This paper reports the application of liquid electrode plasma atomic emission spectrometry (LEP AES) integrated with on-chip solid phase extraction (SPE) for determination of lead (Pb). LEP AES is a novel elemental analysis method employing micro-plasma in the sample solution as excitation source. The integration of SPE to LEP chip shows high potential of application with several merits because on-chip SPE enables the effective use of sample. In the work an improved LEP chip integrated with SPE was developed for trace lead detection. Chip design and pulse voltage were proposed to eliminate the ash generation and minimize the channel expansion. Some analytical parameters were optimized. With sample volume of 1 mL calibration curve in the range of 0-100 ng/mL the correlation coefficient of 0.992 and limit of detection (LOD) of 0.64 ng/mL were obtained. With the support of SPE, LOD was improved about 30 times.
A novel liquid electrode plasma (LEP) driven by AC, which is used as an excitation source for elemental analysis, has been developed for the first time. The conditions such as chip layout and flow rate were found to produce the plasma in the channel. The mechanism of AC LEP generation was determined. AC LEP could be sustained in the resin channel with no severe damage on the channel. The emission spectra of electrolyte, lead and cadmium solution were obtained and compared with those generated by DC LEP. AC LEP was developed for the quantitative determination of lead and cadmium with limits of detection of 75.0 µg/L (ppb) and 4.5 µg/L (ppb), respectively. The novel plasma source is promising for on-chip combination and integration because it could be maintained at low flow rates on a resin-based platform.
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