如何将HPLC流动相溶剂混合以获得结果的一致性？

单个溶剂很少符合使用的分离要求HPLC.。在大多数情况下，需要混合两种或更多种溶剂。在等家庭操作中，在分析运行期间，预先确定组合物并保持不变。另一方面，在梯度洗脱中，最终溶剂组合物与初始组成有很大不同，并且在分析过程中编程变化。

在等家庭模式中，制备溶剂混合物并在线进行混合Considerations for mixing of HPLC mobile phase solvents off-line讨论单个溶剂的物理性质的作用。本文讨论了采用相同混合做法的重要性，以确保结果一致性。

化学计量混合是很少实现的目标。即使消除了混合热量的容量测量误差，也可以防止精确混合溶剂。在溶剂的物理混合过程中，热量的能量要么被吸收或释放。这导致温度变化，导致溶剂混合体积的变化。甲醇和乙腈是两种常用的溶剂HPLC.分离。甲醇与水混合的结果in libetration of heat which can increase the volume after mixing. On the other hand acetonitrile on mixing with water results in absorption of heat resulting in cooling and contraction of mixed volume. Such composition variations result in noticeable changes of polarity of mixtures which have observable variations in separation characteristics of sample molecules.

混合溶剂的实践

溶剂的混合是一种易于拾取的基本操作。通常采用的两种混合实践是：

单独的体积测量

As an example suppose you are required to prepare a one liter mixture of methanol and water having 60% water and 40% methanol. In this method 600 ml of water are measured in a graduated cylinder and transferred to a mixing beaker. Next 400 ml of methanol is measured in the graduated cylinder and is transferred to the water in the mixing beaker and the mixture is stirred for even mixing. Due to heat of mixing temperature rise will result in final volume above 1000ml.

混合体积的化妆

在这种方法中，您将测量刻度圆筒中的600毫升水，然后用甲醇占1000mL标记。然后将总体积转移到混合烧杯中以均匀混合。

Theoretically both the methods serve the requirements of mixing solvents but the volumetric variations are found to be different for both the methods. It is therefore important to adopt the same mixing method for consistency of separations. In case of buffers pH is adjusted in the aqueous phase prior to mixing with the organic phase.

在在线混合的情况下，纯粹的移动面保持在单独的瓶子中，并在覆盖比例阀的帮助下以所需的比例混合。通过软件施加混合热校正后，可以靠近化学计量混合。

Hopefully the article has served to emphasize the need for adopting the same mixing procedure every time. Please show and share your opinion and offer your valued comments.