Supercharging reagents in LC-MS/MS hormone analyses: Enhancing ionization, not limit of quantification

Area of Science:

• Analytical Chemistry
• Biochemistry
• Mass Spectrometry

Background:

• Assay sensitivity in LC-MS/MS hormone analysis is critically dependent on the ionization process.
• Improving ionization efficiency may enhance sensitivity and reduce the limit of quantification (LOQ).

Purpose of the Study:

• To investigate the effect of supercharging reagents on ionization efficiency and LOQ for various hormones.
• To evaluate reagent performance in both test solutions and serum samples.

Main Methods:

• LC-MS/MS analysis of insulin, oxytocin, sex steroids, and corticosteroids.
• Addition of supercharging reagents: m-nitrobenzyl alcohol (m-NBA), sulfolane, propylene carbonate, and o-nitroanisole (o-NA).
• Testing in both standard solutions and pretreated serum samples.

Main Results:

• Supercharging reagents had varied impacts on different hormones; m-NBA increased signal for all tested hormones.
• While m-NBA and o-nitroanisole increased peak area, they also increased noise, failing to improve the signal-to-noise ratio.
• Ionization enhancement in test solutions did not consistently translate to improved sensitivity in serum samples.

Conclusions:

• Supercharging reagents can significantly enhance hormone ionization efficiency in LC-MS/MS.
• Despite enhanced ionization, these reagents do not lead to an improved limit of quantification for routine hormone measurements.