title: Comparison of microbial receptor assay and liquid chromatography for determination of penicillin G and amoxicillin in milk powder.
abstract: A microbial receptor assay (Charm II Tablet Beta-Lactam Test) and liquid chromatography (LC) were compared for determination of penicillin G (PG) and amoxicillin (AMOX) in reconstituted milk powder. Nonfat dry milk and whole dry milk were reconstituted (10%, w/v) to concentrations of 0, 2.5, 5, 7.5, and 10 ppb PG; nonfat dry milk was reconstituted (10%, w/v) to 0, 7.5, 10, and 15 ppb AMOX. Reconstituted samples were analyzed blindly by each method. Concentrations determined by both methods demonstrated good agreement. A significant difference between methods (p < or = 0.05) was observed only for 7.5 ppb PG in defatted dry milk. Significant differences were not observed between known concentrations and concentrations determined by the Charm II assay for PG or AMOX in defatted dry milk and PG in whole dry milk. Results by LC showed significant differences (p < 0.05) between known and measured concentrations at 10 ppb PG in both milks and 0 ppb AMOX in defatted dry milk. These results suggest that both the microbial receptor assay and LC may be useful for determination of PG and AMOX near safe level and tolerance, respectively, in reconstituted milk powder.
authors.affiliation: North Carolina State University, College of Veterinary Medicine, Department of Farm Animal Health and Resource Management, Raleigh 27606, USA. kevin_anderson@ncsu.edu
authors.forename: Kevin L
authors.initials: KL
authors.lastname: Anderson
authors.forename: Roberta L
authors.initials: RL
authors.lastname: Lyman
authors.forename: William A
authors.initials: WA
authors.lastname: Moats
authors.forename: Arthur P
authors.initials: AP
authors.lastname: Hansen
authors.forename: John E
authors.initials: JE
authors.lastname: Rushing
mesh_terms: D000658:Amoxicillin / Q000032:analysis*; D000818:Animals; D002417:Cattle; D002853:Chromatography, Liquid; D004350:Drug Residues / Q000032:analysis*; D008892:Milk / Q000737:chemistry*; D010400:Penicillin G / Q000032:analysis*; D010406:Penicillins / Q000032:analysis*; D011208:Powders
chemical_list: D010406:Penicillins; D011208:Powders; D000658:Amoxicillin; D010400:Penicillin G