Validación del método generador de hidruros por espectrometría de absorción atómica para la determinación de selenio en aguas naturales, de consumo y residuales

Abstract

The purpose of the research was the validation of the hydride generator method associated with the atomic absorption spectroscopy for determining the selenium (Se) in drinking water for consumption, and sewage for Aqlab laboratory. This validation was carried out due to the need of having analytical methods which are validated and recognized by the Ecuadorian Accreditation Organization (SAE), this will allow widening the range of technical accreditation based on the INEN ISO IEC 17025:2017 norm. This research started with the revision of the standardized method for the analysis of metals in waters SM 3114 C, 3500-Se. The method was validated considering the work interval from 0,01 to 0,5 mg/l, in repetitiveness and reproducibility conditions. The drinking water samples were acidulated HCL at 10%, while sewage samples were digested H2SO4 2,5 N and K2 S2 O8 at 5%. HCI at 10% v/v (9ml/min) were used as transporting solution, NaBH4 at 0,2% p/v (4ml/min) diluted in NaOH at 0,5% as reducing agent and argon (120 ml/min) as carrier gas at a temperature of 900°C in the quartz cell. The performance parameters determined through a statistical analysis with a level of trust of 95% are: linearity (0,005-0,01 mg/l), detection limit (LD=0,005 mg/l), quantification limit (LC=0,01 mg/l), precision, accuracy (recovery 94,80-102,00%) and uncertainty (U±17%). This parameters fulfil the predefined validation objectives as well as the performance and acceptance criteria such as: repetitiveness variation coefficient and reproducibility SDR <10% and uncertainty U < 30%, the method reflected valid results with and acceptable level of trust reproducible and accurate data under controlled conditions in which the laboratory works; thus, the validation statement was accepted.