Interface of on line coupling capillary electrophoresis with hydride generation electrothermal atomic absorption spectrometry and its application to arsenic speciation in sediment

doi:10.1016/j.talanta.2013.01.059

Talanta

Volume 109, 15 May 2013, Pages 128-132

https://doi.org/10.1016/j.talanta.2013.01.059 Get rights and content

Abstract

A novel interface for on line coupling capillary electrophoresis with hydride generation electrothermal atomic absorption spectrometry (CE–HG–ETAAS) has been developed. The interface performance was examined in detail. The technique could be used to convert arsenic compounds from CE separation to corresponding volatile hydrides determined by HG–ETAAS. This paper aims to explore the best condition in the speciation analysis of inorganic arsenic by using CE–HG–ETAAS. The application of the developed CE–HG–ETAAS to inorganic arsenic speciation in sediment was investigated. The detection limits of As(III) and As(V) were 135 ng/g and 160 ng/g, respectively. Relative standard deviations of arsenic speciation were better than 2%. The recoveries of As(III) and As(V) in the sample with spiking concentration of 2500 ng/g As(III) and 5000 ng/g As(V) were 97.6% and 96.7%, respectively.

Highlights

► A novel interface for CE–HG–ETAAS was developed. ► The interface has good stability, good reproducibility and easy operation. ► The interface does not need cooling system. ► The method has high selectivity and sensitivity.

Introduction

Speciation analysis of trace elements may lead to better understanding of the chemical/biochemical processes, environmental availability and toxicological risks associated with different species [1], [2]. Arsenic and its compounds are highly toxic and carcinogenic. Different changes of the forms of arsenic in the human body determine the different mechanisms of toxicity and detoxification [3], [4]. Although a series of analytical techniques have been used to analyze arsenic speciation, there are no standard procedures for such purposes [5]. Therefore, it is vitally necessary to develop a new and reliable method for arsenic speciation. Capillary electrophoresis (CE) is a combination of classic electrophoresis and modern micro-column separation. It has many advantages, such as simple operation, rapid analysis, little reagent consumption, easy automation, less environmental pollution and higher resolution [6]. With the utilization of the hydride generation (HG) technology in arsenic and other hydride-forming elements, the detection limits of hydride-forming elements can be improved by 1–3 orders of magnitude [7]. Capillary electrophoresis coupling hydride generation with atomic absorption spectrometry can realize the efficient separation and alternative determination of elements. Currently, the effective analytical techniques for arsenic speciation are hyphenated by coupling different separation procedures with various detection methods [8], [9]. These techniques include hydride generation atomic absorption spectrometry (HG–AAS) and electrothermal atomic absorption spectrometry (ET–AAS) [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20]. In addition, it is also linked with other techniques, including the hydride generation atomic fluorescence spectrometry [21], [22], [23], inductively coupled plasma mass spectrometry [24], [25], [26], [27], [28], [29], [30], [31], [32], [33], [34], [35], [36], inductively coupled plasma optical emission spectrometry [37] and cathodic stripping voltammetry [38]. However, those ICP-based methodologies require expensive instruments and high operational costs, which limits their wide acceptance for routine speciation analysis in general laboratories [39]. Compared with HPLC, CE offers unique characteristics that make it particularly attractive for elemental speciation analysis, such as high resolving power, minimal reagent consumption, rapid analysis and low cost and the possibility of separations with only minor disturbances of the existing equilibrium between the different species [36], [37], [38], [39], [40], [41], [42], [43], [44], [45]. Compared to ICP, atomic absorption spectrometry offers certain advantages in terms of simple structure, easy operation, penny-a-line equipment and operation cost, good selectivity and good precision, so it is still widely employed in the field of chemical, medicine, clinic investigation, food hygiene, etc.

In this paper, a novel interface of capillary electrophoresis coupling hydride generation with electrothermal atomic absorption spectrometry was developed. This novel interface has presented the advantages of good stability, good gas–liquid separation efficiency, less dead volume, good reproducibility and easy operation. The device will combine the efficient separation function of CE with the high detection sensitivity of ETAAS to realize both the trace samples hydride generation and the online connection of CE and ETAAS. As(III) and As(V) were used as the research objects to explore the best condition in the speciation analysis of arsenic by using capillary electrophoresis and hydride generation coupled with electrothermal atomic absorption spectrometry.

Section snippets

CE–HG–ETAAS interface

The interface of CE–HG–ETAAS is made of both interfaces of CE–HG and HG–ETAAS. And the interface of CE–HG is similar to that of previous report [42]. As shown in Fig. 1a, the self-designed CE–HG interface was made by two juxtaposed PTFE tubes: The lower one was connected with NaBH₄ solution; the upper one was inner set with a capillary; the HCl solution passed through between the PTFE tube and CE capillary tube. In order to escape too much gas caused by hydride generation, which would increase

Optimization of parameters of capillary electrophoresis

The pH value of separation buffer solution and electrophoretic voltage play an important role on the capillary electrophoresis separation of As(III) and As(V). With the increasing pH of separation buffer from 5.5 to 8.5, the absorbance of As speciation increased and then decreased. The maximum absorbance occurred at pH 6.5. The absorbance in the present work also changed as a function of the buffer concentration. With the increase of buffer concentration, the absorbance ascended first and then

Conclusions

The results in the present work have demonstrated the feasibility of the self-designed capillary electrophoresis hydride generation electrothermal atomic absorption spectrometry for arsenic speciation. Electrophoretic separation of the two arsenic species can be obtained within 8 min with detection limits less than 160 ng/g for each species. The low cost, easy operation, less dead volume, simple structure, good conductivity, good gas–liquid separation efficiency and good selectivity of ETAAS make

Acknowledgements

This study was supported by the National Natural Science Foundation of China (No.20965001) and the Guangxi Science Foundation of China (No. 2010GXNSFA013051, No.2010GXNSFF013001).

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As an alternative to ICP, AAS offers some advantages in terms of simple structure, easy operation, lower equipment and operation cost, good selectivity and good precision. A novel interface of capillary electrophoresis coupling hydride generation with electrothermal atomic absorption has been proposed by Deng et al. for the quantitative assay of As(III) and As(V) [54]. This novel interface presents the advantages of good stability, good gas–liquid separation efficiency, less dead volume, good reproducibility and easy operation.
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Interface of on line coupling capillary electrophoresis with hydride generation electrothermal atomic absorption spectrometry and its application to arsenic speciation in sediment

Abstract

Highlights

Introduction

Section snippets

CE–HG–ETAAS interface

Optimization of parameters of capillary electrophoresis

Conclusions

Acknowledgements

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Chemosphere

Anal. Chim. Acta

Trends Anal. Chem.

Anal. Chim. Acta

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Talanta

Spectrochim. Acta, Part B

Anal. Chim. Acta

Anal. Chim. Acta

J. Hazard. Mater.

Spectrochim. Acta Part B

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J. Chromatogr. A

Food Chem.

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Anal. Chim. Acta

J. Chromatogr. A

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J. Chromatogr. A