Supalax Srijaranai

A sensitive colorimetric sensor for Cr⁶⁺ was developed using a DES probe (TBABr/AA/EDTA). Cr⁶⁺ was reduced to Cr³⁺ by AA, then formed a purple complex with EDTA, which was quantified by UV-vis spectrophotometry and smartphone detection.

Sprayers’ exposure to glyphosate was analyzed through detection of its biomarker in spot urine biological monitoring, and the health risk was assessed using the biomatrix model. Urine samples were collected from 15 sprayers after spraying, and the glyphosate concentration was determined by using the DLLME-HPLC method with a UV detector. The calibration curve for glyphosate was linear in the range of 0.4–100 µg/L, while the limits of detection and quantification were 0.1 µg/L and 0.4 µg/L, respectively. The human health risk was estimated using the hazard quotient (HQ) and the biomatrix of risk assessment. The internal dose ranged from 0.0001 to 0.0021 mg/kg b.w./day. The non-cancer HQ showed no potential health risk concerns (HQ < 1). The biomatrix of health risk assessment, based on urinary glyphosate concentration, exhibited a strong correlation with the health risk matrix model. This correlation was determined by considering the likelihood of exposure, calculated from the quantity of glyphosate used and the usage of personal protective equipment (r = 0.854, p < 0.001). Although low risk was observed in sprayers, proper PPE use and the application of more knowledge are required. The simplified health risk assessment can be used for easy self-assessment of risk in preventive action regarding health risk awareness among sprayers.

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 in situ formation of ionic liquid was used for preconcentration of four triazole fungicides in food samples. The microextraction method was used for the first time in the literature for preconcentration of triazole fungicides. In the developed method, tributylhexadecylphosphonium bromide ([P₄₄₄₁₂]Br) and potassium hexafluorophosphate (KPF₆) were used for the formation of hydrophobic ionic liquid. After centrifugation, the fine microdroplets were produced in one step, providing the extraction step in a quick and environmentally friendly manner. The functional group of the hydrophobic ionic liquid was investigated using FT-IR. Various extraction parameters were studied and optimized. In the extraction method, 0.01 g of [P₄₄₄₁₂]Br and 0.01 g of KPF₆, centrifugation at 4500 rpm for 10 min were used. The optimized technique provided a good linear range (90–1000 μg L⁻¹) and high extraction recovery, with a low limit of detection (30–50 μg L⁻¹). Methods for the proposed in situ formation of ionic liquid were successfully applied to honey, fruit juice, and egg matrices. The recoveries were obtained in a satisfactory range of 62–112%. The results confirmed the suitability of the proposed microextraction method for selective extraction and quantification of triazole fungicides.

A single-step preconcentration procedure using the in-situ formation of modified nickel–zinc-layered double hydroxides (LDHs) prior to high-performance liquid chromatography (HPLC) is investigated for the determination of neonicotinoid insecticide residues in honey samples. The LDHs could be prepared by the sequential addition of sodium hydroxide, sodium dodecyl sulfate, nickel nitrate 6-hydrate and zinc nitrate 6-hydrate, which were added to the sample solution. The co-precipitate phase and phase separation were obtained by centrifugation, and then the precipitate phase was dissolved in formic acid (concentrate) prior to HPLC analysis. Various analytical parameters affecting extraction efficiency were studied, and the characterization of the LDHs phase was performed using Fourier-transformed infrared spectroscopy and scanning electron microscopy. Under optimum conditions, the limit of detection of the studied neonicotinoids, in real samples, were 30 μg L⁻¹, for all analytes, lower than the maximum residue limits established by the European Union (EU). The developed method provided high enrichment, by a factor of 35. The proposed method was utilized to determine the target insecticides in honey samples, and acceptable recoveries were obtained.

Layered-double hydroxides (LDHs) modified with anionic surfactants via a co-precipitation method were developed for preconcentrating and simultaneous analysis of six benzoylurea insecticides (BUs) by high-performance liquid chromatography (HPLC). The anionic surfactants with different chain lengths, including sodium dodecylbenzene sulfonate (SDBS), sodium dodecyl sulfate (SDS), sodium 1-nonane sulfonate (SNS), and sodium 1-hexane sulfonate monohydrate (SHS) were investigated to improve the extraction efficiency of LDHs. The SDBS-LDHs provided the highest efficiency for the enrichment of the BUs studied. Under the chosen conditions, enrichment factors in the range of 38–69 and detection limits in the range of 0.1–0.3 μg L⁻¹ were achieved. Good reproducibilities (RSD < 13.8%) and recoveries (71.4–118.7%) were also obtained. The proposed preconcentration method, used as an in situ procedure offers rapid and simple simultaneous preparation of LDHs and extraction of BUs. The method was successfully applied for residue analysis of BUs in fruit- and flower-derived soft drink samples.

Ethyl salicylate (EtSA) and ethyl benzoate (EtBZ) as alternative extraction solvents have been evaluated for vortex-assisted surfactant-enhanced emulsification microextraction (VASEME) of target fungicides (e.g. carbendazim, thiabendazole, and fuberidazole) before the high-performance liquid chromatographic analysis. Under optimum conditions, the preconcentration factors about 16–28 (18–33) and limits of detection in the range of 0.01–0.1 µg/L were achieved for both extraction solvents. Good recoveries in the range of 76.2–118.4% (85.7–114.6%) with the acceptable relative standard deviation lower than 10.4 were obtained at the concentration evaluation of 20 µg/L and 50 µg/L each fungicide in different water sample matrices. As a result, the proposed extraction solvents can be used as an alternative to other related solvents like methyl salicylate (MeSA) and methyl benzoate (MeBZ) for the preconcentration of target fungicides.

A rapid and simple preconcentration method using dissolvable Mg/Al layered-double hydroxides (LDHs) and high performance liquid chromatography-photodiode array detection (HPLC-PDA) was developed for the analysis of benzoylurea insecticides (BUs) in water and honey samples. The proposed dissolvable LDHs for the extraction can be prepared in one step by the sequential addition of sodium hydroxide, magnesium chloride, aluminium chloride, and sodium dodecyl sulfate into the sample solution containing the target BUs. The co-precipitate phase was simply obtained after centrifugation, and the phase was then dissolved with formic acid before analysis by HPLC. The developed method provided an enrichment factor of 12.5–23.7. LODs were obtained in the range of 0.1–0.3 μg L⁻¹ for deionized water, 0.2–2.0 μg L⁻¹ for environmental waters, and 0.5–2.0 μg L⁻¹ for the analyzed honey samples. Good recoveries ranging from 78.4 to 117.8% and 72.7 to 117.9% for water and honey samples, respectively, were obtained.

A green, simple and sensitive hydrophobic DES-based dispersive liquid–liquid microextraction coupled with high-performance liquid chromatography (HPLC) was developed for the analysis of neonicotinoid insecticide residues in various samples. A hydrophobic deep eutectic solvent (DES) was synthesized using decanoic acid as a hydrogen bond donor and tetrabutylammonium bromide (TBABr) as a hydrogen bond-acceptor. DESs were synthesized and characterized by Fourier transform-infrared (FTIR) spectroscopy. Two disperser solvents were substituted with surfactants and acetonitrile, which could afford more effective emulsification and make the extraction relatively greener. The hydrophobic DES extraction phase occurred 10 min after centrifugation, being easy to be collected for analysis. Several parameters were investigated and optimized. Under the optimum condition, the calibration curve of this method was linear in the range of 0.003–1.0-µg·mL⁻¹, with a correlation coefficient (R²) higher than 0.99 and a good repeatability, with the relative standard deviations (RSDs) were less than 5.00%. The limits of detection were in the range of 0.001–0.003 µg·mL⁻¹; the limits of quantitation were in the range of 0.003–0.009 µg·mL·mL⁻¹. Finally, the presented method was implemented to determine the neonicotinoid insecticide residues in water, soil, egg yolk samples and acceptable recoveries were obtained.