When a novice in the laboratory sees that it is not easy for the automatic injection needle to draw samples, they will want to load more samples, sometimes filling the autosampler vial, thinking that although the sample autosampler vial is full of liquid, the sample volume is not fixed. The change will not affect the experiment, but Aijiren does not advocate this behavior. Why can’t I fill up the liquid?
From the perspective of the chromatographic autosampler vial, when there are too many samples in the autosampler vial, the injection volume exceeds 200ul, and the lid is tightly closed, when the sample is drawn, a certain negative pressure is likely to be generated above the liquid surface in the autosampler vial. The sample cannot be inhaled smoothly. In extreme cases, if the boiling point of the sample is low, when the automatic sampling needle sucks the sample, the lower air pressure at the top of the autosampler vial will cause the boiling point of the liquid to decrease. Accurate, affect the detection of samples.
So how to avoid this situation?
The easiest way is to put less samples in the chromatographic autosampler vial. Generally speaking, it cannot exceed 3/4 of the sample autosampler vial. The automatic sample autosampler vial produced by Aijiren has a volume of 2ml, but the maximum scale is 1.5ml. Remind users not to pack more than 1.5ml of samples.
The second method is to add an internal standard to the sample, because the concentration of the final sample is calculated by the ratio of the internal standard. The commonly used formula is: content=RF*peak area of the sample/peak area of the internal standard*internal standard content. As long as the ratio is constant, the error of the injection volume can also be eliminated to a certain extent.
The third method, Aijiren provides pre-slit closures, which can balance the air pressure inside and outside the vial during sample injection to avoid negative pressure. In addition to this benefit, the use of the closure of the incision can also avoid more possible injection problems. We will introduce it to you in a special article about the closure of the incision in the future.