Calibrate the iron curve using a spectrophotometer
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When using a spectrophotometer to calibrate the curve for iron, a problem was encountered: the linearity was fairly good, with an R value of three nines, but when measurements were taken using solutions of known concentrations, the results turned out to be too low, with the discrepancy reaching as much as twenty-odd percent Could the experts please help analyze the reasons?
Conduct more repeat experiments; the client should specify the measurement range, as this makes it easier to evaluate certain data
This post was last edited by qugd on 2016-8-13 at 17:17. When determining iron using colorimetry, the sample preparation process is very important; it is also necessary to determine whether one is measuring ferrous iron, ferric iron, or total iron. These three different types of measurements involve significant differences in the sample processing methods; the person posting should pay attention to whether there are any issues with the sample processing procedure. The direct salicylic acid method is used to determine trivalent iron ； The direct o-phenanthroline method is used to determine divalent iron ； To determine total iron, the sample must first be thoroughly acidified, after which an oxidizing agent or reducing agent is added to convert all iron ions to the same oxidation state before measurement can be carried out. Generally, samples that are in full contact with air contain primarily ferric iron, and alkaline samples also mainly consist of ferric iron ； In acidic and reducing environments, iron is predominantly in the divalent form. In some industrial installations, iron can exist in various forms – including divalent and trivalent iron as well as colloidal iron – especially under corrosive conditions; in such cases, the samples must be properly treated before accurate measurement is possible.