Parameters optimization using experimental design for headspace solid phase micro-extraction analysis of short-chain chlorinated paraffins in waters under the European water framework directive

Abstract

The water framework directives (WFD 2000/60/EC and 2013/39/EU) force European countries to monitor the quality of their aquatic environment. Among the priority hazardous substances targeted by the WFD, short chain chlorinated paraffins C10–C13 (SCCPs), still represent an analytical challenge, because few laboratories are nowadays able to analyze them. Moreover, an annual average quality standards as low as 0.4μgL−1 was set for SCCPs in surface water. Therefore, to test for compliance, the implementation of sensitive and reliable analysis method of SCCPs in water are required. The aim of this work was to address this issue by evaluating automated solid phase micro-extraction (SPME) combined on line with gas chromatography-electron capture negative ionization mass spectrometry (GC/ECNI–MS).Fiber polymer, extraction mode, ionic strength, extraction temperature and time were the most significant thermodynamic and kinetic parameters studied. To determine the suitable factors working ranges, the study of the extraction conditions was first carried out by using a classical one factor-at-a-time approach. Then a mixed level factorial 3×23 design was performed, in order to give rise to the most influent parameters and to estimate potential interactions effects between them. The most influent factors, i.e. extraction temperature and duration, were optimized by using a second experimental design, in order to maximize the chromatographic response.At the close of the study, a method involving headspace SPME (HS-SPME) coupled to GC/ECNI-MS is proposed. The optimum extraction conditions were sample temperature 90°C, extraction time 80min, with the PDMS 100μm fiber and desorption at 250°C during 2min. Linear response from 0.2ngmL−1 to 10ngmL−1 with r2=0.99 and limits of detection and quantification, respectively of 4pgmL−1 and 120pgmL−1 in MilliQ water, were achieved. The method proved to be applicable in different types of waters and show key advantages, such as simplicity, automation and sensitivity, required for the monitoring programs linked to the WFD.