Optimization of headspace experimental factors to determine chlorophenols in water by means of headspace solid-phase microextraction and gas chromatography coupled with mass spectrometry and parallel factor analysis

• Published in: Analytica chimica acta 2012-11, Vol.754, p.20-30
• Main Authors: Morales, Rocío, Cruz Ortiz, M., Sarabia, Luis A.
• Format: Article
• Language: English
• Subjects: Analytical chemistry; Chemistry; Chlorophenols; Chlorophenols - analysis; Chromatographic methods and physical methods associated with chromatography; D-optimal design; Exact sciences and technology; Gas chromatographic methods; Gas Chromatography-Mass Spectrometry - instrumentation; Gas chromatography–mass spectrometry; Headspace solid-phase microextraction; Parallel factor analysis; River water samples; Rivers - chemistry; Software; Solid Phase Microextraction - instrumentation; Spectrometric and optical methods; Water Pollutants, Chemical - chemistry
• ISSN: 0003-2670; 1873-4324
• DOI: 10.1016/j.aca.2012.10.003

[Display omitted] ► D-optimal design allows the reduction of experiments from 48 to 18 maintaining the precision. ► A procedure based on HS-SPME–GC/MS to determine chlorophenols, below ppt units, has been used. ► HS-SPME–GC/MS has been used to analyze four chlorophenols in river water samples. ► Decision limits, from 39 to 208ngL−1, has been obtained with a false positive probability fixed at 5%. ► Unequivocally identification of chlorophenols was verified after taking place the PARAFAC decomposition. In this work an analytical procedure based on headspace solid-phase microextraction and gas chromatography coupled with mass spectrometry (HS-SPME–GC/MS) is proposed to determine chlorophenols with prior derivatization step to improve analyte volatility and therefore the decision limit (CCα). After optimization, the analytical procedure was applied to analyze river water samples. The following analytes are studied: 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TrCP), 2,3,4,6-tetrachlorophenol (2,4,6-TeCP) and pentachlorophenol (PCP). A D-optimal design is used to study the parameters affecting the HS-SPME process and the derivatization step. Four experimental factors at two levels and one factor at three levels were considered: (i) equilibrium/extraction temperature, (ii) extraction time, (iii) sample volume, (iv) agitation time and (v) equilibrium time. In addition two interactions between four of them were considered. The D-optimal design enables the reduction of the number of experiments from 48 to 18 while maintaining enough precision in the estimation of the effects. As every analysis took 1h, the design is blocked in 2 days. The second-order property of the PARAFAC (parallel factor analysis) decomposition avoids the need of fitting a new calibration model each time that the experimental conditions change. In consequence, the standardized loadings in the sample mode estimated by a PARAFAC decomposition are the response used in the design because they are proportional to the amount of analyte extracted. It has been found that block effect is significant and that 60°C equilibrium temperature together with 25min extraction time are necessary to achieve the best extraction for the chlorophenols analyzed. The other factors and interactions were not significant. After that, a calibration based in a PARAFAC2 decomposition provided the following values of CCα: 120, 208, 86, 39ngL−1 for 2,4-DCP, 2,4,6-TrCP, 2,3,4,5-TeCP and PCP respectively for a pro