RESUMO
An on-line nickel preconcentration and determination system implemented with inductively coupled plasma optical emission spectrometry (ICP-OES) associated to flow injection (FI) was studied. Trace amounts of nickel were preconcentrated by sorption on a conical minicolumn packed with activated carbon (AC) at pH 5.0. The nickel was removed from the minicolumn with 20% nitric acid. An enrichment factor of 80-fold for a sample volume of 50 ml was obtained. The detection limit (DL) value for the preconcentration method proposed was 82 ng l(-1). The precision for ten replicate determinations at the 0.5 microg l(-1) Ni level was 3.0% relative standard deviation (R.S.D.), calculated from the peak heights obtained. The calibration graph preconcentration method for nickel was linear with a correlation coefficient of 0.9997 at levels near the detection limits (DL) up to at least 100 microg l(-1). The method was successfully applied to the determination of nickel in natural water samples.
RESUMO
BACKGROUND: After repair of tetralogy of Fallot, right ventricular (RV) dilation has been associated with increased risk of ventricular arrhythmias and sudden death. To address this, a modified repair was developed. METHODS AND RESULTS: We followed two postoperative groups: group 1 (n = 20) received repair of tetralogy of Fallot with the modified technique with transatrial ventricular septal defect closure, a short infundibular incision with avoidance of muscle resection, and patch expansion of the RV outflow tract; group 2 (n = 22) received repair of tetralogy of Fallot by the traditional technique with ventricular septal defect closure through a ventriculotomy with resection of obstructing muscle. Six patients were excluded from further follow-up: two patients, one in each group, who required RV-pulmonary artery conduit placement at original repair; one patient in group 1 who developed double-chamber RV; and three patients, two in group 1 and one in group 2, who were lost to our follow-up < 5 years postoperatively. We compared postoperative findings > 10 years after repair. Despite similar residual RV outflow tract stenosis and obligatory pulmonary insufficiency by examination and Doppler echocardiography, RV size was smaller in the modified group, as reflected by RV/left ventricle on M-mode echocardiography (0.66 +/- 0.22 versus 0.81 +/- 0.17, P = .02), cardiothoracic ratio (0.53 +/- 0.04 versus 0.58 +/- 0.06, P = .03), and QRS duration (126 +/- 19 versus 143 +/- 23, P = .03). RV systolic function was more impaired in group 2, as reflected by decreased systolic tricuspid annulus excursion on two-dimensional echocardiography. Exercise endurance time was significantly higher in group 1 patients. Lown grade 4 ventricular ectopy on ambulatory ECG was present in three patients in group 2 and none in group 1. CONCLUSIONS: The modified technique results in significantly less RV dilation and better preservation of RV function at late follow-up.
