I Knew You Were Trouble: Expanding LC Methods to Include Difficult GC Compounds Using a Novel Ionization Technique

Library Number:
Kari Organtini, Susan Leonard, Eimear McCall, Simon Hird, Gareth Cleland and Kenneth Rosnack
Content Type:
Content Subtype:
Related Products:

Novel aspect:

Utilizing a novel ionization source for combination of GC and LC methods in food screening.


Screening food samples for contaminants such as pesticides requires the use of GC-MS and LC-MS techniques. In order to cover a full suite of regulated compounds, several LC and GC methods are usually required that separately incorporate large suites of compounds, single residues and ‘troublesome’ compounds.

We assessed the use of a novel LCMS ionization technique (UNISPRAY) that has potential to bridge the barrier between LC and GC amenable pesticides. This aids in a reduction of the number of methods required to monitor a suite of compounds and offers  advantages with certain compound matrix pairs, such as captan in chlorophyll containing matrices. The evaluation was performed in various food commodities.


Spiked extracts of food samples were assessed by ESI and UNISPRAY using a UPLC separation with a BEH C18 1.7 µm, 2.1 x 100 mm column. The data was acquired using multi reaction monitoring methods on a tandem quadrupole mass spectrometer. The data was first acquired in ESI+ mode and then in UNISPRAY mode to show the utility of the new ionization technique and compared with relevant GC-MS/MS data. Multiple classes of compounds were targeted, including contaminants from agricultural processes such as pesticides. Linearity, reproducibility and robustness were assessed to ensure the methods met local regulations.

Preliminary Data:

This work reports on the utilization of a new ionization source design (UNISPRAY) to expand the scope of compounds analyzed for food and environmental contaminant screening. A variety of residue compound classes were used for the comparison, including several notoriously difficult to analyze GC compounds.  Solvent standards as well as sample extracts were analyzed both in ESI and UNISPRAY modes using a UPLC coupled to a tandem quadrupole mass spectrometer. Robustness and sensitivity results from UNISPRAY were compared to regular LC-MS (ESI) or GC-MS techniques. Initial results show that traditional GC amenable compounds can be added to LC acquisition methods, thus expanding the compound coverage of the method for food screening.  Reproducibility was assessed in matrix matched standards and showed RSDs below 15% for most compounds. Matrix matched calibration curves, in various food matrices, using UNISPRAY achieved linearity with an r2 value of 0.99 and above. 

Title Format File Size
Download PDF PDF 1806.87kB