Determination of gold and silver in parts-per-billion or lower levels in geological and metallurgical samples by atomic absorption spectrometry with a carbon rod atomizer

Abstract

50-100 range and is in excellent agreement with the electrochemical selectivity ratio.A particularly interesting finding is the excellent agreement for the divalent ions Ba2+ and Sr2+. Unfortunately, these are the only multivalent cations for which useful formation constant values have been reported to date.On the basis of our studies on the valinomycin electrode (9) and the present results we propose, for neutral carrier liquid membrane electrodes in general, the useful approximation where ,2 is the potentiometric selectivity coefficient for the electrode's response to ion 1 over 2 while K,J and K,,z are the equilibrium formation constants for complexes between the carrier entity and ions l and 2, respectively. In the usual case, where the formation rate constants are independent of the cation, the right hand side of this expression is equivalent to the inverse quotient of the specific dissociation rates and shows that the electrode is selective ,for the ion held longest in the cavity of the carrier molecule. We expect that this relationship would give an approximate prediction of selectivity coefficients for those electrode systems having no special spatial arrangement of the carrier in the membrane and where the system kinetics are not potential determining. It should, thus, be possible to predict the selectivity properties of suitable neutral carrier electrodes on the basis of homogeneous complex formation data as a first approximation. Similarly, formation constants should be predictable from electrochemical data. We hope that these guidelines will facilitate the selection or synthesis of suitable membrane phase materials and will assist in the practical development of new liquid membrane electrodes. ACKNOWLEDGMENTWe thank H. K. Frensdorff for his gift of the crown compounds and G. Eisenman for some unpublished data.

Pyrolytic graphite-tube microfurnace for trace analysis by atomic absorption spectrometry

“…The sensitivity for gold in the MIBK extract or in the aqueous solution (directly) is essentially the same, 2.9 X 10~n gram (absolute). In view of the primitive heating circuitry used, this value compares favorably with the value of 1 X 10~u gram (absolute) obtained by Bratzel et al (4) with a carbon rod atomization device, and of 1.0 X [10][11][12] gram (absolute) obtained by L'vov (7) with a graphite crucible. The coefficient of variation is about 10% for measurements at the 5.0 X 10~10 gram (absolute) level, compared with 5-8 % obtained by others using either a graphite furnace (7) or a carbon rod atomizer (4).…”

Hanging mercury drop electrodeposition technique for carbon filament flameless atomic absorption analysis. Application to the determination of copper in sea water

“…Thus, these results indicate that coupling controlled potential electrolysis with carbon filament AA is a suitable technique for the determination of Cu in unpolluted sea water with matrix interferences apparently eliminated and selective volatilization of Hg without covolatilization of Cu accomplished. The technique may, therefore, provide an adequate alternative to long, tedious, and sometimes complicated matrix separation procedures in the fields of biological trace metal analysis (6,7,16), health studies (17,18) food and agriculture (8,19,20), geochemistry (9,(20)(21)(22), metallurgy (23), and industrial development and control (24). The tracings in Figure 2 illustrate that essentially the same type of signal is obtained from a sample electrodeposited on a MD as from a directly injected aqueous sam- the graphite tube.…”

The Estimation of Gold in Urine by Flameless Atomic Absorption Spectroscopy

“…The graphite furnace is more sensitive than the air-acetylene flame (Bratzel et al, 1972;Aggett, 1973). The precipitation of gold from urine as telluride was described by Yamanada et al (1971) and Jamieson and Watson (1938), neither of whom published a critical examination of the method.…”