1974 Volume 27 Issue 5 Pages 255-262
When a quantitative analysis on the trace of microgram arsenic contained in salt was conducted by atomic absorption spectrophotometry, the arsenic was reduced to arsine as the result of employment of zinc and hydrochloric acid.
This arsine was trapped in solid form in a U-tube filled with glass beads which had been frozen with liquid nitrogen around-150°, and then evaporated from the U-tube to the room temperature. The gaseous arsine was swept out with nitrogen into a premixed argon-hydrogen flame for absorption measurement. The atomic absorption for the arsenic was measured at the 193.7nm resonance radiated from an electrodeless discharge lamp.
This atomic absorption method indicated that although most of the elements gave no interference with the production of arsine, tellurite and nitrate ions interfered with the reduction of arsenic to arsine.
In case 2 gram salt was used as sample, the most suitable optimum sample weight for arsenic was between 0.05 and 0.4μg. In this range of arsenic, the variation coefficient of the measurement of atomic arsenic was found to be about 7%, and the sensitivity for 1% absorption for arsenic was 6×10-9g.
When the amount of arsenic contained in salt was determined by the above method, the salt produced by old-fashioned making method was found to contain nearly the same amount of arsenic as natural sea-water, but the one produced and extremely refined by the modern making method was found to contain so little that no arsenic could be detected. This pointed out an environmental problem that the human-kind would have to eat salt containing no arsenic in the future.
