Tongdee Mintra, Wilairat Prapin, Praditweangkum Wiboon, Chantiwas Rattikan
Department of Chemistry and Center of Excellence for Innovation in Chemistry and Flow Innovation-Research for Science and Technology Laboratories (FIRST Labs), Faculty of Science, Mahidol University, Rama VI Rd., Bangkok 10400, Thailand.
Analytical Sciences and National Doping Test Institute, Mahidol University, Rama VI Rd, Bangkok, 10400, Thailand.
Food Chem X. 2024 Jul 3;23:101617. doi: 10.1016/j.fochx.2024.101617. eCollection 2024 Oct 30.
Microplate titration quantifies sodium hydroxide generated from formaldehyde reacting with excess sulfite in a 96-microwell plate. Phenolphthalein indicators change from red to colorless when all hydroxide ions react. Methodology optimized reagent concentrations, and reaction time and created a Calibration Chart for semi-quantitative determination. The chart shows formaldehyde concentration ranges corresponding to red well counts from 0 to 200 mM in 20 mM increments. Inter-operator repeatability demonstrates precision (3 replicates), correlating red wells with standard formaldehyde concentrations. This instrument-free technique uses readily available commercial plates, eliminating the need for specialized equipment and calibration. The methodology offers simplicity with its reliance on readily available commercial plates and minimal specialized equipment, hence it is cost-effective and easily transportable 96-microwell plates enhancing the methodology's portability, and efficient semi-quantitative analysis of formaldehyde. The analysis of twelve solutions from food samples agrees with the quantitative values using titration.
微孔板滴定法可在96孔板中对甲醛与过量亚硫酸盐反应生成的氢氧化钠进行定量。当所有氢氧根离子反应完毕时，酚酞指示剂会由红色变为无色。该方法优化了试剂浓度和反应时间，并创建了用于半定量测定的校准图表。该图表显示了甲醛浓度范围，对应于红色孔数从0到200 mM，以20 mM为增量。不同操作人员之间的重复性证明了该方法的精密度（3次重复），将红色孔数与标准甲醛浓度相关联。这种无需仪器的技术使用现成的商用板，无需专门设备和校准。该方法简单易行，依赖于现成的商用板且所需专门设备最少，因此具有成本效益且易于运输，96孔板增强了该方法的便携性，并能对甲醛进行高效的半定量分析。对食品样品的十二种溶液的分析结果与滴定法定量值一致。
