Variables in the Infusion Solution

The principles, and the bolts and nuts of the tools used to derive lipid sample solutions to the ion source (i.e., sample inlets), are discussed to a certain degree in Chapter 3. This section discusses the variations present in the lipid sample solutions prior to the ion source, as well as the effects of these variations on MS analysis of lipids. Because these variables are present in the cases of sample solutions delivered by using any type of inlet, the word infusion used herein generalizes all of those cases, but not for the case of direct infusion. 

1 Polarity, Composition, Ion Pairing, and Other Variations in the Infusion Solution 

Solvent(s) used in the infused lipid solution not only affect the solubility of lipids but also have a large impact on ionization efficiency in addition to the separation in 

2 Variations of the Leveis or Composition of a Modifier in the Infusion Solution 

Similar to the residual ions in the infusion solution, the chemical and physical properties of the modifier added to the infusion solution can significantly influence the ionization sensitivity and efficiency, as well as the molecule-ion profiles of different lipid classes. The effects of the modifier on charge-neutral lipid classes are particularly larger in comparison to anionic lipid classes (Chapter 1). For example, PC species are generally ionized as the cation adduct from the modifier in the positive-ion mode and as an anion adduct from the modifier in the negative-ion mode. 

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