A new approach for the estimation of expanded uncertainty of results of an analytical method developed for determining antibiotics in seawater using solid-phase extraction disks and liquid chromatography coupled with tandem mass spectrometry technique

• A new approach for analysis of pharmaceuticals in environmental samples is presented.
• Estimation of the expanded uncertainty of an analytical procedure is highlighted.
• An alternative clean-up procedure based on the use of SPE speed disks is proposed.
• A new method for the determination of antibiotics in seawater was developed.
• Determination of target compounds in seawater sampled in the southern Baltic Sea.

Although the uncertainty estimate should be a necessary component of an analytical result, the presentation of measurements together with their uncertainties is still a serious problem, especially in the monitoring of the presence of pharmaceuticals in the environment. Here we discuss the estimation of expanded uncertainty in analytical procedures for determining residues of twelve pharmaceuticals in seawaters using solid-phase extraction (SPE) with H2O-Philic BAKERBOND speed disks and liquid chromatography coupled with tandem mass spectrometry (LC–MS/MS). Matrix effects, extraction efficiency and absolute recovery of the developed analytical method were determined. A validation was performed to obtain the method's linearity, precision, accuracy, limits of detection (LODs) and quantification (LOQs). The expanded uncertainty of the data obtained was estimated according to the Guide to the Expression of Uncertainty in Measurement and ISO 17025:2005 standard. We applied our method to the analysis of drugs in seawaters samples from the coastal area of the southern Baltic Sea. As a result, a new approach (concerning the uncertainty estimation as well as the development of analytical method) to the analysis of pharmaceutical residues in environmental samples is presented. The information given here should facilitate the introduction of uncertainty estimation in chromatographic measurements on a much greater scale than is currently the case.