Abstract

BRAMBILLA, Emilio; KLOSTER, Nanci; BONO, Alfredo  and  CAMINA, José. Evaluation Of Different Soil Nitrate Determination Methods. Cienc. suelo [online]. 2013, vol.31, n.2, pp.245-252. ISSN 1850-2067.

New analytical laboratory methods must be validated to test their quality as established by the Argentine Organism of Approval. In this study, three methods were validated for their ability to determine nitrates in soils: 1) Ion Selective Electrode (EIS), 2) Nitracheck (NCH) and 3) Chromotropic Acid (ACr). The following parameters were assessed: accuracy, precision (repeatability and intermediate precision) and uncertainty of the reference samples. Also, the limit of detection (LOD), quantification (LOQ), and range of each method were determined. The determination coefficient obtained in all the evaluated methods was above the acceptance criteria (R²> 0.985). Both EIS and ACr methods showed good sensitivity, unlike the NCH method. However, the accuracy of EIS was not adequate, which could indicate the presence of interfering ions in the sample analyzed. Both the repeatability and intermediate precision of the three methods studied were below the established acceptance criteria (CV<15%). LOQ assessment indicated that t NCH is not valid to quantify concentrations of NO₃^- which are very close to the recommended value for fertilization. Pretreatment methods tested included ambient temperature, frozen and dry samples (to 60 °C). In conclusion, ACr method is suitable for analysis of NO₃^- in dried soil samples, while methods NCH and EIS did not achieve the validation criteria.

Keywords : Precision; Accuracy; Uncertainty; Sample treatment.

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