Investigations beyond standard operating procedure on internal standard response

Internal standard response is routinely monitored in regulated studies to accept or reject individual samples with outlier results due to potential sample processing or instrumentation errors, and processes are typically governed by standard operating procedures. However, acceptance or rejection of individual samples is not always sufficient. Internal standard response trends and substantial systemic differences between spiked and incurred samples using a method with an otherwise stable internal standard response should be investigated. Investigations may range from informal evaluations to detailed studies with formal investigation reports. Atypical internal standard response can be an indicator of systemic problems with a bioanalytical method and modification to allow for a relatively stable internal standard response across an analytical run may be essential.

Matrix effect explained by unexpected formation of peptide in acidified plasma

AIM

Peak distortion and strong signal enhancement was observed when applying a bioanalytical method based on mixed-mode SPE, hydrophilic interaction chromatography and ESI-MS to acidified rabbit plasma samples.

RESULTS

High-resolution ESI-MS and N-terminal peptide sequencing revealed a peptide NFQNAL, which was confirmed by H/D exchange ESI-MS.

CONCLUSION

The peptide causing the observed matrix effect was formed by enzymatic degradation of serum albumin at pH 3. Degradation required both acidification and presence of other plasma constituents in addition to albumin to take place. The degree of signal enhancement correlated to the level of NFQNAL in the ion source as measured by MS, with a maximal enhancement factor of 3 at intermediate levels of NFQNAL. The interference was eliminated by changing to another type of hydrophilic interaction chromatography column.

Choosing the appropriate matrix to perform a scientifically meaningful lipemic plasma test in bioanalytical method validation

Laurence Mayrand-Provencher has obtained a Master of Science in Chemistry from Université de Montréal. With over 3 years of experience as a scientist in the bioanalysis industry, he is now a scientist in method development at Algorithme Pharma. His experiences have led him to conduct robust and effective method development of bioanalytical assays, specifically in the LC–MS/MS field.

Many regulatory agencies include in their guidelines the need to investigate the effect of lipemic plasma on the reliability of the data as part of a bioanalytical assay validation. Lipids can cause matrix effect, specificity and recovery issues, which can potentially lead to inaccurate data if left unaccounted for. However, finding the appropriate matrix type to be used to perform a lipemic plasma test is a major challenge, as the differences between those commercially available are not well known. The work reported herein describes the differences in lipid content between normal plasma, synthetic lipemic plasma mixes, and two types of natural lipemic plasma. The results obtained show that natural plasma with high triglycerides content should be used to perform a scientifically meaningful lipemic plasma test.

A systematic approach for developing a robust LC–MS/MS method for bioanalysis

In order to meet the drug discovery and development needs of pharmaceutical companies, CROs are constantly challenged by the requirements for rapid LC–MS/MS method development prior to method validation and sample analysis. In order to meet this challenge, a comprehensive method development program, nicknamed ‘Amoeba™’, which uses a series of written protocols for standardized and efficient method development was developed. In this paper, the genesis of the Amoeba method development program is elucidated in detail and a number of case studies are presented to showcase the execution of the Amoeba method development program. Using this program, the majority of the most critical information regarding the assay can be captured. While the Amoeba program has been proven to be effective, we recognize that the development of a robust bioanalytical method for use in pharmaceutical industry also requires the careful consideration of many critical parameters and the ability to identify and resolve potential issues. The refinement of the assay relies on further evaluation of several critical factors including, but not limited to, internal standard response, matrix effects (phospholipid or nonphospholipid related) and carryover.

Silica hydride-based chromatography of LC–MS response-altering compounds native to human plasma

Background: An investigation was carried out into the chromatographic behavior, on a silica hydride-based phase and a comparator silica-based phase, of an important group of lipids endogenous to human plasma, which are associated with matrix effect and in the context of quantitative peptide analysis. Results: The propensity for aqueous normal phase (ANP) retention on the silica hydride-based phase was strong and extensive in comparison with the silica-based comparator, and the lipophilic interferences in question were readily eluted using the ANP mode, a contrast to over-retention issues with accompanying implications for method ruggedness typically found with silica-based phases. Conclusion: The silica hydride-based phase, with ANP operation, offered selectivity conducive to rapid lipophilic interferent elimination and the bimodal retention involved in suitable gradient elution was appropriate for general peptide analytical application.