Published:Journal of Chromatographic Science,
ISSN 0021-9665 Volume
46, Number 4, April 2008, pp. 351-355
Determination of Closantel Residues in Milk and
Animal Tissues by HPLC with Fluorescence Detection and SPE with
Oasis MAX Cartridges
Han-wen Sun1, Feng-chi Wang1,2,
and Lian-feng Ai1,2 1College of Chemistry and Environmental Science, Hebei University,
Key Laboratory of Analytical Science and Technology of Hebei
Province, Baoding, 071002, China and 2Hebei Entry-Exit Inspection
and Quarantine Bureau of the People’s Republic of China
A liquid chromatographic method for the determination
of closantel residues in milk and tissues is developed and validated.
An acetonitrile–acetone solution (80:20, v/v) is used for
the extraction of closantel residues from milk and animal tissues,
and the extract is purified by solid-phase extraction with Oasis
MAX cartridges and a mixture of formic acid–acetonitrile
(5:95, v/v) as the elution solution. A C18 bonded
silica column is used for chromatographic separation. The mobile
phase consists of acetonitrile–water (85:15, v/v) containing
0.05% triethylamine at pH 2.5, adjusted with phosphoric acid
with the flow-rate set at 1.0 mL/min. Using the fluorescence
emission of closantel at
λex = 335 nm and λex = 510
nm, the calibration curve is linear, with a correlation coefficient
of 0.9999 over the concentration range of 10–5000 µg/kg
for the tissue sample and 10–5000 µg/L for the milk
sample. The detection limit (s/n = 3) is 3 µg/kg for tissue
sample and 3 µg/L
for milk sample. The intra- and inter-day repeatabilities are
between 3.35–7.66% and 4.04–8.67%, respectively.
The proposed method enables the quantitative determination of
closantel residues at levels as low as 10 µg/kg in animal
tissue samples and 10 µg/L in milk samples.
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