2.5. DLLME procedure
The pHof sampleswas adjustedwithHNO3 or NH4OH solutions. Ten
milliliters of RW2 (with suitable dilution) was transferred to a 15 mL
centrifuge glass tube with conical bottom. Previous to the injection of
mixture of solvents, 500 μL of DDTC solution and 500 μL of NaCl solution
(when necessary) were added. A mixture containing dispersive and
extraction solvent was rapidly injected with a glass syringe into the
sample. After injection, a cloudy solution was formed instantaneously
and the solution was centrifuged. In order to reduce interferences
during the measurements, sedimented phase (extract) was washed
with 5 mL ultrapure water and further submitted to centrifugation
step. This washing procedure was repeated as much as necessary.
After the last washing, the aqueous phase was not removed. Thus, the
capillary of nebulization system of F AAS instrument was introduced
into the aqueous phase and the auto zero of baseline was obtained
aspirating the aqueous solution.When the integration was started, the
capillary was moved to the sedimented phase, which was aspirated
and the analytical signal was obtained. It is important to mention that
this sample introduction procedure was applied for samples and
reference solutions
2.5. DLLME procedureThe pHof sampleswas adjustedwithHNO3 or NH4OH solutions. Tenmilliliters of RW2 (with suitable dilution) was transferred to a 15 mLcentrifuge glass tube with conical bottom. Previous to the injection ofmixture of solvents, 500 μL of DDTC solution and 500 μL of NaCl solution(when necessary) were added. A mixture containing dispersive andextraction solvent was rapidly injected with a glass syringe into thesample. After injection, a cloudy solution was formed instantaneouslyand the solution was centrifuged. In order to reduce interferencesduring the measurements, sedimented phase (extract) was washedwith 5 mL ultrapure water and further submitted to centrifugationstep. This washing procedure was repeated as much as necessary.After the last washing, the aqueous phase was not removed. Thus, thecapillary of nebulization system of F AAS instrument was introducedinto the aqueous phase and the auto zero of baseline was obtainedaspirating the aqueous solution.When the integration was started, thecapillary was moved to the sedimented phase, which was aspiratedand the analytical signal was obtained. It is important to mention thatthis sample introduction procedure was applied for samples andreference solutions
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