Determination of Trace-Level Endocrine Disruptors in Seawater by Online SPE-HPLC Using the SolEx HRP Cartridge

Jing Hong and Rosanne Slingsby, Dionex Corporation

In this application note we present an online SPE-LC method for the determination of trace-level endocrine disruptive compounds (EDCs) in seawater using the new SolEx® HRP cartridge as the solid-phase extraction (SPE) phase. This method shows good recovery of EDCs in 2% sodium chloride solution and seawater.

EDCs in seawater are an environmental concern. It has been reported that there is global contamination of sea sand and seawater with the endocrine disruptor bisphenol A (BPA) (1). Scientists found BPA in sand and seawater from Southeast Asia and North America ranging from 0.01 parts per million (ppm) to 50 ppm (1). In this proposed method, EDCs in seawater are preconcentrated by online SPE using the SolEx HRP cartridge followed by separation on the Acclaim® PolarAdvantage reversed-phase column with UV detection.

Experimental

A Dionex UltiMate® 3000 system with a DGP-3600M dual gradient pump, a SRD 3600 solvent rack with integrated vacuum degasser, a TCC-3200 thermostatted column compartment with two two-position, six-port valves, an AS-HV high volume autosampler, and a PDA-3000 UV detector were used. A SolEx HRP cartridge, 12 µm (2.1 × 20 mm) was used for solid phase extraction; an Acclaim PolarAdvantage reversed-phase column, C16, 3 µm (2.1 × 150 mm) was used for separations.

Figure 1: Online SPE-LC of EDCs spiked into deionized water, 2% sodium chloride, and Half Moon Bay, CA seawater. Flow Rate: 300 µL/min; Injection Volume: 10 mL; Temperature: 25 °C; Detection: UV at 210 nm; Mobile Phases: A) water, B) Acetonitrile, C) 100mM pH 5.4 ammonium acetate; Gradient: to 10.0 min: 55% A, 35% B, 10% C; 20.0 min: 30% A, 60% B, 10% C; 25.0 min: 30 % A, 60% B, 10% C; 25.1 min: 55% A, 35% B, 10% C; Peaks (5 µg/L each): 1). bisphenol A; 2) β-estradiol; 3) estrone.

Results and Discussion

Figure 1 shows online SPE-LC of bisphenol A, β-estradiol, and estrone. Seawater was prefiltered through a 0.45 µm membrane. After preconcentration on the SPE phase, 6 mL DI water followed by 4 mL 5% acetonitrile (CH₃CN) were used to wash the SPE column in order to remove the salty matrix. EDCs trapped in the SPE phase were transferred to the Acclaim PA column using 35% CH₃CN for separation. Peak area RSDs ranged from 0.4% to 0.7% for BPA; 1.4% to 3.7% for β-estradiol; and 0.3% to 1.1% for estrone. Retention time precision was excellent, with RSDs ranging from 0.04% to 0.09%.

Recovery of these three EDCs in 2% sodium chloride solution and seawater collected at Half Moon Bay are calculated by comparing the area responses of EDCs to the same sample spiked in deionized water. All the three EDCs studied show good recovery.

Table I: Recovery of endocrine disruptive compounds in 2% sodium chloride and Half Moon Bay seawater

Conclusion

Using online SPE and HPLC-UV, EDCs were analyzed at low ppb levels on the new Dionex SPE phase, SolEx HRP cartridge. The method was applied to 2% sodium chloride solution and Half Moon Bay seawater sample extracts, showing good recovery at 50 ng. Lower detection limits can be obtained using large injection volume. Replicate injections of standard with very low RSDs of retention times and peak areas confirm the reproducibility of this method.

References

(1) American Chemical Society 239th National Meeting news releases, San Francisco, Mar. 23, 2010.

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