[Massive inferior vena cava thrombosis associated with protein C deficiency. Clinical case]. / Trombosis masiva de vena cava inferior asociada a déficit de proteína C. Caso clínico.

Inferior vena cava thrombosis is infrequent and in 30% of cases, the potential cause is an alteration of the natural anticoagulant protein system. We report a 18 years old male with an inferior vena cava thrombosis that was associated to a protein C deficiency. He was successfully treated with an infusion of intravenous streptokinase during 30 hours and intravenous heparin during 10 days, followed by oral anticoagulation therapy.

Determination of gallium by square-wave voltammetry anodic stripping, based on the electrocatalytic action of 2,2'-bipyridine in dimethylsulphoxide: comparison with an aqueous NaSCN/NaClO(4) electrolyte.

Deposition potential, deposition time, square-wave frequency, 2,2'-bipyridine concentration, and gallium concentration have been studied in detail, for the determination of trace concentration levels of the metal by square-wave voltammetry anodic stripping analysis, in dimethylsulphoxide. Optimum conditions have been found for gallium(III) determination and results compared to those obtained in 0.5M NaSCN + 4.2M NaClO(4) aqueous electrolyte by obtaining calibration graphs for the range 1 x 10(-8)M-1 x 10(-5)M gallium. Accuracy (+/- 3%) and precision (4-6% SD) of this method were assessed with both 4 x 10(-8)M and 4 x 10(-7)M gallium solutions used as synthetic samples. The efficiency of solvent extraction of gallium with di-isopropyl ether was found to be 99.98% at a 4 x 10(-7)M gallium concentration. The proposed method was applied to the determination of the gallium content in rock mineral samples (using the above mentioned solvent extraction procedure), are compared to those obtained with the NaSCNNaClO(4) based electrolyte. No statistically significant difference was observed. Analytical procedures followed are given in detail.

Electrochemical reduction of gallium(III) in non-aqueous solvents, assisted by 2,2'-bipyridine.

The electrochemistry of gallium(III) perchlorate in dimethylsulfoxide (DMSO) and acetonitrile (MeCN) at a mercury drop electrode is described and compared to that in water. The reduction of 2,2'-bipyridine (DIPY) and its interaction with free protons in the solvents mentioned is also surveyed. The electrochemistry of tris-(2,2'-bipyridine) gallium(III) perchlorate was studied in DMSO and MeCN. A gallium metal deposit is obtained by reduction of the complex compound in the first solvent, whereas lower valence gallium-DIPY species are obtained in the second. The existence of different catalytic prepeaks in DMSO is described. The first catalytic peak, which renders a metal deposit, is studied in detail, together with the possible interference of oxygen and free protons. These studies serve the basis of future development of an analytical procedure for the determination of trace concentrations of gallium.

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).

Determination of silver in dore metal by weight titration with equivalence-point detection by differential electrolytic potentiometry.

Use of weight titrimetry, with differential electrolytic potentiometry for detection of the equivalence point, instead of gravimetry, has been critically tested for the determination of silver in doré metal. The electrode response in the presence of possible interferences (Sb, As, Se, Cu, Ni, Fe, Pb and Co) was studied by voltammetry. Titration curves for six different samples were obtained and their differences from those for pure silver were interpreted. Positive errors were found to occur in the presence of 0.1% Fe(III) and Se(IV) but not in the presence of 1% Cu(II). The results obtained by gravimetry and weight titrimetry were compared. The imprecision of the proposed method was between 0.03 and 0.05% (relative standard deviation); that of gravimetry was between 0.05 and 0.08%. The absolute difference from the gravimetric results was between + 0.05 and + 0.08%. The time for analysis of one sample was between 60 and 80 min.