Solid Phase Extraction (SPE) to Analyze Water Samples for Bisphenol A

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Solid phase extraction (SPE) is an effective preparation technique for concentrating analytes before HPLC analysis. Traditionally, this technique is performed offline; involving a series of time-consuming steps.

The benefits of online coupling include decreasing analysis time, analyte loss, and sample contamination. This automated technique is ideally suited to pre-concentration of BPA in drinking water. The primary source for BPA is the industrial production of polyvinyl chloride (PVC) and polycarbonates, where it is a key constituent. It is also a significant monomer in polycarbonate production. BPA has been shown to have an impact on the endocrine system, with effects similar to the estrogen hormone, even at extremely low dosage, and it is also connected with health and environmental issues. Based on earlier studies, a maximum entry <1 µg/mL in cold drinking water is anticipated. In warmed-up water (70 °C) a concentration up to 30 µg/mL is achievable.

This article describes a method for the sensitive determination of bisphenol A (BPA) in water samples. The use of online solid phase extraction (SPE) coupling prevents manual sample preparation steps and saves significant amounts of time, making the method suitable for routine analyses of BPA in drinking water and similar low concentration samples.

Results

Once calibration by direct injection using an autosampler has been carried out, the recovery rate is determined using the online SPE column in the flow path. Differing concentrations as low as 0.07 ng/mL have been extracted from prepared water samples with steady extraction time. Figure 1 illustrates the chromatogram of three varied concentrations with the same online SPE extraction time. An original drinking water sample is spiked with BPA (Figure 2). Later, the extraction time was varied, using a solution with a steady concentration of 0.1 ng/ml. A recovery rate of 98 % was achieved.

To determine the recovery rate of calibration points, two different methods are taken as a basis. Firstly, three differing concentrations, (c1=0.07 ng/mL,

Figure 1. To determine the recovery rate of calibration points, two different methods are taken as a basis. Firstly, three differing concentrations, (c1=0.07 ng/mL, c2=0.4 ng/ mL, c3=1 ng/mL), have been extracted with the same extraction time. In this part, recovery rates of 93 % for bisphenol A were found (n=4 for each concentration).

Chromatogram of three different concentrations with the same online SPE extraction time

Figure 2. Chromatogram of three different concentrations with the same online SPE extraction time

Materials and Method

For this research, an AZURA Analytical HPLC Plus system was used. It is comprised of an AZURA P 6.1 L LPG pump, a AZURA MWD 2.1 L multi wavelength detector, an AZURA CT 2.1 column thermostat, an autosampler 3950, and an assistant AZURA ASM 2.1 L, provided with a 12-port multi position valve, a pump with 10 mL pump head, and a 6-port/2-position injection valve.

The analytical technique runs isocratic at a flow rate of 0.6 mL/min with a mixture of water and acetonitrile 50:50 (v/v). The column thermostat was fixed at 30 °C and the detector recorded at 227 nm. KNAUER Eurospher II 100-3 C18A silica was put into the used columns. The SPE technique parameters are divided into different steps, including sample extraction, column conditioning, reconditioning of the SPE column, and sample analysis.

Conclusion

The technique described in this article is best suited to the analysis of bisphenol A in water samples such as drinking water. It facilitates varying the extraction time, based on the anticipated bisphenol A concentration. For a higher and improved evaluable peak signal, the time that the sample flushes over the extraction cartridge can be very simply increased. Utilizing this sensitive technique, it is possible to effectively quantify even low concentrated samples and extracts. Additionally, equipped with the AZURA ASM 2.1 L, the system can be readily used in continuous operation.

References

[1] Ligang Chen, Hui Wang, Qinglei Zeng, Yang Xu, Lei Sun, Haoyan Xu, Lan ding, “Online Coupling of Solid-Phase Extraction to Liquid Chromatography—A Review”, Journal of Chromatographic Science, Vol. 47, September 2009

[2] Jordáková I., Dobiás J., Voldrich M., Poustka J. Determination of Bisphenol A, Bisphenol F, Bisphenol A diglycidyl Ether and Bisphenol F Diglycidyl Ether migrated from food cans using Gas Chromatography- Mass spectrometry. Czech J. Food Sci.2003 Vol. 21, No. 3: 85-90

[3] Umweltbundesamt, Abteilung Umwelthygiene. Telegramm: Umwelt + Gesundheit. „Bisphenol A“ – Wir haben ein Problem. Ausgabe 04/2008

[4] Umweltbundesamt, Pressestelle „Bisphenol A Massenchemikalie mit unerwünschten Nebenwirkungen“, aktualisierte Fassung Juli 2010

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