Evans A O, Marsh J M, Wickett R R
James L. Winkle College of Pharmacy, University of Cincinnati, 3225 Eden Avenue, Cincinnati, OH 45267-0004, USA.
J Cosmet Sci. 2011 Jul-Aug;62(4):383-91.
The objective of this work was to examine the variables that influence the interaction between water hardness metals and human hair. Hair extracts various constituents from the tap water used during daily hygiene practices and chemical treatments. Calcium and magnesium metal ions are the most prevalent and give water "hardness." Inductively coupled plasma atomic emission spectroscopy (ICP-AES) was employed to quantify the metal content of hair, which was studied as a function of the following variables: hair condition (oxidative damage), level of water hardness, and water pH. We have demonstrated that these variables impact water hardness metal uptake to varying extents, and the effects are driven primarily by the binding capacity (available anionic sites) of the hair. The condition of the hair, a key representation of the binding capacity, was most influential. Interestingly, water hardness levels had only a small effect on uptake; hair became saturated with notable amounts of water hardness metals even after repeated exposure to soft water. Water pH influenced metal uptake since side chains of hair proteins deprotonate with increasing alkalinity. These insights highlight the importance to the hair care industry of understanding the interaction between water hardness metals and hair.
这项工作的目的是研究影响水硬度金属与人类头发相互作用的变量。头发会从日常卫生习惯和化学处理中使用的自来水中提取各种成分。钙和镁金属离子最为常见，赋予水“硬度”。采用电感耦合等离子体原子发射光谱法（ICP-AES）对头发中的金属含量进行定量分析，并研究其作为以下变量的函数：头发状况（氧化损伤）、水硬度水平和水的pH值。我们已经证明，这些变量对水硬度金属的吸收有不同程度的影响，其影响主要由头发的结合能力（可用阴离子位点）驱动。头发状况作为结合能力的关键表征，影响最为显著。有趣的是，水硬度水平对吸收的影响很小；即使反复接触软水，头发也会被大量的水硬度金属饱和。水的pH值会影响金属吸收，因为头发蛋白质的侧链会随着碱度的增加而发生去质子化。这些见解凸显了了解水硬度金属与头发之间相互作用对护发行业的重要性。
