Determination of iodate in iodized edible salt based on a headspace gas chromatographic technique

Dispersive liquid-liquid microextraction and diffuse reflectance-Fourier transform infrared spectroscopy for iodate determination in food grade salt and food samples

A novel method based on diffused reflectance Fourier-transform infrared spectroscopy (DRS-FTIR) was employed for iodate determination in food grade salt and food products. The method attained sensitivity that was comparable to or better than that in most of the contemporary spectrophotometric methods. This was realized through a combination of azo dye formation and dispersive liquid-liquid microextraction of dye when a 37-fold enrichment was obtained. FT-IR enabled integrating alternative target peak, and freedom in sample solvent composition relative to UV-visible spectrophotometry where the solvent polarity, pH, and presence of ions may affect the spectral properties of the measurable coloured species. Food samples containing iodide or covalently bonded iodine were oxidized with alkaline permanganate for mineralization and iodate formation. Optimization of both reaction conditions was carried out by means of response surface methodology. The method had a linear range 0.04-10 mg kg^-1 iodate and limit of detection of 4.4 µg kg^-1.

Smartphone-based optical transduction for the rapid microscale assessment of iodate in table salt

The measurement of iodine in table salt is vital for the successful implementation of the universal salt iodization (USI) program to fight iodine deficiency disorders (IDDs). This paper presents a smartphone-based optical transduction system for iodine measurement in table salt. The method was based on the response in the blue color space generated by the complex formed between the starch/iodide reagent and iodate in the salt sample. The parameters for the color reaction and for the image capture affected the response and were optimized. A matrix effect caused by NaCl was observed and was eliminated through matrix matching by incorporating NaCl in the standard solutions. The optimized method yielded a highly linear response to iodate concentrations ranging from 10 to 160 mg kg^-1 (r = 0.9993) with a limit of detection of 2.8 mg kg^-1. The method exhibited good accuracy and precision, based on AOAC standards. It produced results that were in agreement with those obtained using the reference method at the 95% confidence level. The smartphone performs optical transduction, as well as signal processing, to yield a display of the iodate concentration in the salt sample. The use of smartphones presents a simple, inexpensive, portable, and widely available device for on-site analysis of iodate in table salt.

Foldable paper-based analytical device for membraneless gas-separation and determination of iodate based on fluorescence quenching of gold nanoclusters

A new design of a paper-based analytical device (PAD) for membraneless gas-separation with subsequent determination of iodate is presented. The rectangular PAD was invented as the folded pattern, where two circular reservoirs: the donor reservoir and the acceptor reservoir were situated in "a single paper" for convenient use. The hydrophobic barrier of each reservoir was easily fabricated by painting with a permanent marker. The PAD was demonstrated for the quantitative analysis of iodate, based on the fluorescence quenching of the bovine serum albumin-stabilized gold nanoclusters (BSA-AuNCs). The BSA-AuNCs were fast prepared by a microwave-assisted approach. The nanoclusters solution was applied into the acceptor reservoir, while the sample, iodide and sulfuric acid were sequentially aliquoted into the donor reservoir. After folding the PAD, the donor and the acceptor were mounted together via a two-sided mounting tape. The headspace between the two reservoirs allows membraneless gas-separation of free iodine from the donor to diffuse into the acceptor. Etching of gold core of the nanoclusters in the acceptor resulted in quenching of the red emission, was monitored by two methods, i.e. "fluorometric detection" (λ_ex: 490 nm, λ_em: 630 nm) and "image capture" of the acceptor under the UV irradiation by a smart phone's camera. Two calibrations were plotted accordingly to their detections and good linearities (r² ˃ 0.98) were observed from 0.005 to 0.1 mmol L^-1 iodate. High accuracy (mean recovery: 95.1 (±4.6) %) and high precision (RSD < 3%) were obtained. The lower limits of detection were 0.005 mmol L^-1 (with fluorometric detection) and 0.01 mmol L^-1 (with image capture). The method was effectively applied for the measurement of iodate in iodized salts and fish sauces without prior sample pre-treatment.

Smartphone digital image colorimetry combined with solidification of floating organic drop-dispersive liquid-liquid microextraction for the determination of iodate in table salt

Smartphone digital image colorimetry (SDIC), combined with solidification of floating organic drop-dispersive liquid-liquid microextraction (SFOD-DLLME), was proposed for the determination of iodate ions. A colorimetric box was designed to capture images of sample solutions. Factors affecting the efficiency of SDIC included type of phone, region of interest, position of camera, and distance between camera and sample solution. Optimum SFOD-DLLME conditions were achieved with 1-undecanol (500 µL) as the extraction solvent, ethanol (1.5 mL) as the disperser solvent within 20 s extraction time. Limit of detection (LOD) was found as 0.1 µM (0.2 µg g^-1) and enrichment factors ranged between 17.4 and 25.0. Calibration graphs showed good linearity with coefficients of determination higher than 0.9954 and relative standard deviations lower than 5.6%. The proposed method was efficiently applied to determine iodate in table salt samples with percentage relative recoveries ranging between 89.3 and 109.3%.

An efficient headspace gas chromatographic technique for determining humic acid content in fertilizer

A fast, convenient and commercially available approach for analyzing humic acid content in fertilizer using headspace gas chromatography (HS-GC) is presented in this paper. Humic acid is converted into carbon dioxide based on the oxidation of humic acid in strong acidic medium and can be measured via automatic HS-GC. Conditions for the alkaline extraction and the humic acid oxidation process are also optimized. The new technique proved to be precise (RSD ≤ 3.59%) and accurate (relative errors≤9.46% as compared with the spectrophotometric approach). The newly established technique presents a practical tool to routinely analyze humic acid content in fertilizer during the fertilizer production.