残留溶剂测定甲醇有干扰

应助达人

具体分析条件如何

应助达人

顶空？直接进样？

应助达人

有没有图看看，对测量结果有影响吗

应助达人

安谱的或默克的。

应助达人

请问测试过溶剂空白吗？

安普的试过了，也有，邪门了，以前做个甲醇感觉轻轻松松，这次好几个项目都是这个问题，我感觉是不是仪器的原因，以前是安捷伦的7694E，现在换了7697A，气路改了，我仔细看了下进样口，发现里面衬管的直径变得好小，估计只有普通安捷伦衬管的一半，我感觉这个峰会不会是DMF降解引起的。

测试了不同级别，不同品牌的DMF，都有。以前同一种试剂只有很小的一个溶剂峰，而且不在这个位置。

对测量基本没有影响，定量限以下，但是定量限的图不好弄。

有人遇到了同样的问题：
Hi
i am running a gc headspace residual solvents method. one of the residual solvent of interest is methanol. I am using DMF as the diluent and when i run a blank injection of the diluent i get a significant peak at the methanol retention time which would cause interference. The brand of DMF I am using is sigma aldrich gc headspace tested >= 99.9%. any suggestions on what one should do? would other grades of DMF provide less interference? use this DMF and when determining methanol in the samples account for the area obtained in the diluent?

thanks

有人给的回答是
If water contaminates the DMF, a reaction by-product will be formed called methylamine. It will elute very close to methanol on most columns and appear to be methanol. It only takes a few parts per million to produce an interfering peak.

You have a choice of distilling the DMF to remove the methylamine or purchasing a fresh bottle or another brand.

I advise you to buy bottles in smaller sizes so the DMF is used more quickly from container to container and to purge the bottle after opening with an inert dry gas after each use.

Do not keep bulk amounts in storage but have a continuing purchase and delivery of fresh solvent if you wish to avoid this contamination in the future.

Of course, if the stock you purchase is old and was packaged some time ago this contamination may be unavoidable.

这个人认为是DMF和水反应，产生了甲胺，与甲醇共洗脱。但DMF水解的主要产物是二甲胺，可能有少量的甲胺生成，当然我也观察到一个以较大的溶剂峰，但是不干扰检测，所以没有在意，现在看来这个大的峰很可能是二甲胺，而那个小的干扰甲醇检测的就是甲胺。