title: Hyphenation of sorbent extraction and solid-matrix time-resolved luminescence using tetracycline in milk as a model analyte.
abstract: Hyphenation of sorbent extraction and solid-matrix time-resolved luminescence (TRL) was demonstrated using tetracycline (TC) in milk as a model analyte. The performance of a C18-impregnated silica layer was evaluated as both an extraction sorbent and a TRL substrate. To extract TC, a 10 x 6 mm glass-backed C18 layer was dipped into a 10 mL milk sample for 10 min followed by a 3-min water immersion for cleanup. The sorbent was then spotted with a TRL reagent solution at pH 9 that contained 5 mM europium nitrate and 5 mM EDTA. After a brief desiccation period, TRL was measured directly on the sorbent surface with a commercial fluorescence spectrophotometer. By eliminating the need to elute the analyte from the sorbent, organic solvent was not needed and sample preparation was greatly simplified. The integrated signal showed a linear dependence (R(2) = 0.9938) on TC concentration in the 0-3000 microg/L range. The same protocol was applicable to screening TC in fat-free, 2% low-fat, and whole milk at 300 microg/L, the US. regulatory tolerance level set by the Food and Drug Administration (FDA). This easy, fast, and low-cost screening method is friendly to the environment and particularly suitable for liquid samples.
authors.affiliation: Microbial Biophysics and Residue Chemistry and Core Technologies (MBRCCT), Eastern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, 600 East Mermaid Lane, Wyndmoor, PA 19038, USA. gchen@errc.ars.usda.gov
authors.forename: Guoying
authors.initials: G
authors.lastname: Chen
authors.forename: Linshu
authors.initials: L
authors.lastname: Liu
mesh_terms: D000818:Animals; D007202:Indicators and Reagents; D008163:Luminescent Measurements / Q000379:methods*; D008892:Milk / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D013752:Tetracycline / Q000032:analysis*; D013997:Time Factors
chemical_list: D007202:Indicators and Reagents; D013752:Tetracycline