Quantitative Determination of Escherichia Coli in Water Sources in the Environment Using a Surface Acoustic Wave Impedance System Modified with a Syringe Filter
A novel surface acoustic wave (SAW) sensor was developed in the study to measure the density of Escherichia coli in water sources in the environment. With a modified syringe filter sealed by a Teflon cover, the sensor system ensured that the CO2 gas produced by bacteria flowed upward and accumulated at the headspace of the syringe filter. The measurements were obtained by immersing a pair of electrodes into a sealed syringe filter which contained a culture solution containing lauryl sulfate trytose (LST) The changes in frequency of the two electrodes were caused by generation of small CO2 bubbles on the surface of the electrodes, which were connected in series to a SAW resonator. The signals obtained by the system were 10 times greater than those obtained by conventional SAW systems. The calibration curve of detection time versus density of E. coli showed a linear relationship with a correlation coefficient (R 2 of 0.9434 over the range of 102 to 107 cells/mL. Further integration of this sensing system with a suitable automated sampling device will enable this device to be used on site for analysis and field studies.