Study
In this case, one of our clients sought help with LC MS method development, optimization, and validation. During sample analysis, we noticed a small peak appearing as a shoulder to the analyte peak. The analyte at hand had a retention time of 1.5 minutes. Our experimental approach increased that and separated the analyte peak from endogenous material eluting earlier, as LC MS sample preparation was based on protein precipitation. We aimed to achieve this by changing chromatographic conditions, including change of mobile phase and columns. Our scientists confirmed this was not a split peak due to improper chromatography or interference in control plasma but rather due to another compound with the same MS transition. Thus, we hypothesized and started investigating whether this issue was due to a metabolite with a similar transition.
During this investigation, we also explored the possibility of utilizing an ELISA assay method or immunoassay services to complement the LC-MS/MS assay. These methods could provide additional specificity and sensitivity, particularly in detecting and quantifying the target analyte and potential interfering compounds. However, we initially prioritized optimizing the LC MS method development to address the observed peak interference, as it offered direct quantification and identification of the analyte and potential metabolites. Nonetheless, incorporating complementary techniques like the ELISA assay method or immunoassay services could be considered in future studies to enhance the analytical robustness and accuracy of the analysis.
LC MS method validation and LC MS sample preparation are essential components of our approach to ensure the reliability and accuracy of our analytical methods.
In our process of separating the two peaks through LC MS method validation, we found that the intensity of the interfering peak was changing from sample to sample. This established that the noise was emanating from a metabolite. We further estimated this metabolite to be a glucuronide conjugate, given the peak under consideration was eluting earlier than the analytes. However, we had no available reference standard for glucuronide then. Finally, we confirmed that this peak was a glucuronide conjugate after examining the plasma samples using enzymatic hydrolysis. Consequentially, we successfully validated and applied the method to analyze plasma samples.
Although we focused on LC MS method development, optimization, and validation, we also provide ELISA assay method development and immunoassay services to cater to diverse client needs in bioanalytical research.