Chromatography Forum

I am using following protocol to quantify solanine/chaconine from freeze dried potato samples and the matrix spike recoveries are very low (below 60%)
:
1.Weigh 0.5 gm of powdered potato samples in 50 mL polypropylene tubes.
2.Add matrix spike. Let it sit for a few minutes to ensure good mixing.
3.Add 5 mL water using class A pipettes and vortex for 3 minutes.
4.Add 25 mL extraction solvent (Acetonitrile with 1% formic aid) using class A graduated cylinder to the tube and vortex for 3 minutes.
5.Add 2 gm of magnesium sulfate and 1 gm of sodium acetate and shake the solution vigorously by hand for 30 seconds followed by vortexing for another minutes to separate water and acetonitrile layers.
6.Centrifuge the sample at 4°C at 9000 rpm for 8 minutes.
7.Transfer the 0.5 mL aliquot of supernatant in 15 mL tube.
8.Add 10 mL of methanol:water (50:50) using class A pipette.
9.Filter 1 mL aliquot of the solution through 0.45 µm filter membrane. Samples are ready for LC-MS/MS analysis.

Instrument is calibrated and compound optimization is performed using direct infusion and FIA. The calibration looks good (r2 more than 0.995). I have started looking into using internal standard. but, I was wondering if anything can be added/omitted from the current protocol to improve recoveries without using internal standard?

Thank you,

You can try using a matrix matched calibration to help compensate for matrix effects.

Matrix matched calibration can compensate matrix effect, also these 2 compounds are polar, thus Quechers is not very suitable, you may see better recovery if you skip the addition of 5 mL water to the sample, which make the partition of the 2 polar compounds less efficiently.

Thank you everyone for reply. Matrix matched calibration was ntot possible since we could not obtain LCS for potato samples.
I added 15 mins of ultrasonication after adding the extraction solvent and I have good recoveries now, chaconine (90-110%) and solanine (80-100%) with less that 5% RSDs.

Thank you!