Validation of an in-house measurement procedure for determination of selected priority hazardous substances in water and estimation of measurement uncertainty

This study investigates measurement procedure validation for the determination of hexachlorobenzene, pentachlorobenzene and trifluralin as priority hazardous pesticides in water with suspended solids < 12 mg/L by liquid-liquid extraction with hexane and gas chromatography with electron capture detector analysis. Two water matrices were used: synthetic matrix and a natural matrix-Danube surface water. Limit of detection was in the range 2.2 ng/L-3.9 ng/L. Trueness expressed as recovery was determined at pesticide concentrations of 20 ng/L and 50 ng/L in both water matrices. The intermediate precision was determined as relative standard deviations (RSD) and represents an agreement between replicates. Trueness was 72 %-121 % with RSD < 20 %. Expanded uncertainty of measurement was similar for all compounds (33.3 %-37.5 %) with a 95 % confidence level, for coverage factor k = 2. The validity of the measurement procedure was confirmed by participation in a PT Scheme with satisfactory vertical bar z vertical bar-score smaller than 2. Based on these results, it can be concluded that this low-cost measurement procedure is fit for the intended use measurements.