Exploiting the bead injection LOV approach to carry out spectrophotometric assays in wine: Application to the determination of iron

Abstract

A sequential injection lab-on-valve (SI-LOV) system was used to develop a new methodology for the determination of iron in wine samples exploiting the bead injection (BI) concept for solid phase extraction and spectrophotometric measurement. Nitrilotriacetic Acid (NTA) Superflow resin was used to build the bead column of the flow through sensor. The iron (III) ions were retained by the bead column and react with SCN(-) producing an intense red colour. The change in absorbance was monitored spectrophotometrically on the optosensor at 480 nm. It was possible to achieve a linear range of 0.09-5.0 mg L(-1) of iron, with low sample and reagent consumption; 500 μL of sample, 15 μmol of SCN(-), and 9 μmol of H(2)O(2), per assay. The proposed method was successfully applied to the determination of iron in wine, with no previous treatment other than dilution, and to other food samples.

Lab-In-Syringe with Bead Injection Coupled Online to High-Performance Liquid Chromatography as Versatile Tool for Determination of Nonsteroidal Anti-Inflammatory Drugs in Surface Waters

“…Typically, the task is done by implementing a mixing chamber into the flow manifold, by multiple alternation of solution aspiration and mixing the stacked zoned by dispersion, or by the confluent addition of the secondary solution. For LOV, various modes to implement a second pump for confluence mixing have been proposed [ 36 , 37 , 38 ]. Here, we combined for the first time LOV with bead injection with the LIS operation principle, i.e., the sample and loading buffer were homogenously mixed inside the syringe void by magnetic stirring before loading, which enabled preconcentration from volumes as large as 4 mL at once.…”

“…Here, we decided on a hydrophilic–lipophilic balanced sorbent of 30 µm particle diameter, following a previous, yet far more complex BI approach [ 28 ]. Thus far, BI-LOV has proven versatile for SPE of insecticides [ 35 ], food additives [ 36 ], metals in various matrices [ 37 , 38 , 39 ], and polychlorinated bisphenyls [ 40 ], among others.…”

Iron speciation by microsequential injection solid phase spectrometry using 3-hydroxy-1(H)-2-methyl-4-pyridinone as chromogenic reagent

“…Having set the column packing procedure, the preparation of the Hmpp reagent and the respective volume to be used, parameters for the SPE step were assessed. The flow rate of propelling through de beads was set as previously reported [9]: 10 μL/s. 9…”

“…In order to determine the total iron content, it was necessary to oxidise the Fe(II) to Fe(III), as Fe(II) was not retained in the beads. Hydrogen peroxide was chosen as the oxidising agent for the determination of total iron and two steps were added to the analytical cycle, in order to sandwich the sample between two oxidant plugs [9]. The volume of oxidant was 5 µL per plug, the reported minimum volume to attain an effective overlapping [12].…”

“…To accomplish SPS, a NTA resin was used as solid phase due to its favourable characteristics for this purpose: being relatively transparent to radiation and its affinity for iron (III). Actually, NTA resin has been effectively used for retaining iron in a pre-concentration procedure for water analysis [6][7][8] and in solid phase spectrophotometry detection [9,10]. The proposed method for iron speciation comprises two cycles: i) direct perfusion of the resin with the ligand for the determination of iron (III); ii) performing a preliminary in-line mixing of the sample with peroxide and subsequent retention of total iron.…”