Chromatography Forum

The HPLC system I am using has an autosampler and has a high frequency of misinjection. Is there anything i can do to fix it?

Let me be the one to have the voice of reason:
What brand of HPLC/autosampler?
What model number?
How old is it?
What does "high frequency of misinjection" mean? doesn't pick up vial, doesn't suck up any sample, to quote Yul Bryner "etc., etc., etc."

A couple of other things you can check are:
By mis-injection do you mean you don't get any peaks or variable peak sizes?
Does anything else change in the chromatography on the mis-injections i.e. retention times or baseline profile?
Is there anything in the HPLC electronic log that is different between a 'good' and a bad' injection?
What is the sample solvent?

In addition to what has already been mentioned, you can include a check of the autosampler vials.

Are you using the vials recommended by the manufacturer? Or at least are you using an appropriate/equivalent substitute vial? Some autosamplers are not forgiving if the wrong vial is used and missed/skipped/bad injections can result.

Regards,
Dan

thans for your reply.

It's Agilent 1200 series model G1329A. It's a new one. It draw less volume so getting a low peak area. In a batch of 40 to 50 samples it would happen once or twice. I don't think it's normal compared to other HPLC we have. I have tried to change the draw and eject speed, But it didn't help a lot. Any advice?

Since you didn't mention adjusting it, I'll mention the obvious - the draw position. Just below the settings for the draw and eject speeds is the draw position. I think the default is 0.0mm which should pick up sample from about the 0.2mL position in the autosampler vial. If you have very limited volume of sample, you can lower the draw position as low as -2.5 mm, but verify that the injection needle doesn't touch the bottom of the autosampler vial.

And if you have a new 1200, it should be still under warranty (1 year?), call 1-800-227-9770, option #3.