| A sample introduction technique has been developed to allow for on-line, dropwise injections
of effluent into a mass spectrometer. The incorporation of a flowing rinse into the system makes
dropwise resolution possible for any liquids capable of forming drops under ambient conditions.
Additionally, this technique provides independent flow control of the liquid chromatography and mass
spectrometry portions of liquid chromatography-mass spectrometry (LC-MS) systems. This allows for
coupling of chromatography techniques that require slower flow rates than what are optimal for mass
spectrometry instruments, as well as chromatographic systems that are not driven by pumps. The
technique has been demonstrated utilizing Gas Pressurized Extraction Chromatography (GPEC) and
Inductively Coupled Plasma-Time-of-Flight Mass Spectrometry (ICP-TOFMS) to illustrate its
qualitative applications for rapid separation development and procedure evaluation. The method’s
quantitative applications were evaluated using single and double isotope dilution mass spectrometry
(IDMS) with an external mass bias correction to measure analytes in volumes as small as single drops.
The findings reported herein show that the developed sample introduction technique can be applied to
generating chromatograms and k’ plots for the separation conditions being tested. Linear regression
slope (LRS) quantification through single and double IDMS of full samples returned elemental results
that fell within the uncertainty of a surrogate fuel sample. The same measurements performed on drops
that reached >10k cps Nd-144 gave results that were very similar to the full sample analyses. More
dilute drops that were analyzed showed lower accuracy and precision.
Key Words: LC-MS, Extraction Chromatography, Dropwise, GPEC, ICP-TOFMS |