Chromatography Forum

Hi Everyone,

We tested 6 lots of sample for BAK using HPLC. For the last sample - no BAK was observed. There was no sample prep. upon reanalysis of the vial - the BAK was present. We have opened an investigation into this but i am not able to determine a cause.
all parameters have been checked such as inj volumne, the vial was pierced the first time, pressure channels etc.
The sample was tested in duplicate and both sample showed no BAK present; however it reappeared in both vials when re-analyzed.
A waters engineer has also gone through the chromagraphy with me so i have had everything double checked and we are not able to conclude the cause of these results

has anyone see this happen to BAK before?

Thanks for your help

KR

Google, BAK = Biking Across Kansas, must be a relevant Lone Ranger quote hiding around here somewhere.

Assuming BAK = benzalkonium chloride, the obvious question would be whether, upon magnification, the solvent upset from an injection was present in the zero content runs, and if it matched earlier sample injection upsets.

My first suggestion would be a vial that was near full, and very well sealed ( not split septa type ) , and the liquid sample sucked out of the needle. Why only on that vial, and twice, may be evident on close examination of the vial and it's contents, compared to other vials.

I'd also check to ensure the cap has not got two septa, which I occasionally find. I'd also perform some experiments with vials filled to different levels, and very well sealed.

If the baseline injection upset isn't present ( when it should be ), also check to ensure that the septum has not cored and temporarily blocked the needle. I'd worry about the injector, and perform a full service, especially a replacement needle and seat.

Please keep having fun,

Bruce Hamilton

Have you tried injection with needle wash?

You aren't filtering your samples through Nylon membranes are you?