title: Determination of tetracyclines in surface water and milk by the magnesium hydroxide coprecipitation method.
abstract: A simple coprecipitation method was developed for the determination of tetracyclines (TCs) in surface water and milk by high-performance liquid chromatography with diode-array detection (HPLC-DAD). Magnesium ion was added into the surface water or the acetonitrile (MeCN) extract of milk. After alkalinization, magnesium hydroxide precipitates which had been formed can be separated from the matrix solution easily by centrifuging and then a dissolution step was performed by adding a small amount of acid. The final solution could be introduced directly into HPLC system for the determination of the analytes. Under optimal conditions, recoveries for the analysis of spiked surface water samples ranged from 83.6% to 95.1% with relative standard deviation of 2.0-5.5%. For milk samples, relative recoveries were 95.9-104.6% with relative standard deviation of 3.4-6.7%. The enrichment factors ranged from 41.5 to 48.1 for 10 mL water samples, and from 3.6 to 4.4 for 1 mL MeCN extracts of milk. Limits of detection ranged from 0.13 to 0.51 ng/mL, and from 3.0 to 8.5 ng/g for four TCs in surface water and milk samples, respectively.
authors.affiliation: Department of Food Science, National Pingtung University of Science and Technology, Pingtung 912, Taiwan.
authors.forename: Wen-Hsien
authors.initials: WH
authors.lastname: Tsai
authors.forename: Tzou-Chi
authors.initials: TC
authors.lastname: Huang
authors.forename: Ho-Hsien
authors.initials: HH
authors.lastname: Chen
authors.forename: Joh-Jong
authors.initials: JJ
authors.lastname: Huang
authors.forename: Min-Hsien
authors.initials: MH
authors.lastname: Hsue
authors.forename: Hung-Yi
authors.initials: HY
authors.lastname: Chuang
authors.forename: Yuh-Wern
authors.initials: YW
authors.lastname: Wu
mesh_terms: D000818:Animals; D002498:Centrifugation; D011232:Chemical Precipitation; D002851:Chromatography, High Pressure Liquid; D006863:Hydrogen-Ion Concentration; D008276:Magnesium Hydroxide / Q000737:chemistry*; D008892:Milk / Q000737:chemistry*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013754:Tetracyclines / Q000032:analysis*; D014867:Water / Q000737:chemistry*
chemical_list: D013754:Tetracyclines; D014867:Water; D008276:Magnesium Hydroxide