Development of a method for the determination of pyrimethamine concentrations in feeds by ion-pairing high-performance liquid chromatography.

An ion-pairing reversed-phase high-performance liquid chromatography (HPLC) method with diode array detection at 280 nm was developed to determine pyrimethamine concentrations in feed for laying hens. Pyrimethamine was extracted with a mixture of 5% isobutanol and 95% benzene, and the extract was cleaned up on an alumina column. The drug was eluted from an Intersil ODS-3V column (250 by 4.6 mm) with a mixture of 25% acetonitrile and 75% water (vol/vol) containing 0.01 M tetramethylammonium chloride as an ion-pairing agent and adjusted with acetic acid to pH 3.5. The flow rate was 1.0 ml/min. Mean recovery of pyrimethamine from supplemented feeds at concentrations of 2, 4, and 5 microg/g of feed were 100.5, 103.5, and 100.8%, respectively. Precision within a day ranged from 4.3 to 7.0% for the three concentrations, and day-to-day precision was 5.3% for feed supplemented at a concentration of 4 microg/g. No chromatographic interference was detected from other 2,4-diaminopyrimidine compounds or other major drugs used in poultry.

High-performance liquid chromatographic determination of carbadox, olaquindox, furazolidone, nitrofurazone, and nitrovin in feed.

A high-performance liquid chromatography with gradient programming method was developed to determine the amount of carbadox (CBX), olaquindox (OLQ), furazolidone (FZ), nitrofurazone (NF), and nitrovin (NTV) in feed simultaneously. Complete separation of the drugs was obtained using a C8 silica gel column with gradients of acetonitrile as mobile phase. The mobile phase used an acetonitrile gradient with an initial hold time of 1 min at 0% acetonitrile, followed by an increase to 50% acetonitrile over 10 min. The correlation coefficients (r) for calibration curves of the five feed additives were greater than 0.999. The relative standard deviations (RSDs) of peak areas from four injections for these drugs at three concentrations were less than 3.0%, although the RSD for NTV at 5 ppm was somewhat large (6.7%). The medicated feeds were extracted by pretreating with water, extracted with 95% dimethylformamide overnight at room temperature, and cleaned up on a column of alumina oxide. Recoveries of CBX, OLQ, FZ, NF, and NTV from low level spiked feed were 102.0, 94.6, 97.4, 110.6, and 66.0%, respectively, and from high level spiked feed, they were 114.09, 99.1, 97.3, 109.9, and 62.7%, respectively.

Effect of lead ingestion on concentrations of lead in tissues and eggs of laying Tsaiya ducks in Taiwan.

This experiment was conducted to investigate Pb concentrations in soft tissues and eggs from laying Tsaiya ducks (Anas platyrhynchos var. domestica), dosed via gelatin capsule with 10 or 20 mg Pb/kg BW daily for 3 mo. Body weights of ducks were not influenced by Pb treatment. In addition, no clinical syndromes involving Pb intoxication were found throughout the experiment. The two levels of Pb consistently resulted in increases in the Pb content of blood, kidney, liver, and gizzard, whereas only 20 mg Pb/kg BW per d of dose additionally increased the Pb in femoral muscle. More Pb was deposited in the kidney and liver after Pb exposure than in the gizzard or femoral muscle. Lead residues in yolk and eggshell from Pb-dosed ducks were significantly higher than in controls; however, Pb in albumen was generally low and was not influenced by Pb treatment.

Determination of lead, cadmium, mercury, and copper concentrations in duck eggs in Taiwan.

Samples of duck eggs were collected from 65 farms distributed in 6 counties in Taiwan to analyze the contents of Pb, Cd, Hg, and Cu in albumen and yolk. Lead, Cd, and Cu determinations were performed by microwave digestion together with atomic absorption spectrophotometry, whereas Hg was analyzed by sulfuric acid-nitric acid digestion and cold vapor atomic absorption spectrophotometry. Expressed on a wet weight basis, the average concentrations (ranges) of the four metals were as follows: Pb, 13.6 ng/g (.8 to 27.5) in albumen and 84.7 ng/g (44.8 to 224.7) in yolk; Cd, 1.8 ng/g (< .5 to 4.4) in albumen and 3.8 ng/g (< 1.0 to 5.7) in yolk; Hg, 17.8 ng/g (2.5 to 47.5) in albumen and 9.7 ng/g (1.2 to 20) in yolk; Cu, .83 micrograms/g (.56 to 1.08) in albumen and 1.36 micrograms/g (.95 to 1.95) in yolk. Comparison of the calculated daily intakes of Pb, Cd, and Hg from eggs with the World Health Organization-Food Agriculture Organization provisional tolerated daily intakes suggest that duck eggs are safe with respect to the contents of the three metals. Eggs are poor sources of Cu, supplying less than 2% of the Recommended Dietary Allowance.

Determination of cadmium and lead in raw milk by graphite furnace atomic absorption spectrophotometer.

A simple, uncontaminated method was described for graphite furnace atomic absorption spectrophotometry used for determination of Cd and Pb in milk serum prepared by spontaneous souring. Samples of raw milk were collected from the bulk holding tanks of 107 dairy farms in six counties in Taiwan. Raw milk samples were placed at room temperature (28 degrees C) for 48 h, to allow the pH to decrease below 4.6 and the casein and fat to precipitate. Milk serum was filtered and then directly injected into a graphite tube. The standard addition method was employed, and .1% phosphoric acid was the matrix modifier. During ashing, a 15-s oxygen influx prevented charcoal accumulation on the graphite tube. The mean recoveries of Cd and Pb from three added concentrations were 93.7% and 94.5%, respectively. The analyzed Cd and Pb concentrations in milk powder using this method were close to the certified values. The mean Cd and Pb contents obtained from 107 samples were .044 ng/ml, ranging from .021 to .173, and 2.03 ng/ml, ranging from .98 to 4.45, respectively. There were no significant differences among the six counties.

Estimating population size for capture-recapture data when capture probabilities vary by time and individual animal.

There have been no estimators of population size associated with the capture-recapture model when the capture probabilities vary by time and individual animal. This work proposes a nonparametric estimation technique that is appropriate for such a model using the idea of sample coverage, which is defined as the proportion of the total individual capture probabilities of the captured animals. A simulation study was carried out to show the performance of the proposed estimation procedure. Numerical results indicate that it generally works satisfactorily when the coefficient of variation of the individual capture probabilities is relatively large. An example is also given for illustration.