Journal of Chromatography A, 1304 (2013) 138–146 Contents lists available at SciVerse ScienceDirect Journal of Chromatography A j our nal homep age: www.elsevier.com/locate/chroma 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 Marta Borecka a , Anna Białk-Bieli ´ nska a,∗ , Grzegorz Siedlewicz b , Kinga Kornowska c , Jolanta Kumirska a , Piotr Stepnowski a , Ksenia Pazdro b a Department of Environmental Analysis, Faculty of Chemistry, University of Gda´ nsk, ul. Sobieskiego 18, 80-952 Gda´ nsk, Poland b Institute of Oceanology, Polish Academy of Sciences, ul. Powsta´ nców Warszawy 55, 81-712 Sopot, Poland c Physicochemical Laboratories, Faculty of Chemistry, University of Gda´ nsk, ul. Sobieskiego 18, 80-952 Gda´ nsk, Poland a r t i c l e i n f o Article history: Received 4 March 2013 Received in revised form 4 June 2013 Accepted 4 July 2013 Available online 10 July 2013 Keywords: Expanded uncertainty Antibiotics SPE disks LC–MS/MS Seawaters a b s t r a c t Although the uncertainty estimate should be a necessary component of an analytical result, the pre- sentation 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 H 2 O-Philic BAKERBOND speed disks and liquid chro- matography 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 analy- sis 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. © 2013 Published by Elsevier B.V. 1. Introduction Since pharmaceutical residues have been widely recognized as new emerging pollutants, there has been increasing interest in the development of new, more selective and sensitive methods for their monitoring in environmental samples. Chromatographic techniques (gas chromatography (GC) or liquid chromatogra- phy (LC)) coupled to mass spectrometry (GC–MS or LC–MS) or tandem mass spectrometry (GC–MS/MS, LC–MS/MS) have been extensively employed in this manner [1,2]. As environmental con- centrations of these compounds are mostly in the ng L -1 to g L -1 ranges, depending on the sample matrices, analytes in the sam- ples need to be extracted and concentrated prior to instrumental analysis. For aqueous samples, solid phase extraction (SPE) is nowadays the most common technique [3–5].Nevertheless, the ∗ Corresponding author. Tel.: +48 58 5235401. E-mail address: abialk@chem.univ.gda.pl (A. Białk-Bieli ´ nska). analysis of pharmaceuticals in environmental samples is still a very difficult and demanding task. It involves many problems associated with the reliable identification and quantification of these compounds in such complex matrices [6]. Therefore, the focus has intensified on the quality and reliability of data, as it is essential not only to perform a meaningful assessment of environmental hazards but also to be able to compare the results between laboratories or establish standard protocols for their determination. Konieczka and Namie´ snik emphasized that decisions taken in many fields of science and also in other areas of life are based on the results of analytical studies; the quality of such results is thus of the utmost importance [7]. We recently discussed the problems involved in the assess- ment of matrix effects and recovery calculations in the analysis of pharmaceuticals [8]. In the present paper we focus on the prob- lem of estimating expanded uncertainty in analytical procedures for determining pharmaceutical residues in environmental sam- ples using chromatographic techniques. 0021-9673/$ – see front matter © 2013 Published by Elsevier B.V. http://dx.doi.org/10.1016/j.chroma.2013.07.018