Validation of the Miniaturized Spectrophotometric Determination of Organic Carbon and Phosphorus in Soils

Abstract

ABSTRACT The developments and innovations in green miniaturized technologies suggest that a complete miniature approach (MA) to determine organic carbon (OC) and phosphorus (P) in soils may enable handling a large number of samples. In comparison to the conventional approach (CA), this approach also reduces waste generation and analysis costs. Here we have miniaturized all the steps of the conventional analytical procedures for OC and P analysis and carried out an in-depth validation of MA on various aspects, including linearity, biases, precision, inaccuracy, and imprecision. This rigorous assessment aimed to delineate the effect of miniaturization on the quality of determination along with its associated benefits and limitations. The findings revealed a strong correlation between the MA and CA in the OC test, indicating an R2 >0.84, with the Deming regression producing a model equation demonstrating a highly significant slope and an intercept closely approximating zero. Similarly, the P values obtained by MA and CA exhibited a correlation with an R2 > 0.99, alongside the Deming regression displaying a minimal intercept and a slope approaching one. The Bland–Altman analysis indicated a mean bias of 0.01 (95% CI, −0.51 to 0.54) for OC values and −1.7 (95% CI, −9.04 to 5.57) for P values. This cross-validation study highlights the applicability and limitations of the MA in estimating OC and P levels across a diverse range of soils.