Further to the article by MD Nelson and JW Dolanin in LCGC (Feb 2002, p73), I am looking for a reliable method for check ion suppression by PEG and any biochemicals in a biological matrix.

In the above article, it was mentioned that a dilute solution of the anlayte should be infused into the LC-MS system (using a t-piece) and a base-line obtained. It was not clear in the article how this was achieved. My own interpretation was to inject a solvent blank, whilst performing the infusion, to obtain a baseline. This was followed by injecting the "blank matrix" which is suspected to cause the ion-suppression. According to the article, this should cause a decrease (like a valley) in the signal. The above signal were collected as TIC (total ion current), using an appropriate gradient.

Ps - I am using a Platinum Ultima (micromass), with biniary HP pumps, CTC autosampler, and the eluent is split (300 ul) into the source. The instrument is run in the MRM mode.

Does any one have a better suggestion as to how to set up a generic method to check for ion suppression due to the formulation (e.g. PEG) or biological matrix (e.g. bile - diluted x10 still gives some suppression) ?

If you can help, an email will be most appreciated.