Flow-injection inductively coupled plasma mass spectrometer incorporated with an ultrasonic nebulizer-membrane dryer: Application to trace lead detection in aqueous solution and seawater

Flow-injection (FI) incorporated with inductively coupled plasma mass spect rometry (ICP-MS) was used to determine lead in aqueous solutions and seawat er. Lead was retained in the form of Pb-DDPA complex in a sorbent microcolu mn packed with C-18-bonded silica, and then carried to an ultrasonic nebuli zer with methanol as eluent. The ultrasonic nebulizer removed about 66% of methanol solvent vapors from entering the detector. A multi-tube Nafion (R) membrane dryer, installed along the passage prior to the ICP torch, furthe r removed 50% of methanol. Reducing the amount of methanol solvent signific antly improved the signal-to-background ratio of the detector. Accordingly, when the sample was Loaded for 15 and 60 s, respectively, Pb detection lim its were determined to be 0.162 and 0.028 ng/L, one to two orders of magnit ude lower than those reported. The enrichment factors were also measured to be 7 and 28, with the sampling frequencies of 31 and 21 h(-1), respectivel y, The method was applied for the determination of Pb in a reference seawat er. The obtained result was 0.013 +/- 0.001 ng/mL, consistent with the cert ified value of 0.013 +/- 0.005 ng/mL.