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min1986

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[交流] 请问各位缓冲盐溶液里面加入有机相后再测pH值还有意义吗？？？？？？？

请问各位缓冲盐溶液里面加入有机相后再测pH值还有意义吗？？？？？？？有机相对pH测定有什么影响呢？

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4.5.1 Mobile-Phase pH. Practical Considerations
The pH specified in analytical methods for pharmaceutical analysis should be
that of the aqueous solvent. Note that the addition of organic modifier to
aqueous buffer generally results in a shift in mobile-phase pH.The pKa of the
solute is also subject to variation and is dependent on the type and concen-
tration of the organic modifier in the eluent.
Practical Recommendations
The pH of the aqueous portion of the mobile phase must be accurately controlled
with a calibrated pH meter.That is, the desired pH of the aqueous portion of the
mobile phase must be within the calibrated pH range. The calibration standards
should be close in ionic strength and temperature of the buffer solutions that will
be measured.Typical standards include pH 1, pH 2, pH 4, pH 7, and pH 10. Some
pH meters allow a three-point calibration curve, and others allow for a two point
calibration curve. In any event, the appropriate criteria for the slope of the cal-
ibration curve should be met and recorded in a log book and/or notebook and
should be calibrated each time prior to use.The pH of the buffer should be con-
trolled within ±0.1 pH units. Additionally, buffers can be made by weighing a
known amount of salt of the acid or base to make the buffer and adding, if nec-
essary, a known volume of acid or base to generate the desired pH. Once this is
performed, the pH of the aqueous portion of the mobile phase can be measured
as an additional precautionary measure.
出处：HPLC for Pharmaceutical Scientist 158-159pp
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