QUALITY ASSURANCE AND CONTROL IN A PLANT ANALYSIS LABORATORY

The plant samples are mineralized using the CII reference method, then K, Ca, Mg, Na, P, B, Fe, Cu, Mn, Zn, and Al are determined with a mul ti-channel AES-Inductively coupled plasma (ICP) emission spectrometer. The measurement protocol is based on the repeatability and the precis ion of the whole of these elements: the calibration is done again ever y 20 samples. The results computation takes the shift into account. Wh en a complex 10 mg/L solution is analyzed for six hours (120 measures) , the variation coefficients are less than 2.5%. The routine analyses control is done introducing internal reference samples (palm tree, pin eapple, and maize leaves powders). Control charts are drawn to check t he global quality, including the mineralization and the instrumental m easure. The yearly variation coefficients are less than 6%, except for Cu and Zn in the ananas sample. The laboratory proficiency is tested with the International Plant Exchange program. Our results are very cl ose to the published medians, except for Al. In this case, we observe a systematic deviation.