Tributyl Phosphate as a Sensitivity-Enhancing Solvent for Organotin in Carbon Furnace Atomic Absorption Spectrometry

Tributyl phosphate (TBP) has been found to be a sensitivity-enhancing solvent for organotin compounds in graphite furnace atomic absorption spectrometry;
(C4H9)2Sn(O2CCH3)2,
(C4H9)2Sn(O2CC11H23)2,
(C4H9)3SnCl, and
(C4H9)4Sn all give 1 order of
magnitude higher sensitivities in TBP than in toluene or ethyl acetate. The
sensitivities are enhanced further 1−2 orders of magnitude in
TBP, when PdCl2(CH3CN)2 is
added as a matrix modifier
in the organic solvent. Among the four organotin compounds,
(C4H9)2Sn(O2CCH3)2
and
(C4H9)2Sn(O2CC11H23)2
give better sensitivities than
(C4H9)3SnCl and
(C4H9)4Sn
in the absence of palladium in any organic solvent, which
suggests that the oxygen atom in the tin compound might
form tin oxides that are resistant to volatilization loss
during ashing. Scanning electron microscopic, electrothermal vaporization ICPMS, and powder X-ray diffraction
studies show that the final products before atomization
include phosphorus-containing compounds
Sn2P2O7,
SnP2O7, and Pd9P2,
besides tin−palladium alloys, PdSn,
Pd3Sn, Pd2Sn,
Pd3Sn2, and PdSn3. These
phosphorus-containing compounds would more efficiently stabilize tin
and suppress tin vaporization loss during ashing, to give
higher sensitivity.