Drugs of abuse and tranquilizers in Dutch surface waters, drinking ...

RIVM Report 703719064Quality control and additional method characteristicsThe quality control of the analysis was tested by injecting three quality controlsamples (QCs), i.e., a tap water sample (previously analysed) spiked at differentconcentrations to every sequence of analysis (for the concentrations see tableB.2). Water samples and QCs were analysed between two calibration curves.Recovery experiments were performed by adding known concentrations of thecompounds to the different types of water. These experiments were used forestablishing the limit of quantification (LOQ), which is defined here as the lowestconcentration at which the signal-to-noise ratio of the quantification ion is ≥10.Limits of quantification were compound and sample-matrix dependent.Internal standards were used to compensate for possible losses resulting fromthe sample treatment and for correction of matrix effects (enhancement orsuppression of the signal). Analyte isotope labelled internal standards wereavailable for each selected drug of abuse.Page 59 of 90