RESUMO
A novel method using a micro-column packed with active alumina as solid phase was proposed for separation of trace lithium from uranium compounds prior to determination. The method is based on a preliminary chromatographic separation of the total amount of uranium. This separation involves passing the solution containing sodium carbonate through active alumina and then eluting the trace lithium retained by the solid phase with a solution of sulfuric acid. Two modes, off-line and on-line micro-column preconcentration, were performed. In conjunction with atomic absorption spectrometry, this on-line preconcentration technique allows a determination of lithium at 10(-9) level. Both off-line and on-line mode operation conditions were investigated in separation and determination of trace lithium by micro-column method (length of column bed, flow rate, etc.). The adsorption capacity of activated alumina was found to be 343 microg g(-1) for lithium. Under the optimal operation condition, the detection limit (DL) of on-line preconcentration corresponding to three times the standard deviation of the blank (S/N = 3) was found to be 1.3 ng mL(-1) and the RSD of this method is 3.32% (n = 5). The on-line calibration graph was linear over the range 20 - 200 ng mL(-1). A good preconcentration factor 820 was achieved by experiment under the on-line mode. The developed method was applied to the analysis of trace lithium in nuclear grade uranium compounds.
RESUMO
OBJECTIVE: To explore the effect of aminoguanidine (AG) on hemodynamics and nitric oxide (NO) in hemorrhagic shock in rabbit. METHODS: Shock was produced in twenty rabbits by femoral artery blood letting, and they were randomly divided into two groups with treatment with saline (control group) or AG (each n=10). Pclab system and nitric acid reductase methods were performed to detect hemodynamics parameters and NO levels at preshock, postshock (30 minutes and 150 minutes) and 30 minutes and 180 minutes after resuscitation respectively. RESULTS: No significant differences were observed in hemodynamics parameters and NO levels between the two groups before resuscitation. Whereas after resuscitation, hemodynamics parameters such as systolic arterial pressure (SAP), heart rate (HR), mean arterial pressure (MAP), left ventricular systolic pressure (LVSP) and the max and minimum first derivative of left ventricular pressure (+/-dp/dt max) were all improved greatly in the two groups. AG decreased serum NO level significantly, while saline did not have such effect, suggesting that AG had a longer and more efficient effect against hemorrhagic shock (P<0.05 or P<0.01). CONCLUSION: AG can improve hemodynamics parameters and decrease NO level in hemorrhagic shock in rabbit.
