progesterone treated ewes are compared employing a competitive inhibition radioimmunoassay system which appears to be less specific for progesterone than the gas chromatography-mass spectrometry method employing selective ion monitoring detection.

In vitro and in vivo considerations of a novel matrix-controlled bovine progesterone-releasing intravaginal device.

An in vitro system measuring progesterone release from silicone matrixes into serum is described. Drug release followed a matrix-controlled diffusion model in which the cumulative quantity released was linear with the square root of time. A bovine intravaginal device, consisting of a steel coil coated on both sides with a progesterone silicone matrix, was used as an in vivo drug delivery system. In vivo drug release also was matrix controlled, with rates comparable to those obtained in vitro. However, lag times of 1.7 and 4.2 days before reaching the steady-state rate were obtained for the outer and inner surfaces, respectively. The combination of effects resulted in a pseudo-zero-order drug-releasing device in which cumulative drug released was linear with time for at least 16 days.

Collaborative study of assay method for erythromycin in pelleted feeds containing binding agents.

A modified method for analysis of erythromycin in feeds containing the pelleting adjuvants bentonite and Masonex has been evaluated by collaborative study. Erythromycin is freed from the binding action of these adjuvants by an aqueous methanolic pH 8 buffer presoak before extraction with methylal. The recovery values for mash and pellets of 6 different sample types range from 86.6 to 103.0% of theory with a grand mean of 96.8%. This modification has been adopted as official first action.