Capillary GC-ECD and ECNI GCMS characterization of toxaphene residues in primate tissues during a feeding study.

Toxaphene is a pesticide whose use was banned in North America because of concerns regarding its toxicity. To obtain better data on the metabolism and toxicity of toxaphene in primates, a one year feeding study was carried out in cynomologous monkeys at a dose of 1 mg/kg/day for one year. Levels of toxaphene residues in blood and adipose tissue during the dosing period were measured by GC-ECD and ECNI GCMS. The dosing toxaphene mixture was found to be extensively metabolized. Four chlorinated bornane congeners were the predominate residues found in the tissue samples. Blood levels of toxaphene residues plateaued at 40 ppb, adipose levels at approximately 4000 ppb. Kidney, liver, feces and urine were analyzed for toxaphene residues after necropsy.

Interlaboratory study on determination of 2,3,7,8-tetrachlorodibenzo-p-dioxin in fish.

An interlaboratory round robin study was carried out to estimate the reliability of data on 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in fish. Using different methods, 13 laboratories (4 Canadian, 9 American) agreed to analyze 4 fish samples; 3 were Great Lakes salmonids containing bio-incurred levels of TCDD below 100 ppt and the fourth was an ocean fish fillet containing no measurable TCDD. Samples were sent as freeze-dried portions as it was shown that no change of TCDD occurred by this sample preparation. Results were normalized between laboratories by supplying each with an aliquot of the same 2,3,7,8-TCDD standard. Eight laboratories reported a set of results of which one set was rejected. Values from the 7 remaining laboratories for the 3 positive fish showed mean concentrations in pg/g (ppt) and (CV, %) of 61.2 (13.9), 30.4 (18.4), and 32.3 (25.4). Detection limits averaged 3.6 ppt and ranged between 1 and 10 ppt. No significant differences appeared in the concentration of 2,3,7,8-TCDD in fish samples from methods differing in the use of: (i) digestion or extraction techniques, (ii) high or low resolution mass spectrometry, and (iii) isomer specific or nonspecific separations. Overall recovery values using internal standards varied greatly (29-109%) even within the same laboratory and pointed to the need to use an internal standard to obtain precise results. Agreement among laboratories was good considering the level quantitated (ppt) and the diverse methodology.

Polyaromatic hydrocarbons as high-performance liquid chromatographic calibration standards for the low level determination of chlorinated dibenzo-p-dioxins and chlorinated dibenzofurans in biological samples.

A series of polyaromatic hydrocarbons (PAHs) has been used to calibrate the retention times of chlorinated dibenzo-p-dioxins (dioxins) and chlorinated dibenzofurans (furans) on high-performance liquid chromatography (HPLC) in the ultra-trace analysis of biological samples. Fraction collection is then based on the HPLC retention times of the PAHs without the need for the dioxins or furans. Because of the variety of PAHs, a particular one can be chosen that will co-chromatograph near any given dioxin or furan. It has been shown that the effect of solvent changes and sample co-extractives on the HPLC eluting properties of the PAHs is minimal. The use of PAHs as secondary standards for HPLC calibration in dioxin trace analysis diminishes both the potential for contamination of the sample by the standard and the handling of the chlorinated dioxins and furans. The PAH standards could also be useful for those laboratories who are limited in their safety facilities or in the number and amount of dioxin-furan standards available to them.

Composite sampling in the determination of pyrethrins in fruit samples.

A residue method is described for measuring up to 6 naturally occurring pyrethrins in several varieties of fruits. Fresh samples are extracted into acetone, partitioned between water and hexane-dichloro-methane, and cleaned up by adsorption on a Florisil column followed by elution with acetone-hexane (15 + 85). Residues are detected and quantitated by gas chromatography with electron capture detection. Detection limits for single 10 g samples are about 10-30 ng/g. The method was applied to a survey of pyrethrins in fruit samples. Because of the high tolerance (1 ppm) allowed for pyrethrins, the expected low incidence, and the low detection limits of the method, composite samples (up to 5-6) of fruit were used to quickly determine residue levels. This procedure allowed 130 samples to be processed in the time normally needed for 30-40. Provided the above conditions can be met, composite sampling is proposed as an attractive approach to data gathering in pesticide residue analysis.

Chemical confirmation of diethylstillbestrol residues in beef livers.

A simple chemical technique was developed to confirm the presence of diethylstillbestrol (DES) residues in beef tissues at 2 ppb. The DES-trifluoroacetate (TFA) from the previously published method is hydrolyzed in water-methanol at 55 degrees C for 20 min to free DES which is then extracted into benzene. Trimethylamine and a small amount of heptaafluorobutyric (HFB) anhydride are added to effect the smooth conversion of DES to its di-HFB at either room temperature or 60 degrees C. DES-HFB is determined by gas-liquid chromatography with electron capture detection on a 6' x 4 mm id column of 3% OV-210 at 190 degrees C. This procedure yields 2 peaks for DES-HFB (retention times 2.7 and 4.8 min for the cis and trans, respectively) which are resolved from the 2 DES-TFA peaks (retention times 2.3 and 3.3 min for cis and trans, respectively). The sensitivity of detection of DES-HFB is increased by a factor of 4-5 over that for DES-TFA. This chemical technique was successfully applied to purified extracts of beef liver fortified with DES at 2-10 ppb with recoveries from 60 to 110%.