Kraingkrai Ponhong

A cost-effective smartphone-based digital image colorimetric sensor was developed to determine tetracyclines by inducing in situ growth of gold nanoparticles using naturally occurring phenolic compounds derived from para rubber tree bark waste.

A green flow injection spectrophotometric technique for the determination of ascorbic acid was described based on the redox and complexation reactions. Iron(III) was reduced to iron(II) by ascorbic acid with subsequent complexation reaction of remaining iron(III) with a natural reagent extracted from Areca catechu L. at pH 5.0 yielding a dark-blue color. Absorbance decreased with increasing ascorbic acid concentration. A linear range of 1–10 mg/L for ascorbic acid was obtained with r² of 0.9986. Limit of detection and limit of quantification were 0.3 and 0.9 mg/L, respectively. Relative standard deviation was less than 5.0%. This method was utilized to quantify ascorbic acid in pharmaceuticals and soft drinks with a sampling rate of 40 h⁻¹. Ascorbic acid contents of 96–100% in pharmaceutical samples were obtained, while recoveries for spiked ascorbic acid standard at 3 mg/L in soft drinks were 92–113%.

An in situ coacervative extraction (IS-CAE) based on a double-solvent supramolecular system coupled to liquid–liquid microextraction is investigated for extraction and enrichment of triazole fungicides. The formation of a double-solvent supramolecular system was generated by in situ formation and used as an extraction solvent for the coacervative extraction method. No disperser solvent was required. This new double-solvent supramolecular system has a higher extraction ability than any of its components alone. The different factors that could affect the extraction capability were studied and optimized, including the type of double extractant and its volume, salt addition, vortex time, and centrifugation time. Under optimum extraction conditions, this method provides high enrichment factors (EFs) of 73–318 with low limits of detection (LODs) of 0.3–1 μg L⁻¹ and limits of quantitation (LOQs) of 1–3 μg L⁻¹. In addition, the proposed method was prosperously applied for the determination of triazole fungicides in water, fruit juice, and soy milk samples.

An ultrasound-assisted, one-pot cloud point extraction was developed for the determination of iron in vegetable samples by UV-Visible spectrophotometry. This method was based on the complexation of iron with an environmentally-friendly natural chelating agent extracted from Dipterocarpus intricatus Dyer fruit at pH 5.5 in the presence of Triton X-114. Reagent extraction, complexation, and preconcentration were performed simultaneously using ultrasound-assisted extraction at 45 °C. The surfactant-rich phase was diluted with ethanol and loaded through a syringe barrel packed with cotton that acted as a filter to trap the reagent powder. Analyte-entrapped on cotton was eluted using 0.1 mol·L⁻¹ nitric acid solution. Filtrate and eluate solutions were measured absorbance of the dark-blue product at 575 nm. Influential parameters for the procedure were investigated. Under the optimum experimental conditions, the calibration curve was linear, ranging from 0.1 to 1.0 mg·L⁻¹ with r² = 0.997. Limits of detection and quantification were 0.03 and 0.09 mg·L⁻¹, respectively while precision values of intra-day and inter-day were less than 5%. Recovery at 0.5 mg·L⁻¹ ranged from 89.0 to 99.8%, while iron content in vegetable samples ranged from 2.45 to 13.36 mg/100 g. This method was cost-effective, reliable, eco-friendly, and convenient as a green analytical approach to determining iron content.