‘LC‐electrolyte effects’ improve the bioanalytical performance of liquid chromatography/tandem mass spectrometric assays in supporting pharmacokinetic study for drug discovery

Abstract

The development of rapid and sensitive bioanalytical methods in a short time frame with acceptable levels of precision and accuracy is imperative for successful drug discovery. We previously reported that the use of a mobile phase containing an extremely low concentration of ammonium formate or formic acid increased analyte electrospray ionization (ESI) response and controlled against matrix effects. We designated these favorable effects 'LC-electrolyte effects'. In order to support rapid pharmacokinetic (PK) studies for drug discovery, we applied LC-electrolyte effects to the development of generic procedures that can be used to quickly generate reliable PK data for compound candidates. We herein demonstrate our approach using four model tested compounds (Compd-A, -B, -C, and -D). The analytical methods involve generic protein precipitation for sample clean-up, followed by application of fast liquid chromatographic (LC) gradients and the subsequent use of electrospray ionization tandem mass spectrometry (ESI-MS/MS) for individual measurement of the tested compounds in 20-microL plasma samples. Good linearity over the concentration range of 1.6 or 8-25000 ng/mL (r(2) > 0.99), precision (RSD, 0.45-13.1%), and accuracy (91-112%) were achieved through the use of a low dose of formic acid (0.4 mM or 0.015 per thousand) in the methanol/water-based LC mobile phase. The analytical method was quite sensitive, providing a lower limit of quantification of 1.6 pg on-column except for Compd-C (8 pg), and showed negligible ion suppression caused by matrix components. Finally, the assay suitability was demonstrated in simulated discovery PK studies of the tested compounds with i.v./p.o. dosing of rats. This new assay approach has been adopted with good results in our laboratory for many recent discovery PK studies.

Simultaneous determination of ginkgo flavonoids and terpenoids in plasma: Ammonium formate in LC mobile phase enhancing electrospray ionization efficiency and capacity

“…It represents a combination of analyte charging, droplet evaporation, and ion transmission efficiencies in the vacuum system. The results from our current and earlier studies [4,6,7] indicate that the electrolyte modification of mobile phase can significantly improve the ESI efficiency, resulting in enhanced analyte responses. For quantification purposes, the magnitude of ionization efficiency should be maintained constantly throughout an analyte concentration range; the ability to hold the ionization efficiency is called the "ionization capacity".…”

“…ESI signal intensity of a given analyte is a function of the percentage of electrolytic content in mobile phase [6,7]. We found that the highest ESI response was achieved for all analytes when the mobile phase included 0.2 mM HCOONH 4 .…”

Renal Tubular Secretion of Tanshinol: Molecular Mechanisms, Impact on Its Systemic Exposure, and Propensity for Dose-Related Nephrotoxicity and for Renal Herb-Drug Interactions

“…The mobile phase, which consisted of solvent A (water/acetonitrile, 98:2, v/v, containing 1 mM formic acid) and solvent B (water/acetonitrile, 2:98, v/v, containing 1 mM formic acid), was delivered at 0.35 ml/min, except for in the analysis of creatinine at 0.7 ml/min. A pulse gradient elution method was used in the measurement of the compounds (except for creatinine), with an analytedependent start proportion (0-50% solvent B) and analyte-independent elution proportion (100% solvent B), elution proportion segment (1.5 minutes), and column equilibrium segment (3.5 minutes) (Wang et al, 2007); for creatinine, the gradient parameters were 100% solvent B and 80% solvent B, 1 minute and 7 minutes, respectively. …”

Absorption and Disposition of Ginsenosides after Oral Administration of Panax notoginseng Extract to Rats

“…The LC separation was achieved on a Synergi 5 m C18 column (Phenomenex, Torrance, CA). The LC mobile phases were CH 3 OH/H 2 O (2:98, v/v, containing 0.08 mM HCOONH 4 ) for A and CH 3 OH/H 2 O (98:2, v/v, containing 0.08 mM HCOONH 4 ) for B, which were used for pulse gradient chromatography (Wang et al, 2007). The gradient parameters including the start proportion, the elution proportion, the elution proportion segment, and the column equilibrium segment were 15% B, 100% B, 5.4, and 4.4 min, respectively, except for excretory samples requiring a 5-min start proportion segment.…”