DETERMINATION OF ARSANILIC ACID IN LIVESTOCK FEEDS BY HPLC USING AN ANION EXCHANGE COLUMN AND ULTRAVIOLET DETECTION

Abstract

A liquid chromatography method was developed for the determination of arsanilic acid in livestock feeds. A variety of livestock feeds typical of those used in commercial practice were obtained from a local feed mill. The samples included complete swine and poultry feeds, swine and poultry concentrates (high in protein), and a swine premix (high in vitamins and minerals). The feeds were spiked with various levels of arsanilic acid. The first step in determining arsanilic acid content was to extract the arsanilic acid from the feed. Ground complete feeds and concentrates were extracted with 25 mmol/L sodium hydroxide in a water bath at 50 °C. For the vitamin-mineral premix, extraction was conducted at ambient temperature since contamination by organic matter was lower for these samples. The analysis of arsanilic acid was performed by means of high performance liquid chromatography using an anion exchange column and ultraviolet detection at 244 nm. The mobile phase consisted of 40 mmol/L sodium dihydrogen phosphate-methanol (960 + 40, v/v) and the running time for an analysis was about 12 min. Average spike recoveries for samples prepared at spike levels of 10, 50, 100, 150, 300, and 1250 mg/kg were 92.8, 92.4, 96.1, 94.7, 98.3, and 99.6%, respectively. The limits of detection and quantification were 0.05 and 0.4 mg/kg, respectively. One advantage of the method is that it determines the arsanilic acid content of feeds directly, without conversion to arsenic.

ACKNOWLEDGMENTS

We thank the High-Level Talents Funds of Henan University of Technology (No. 2006BS004) for financial support. We would also like to thank Dr. Philip A. Thacker for his time and revision contributions.

Notes

Regression equation (from 2 to 10 µg mL⁻¹): y = −0.021 + 1.62 × 10⁻³ x (r ² = 0.9999); y represents the quantity of arsanilic acid injected in µg; x represent peak areas.