Absolute quantitation is an analytical technique designed to measure, as accurately as possible, the concentration of an analyte within a given matrix. The term “absolute” is a bit of a misnomer—there are many sources of error that affect the final number, including systematic error, matrix-related effects and the nature and purity of the standards used in the experiment. Indeed, most quantitative assays are defined by parameters such as the limit of quantitation (LOQ), the dynamic range of analysis, accuracy, and precision. These values provide context for the term “absolute,” and are used to describe the quantitative power of a validated assay.
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The field of lipidomics aims to quantitatively define lipid classes at the molecular species level in biological systems. Mass spectrometry is the primary means by which lipidomics analysis is performed, but there are significant challenges associated with this technique, including isobaric interference, differential ionization and fragmentation of lipids and the need for complex internal standard strategies for quantitation. Lipidomics studies have evolved tremendously over the last 10 years, progressing from sum composition analysis by shotgun analysis to untargeted analysis by HRAM.
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There are two significant challenges in the field that still must be better addressed before lipidomics can become “mainstream: Isobaric Interference and Quantitation (the subject of this post)!
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