Novel Approach to Automated Flow Titration for the Determination of Fe(III)

Abstract

A novel approach to automated flow titration with spectrophotometric detection for the determination of Fe(III) is presented. The approach is based on the possibility of strict and simultaneous control of the flow rates of sample and titrant streams over time. It consists of creating different but precisely defined concentration gradients of titrant and analyte in each successively formed monosegments, and is based on using the calculated titrant dilution factor. The procedure was verified by complexometric titration of Fe(III) in the form of a complex with sulfosalicylic acid, using EDTA as a titrant. Fe(III) and Fe(II) (after oxidation to Fe(III) with the use of H2O2) were determined with good precision (CV lower than 1.7%, n = 6) and accuracy ( | RE | lower than 3.3%). The approach was applied to determine Fe(III) and Fe(II) in artesian water samples. Results of determinations were consistent with values obtained using the ICP–OES reference method. Using the procedure, it was possible to perform titration in 6 min for a wide range of analyte concentrations, using 2.4 mL of both sample and titrant.

Novel Integrated Flow-Based Steam Distillation and Titration System for Determination of Volatile Acidity in Wines

“…To develop an integrated sample distillation and titration system, an on-line distillate titration part of the system was also developed (Figure 1B). To this aim, a previously developed complexometric titration system was adapted for the first time to acid-base titration [39]. To obtain accurate results, it was necessary to reduce the volumes of the sample and the titrant introduced into the monosegments formed in the system to 5 µL, and to develop a novel approach for determination of the end point of the titration.…”

“…The location of the readout of the end point of the titration is shown in Figure 2, and the detailed procedure of titration presented in Table S1 (Supplementary Material). Based on the volumes of sample (V s ) and titrant (V Tt ) solutions introduced into the monosegment corresponding to the end point of titration (T EP , Figure 2), the titrant dilution factor (f Tt ), titratable acidity, and VA (C A, g L −1 , A-analyte) were calculated using Equations ( 1) and ( 2), respectively [39]:…”

“…Regarding monosegmented flow titration, it is based on formation of segments of a mixture of sample and titrant separated on both sides from the carrier by segments of air (or inert gas) [31][32][33][34][35][36][37][38][39]. Sample and titrant can be introduced into monosegments in various ways.…”

“…The titration proposed in this work is the first adaptation to acid-base titration, of the method developed for complexometric Fe(III) titration with spectrophotometric detection [39]. It consisted in creating in the flow system different, precisely defined concentration gradients of titrant and analyte in each of the successively formed monosegments and was based on using the calculated titrant dilution factor.…”

Modern Flow Analysis

“…In work [ 14 ], the mono-segments were created for the titration purpose with use of three syringe pumps equipped with nine-position selection valves. During the titration process, two syringe pumps dispensed well-known decreasing and increasing volumes of the sample and titrant, respectively, which were then introduced simultaneously into the system, joined at the confluence point, and merged in the mixing coil to complete the reaction.…”