FIA-coupled spectrophotometric method for determination of Cr (VI) traces in natural waters: application of in-line dissolution of 1,5-diphenylcarbazide after heat treatment and activated alumina as adsorbent for preconcentration.

This work proposes the quantification of Cr (VI) ions in natural waters in trace level, using activated alumina (Al2O3) as preconcentration support, controlled in-line dissolution of the solidified chromophore diphenylcarbazide after heat treatment and spectrophotometric detection. The manifold ensures high sensitivity of analytical response, good repeatability, and stability. In this work, optimization of experimental conditions of a flow injection system was chosen as the parameters for greater sensitivity and better selectivity. The selected optimized conditions were 0.30 mol L-1 for H2SO4 concentration, system flow rate as 0.40 mL min-1, sample injection volume of 192.50 µL, 2 min for preconcentration time, and 0.10 mol L-1 for eluent concentration. The analytical curves obtained for real sample analysis show linear range from 0.192 to 0.961 µM, linear correlation coefficient R = 0.9997 and LOD = 0.024 µM. The preconcentration factor of about four times was obtained through the passage of 800 µL of a standard solution containing 0.961 µM of Cr (VI) through mini-column of preconcentration followed by elution at 192.5 µL of NH4OH 0.1 mol L-1 solution. The solid chromogenic reagent presented high durability (weeks in daily use with mass of 0.0993 g) and good reproducibility in analytical signal. The reactivation of the mini-column of alumina should be executed after ten injections of eluent, using 800 µL of HCl 0.02 mol L-1 solution in flow through the same. Each cycle of injection and elution of the sample takes about 5 min on the proposed terms. Despite the length of each cycle still be high, low concentrations can be detected using a technique of relatively low cost. This is due in part, the association dissolution of the chromogenic reagent directly in the line and the preconcentration step. Another important factor is the economy of reagent chromogenic, low generation of reject contributing to better quality of the environment, and the high potential for applications to work in field.

Systemic hemodynamic changes in young and elderly normotensive individuals after ingestion of meals with high lipid, protein, and carbohydrate contents.

OBJECTIVES: The changes in blood pressure and in the cardiac function were studied in two groups of patients: an elderly group (EG) with 10 healthy normotensive elderly patients, and a young group (YG), with eight normal volunteers. METHODS: Both groups were provided meals with high contents of lipids (LM), carbohydrates (CM), and proteins (PM). The systemic hemodynamic changes in each group were compared. RESULTS: The maximum reductions (Δ(max)) observed in the mean arterial pressure in the EG were -10.3% and -8.9% for LM and CM, respectively (P<0.05), and -6.5% for PM (NS). No significant changes in the mean arterial pressure were found in YG. After the CM, EG showed a reduction in the total peripheral resistance (TPVRi) from 3212 ± 225 to 2537 ± 165 dyne s/cm(5); (P<0.05), and the cardiac index (CI) increased from 2.4 ± 0.17 to 2.8 ± 0.19 l/min/m(2); (P<0.05). After LM, the EG reduced the TPVRi from 3630 ± 273 to 2529 ± 247 dyne s/cm(5); (P<0.05), and CI increased from 2.1 ± 0.15 to 2.8 ± 0.15 l/min/m(2); (P<0.05). The PM did not alter CI. The YG showed, after CM, no significant decreases in TPVRi, but CI increased from 3.2 to 3.9 ± 0.16 ± 0.28 l/min/m(2); (P<0.05), and after the LM, there was an increase in CI from 3.3 to 4.2 ± 0.21 ± 0.17 l/min/m(2); (P<0.05) and a concomitant reduction in TPVRi from 2094 ± 173 to 1657 ± 139 dyne s/cm(5); (P<0.05). CONCLUSION: In conclusion, the modifications in cardiac function in our elderly population were observed after eating and were related to the type of food ingested. No significant changes were observed in heart function after the ingestion of a protein meal.