In-Sample Calibration Curve for LC-MS/MS Quantification
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Solution Overview
Problem
The challenge in pre-clinical and clinical studies is the difficulty in developing accurate and robust liquid chromatography-tandem mass spectrometry (LC-MS/MS) assays for biomarker measurement due to the endogenous nature of biomarkers, which makes it impractical to use external calibration curves prepared in the same biological matrix, and the high cost and time required for stable isotopically labeled (SIL) analytes, especially for protein analysis.
Innovation Solution
The method involves constructing In-Sample Calibration Curves (ISCC) using Multiple Isotopologue Reaction Monitoring (MIRM) of stable isotopically labeled analytes within the sample, where the concentration of the analyte is quantified by measuring peak areas and calculating analyte concentration equivalents based on theoretical isotopic abundances, eliminating the need for external calibration curves and reducing instrument run time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external calibration curves with authentic reference standards in authentic matrix are used, then measurement precision is improved, but ease of manufacture deteriorates due to the endogenous nature of biomarkers making it impractical
Solution Approach 1:
The patent introduces stable isotopically labeled (SIL) analytes as intermediary substances that serve dual purposes: they act as both the calibration curve standards and the internal standards. The SIL analytes have identical physicochemical properties to authentic analytes but can be distinguished by mass spectrometry due to their different mass-to-charge ratios, enabling accurate quantification without requiring authentic reference standards in authentic matrix.
Solution Approach 2:
The patent creates a copy of the authentic analyte by using stable isotopically labeled versions that replicate all physicochemical properties (extraction, chromatographic separation, ionization, fragmentation) but differ in mass. This copying approach allows the SIL analyte to serve as a perfect surrogate for the authentic analyte in calibration curve preparation.
2Measurement precision
If SIL surrogate analyte is used in authentic matrix for external calibration curve, then measurement precision is improved, but loss of substance worsens due to need for two versions of SIL analyte
Solution Approach 1:
The patent makes the SIL analyte universal by designing it to serve multiple functions simultaneously: it acts as the calibration curve standard, the internal standard, and the quantification reference. By spiking a single known amount of SIL analyte into the sample, the system generates multiple isotopologue signals that provide both calibration information and internal standard normalization, eliminating the need for separate SIL versions.
Solution Approach 2:
The patent utilizes parameter changes in the mass-to-charge ratio of the SIL analyte to generate multiple isotopologue signals. By monitoring multiple MRM transitions corresponding to different isotopic compositions (13C, 15N, 2H labels), the system extracts multiple pieces of information from a single SIL analyte addition, reducing overall consumption.
3Measurement precision
If multiple versions of SIL analyte are used for external calibration curve, then measurement precision is improved, but productivity deteriorates due to high cost and time consumption
Solution Approach 1:
The patent extracts the calibration curve construction process from the traditional external calibration approach and integrates it directly into the sample analysis process. By performing in-sample calibration curve construction using the SIL analyte's isotopologue signals, the method eliminates the need for separate external calibration curve preparation and instrument run time, allowing calibration and sample analysis to occur simultaneously.
4Measurement precision
If external calibration curves are used, then measurement precision is improved, but loss of time worsens due to instrument run time requirements
Solution Approach 1:
The patent merges the external calibration curve analysis and the sample analysis into a single integrated process. The SIL analyte spiked into the sample serves as both the calibration standard and the analyte of interest, allowing the mass spectrometer to simultaneously perform calibration curve construction and sample quantification without requiring separate instrument runs.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for accurate and efficient quantification of analytes, including proteins and small molecules, by generating calibration curves within the sample itself, thereby simplifying the LC-MS/MS process and reducing the need for costly and time-consuming external standards, especially in cases where authentic biological matrices are not available.
Implementation Method 1
the analyte, the SIL analyte, and the naturally occurring isotopologues of the SIL analyte are ionized in the mass spectrometer to produce protonated (or deprotonated) parent ions
Implementation Method 2
the parent ions of the analyte, the parent ions of the SIL analyte, and the parent ions of the naturally occurring isotopologues of the SIL analyte in the mass spectrometer are fragmented at the same cleavage site to produce neutral losses and daughter ions
Data Source
AI summary
This disclosure provides several methods in LC-MS/MS analysis: (1) a method of LC-MS/MS analysis technique to determine the analyte concentration of a sample wherein an In-Sample Calibration Curve (ISCC) is used instead of an external calibration curve through monitoring of multiple isotopologue transitions of an added stable isotopically labeled (SIL) analyte in each sample via MS/MS in multiple isotopologue reaction monitoring (MIRM) mode; (2) a method of LC-MS/MS analysis to determine the analyte concentration of a sample wherein a One-Sample Multipoint External Calibration Curve (OSMECC) is used instead of a multisample external calibration curve; and (3) a method of LC-MS/MS analysis to determine the analyte concentration of a sample with an analyte concentration beyond the assay's ULOQ wherein isotope sample dilution is used instead of diluting sample physically during sample preparation based on calculating the isotopic abundance of the MIRM channel monitored.