Neutralization with alkaline compounds is one of the most common adulterations in milk. The rosolic acid method is a classical test widely used in different countries for detection of neutralizers in milk. The official and a modified version were validated in a single laboratory validation process considering four adulterants: sodium bicarbonate(BI), sodium carbonate(CA), sodium hydroxide(HY) and sodium citrate(CI). The modified version, which presented better performance was selected for interlaboratory validation. In this process, samples of raw milk with acidities of 0.19% were neutralized with different concentrations of BI, CA, HY and C and tested for homogeneity and stability. Eight laboratories, which represented different sectors of the milk production chain, received and analysed these samples. The collaborative trial results confirmed the method performance, although sensitivity and precision were inferior to those obtained in the intralaboratory process, demonstrating its applications and limitations.

A method for determination of organohalogen pesticides in strawberry by gas chromatography with electron capture detection was validated and applied in a monitoring program. Linearity, matrix effects, and day effect were evaluated for the analytes alpha-endosulfan, beta-endosulfan, endosulfan sulphate, lambda-cyhalothrin, procymidone, and trifluralin. The linear range varied according to the chromatographic response of the analyte. Significant matrix effects were observed. The mean recoveries ranged from 74.6 to 115.4%, with repeatability standard deviations between 1.6 and 21.0% and intermediate precision between 5.9 and 21.0%. Detection, quantification and decision limit, and detection capacity ranged from 0.003 to 0.007 mg/kg, 0.005 to 0.013 mg/kg; 0.003 to 3.128 mg/kg; and 0.005 to 3.266 mg/kg, respectively. The method was fit for the purpose of monitoring organohalogen residues in strawberries. Residues of these pesticides were detected in 124 of the 186 samples analyzed between 2009 and 2011 in the state of Minas Gerais. Nine of them did not comply with the current legislation requirements; among them, seven (3.8%) had residues of unauthorized pesticide for the culture of strawberry, one (0.5%) had residues above the maximum residue limit, and another one (0.5%) exhibited both non-conformities.

The aim of this work was the single-laboratory validation of a quantitative method for the determination of amoxicillin residues in support of cleaning control and validation. Linearity was demonstrated between 2.5 and 17.5 μg/mL, without matrix effects. Mean recoveries ranged from 84.00 to 103.74% and the relative standard deviation under repetitivity and within-reproducibility conditions were from 0.58 to 4.20% and from 0.79 to 4.39%, respectively. The theoretical limits of detection and quantification were 0.133 and 0.442 μg/mL, respectively. The studied method was suitable for cleaning control purpose within good manufacturing practices.

Um procedimento detalhado para validação intralaboratorial de métodos, incluindo delineamento experimental, estatísticas e avaliação de premissas foi proposto e aplicado à validação de um método para ensaio de avermectinas em leite bovino por cromatografia líquida de alta eficiência com detector de fluorescência. Foram realizados ensaios com curvas de solventes e de matriz, amostras de leite bovino brancas e adicionadas. As premissas relacionadas às estatísticas empregadas foram avaliadas e confirmadas. Linearidade foi obtida entre 25 e 150 ng.mL-1. Não foram observados efeitos de matriz significativos nesta faixa. As médias de recuperação aparente variaram de 87,2 a 101,4%. Desvios padrão relativos sob condições de repetitividade estiveram entre 3,3 e 11,2%, enquanto os desvios padrão relativos de reprodutibilidade parcial foram de 7,4 a 14,7%. Estes resultados indicaram exatidão e precisão do método entre 10 e 30 µg.L-1 para os quatro analitos estudados. Os limites de detecção e quantificação experimentais foram 5 e 10 µg.L-1, respectivamente. Limites de decisão (12,6 a 13,7 µg.L-1) e capacidades de detecção (15,1 a 17,4 µg.L-1) foram estimados, assumindo um limite máximo de resíduo de 10 µg.L-1.

A detailed procedure for in-house validation of methods, including experimental design, statistics and evaluation of assumptions, was proposed and applied to the validation of a method for screening avermectins in cow's milk by high performance liquid chromatography coupled with fluorescence detection. Assays were performed with solvent and matrix-matched calibration curves, milk blanks and spiked samples. The assumptions about the statistics employed were evaluated and confirmed. Linearity was achieved between 25 and 150 ng.mL-1. No significant matrix effects were observed in this range. Mean apparent recoveries varied from 87.2 to 101.4%. The relative standard deviations under conditions of repeatability ranged from 3.3 to 11.2%, while the relative standard deviations of partial reproducibility varied from 7.4 to 14.7%. These results indicated exactness and precision of the method between 10 and 30 µg.L-1 for the four analytes studied. The experimental limits of detection and quantification were 5 and 10 µg.L-1, respectively. Decision limits (12.6 to 13.7 µg.L-1) and detection capabilities (15.1 to 17.4 µg.L-1) were estimated, assuming a maximum residue level of 10 µg.L-1.