Abstract:
Improvements have been made on the currently available hydride
generator system manufactured by SpectraMetrics Incorporated, because the
system was found to be unsatisfactory with respect to the following:
1. the drying agent, anhydrous calcium chloride,
2. the special sample tube,
3. the direction of argon flow through the Buchner funnel when it came
to dealing with real sample, that is, with reference only to aqueous
extracts of soil samples.
Changes that were made on the system included the replacement of
anhydrous calcium chloride with anhydrous calcium sulphate and the
replacement of the special sample tube with a modified one made from
silica. Re-directing the flow of argon through the top of the Buchner
funnel appeared to make the system compatible with aqueous extracts of
soil samples.
The interferences from 1000 ~g/mL of nickel(II) , cobalt(II),
iron(III), copper(II) have been eliminated with the aid of 1.4 M
hydrochloric acid and 1% (weight/volume) L-cystine. Greater than 90%
recovery of 0.3 ~g/mL arsenic signal was achieved in each case.
Furthermore, 103% of arsenic signal was accomplished in the presence of
1000 ~g/mL cadmium with 5 M Hel. tVhen each of the interferents was present
in solution at 1000 ppm, a recovery of 85% was achieved by using 5 M hydrochloric acid and 3% (weight/volume) L-cystine. Without L-cystine
and when 1.4 M hydrochloric acid was used, the recoveries were 0% (Ni),
0% (Co), 88% (Fe), 15% (Cu), 18% (Cd). Similarly, a solution containing
1000 ppm of each interferent gave a zero percent recovery of arsenic.
The reduction of trivalent and pentavalent arsenic at a pH less than
one has also been investigated and shown to be quantitative if peak areas
are measured.
The reproducibility determination of a 0.3 Vg/mL standard arsenic
solution by hydride generation shows a relative standard deviation of
3.4%. The detection limits with and without Porapak Q have been found to
be 0.6 ng/mL and 1.0 ng/mL, respectively.
