Avaliação intralaboratorial do desempenho de analistas na análise de carotenoides utilizando material de referência certificado / Intralaboratory assessment of analysts’ proficiency for carotenoidanalysis using a certified reference material

ABSTRACT

Carotenoid analysis is inherently challenging, requiring the analysts’ expertise and attention to manydetails. To guarantee the reliability of carotenoid data generated in our laboratory, aside from methoddevelopment, optimization and validation, periodic evaluation of the analysts’ performance is carried out.This paper reports the results obtained in one of our evaluations, using a certified reference material. Fiveanalysts with varying experience in carotenoid analysis participated. The same liquid chromatograph andstandard curves were used, restricting the evaluation to the analysts’ performance. The HPLC methodconsisted of extraction with acetone, partition to petroleum ether, saponification with 10 % methanolicKOH, washing with water, concentrating in a rotary evaporator, drying with nitrogen, dissolving inacetone, separation, identification and quantification. The z-score for each carotenoid was calculated.There was very good agreement in terms of the carotenes and b-cryptoxanthin for the five analysts. Forlutein and zeaxanthin, the analyst with little experience in carotenoid analysis obtained lower values,but the z-scores were still satisfactory. One analyst who had experience only with carotene analysis alsogot lower concentrations for the xanthophylls. This was due to the fact that ethyl ether was not used inpartitioning the carotenoids from the extracting solvent to petroleum ether.