We are speaking about ESI? Unfortunately, significant matrix reduction by dilution usually works logarithmic - so below 1/10 dilution of your sample/sample extract your success is limited. An isotopically labelled compound is a very good solution for a quantitative compensation but they are sometimes not available and/or highly expensive. On the other hand (at least for +ESI) the matrix effects mostly depend on the retention time. This allows for using any compound as internal standard which coelutes with your analyte.

Other possibilities for significant matrix-reduction are special clean-up steps and other selective sample pre-treatment steps but this highly depends on your sample matrix and analytes.

Thank you karsten for your reply. As of now i am using deuterated standard as internal standard,this has reduced my matrix effect to significant amount but at higher concentration of analyte it is showing charge competition.so now i have to make a compromise between these two. Can u elaborate a bit more on how retention time can play a role in reduction of matrix effect.we have worked on sample cleanup also like optimized washing steps.more to inform you we are following solid bed extraction.

Hi, mostly it is not possible or difficult to remove matrix effects of your sample in LC-MS and LC-MS/MS analysis. What is possible is to eliminate these effects as far as possible by a better sample clean-up, switch from RP-columns to for example HILIC and application of stable isotope labeled internal standards.Dilution of your samples will decrease the matrix effects but you might come into problems with sample near to LOQ and/or LOD limits.

Thank you meesteres for your answer.can u throw some light on how RP columns contribute to ME.We use mostly mobile phase with 60 or more % of organic content so we dont prefer HILIIC since in this we have to increse aqueous content.we have worked on sample cleanup techniques also.my main problem with using deuterated standard is charge competition.Having a competiton at ULOQ upto 50% in ESI mode.

Hi Santosh,

it is not that RP columns contribute to matrix effects, what I wanted to say is the fact that if you switch from column type from RP to HILIC for example it is possible to influence the retention time of matrix effect causing compounds so you could in principle eliminate the matrix effects in case your analytes of interest have a retention time of about the same retention time of the matrix effects causing compounds. It is just a chromatographic trick! What do you exactly mean with charge compettion ?

Hi Meesters,

In charge competition my point is in calibration curve as it starts from LOQ to ULOQ (higher standard). so when i am using deuterated standard as internal standard it shows charge competition in ion source of MS and there is fall in response of internal standard.so at higher level i get saturation.so this is restricting me from using isotopically labelled internal standard.

I am not having any technical experienced in HILLIC and RP columns, but somehow to feel that, why the buffering effect is doest show any significant role to minimize such a charge competition Mr. Santhosh. I may suspect, at particular pH deuterium ion counter balance with your other standards. Ultimately such a problem could be comes at higher concentration of your internal standards. In a volumetric analysis that can be solved by calculation of ionic strength with counting solubility of the product (Ksp), but I doesn’t know it is workout for deuterium and also the same in your columns.

Hi Hari,Thank you for your answer i have tried different bufferes like ammonium formatre and ammonium acetate.but it didnt i improved a lot. we are working on ESI mode so will try with APCI once then will share the results.

Santhosh i feel it minor problem, the charge competitions between the counter ions can be solve by ionic strength i think so. if you get error again in APCI/ESI try this method. All the best

Hi hari haran,

i will try this again.thankyou for your answer.

Yeah, competition at higher analyte concentration is sometimes a problem. But the you could dilute without a loss of sensitivity.

Maybe my sentence regarding retention time was misleading. I meant that it is not important how much the internal standard is "similar" to the analyte as long as they elute within a comparable time-scale. Regarding the probability of matrix effects and RT I've heard different opinions. From a review paper I learnt that the most significant matrix effects will occur at the beginning and at the end of a chromatogram. At a symposium I heard recently from a group that they have the most significant matrix effects in the middle...