Quantitative analysis of squalamine, a self-ionization-suppressing aminosterol sulfate, in human plasma by LC-MS/MS

The special physico-chemical property of squalamine enables the formation of intra- or inter-molecular non-volatile strong salt, which is difficult to ionize in a mass spectrometer's interface. A sensitive, accurate, precise, and specific method for the quantitative determination of this self ion-suppressing compound in human plasma has been developed and validated using high performance liquid chromatography (HPLC) coupled with positive electrospray tandem mass spectrometry (MS/MS). Solid phase extraction (SPE) technique was utilized to extract human plasma samples using the Waters Oasis HLB cartridges. Deuterated squalamine was used as the internal standard (IS). Positive multiple reaction monitoring (MRM) mode was used to achieve both sensitivity and selectivity. A quadratic linearity range over 5-1000 ng/ml, R > 0.999 was achieved. Performance of the method has been validated and met all the specifications set forth in the US Food and Drug Administration's May 2001 "Bioanalytical Method Validation Guidance for Industry". Different sample reconstitution solutions were found to have dramatic impact on sensitivity of mass spectrometer used to squalamine. This is the first quantitation method using a positive and true multiple reaction monitoring mode detection for squalamine.