title: Molybdenum blue spectrophotometry for trace arsenic in ground water using a soluble membrane filter and calcium carbonate column.
abstract: An improved molybdenum blue spectrophotometry using a soluble membrane filter and CaCO(3)-column was proposed for determining arsenic in drinking water supplied from ground water in the presence of phosphate.  A 100 mL sample solution containing 0.5 - 10 μg arsenic was passed through a CaCO(3)-column to remove phosphate, arsenate (As(V)).  Arsenite (As(III)) which was not retained on the column was oxidized to As(V).  As(V) was converted into a heteropolymolybdenum blue anion.  The blue anion was collected on a membrane filter as an ion-associate with n-dodecyltrimethylammonium ion by filtration.  The filter was dissolved in 2 mL of 2-methoxyethanol.  The absorbance of the solution was measured at 810 nm against a reagent blank.  Total inorganic arsenic was determined by reducing As(V) to As(III) before the column treatment.  The RSDs for 10 μg L(-1) of As(III) and As(V) were 2.9%.  Phosphate 0.2 mg L(-1) (as P) and iron 0.1 mg L(-1) did not interfere with the determination of 10 μg L(-1) arsenic.  The proposed method was successfully applied to ground waters.
authors.affiliation: Department of Environmental Biology and Chemistry, Graduate School of Science and Engineering for Research, University of Toyama, Gofuku 3190, Toyama, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Okazaki
authors.forename: Wenjing
authors.initials: W
authors.lastname: Wang
authors.forename: Hideki
authors.initials: H
authors.lastname: Kuramitz
authors.forename: Noriko
authors.initials: N
authors.lastname: Hata
authors.forename: Shigeru
authors.initials: S
authors.lastname: Taguchi