title: Rapid determination of ions by combined solid-phase extraction--diffuse reflectance spectroscopy.
abstract: We introduce colorimetric solid-phase extraction (C-SPE) for the rapid determination of selected ions. This new technique links the exhaustive concentration of an analyte by SPE onto a membrane disk surface for quantitative measurement with a hand-held diffuse reflectance spectrometer. The concentration/measurement procedure is complete in approximately 1 min and can be performed almost anywhere. This method has been used to monitor iodine and iodide in spacecraft water in the 0.1-5.0 ppm range and silver(I) in the range of 5.0-1000 microg/l. Applications to the trace analysis of copper(II), nickel(II), iron(III) and chromium(VI) are described. Studies on the mechanism of extraction showed that impregnation of the disk with a surfactant as well as a complexing reagent results in uptake of additional water, which markedly improves the extraction efficiency.
authors.affiliation: Microanalytical Instrumentation Center, Ames Laboratory, US Department of Energy, Department of Chemistry, Iowa State University, Ames, IA 50011, USA. kniss@ameslab.gov
authors.forename: James S
authors.initials: JS
authors.lastname: Fritz
authors.forename: Matteo P
authors.initials: MP
authors.lastname: Arena
authors.forename: Steven A
authors.initials: SA
authors.lastname: Steiner
authors.forename: Marc D
authors.initials: MD
authors.lastname: Porter
mesh_terms: D002412:Cations / Q000032:analysis; D002857:Chromium / Q000032:analysis; D003124:Colorimetry / Q000379:methods*; D003300:Copper / Q000032:analysis; D007454:Iodides / Q000032:analysis; D007455:Iodine / Q000032:analysis; D007477:Ions / Q000032:analysis*; D007501:Iron / Q000032:analysis; D008670:Metals / Q000032:analysis; D009532:Nickel / Q000032:analysis; D012834:Silver / Q000032:analysis; D013057:Spectrum Analysis / Q000379:methods*; D014867:Water / Q000737:chemistry
chemical_list: D002412:Cations; D007454:Iodides; D007477:Ions; D008670:Metals; D014867:Water; D002857:Chromium; D012834:Silver; D003300:Copper; D009532:Nickel; D007455:Iodine; D007501:Iron