This work aimed to identify the most effective method to estimate the coefficient of repeatability in genotypes of U. brizantha and predict the minimum number of measurements required for some qualitative traits. It were evaluated 9 genotypes in a randomized block design with two replications in the rainy season and drought in 2000. It were evaluated the following qualitative traits: volume of gas, in mL, packed in fast and slow fraction, crude protein; neutral detergent fiber, acid detergent fiber, cellulose, lignin sulfuric acid, silica and in vitro digestibility of organic matter. The repeatability coefficient (r) was estimated considering different strategies: Analysis of variance, principal component analysis based on the correlation matrix (CPCOR), principal components analysis based on the matrix of phenotypic variance and covariance and structural analysis based on the correlation matrix. The CPCOR method, provided more accurate estimates of r and the number of measurements required for the qualitative traits assessed due to the cyclical behavior of genotypes of U. brizantha. The traits neutral detergent fiber, cellulose and silica require two measurements, while the remaining characters require four measurements to predict the actual value of genotypes of U. brizantha with a minimum accuracy of 80%, by CPCOR method.

The proficiency testing for determination of pesticides residues in mango pulp was the third work of the partnership established by INMETRO and INCQS/Fiocruz. Three mango pulp samples were sent to each participant laboratory, two being spiked with the pesticides and one exempt of pesticides. The added pesticides were: deltamethrin, ethion, fenitrothion, malathion, and permethrin. The evaluation of the results of the homogeneity and the stability tests, as well as the determination of the assigned value was made in agreement with ISO GUIDE 35 and ISO 13528, assuming the samples were considered homogeneous and stable for the studied period. The assigned values and the standard deviation for proficiency evaluation was calculated using the robust algorithm, according to ISO 13528, and the evaluation of the results was carried through in accordance with ABNT ISO/IEC Guide 43-1. The z-score graphs and confidence ellipse was also used in the evaluation of the results. In the evaluation carried through from the values of the z-scores, 71% of the reported results were considered satisfactory based on the results found for this index. The evaluation of the analytical viability for the determination of each pesticide and of the analytical capacity of the participant laboratories was carried through. A summarized view of the chromatographic techniques and of preparation of sample used by the participant laboratories was also carried through in this work.