電位滴定法測(cè)量Zeta電位和PH的關(guān)系

Potentiometric Titrations are useful for determining a sample's IEP. As mentioned above, the IEP may be desirable or otherwise. Potentiometric Titration plots may display plateau regions for Zeta potential vs. pH. Such measurements enable manufacturers to optimize use of acids or bases for transportation and storage. Figure 2 shows a potentiometric titration on a Ludox-TM silica sample by automatic addition of 1N HCl. This titration was performed automatically by a Zeta-APS, Zeta Acoustic Particle Sizer, instrument from Matec Applied Sciences, Northborough, MA USA 3. Figure 2 shows that below pH 4, the Zeta curve approaches a plateau region while Conductivity increases more rapidly. This suggests that the silica particles are becoming saturated with H+ ions as the pH is lowered. Conductivity increases more rapidly as more of these H+ ions stay in the continuous water solvent as opposed to diffusing through the slipping plane toward the particle surface.

電位滴定法可用于測(cè)定樣品的等電點(diǎn)。如上所述，IEP可能是可取的或者相反。電位滴定圖可以顯示Zeta電位與pH值之間的關(guān)系變化。這樣的測(cè)量使制造商通過(guò)酸或堿的使用，優(yōu)化產(chǎn)品的運(yùn)輸和儲(chǔ)存。圖2顯示在Ludox TM二氧化硅樣品上自動(dòng)添加1N HCl時(shí)，Zeta電位及電導(dǎo)率的變化。該過(guò)程是由美國(guó)MAS公司生產(chǎn)的超聲電聲法粒度及Zeta電位分析儀Zeta-APS設(shè)備完成的。圖2顯示，在pH＜4時(shí)，Zeta曲線(xiàn)接近一個(gè)穩(wěn)定區(qū)域，而電導(dǎo)率增加得更快。這表明，隨著pH值的降低，二氧化硅顆粒逐漸被H+離子飽和。當(dāng)更多的H+離子停留在連續(xù)的水溶劑中時(shí)，電導(dǎo)率增加得更快，而不是通過(guò)滑面向顆粒表面擴(kuò)散。

圖2通過(guò)自動(dòng)電位滴定法將1N HCl加入到10%體積的Ludox TM二氧化硅溶液中

Figure 2. Automatic potentiometric titration of 10%-vol Ludox-TM by 1N HCl addition.