A Novel Approach to Internal Standardization in LC/MS/MS Analysis; Sensitive LC/MS/MS Analysis of Gentamicin

A novel approach to internal standardization in LC/MS/MS is demonstrated. Gentamicin, a multi-component aminoglycoside, is derivatized with propyl-d7 chloroformate making the internal standard. Gentamicin components in the samples are derivatized with non-labeled propyl chloroformate making them analogous to the internal standard. Additional benefits of the derivatization are increased hydrophobicity and excellent MS/MS fragmentation allowing for a sensitive LLOQ of 2 ng/mL total Gentamicin using only 50 uL of plasma.