Cheng Chi-Yuan, Balsandorj Zoljargal, Hao Zhigang, Pan Long
Colgate-Palmolive Company, 909 River Rd., Piscataway, NJ 08855, USA.
Colgate-Palmolive Company, 909 River Rd., Piscataway, NJ 08855, USA.
J Magn Reson. 2020 Aug;317:106771. doi: 10.1016/j.jmr.2020.106771. Epub 2020 Jun 25.
The pH of toothpaste is a critical factor for product stability and customer acceptance. However, no reliable and consistent method is currently available to precisely quantify pH in toothpaste as it is. In this study, a new method to directly determine pH value in the full toothpaste contained sodium bicarbonate (NaHCO) was developed. Briefly, we utilized the C NMR chemical shift of a small molecule that has been formulated in the toothpaste as a sensitive probe to consistently respond to the pH value of the full toothpaste. The ideal pH probe molecule has the following characteristics: (1) its NMR chemical shift is sensitive to pH within a certain range, and (2) the chemical shift only responses to pH value, not to other factors, such as molecular interaction. NaHCO is a common ingredient in many toothpaste products used as a mild abrasive and an effective pH adjustment compound. Its chemical shift is very sensitive to pH; therefore, it was used as a candidate molecule to test this concept. This technique was demonstrated on select toothpaste formula contained arginine and sodium bicarbonate with different abrasive bases. The result shows that the pH value of full toothpaste is significantly higher than the pH of the toothpaste slurry. Arginine is a key active ingredient in these toothpastes, and it does not interfere with the chemical shift of sodium bicarbonate. The traditional method to determine the pH of toothpaste using pH electrode in toothpaste slurry typically has a larger measuring error, ranging from 0.1 to 0.3. This new method greatly reduced the measuring error, providing a consistent way to reliably determine pH in the full toothpaste, and enabling the stability test of toothpaste with smaller variations. This newly developed method can be further extended to other low-water gel or paste products at a different pH range by using different probe molecules.
牙膏的pH值是影响产品稳定性和消费者接受度的关键因素。然而，目前尚无可靠且一致的方法来精确量化牙膏原样中的pH值。在本研究中，开发了一种直接测定含碳酸氢钠（NaHCO₃）的完整牙膏pH值的新方法。简而言之，我们利用牙膏中配制的一种小分子的¹³C NMR化学位移作为灵敏探针，以持续响应完整牙膏的pH值。理想的pH探针分子具有以下特性：（1）其NMR化学位移在一定范围内对pH敏感；（2）化学位移仅对pH值有响应，而不受其他因素影响，如分子间相互作用。NaHCO₃是许多牙膏产品中常用的成分，用作温和磨料和有效的pH调节化合物。其化学位移对pH非常敏感，因此被用作测试该概念的候选分子。该技术在含有精氨酸和碳酸氢钠且具有不同磨料基质的特定牙膏配方上得到了验证。结果表明，完整牙膏的pH值显著高于牙膏浆的pH值。精氨酸是这些牙膏中的关键活性成分，且不干扰碳酸氢钠的化学位移。传统的使用pH电极测定牙膏浆中牙膏pH值的方法通常测量误差较大，范围在0.1至0.3之间。这种新方法大大降低了测量误差，提供了一种可靠地测定完整牙膏中pH值的一致方法，并能以较小的变化进行牙膏的稳定性测试。这种新开发的方法可以通过使用不同的探针分子进一步扩展到其他不同pH范围的低水凝胶或膏状产品。
