Taking part of the lab to the sample: On-site electrodeposition of Pb followed by measurement in a lab using electrothermal, near-torch vaporization sample introduction and inductively coupled plasma-atomic emission spectrometry

摘要

An electrodeposition method for preconcentration and separation of labile Pb from liquid samples with a complex matrix is described. For the first time, Pb was electrodeposited on-site on Re coiled-filament assemblies that were developed for use with an electrothermal, near-torch vaporization (NTV) sample introduction system and inductively coupled plasma-atomic emission spectrometry (ICP-AES). The coiled-filament assemblies (or simply coils) were purposely designed to be removable and were fabricated to have identical coupling-mechanisms so that they can be used interchangeably. In addition to their small size (2.75. cm long and 0.65. cm wide), coiled-filament assemblies weighed only 1.4. g, which made them portable for on-site use. The detection limit from diluted seawater Certified Reference Material (CRM) and NTV-ICP-AES was 25. pg/mL following a 3. min electrodeposition. This detection limit represents a 40-fold improvement as compared to the detection limit obtained by pipetting 5 μL of dilute Pb standard solution directly on the coil. The detection limit improved by 400-times (to 2. pg/mL) when the electrodeposition time was increased to 60. min. Lead from very hard tap water was electrodeposited on coiled filaments on-site using a shirt-pocket size, battery-operated potentiostat and portable electrodeposition instrumentation. Concentration was determined in the lab using NTV-ICP-AES. The Pb concentration was used to test for compliance with the Pb-Cu rule set by the United States Environmental Protection Agency (US EPA). Overall, on-site electrodeposition permitted determination of Pb at the environmental conditions (e.g., pH, temperature) recorded at the time of sampling. On-site electrodeposition also opens the possibility for shipping portable coils with Pb electrodeposited on them to the lab rather than shipping large volumes of sample, thus reducing shipping, handling and storage costs.