Determination of polychlorinated biphenyls in water using dynamic hollow fiber liquid-phase microextraction and gas chromatography–mass spectrometry

doi:10.1016/j.chroma.2008.07.081

Journal of Chromatography A

Volume 1204, Issue 1, 12 September 2008, Pages 119-122

https://doi.org/10.1016/j.chroma.2008.07.081 Get rights and content

Abstract

The application of dynamic hollow fiber liquid-phase microextraction (dynamic HF-LPME) and gas chromatography–mass spectrometry (GC–MS) for the determination of trace amounts of polychlorinated biphenyls (PCBs) in water was investigated. The experimental parameters were optimized. Under the optimum conditions, the concentration enrichment factors for PCBs were from 718-fold to 840-fold. The calibration curves were linear over a range of 0.05–90 μg/L, with a correlation coefficient (r²) of 0.9957–0.9979. The relative standard deviation (RSD) ranged from 3.4% to 5.8% for intra-day variation and from 4.1% to 7.3% for inter-day variation. The limits of detection (LODs, S/N = 3:1) were in the range of 13–41 ng/L. The recoveries for spiked water samples ranged from 85.9% to 92.0%.

Introduction

In the past few years, a simple and virtually solvent free method known as liquid-phase microextraction (LPME) has emerged dramatically as an alternative sample preparation technique [1], [2]. The first LPME, also called single drop microextraction (SDME), was developed by Cantwell and Jeannot [3], [4]. This novel technique combines extraction, concentration and sample introduction in a single step and overcomes a few disadvantages of conventional liquid–liquid extraction, such as time-consuming, labor-intensive, and use of large amounts of toxic organic solvents which may result in secondary environmental pollution [5], [6], [7], [8]. However, the stability of the suspended organic drop is easily affected by temperature, stirring rate, air bubbles, etc. [9], [10], [11]. To improve the solvent stability, hollow fiber LPME (HF-LPME) was thus developed [12]. Since the organic phase is protected by the hollow fiber, the stability is greatly improved, and higher stirring rates can be used to reduce the equilibrium time and extraction time. As a result, better extraction efficiency and sensitivity are achieved [9], [10], [13]. Moreover, the hollow fiber can also prevent from the interferences caused by large molecules or suspended solid particles in sample solutions [14], [15], [16], [17], [18]. The current LPME techniques include direct immersion liquid-phase microextraction based on microdrop of solvent (static DI-LPME [5], [6], [7] and dynamic DI-LPME [8]), headspace liquid-phase microextraction (static HS-LPME [19], [20], [21] and dynamic HS-LPME [22]), and hollow fiber liquid-phase microextraction (static HF-LPME [9], [10], [13], [23] and dynamic HF-LPME [24], [25]). These LPME techniques have been widely applied to analyze various organic pollutants, such as herbicides [9], [26], [27], [28], PAHs [5], [10], [19], [29], organochlorine pesticides (OCPs) [6], [24], organophosphorus pesticides [2], aromatic amines [30], [31], etc.

Polychlorinated biphenyls (PCBs) are one of the twelve categories of persistent organic pollutants (POPs), and they have 209 PCB congeners. Due to their lipophilicity, persistence and high toxicities, PCBs can be readily accumulated in the tissues of non-target living organisms, where they may cause detrimental effects. Traditional analytical methods for trace levels of PCBs include liquid-liquid extraction, accelerated solvent extraction, and solid-phase extraction [32], [33]. Recently, solid-phase microextraction (SPME), a totally solvent free sample preparation technique, has been used for the determination of PCBs [34], [35]. However, SPME apparatus is relatively expensive and the fiber used for extraction is fragile, and its lifetime is limited. Another problem associated with SPME is sample carry-over between runs when SPME is coupled with gas chromatography [36]. These drawbacks of SPME can be easily overcome by using LPME [2]. The determination of PCBs in marine sediments, water and blood plasma by LPME has been reported recently [37], [38], [39]. However, to the best of our knowledge, there is no report on the use of dynamic HF-LPME technique for the analysis of PCBs in water sample. The objective of the present study was to investigate the applicability of dynamic HF-LPME to the determination of PCBs in water.

Section snippets

Materials and chemicals

A porous polypropylene hollow fiber membrane (550 μm i.d., 50 μm wall thickness, and 0.02–0.2 μm pore size) was obtained from Junhua Water Purification Equipment Co., Ltd. (Hangzhou, China).

A mixture standard solution of PCBs (Aroclor 1242, which containing 181 mg/L of PCBs) was purchased from Institute for Reference Materials of State Environmental Protection Administration (IERM) (Beijing, China). A stock standard solution of PCBs (7.24 mg/L) was prepared by diluting the Aroclor 1242 with methanol

Extraction mode and organic solvent

Selection of an appropriate organic extraction solvent is important for liquid-phase microextraction. Three candidate solvents (1-octanol, toluene and n-hexane) were selected and tested to compare the extraction efficiencies in three different extraction modes (DI-LPME, static HF-LPME and dynamic HF-LPME). In DI-LPME, to prevent the suspended organic drop from falling off the needle tip, the volume of organic phase was reduced to 2 μL and the stirring rate was decreased to 300 rpm. The enrichment

Conclusion

In the present work, the dynamic HF-LPME procedure combined with GC–MS was developed for the analysis of trace level of PCBs in water samples. The LODs of the proposed method are comparable to those obtained by SPME-GC–MS [34], and better than those obtained by the EPA 608 method. In terms of the concentration enrichment factors for PCBs, the proposed method is similar to a dispersive liquid–liquid microextraction method (up to a 540-fold) [39]. The dynamic HF-LPME as a simple, economic,

Acknowledgement

The authors thank the financial support of Science & Technology Program of Suzhou, China (SS0734).

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Short communicationDetermination of polychlorinated biphenyls in water using dynamic hollow fiber liquid-phase microextraction and gas chromatography–mass spectrometry

Abstract

Introduction

Section snippets

Materials and chemicals

Extraction mode and organic solvent

Conclusion

Acknowledgement

Anal. Chim. Acta

J. Chromatogr. A

J. Chromatogr. A

Anal. Chim. Acta

J. Chromatogr. A

Anal. Chim. Acta

J. Chromatogr. A

J. Chromatogr. A

J. Chromatogr. A

Talanta

J. Chromatogr. A

Anal. Chim. Acta

J. Chromatogr. A

J. Chromatogr. A

J. Chromatogr. A

Anal. Chim. Acta

J. Chromatogr. A

J. Chromatogr. A

J. Chromatogr. A

Short communication
Determination of polychlorinated biphenyls in water using dynamic hollow fiber liquid-phase microextraction and gas chromatography–mass spectrometry