Determination of gallium by anodic stripping square-wave voltammetry Detection of a GaZn intermetallic compound and its destruction by Sb in an NaSCNNaClO(4) supporting electrolyte.
Reproducibility for successive determinations with a hanging mercury drop electrode is assessed in relation to solution stirring, drop size and back-diffusion to the mercury thread. The effect of experimental parameters such as drop size, deposition time and gallium concentration on the observed stripping current is investigated. The interference of zinc present in a 0.5M NaSCN + 4.2M NaClO(4) supporting electrolyte on the gallium detection limit and calibration plots is described. Formation of an intermetallic compound with a Zn:Ga ratio of 2:3 and its destruction by co-deposition of zinc with Sb are reported. A detection limit of 10(-8)M gallium was obtained in the presence of 10(-5)M Sb(III).
Separation and determination of parts-per-billion concentrations of gallium in biological materials.
Gallium is separated from an aqueous digest of a biological matrix, by the selective extraction of the ion pair GaCl/sub 4//sup -/ x R/sub 4/N/sup +/, into a hexane-methyl isobutyl ketone mixture (R/sub 4/N/sup +/ represents the methyltricaprylammonium ion). The extracted gallium species reacts with the ligand, 1,5-bis(salicylidene)-thiocarbohydrazone, to form a complex that fluoresces at 440 nm when the excitation wavelength is 395 nm. This fluorometric method has been used to determine 0.10-40 ppb of gallium in biological materials with a relative precision of 7%. The principal interferences with the fluorometric method in aqueous solutions are Fe/sup 3 +/, Fe/sup 2 +/, Cu/sup 2 +/, and Zn/sup 2 +/. In the aqueous digest, the Fe/sup 3 +/ is reduced to Fe/sup 2 +/ and the Cu/sup 2 +/ is masked with S/sub 2/O/sub 3//sup 2 -/. The Fe/sup 2 +/ and Zn/sup 2 +/ are not extracted into the organic phase and do not interfere with the fluorometric method.
Reduction of patient exposure during dental radiography.
We investigated the effect of using additional accessories with a conventional X-ray machine to reduce patient exposure during full-mouth dental radiography. LiF extruded-rod thermoluminescent dosimeters were placed in 23 anatomical sities of a Randophantom and the phantom was exposed to a Turkish dental X-ray machine operated at 60 kV, 10 mA for 0.5 sec periods. Maximum reductions were observed at the eyes (80%), in the thyroid (70.6%). under the collar bone (59.9% average) and the gonads