Published in Scientific Papers. Series A. Agronomy, Vol. LXIV, Issue 2
Written by Ana-Maria STĂNESCU, Adriana GRIGORE, Carmen SÎRBU, Daniela MIHALACHE, Bogdan RUJOI, Nicoleta MARIN
This study evaluates the measurement uncertainty of total phosphorus determinations in organo-mineral ferilizers. Total phosphorus was determined by UV-VIS spectrophotometry using an in-house ammonium molybdate and ammonium metavanadate method. The main parameters controlling the result of the analysis were identified and combined uncertainty (Uc) was calculated. The expanded uncertainty (U) of the method, obtained by multiplying the combined uncertainty by the coverage factor k = 2 (confidence level 95%) was 6.43%. It was noticed, that the main sources of uncertainty were: type A (i.e. repeatability) and type B (i.e. uncertainties related to the analytical balance, volumetric glassware, stock solution and spectrophotometer).
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