Streamlined microfluidic analysis of phosphopeptides using stable isotope-labeled synthetic peptides and MRM-MS detection

On-line multi-residue analysis of fluoroquinolones and amantadine based on an integrated microfluidic chip coupled to triple quadrupole mass spectrometry

An on-line multi-residue qualitative and quantitative analysis method for fluoroquinolones and amantadine using an integrated microfluidic chip was developed prior to directly coupling to triple quadrupole mass spectrometry (QQQ-MS). Six parallel channels consisting of sample filtration units and micro solid phase extraction (micro-SPE) columns were present in the specifically designed microfluidic device. Firstly, the impurities in the sample solution were trapped by the micropillars in the filtration units. The solution passed through the micro-SPE units packed with hydrophilic-lipophilic balanced (HLB) particles, and then the two classes of drugs were enriched. After washing, the targets were eluted and immediately electrosprayed for MS analysis. This approach allowed effective filtration, enrichment, elution, and MS detection without the introduction of an additional separation step after SPE. Direct electrospray ionization (ESI)-MS in multiple reaction monitoring (MRM) mode could not only ensure the high sensitivity of quantitative analysis, but also achieved accurate qualitative analysis towards targets using the MRM ratios, reducing the possibility of false positives. Good linear relationships were obtained by the internal standard (IS) method with a linear range of 1-200 ng mL^-1 (R² > 0.992). The mean recoveries of the eight target analytes were from 85.2% to 122% with the relative standard deviation (RSD) ranging from 5.6% to 20.3%. All this demonstrated that the developed microfluidic device could be a useful tool for rapid detection in the field of food safety.

3D Printed Microfluidic Devices for Solid-Phase Extraction and On-Chip Fluorescent Labeling of Preterm Birth Risk Biomarkers

Solid-phase extraction (SPE) is a general preconcentration method for sample preparation that can be performed on a variety of specimens. The miniaturization of SPE within a 3D printed microfluidic device further allows for fast and simple extraction of analytes while also enabling integration of SPE with other sample preparation and separation methods. Here, we present the development and application of a reversed-phase lauryl methacrylate-based monolith, formed in 3D printed microfluidic devices, which can selectively retain peptides and proteins. The effectiveness of these SPE monoliths and 3D printed microfluidic devices was tested using a panel of nine preterm birth biomarkers of varying hydrophobicities and ranging in mass from 2 to 470 kDa. The biomarkers were selectively retained, fluorescently labeled, and eluted separately from the excess fluorescent label in 3D printed microfluidic systems. These are the first results demonstrating microfluidic analysis processes on a complete panel of preterm birth biomarkers, an important step toward developing a miniaturized, fully integrated analysis system.