Capillary Electrophoretic Determination of Selenium and Tellurium Oxyanions

Capillary Electrophoretic Determination of Selenium and Tellurium Oxyanions in Bacterial Cultures by Bala Krishna Pathem and Thomas G. Chasteen Department of Chemistry Sam Houston State University 1

Instrument configuration Source: ceandcec. com 2

Flow reversal n For Anions: – In order to speed up the separation, the EOF can be reversed by addition of cationic surfactants. – A negative voltage is applied. – We have used TTAB and HTAB in our work. 3

Source: ceandcec. com 4

Method development n We developed a method for the identification of selenium species in presence of TSB or LB bacterial growth medium, complex and well-defined media. n We applied the method for simultaneous estimation of selenate and selenite or tellurite in live cultures during their biological reduction by bacteria. 5

Capillary n Fused silica capillaries were used for all the studies done in this research. n Dimensions: 50 cm effective length, 75 µm i. d, 375 µm O. D. 6

Method n Buffer: 15 m. M KH 2 PO 4 + 1 m. M TTAB n p. H - 10. 5 n Injection Pressure: 0. 5 psi Time: 5 sec n Separation Voltage: – 25. 0 KV n Capillary temp: 25 o. C n Run time: 5 min n Detection: 190 nm for selenium oxyanions 220 nm for tellurium oxyanions 7

Bacterial growth conditions n Two bacterial species were used in our research. 1. Precultures of Bacillus sp. were grown in TSB (p. H 7. 0) at 30 o. C and then amended with 1. 0 m. M selenate. 2. Precultures of genetically modified clone of E. coli K 12 (1 VH) were grown in LB medium with Ampicillin (p. H 7. 0) at 37 o. C and then amended with 0. 05 m. M tellurite. 8

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Bioreduction of selenate by Bacillus sp. Figure 2 10

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Bioreduction of 0. 05 m. M tellurite by 1 VH m. AU Te. O 32 - 0 h 5 h 24 h after inoculation Figure 6 14

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Conclusions n Once bacteria enters stationary phase (4 h): – Rate of selenate reduction decreases – Selenite reduction process begins or increases significantly, 25% drop in Se. O 32 - in 1 h n Varied bacterial response to toxic salts – Selenite is more toxic than selenate for both these organisms, based on specific growth rates 16

Conclusions n Method offers excellent LOD (3 S/N) – Selenate : 1. 0 ppm or 0. 007 m. M – Selenite : 0. 25 ppm or 0. 002 m. M n Linearity – Selenate: 0. 9996 (0. 1 m. M to 1. 0 m. M) – Selenite : 0. 9998 (0. 1 m. M to 1. 0 m. M) 17

Conclusions n This method affords high sample throughput and minimal or no sample preparation for biological samples. n Perfect tool for the Qualitative or Quantitative analysis of selenium and tellurium oxyanions in solution. n Applicable for analysis in environmental or agricultural samples. 18

Acknowledgements This work was supported by Sam Houston State University’s Faculty Enhancement Research Fund The Robert A. Welch Foundation 19

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