Austin R. Long

Isolation of drug residues from tissues by solid phase dispersion

A new method based on solid phase dispersion of tissue for the subsequent isolation of drugs is reported. By blending tissues with a polymeric phase bound to a solid support one obtains a semi-dry material which can be used as a column packing material from which one can isolate drugs in a stepwise fashion based on the solubility characteristics of the drugs in this matrix. The applicability of this approach for multidrug residue extraction from a single sample is demonstrated for compounds representing the organophosphate, benzimidazole anthelmintic and beta-lactam antibiotic drug classes.

Method for the isolation and liquid chromatographic determination of eight sulfonamides in milk

A method for the isolation and liquid chromatographic determination of eight sulfonamides in milk is presented. Fortified or blank milk samples (0.5 ml) were blended with octadecylsilyl (C18T) derivatized silica (2 g). A column made from the sample C18T matrix was first washed with hexane (8 ml) following which the sulfonamides were eluted with methylene chloride (8 ml). The eluate contained sulfonamide analytes which were free from interferences when analyzed by high-performance liquid chromatography (HPLC) utilizing UV detection (270 nm, photodiode array). Standard curve correlation coefficients (range, 0.998 +/- 0.002 to 0.999 +/- 0.001), average percentage recoveries (73.1 +/- 7.4 to 93.7 +/- 2.7%), and the inter-(3.9-9.6%) and intra-assay (2.2-6.7%) variabilities, were determined for the concentration range examined (62.5-2000 ng/ml) and resulted in a minimal detectable limit of 1.25 ng on column (62.5 ng/ml, 20 microliters injection from a final sample volume of 0.5 ml). Savings in terms of time and solvent make this procedure attractive when compared to classical isolation techniques for sulfonamides.

Disruption and fractionation of biological materials by matrix solid-phase dispersion

The isolation of drug residues, environmental contaminants or naturally occurring component molecules from biological materials is often a complex undertaking. We report here the development and application of a simple approach to the disruption of biological samples that also allows for the rapid fractionation and isolation of the samples natural components or incurred residues. This process, called matrix solid-phase dispersion (MSPD), combines the use of mechanical forces generated from the grinding of samples with irregular shaped particles (silica or polymer based solid supports) with the lipid solubilizing capacity of a support-bound polymer (octadecylsilyl or others) to produce a sample column material from which dispersed sample matrix components can be selectively isolated. The factors governing this process and examples of its various applications are presented.

Lysis and fractionation of Mycobacterium paratuberculosis and Escherichia coli by matrix solid-phase dispersion

A novel method for the lysis and subsequent fractionation of bacterial constituents from Mycobacterium paratuberculosis strain 19698 (M. paratuberculosis) and Escherichia coli strain DH5 alpha utilizing the technique of matrix solid-phase dispersion (MSPD) is described. Bacteria were blended with octadecylsilyl (C18) derivatized silica to obtain cellular lysis. The blended material was used to prepare a column which was sequentially eluted with solvents of increasing polarity. Fractionation of cellular components was confirmed by analysis of the solvent extracts. The possible applicability of the MSPD technique as a general method for the lysis and fractionation of bacterial components is proposed.

Matrix solid phase dispersion (MSPD) extraction and liquid chromatographic determination of five benzimidazole anthelmintics in pork muscle tissue

Abstract A method for the extraction and liquid chromatographic determination of five benzimidazole anthelmintics (thiabendazole, oxfendazole, mebendazole, albendazole, and fenbendazole) in pork muscle tissue is presented. Blank or benzimidazole-fortified pork muscle tissue samples were blended with octadecylsilyl (C18, 18% load, endcapped) derivatized silica packing material. A column made from this tissue/C18 blend was washed with hexane then the benzimidazoles were eluted with acetonitrile. The acetonitrile eluate was purified by passing it through an activated alumina column. The purified eluates contained the benzimidazoles and were free of interferences as determined by liquid chromatography on ODS columns. The standard curves of individual benzimidazoles isolated from fortified samples, utilizing internal standards, were linear with average relative percentage recoveries of 86, 92, 85, 93, and 98% for thiabendazole, oxfendazole, mebendazole, albendazole, and fenbendazole, respectively, over the concentration range of 100 to 3200 ng benzimidazole/g tissue. The interassay variabilities ranged from 4 to 7% and intraassay variabilities ranged from 2 to 3%.

A Multiresidue Method for the Isolation and Liquid Chromatographic Determination of Seven Sulfonamides in Infant Formula

Abstract A multiresidue method for the isolation and high performance liquid chromatographic (photodiode array, UV 270nm) determination of sulfathiazole, sulfisoxazole, sulfamerazine, sulfamethazine, sulfamethoxazole, sulfisoxazole and sulfadimethoxine in a milk-based infant formula is presented. Blank or sulfonamide spiked infant formula samples were blended with octadecylsilyl derivatized silica (C-18) packing material. A column made from the C-18/infant formula matrix was first washed with hexane following which the sulfonamides were eluted with methylene chloride. The eluate contained sulfonamide analates which were free from interfering compounds when analyzed by liquid chromatography. This resulted in correlation coefficients (0.9973 ± 0.0016 to 0.9992 ± 0.0006), recovery percentages (75.91 ± 11.12% to 112.01 ± 8.15%) and inter- (5.51 ± 1.74% to 15.27 ± 8.14%) and intra-assay (1.71 to 8.89%) variabilities for individual sulfonamides, over the concentration range (62.5 to 2000 ng/mL) examined, that a...

Characterization of the thermal decomposition products of the sulfonylurea herbicide chlorsulfuron

Abstract Gas chromatography injection port thermal decomposition of chlorsulfuron resulted in two volatile decomposition products (2-amino-4-methoxy-6-methyl-1,3,5-triazine and 2-chlorobenzenesulfonamide) which were characterized by gas chromatography and gas chromatography-mass spectrometry. Quantitation of chlorsulfuron as its volatile thermal decomposition product 2-amino-4-methoxy-6-methyl-1,3,5-triazine was accomplished by gas chromatography-nitrogen-phosphorus detection analysis and the linearity of standard curves so obtained was independent of injection volume (0.5–3 μl) and injection port temperature (230–270°C) for the concentration range examined (62.5–1000 ng/ml).

Method for the Isolation and Liquid Chromatographic Determination of Furazolidone in Chicken Muscle Tissue

Abstract A method for the isolation and quantitation of furazolidone as a residue in poultry muscle tissue is presented. Blank control and furazolidone fortified chicken muscle (7.8–250 ng/g tissue) (0.5g) were blended with 2g of octadecylsilyl derivatized silica (C18). The C18/chicken muscle matrix blend was used to prepare a column that was subsequently washed with 8mL of hexane to remove lipids. The furazolidone was then eluted with 8mL of dichloromethane (DCM). The DCM eluate contained furazolidone analyte that was free from interfering compounds when examined by HPLC utilizing UV detection (365nm, photodiode array). The extracted standard curves (linear regression analysis correlation r=0.9995 /pm 0.0002, n=5), average percentage recovery (99.8/pm 4.42%, the Major Metabolite of Δ-9-Tetrahydrocannabinol in Urine., J. Anal. Toxicol., 2, 6–9 (1985).