This study involved an animal experiment in which testosterone propionate was intramuscularly injected into four steers, and the ensuing urine samples were analyzed using high-performance liquid chromatography-tandem mass spectrometry. The enzymatic hydrolysis conditions were analyzed using analysis of variance (ANOVA) and response surface methodology employing a 33 Box-Behnken design. A survey study was performed in which 48 urine samples were collected from eight untreated steers to estimate the endogenous levels of testosterone metabolites, and it was found that 17β-testosterone was not detected in the majority of the samples, whereas 17α-testosterone was present in 43 of the 48. Drug abuse was identified within 11 days of 17β-testosterone administration. The ratio between both isomers was also assessed; however, a cut-off limit based on an untreated population could not be estimated due to the absence of the beta isomer. Therefore, there may be a correlation between the exogenous use of testosterone in castrate animals and high levels of 17β-testosterone, although confirmation through further investigation would be required.

A quantitative and confirmatory method for detecting the presence of triphenylmethane dyes in shrimp muscle using ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) and a quick, easy, cheap, effective, rugged and safe (QuEChERS) extraction approach was validated. The method exhibited linearity and selectivity and the coefficient of determination (R2) was higher than 0.95 for all studied analytes. Limits of detection (LODs) varied from 0.32 to 0.44 µg kg-1 and the limit of quantification (LOQ) was determined to be 0.5 µg kg-1 for all studied analytes. The trueness, precision, decision limits (CCα), detection capability (CCβ) and uncertainty presented adequate performance. In addition to the validation in shrimp muscle, fish and salmon muscle were also satisfactory validated as an extension of scope. The suitability of the proposed method was also evaluated through an interlaboratory proficiency test, in which satisfactory results were obtained. The fully validated method is thus suitable for the analysis of triphenylmethane dyes in shrimp, fish, and salmon muscle.

This work involved the validation of a multiresidue method according to the Normative Instruction 24/2009-MAPA for determining 25 analytes, among fluoroquinolones, sulfonamides and trimethoprim in samples of poultry and porcine kidney. The extraction procedure was based on a QuEChERS approach. A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed using the selected reaction monitoring mode (SRM) and ESI+ ionization. All of the validated figures of merit were evaluated as satisfactory. Accuracy was assessed by recovery studies, varying from 82.7 to 115.5% for porcine kidney and from 91.5 to 110.4% for poultry kidney. Relative standard deviations were lower than 25.5% for porcine kidney, and 29.8% for poultry kidney. Decision limits (CCα) comprised values from 10.37 to 3298.43 µg kg-1 for porcine kidney and 10.08 to 3176.59 µg kg-1 for poultry kidney. Detection capabilities (CCβ) varied from 10.73 to 3396.86 µg kg-1 for porcine kidney and 10.67 to 3253.19 µg kg-1 for poultry kidney. The developed method has been successfully employed in the routine analysis of incurred samples.

This work presents an optimization of a quick, easy, cheap, effective, rugged and safe (QuEChERS) extraction approach of eleven fluoroquinolones in poultry muscle and kidney using a 33 Box-Behnken factorial design. All the data treatment was performed using Microsoft Excel® 2010. The suitability of the developed method was confirmed by two proficiency tests for ciprofloxacin and enrofloxacin.