Estimating the decision limit (CCα) and the capability of detection (CCβ) from analytical curves on water analysis for substances with permitted limits: an electronic spreadsheet for results interpretation in Public Health Laboratories

Abstract

In this paper the electronic spreadsheets built in Microsoft ExcelR software are presented, and these parameters enable to estimate the decision limit (CCα) and the detection capability (CCβ) at the detection limit and of the maximum permitted value (MVP) regions. The estimates are evaluated from linear and homoscedastic analytical curves obtained in calibration procedures based on ISO standards and IUPAC guidelines. After validating by means of manual data processing, the electronic spreadsheets were used for determining the nitrite in bottled waters (MVP = 0.02 mg/L) and the fluoride contents in public supply waters (compliance interval = 0.6 to 0.8 mg/L). For fluoride analysis there are the minimum required value (0.6 mg/L) and the maximum acceptable value (0.8 mg/L) for its concentration; therefore, the spreadsheet computes the critical concentration at both limits with a probability of a type I error equal to 0.05. On that account, the electronic spreadsheets provide the rapid decision between compliant and non-compliant data in the interpretation of results.