Abstract:One catalytic discoloring spectrophotometry with double indicators and dual wavelength is proposed in the Thesis to measure the content of trace iron in three kinds of hematinic, artemisia integrifolia and other vegetables. In HCI medium, methyl orange and methylene blue are indicators. At wavelength of 500 nm and 665 nm, the change value ΔA in absorbance of catalytic system and non-catalytic system is measured and thus the iron content is measured. The conclusion is that the Method is characterized by simple operation, high sensitivity, favorable selectivity and reliable results.
Using on-line pre-chlorine and sulfate removal technique, a rapid and direct method was established for the simultaneous determination of nitrite-N, nitrate-N and phosphate-P in seawater by ion chromatography (IC) with suppressed conductivity detection. In this method, an IonPac AG23 column was used as the enrichment column, an IonPac AS23 column with high capacity as the analytical column, and KOH solution as the eluent for gradient elution produced by an eluent generator on-line automatically. The results showed that the determination of the targets was not interfered when a seawater sample diluted 5 to 10 times was directly injected. The method detection limits (MDL) of nitrite-N, nitrate-N and phosphate-P were 0.3, 0.4 and 0.2 microg/L respectively, under the conditions of 500 microL sample volume and 1 mL/min elution rate. The linear ranges of nitrite-N, nitrate-N and phosphate-P were 10 - 500 microg/L, 14 - 680 microg/L and 3.4 - 170 microg/L respectively, and the correlation coefficients (r) were all greater than 0. 999 0. The average recoveries of the 3 analytes spiked in a sample ranged from 92% to 106% with the relative standard deviations (RSDs, n = 6) of 1.2% - 7.7%. The whole sample analysis process can be completed in 13 min. The method has the advantage of simple operation, reagent-free and pollution-free, and can meet the quantitative analysis requirements of seawater.
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