Microfluidic technology offers multiple advantages including ease of use, robustness and sensitivity. Coupled with a tandem quadrupole mass spectrometer, such as the Xevo TQ-S, we can create an optimal and versatile “middle ground” platform in which these advantages can be exploited for both small molecule and peptide quantitative applications.
For example, most small molecule applications are performed using standard flow chromatography (in the range of 600-100 μL/min), consuming a high level of both solvent and sample which increases the cost (both fiscally and environmentally). The use of microfluidic technology for these small molecule applications can reduce solvent consumption by upwards of 150-fold and can significantly increase on-column sensitivity, thus reducing sample consumption.
Conversely, quantitative peptide assays are almost exclusively performed using nanoscale chromatography (~400 nL/min) to achieve the required sensitivity for detection of these low abundance molecules within a complex matrix (e.g. serum, urine, etc.).
We have found that the use of microfluidic technology for peptide quantitation yields the same or better sensitivity when compared to a nanoscale platform and has the additional, very significant advantages of ease of use, robustness, and improved chromatographic resolution (e.g. peak capacity). Thus, with a single analytical platform we can perform quantitative analysis for a wide range of compounds spanning from small molecules to peptides.
One application in which the technology has struggled is the analysis of compounds in negative ionization mode. This limitation has been overcome in the development of a next generation microfluidic device that incorporates post-column addition of isopropanol to improve ionization and spray stability in negative mode applications. With this new capability we can now perform quantitative experiments in negative mode or with polarity switching.