การพัฒนาเทคนิคเพื่อการวิเคราะห์สารปริมาณน้อยและน้อยมาก

Thesis (Ph.D., Chemistry)--Prince of Songkla University, 200

Enhalus acoroides seedlings exhibit different high light responses under varying light qualities

Abstracts: Seagrasses are vital components of coastal ecosystems, and the intensity and quality of light significantly influence their growth and physiology. In this study, we investigated the responses of Enhalus acoroides seedlings to high light under different light qualities. The results indicated that high light had varying effects on seedling growth, depending on the quality of light. Root growth was promoted in high red light, while high blue light significantly suppressed shoot and root growth. Photoinhibition was not detected but rapid light response curves showed photoacclimation. High light exposure resulted in an increase in the maximum electron transport rates and the minimum saturating irradiance in white and red light, while blue light exposure reduced the initial slope of the light response curve. Furthermore, high light affected chlorophyll content, leading to a lower chlorophyll b/a ratio across all spectra, whereas carotenoid content was decreased under white and blue light. High light exposure also enhanced the non-photochemical quenching and de-epoxidation state of xanthophyll in white light but significantly reduced the xanthophyll pigment pool in blue light. Overall, our results suggest that the growth and photosynthetic characteristics of E. acoroides seedlings are influenced by the intensity and quality of light, highlighting the importance of light environments for seagrass health. These findings provide valuable insights into managing and conserving seagrass ecosystems, particularly in areas experiencing high light stress

Novel pipette-tip graphene/poly (vinyl alcohol) cryogel composite extractor for the analysis of carbofuran and carbaryl in water

<div><p>A novel pipette-tip extractor of a graphene/poly (vinyl alcohol) cryogel (graphene/PVA) composite sorbent was prepared to preconcentrate carbamate pesticides in environmental water samples before analysis with a gas chromatograph-flame ionization detector (GC-FID). This novel pipette-tip extractor with the graphene/PVA sorbent exhibited a high porosity when observed through a scanning electron micrograph (SEM). Under optimal conditions, using only 1.0 mL of sample and 0.75 mL of eluting solvent, the developed method provided a wide linear range of 10–700 ng mL⁻¹ and 10–500 ng mL⁻¹ with limit of detection (LOD) of 6.40 ± 0.18 and 9.17 ± 0.34 ng mL⁻¹ for carbofuran (2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate) and carbaryl (1-naphthyl methylcarbamate), respectively. The pipette-tip extractor provided high extraction efficiency with high accuracy indicated, by good recoveries in the range of 74.5 ± 4.8% to 119.7 ± 1.6% and 76 ± 15% to 114 ± 19% for carbofuran and carbaryl, respectively. In addition, the fabrication procedure showed a good pipette-tip extractor-to-pipette-tip extractor reproducibility with a relative standard deviation of 1.3–9.8% (n = 5). When the developed pipette-tip extractor was applied for the extraction of carbofuran and carbaryl in surface water samples near vegetable plantation areas, 25.9 ± 8.2 ng mL⁻¹ of carbofuran was found, and carbaryl was also detected in concentrations that ranged from 45.0 ± 4.0 to 191 ± 13 ng mL⁻¹.</p></div

Optical responses, permeability and diol-specific reactivity of thin polyacrylamide gels containing immobilized phenylboronic acid

Thin semitransparent gels were prepared by radical copolymerization of N-acryloyl-m-aminophenylboronic acid (NAAPBA) and acrylamide (AAm) taken in molar ratios from 8:92 to 16:84, respectively, in water. The gels were characterized by the content of immobilized NAAPBA and monomer conversion. Scanning electron microscopy revealed the micrometer size pores in the dried gels. The wet gels displayed a linear optical response to sugars with sensitivity decreasing in the series: D-fructose, D-galactose, D-glucose, D-mannose, N-acetyl-D-glucosamine in the sugar concentration range from 1 to 40-60 mM at pH 7.3. Cross-linking of the gels with N,N-methylene-bis-acrylamide decreased the strength of optical response. Specific binding capacity of a diol-containing dye Alizarin Red S in the gels at pH 7.0 coincided with the content of immobilized NAAPBA indicating the 1: 1 stoichiometry of the reaction and, therefore, good accessibility of the boronic acid ligands for water-soluble diols. Permeability of the gels was studied with a non-interacting dye Ethyl Orange exhibiting the pore diffusion coefficient of 1.4 x 10(-7) cm(2)/s. The rate of optical response of the gels to glucose was found to be determined by diffusion of sugar into the relatively thick gels (1 = 0.35-1 mm) with effective diffusion coefficients of 2 x 10(-7) cm(2)/S. In the thinner gels (l = 0.1 mm) the input of other kinetic processes, such as affinity binding or structural rearrangements of the gel, was noticeable. (c) 2008 Elsevier Ltd. All rights reserved

Thin semitransparent gels containing phenylboronic acid: porosity, optical response and permeability for sugars.

Radical copolymerization of acrylamide (Am) (90 mol%) with N-acryloyl-m-aminophenylboronic acid (NAAPBA) (10 mol%) carried out on the surface of glass slides in aqueous solution and in the absence of chemical cross-linkers, resulted in the formation of thin semitransparent gels. The phenylboronic acid (PBA) ligand density was ca. 160 micromol/ml gel. The gels exhibited a macroporous structure and displayed optical response to sucrose, lactose, glucose and fructose in 50 mM sodium phosphate buffer, in the pH range from 6.5 to 7.5. The response was fairly reversible and linearly depended on glucose concentration in the wide concentration range from 1 to 60 mM at pH 7.3. The character of response was explained by the balance of two competing equilibrium processes: binding of glucose to phenylboronate anions and binary hydrophobic interactions of neutral PBA groups. The apparent diffusion coefficient of glucose in the gels was ca. 2.5 x 10(-7) cm(2)/s. A freshly prepared gel can be used daily for at least 1 month without changes in sensitivity. Autoclaving (121 degrees C, 1.2 bar, 10 min) allows for the gels sterilization, which is important for their use as glucose sensors in fermentation processes. Copyright (c) 2008 John Wiley & Sons, Ltd