Modified ionspray interface for supercritical fluid chromatography/mass spectrometry: Interface design and initial results

Abstract

A pneumatically assisted electrospray liquid chromatographyhass spectrometry interface has been modified for use with open-tubular supercritical fluid chromatography (SFC). The modified interface houses the SFC flow restrictor within the spray device. A sheath-flow liquid of methanol or methanol/water containing ammonium acetate flows coaxially to the restrictor. The addition of the sheath-flow liquid results in the ionization of analytes known to be in a neutral charge state during the chromatographic separation. The sheath-flow liquid also allows for the independent operation of the chromatograph and the mass spectrometer. Both could be operated under optimum conditions. The operation of the interface was optimized using a solution of poly(dimethy1siloxane) in C o t introduced by continuous infusion. We also report the application of the modified instrument to samples containing amines and propoxylated alcohols.

Preliminary investigation of supercritical-fluid-assisted nebulization for enhanced response in electrospray mass spectrometry

“…During our development of a modified electrospray interface for open-tubular [11] and then packed-column [12] supercritical-fluid chromatography/mass spectrometry (otSFC/MS and pcSFC/MS, respectively), we noted analyte response exceeding our expectations. We speculated that the enhanced response might be due to an improved spray plume (finer droplets) caused by a mobile phase consisting primarily of CO 2 with a lesser amount of polar organic solvent such as methanol, an essentially "self-nebulizing" mobile phase.…”

Characterization of low molecular weight alkoxylated polymers using long column SFC/MS and an image analysis based quantitation approach

“…Other low-MW polymer samples were obtained from a variety of commercial sources. Neodol 25-12 (C 12 , C 13 , C 14 , and C 15 alcohols ethoxylated to an average ethoxylate chain length of 12) was obtained from Shell Chemical (Houston, TX). Solutions of low-MW polymer samples were prepared at approximately 0.05 mg/mL in toluene.…”

“…Interfacing SFC to mass spectrometry using an atmosphericpressure-ionization source is relatively straightforward and has been described previously [13][14][15]. The selfnebulizing nature of a mobile phase consisting of CO 2 and an organic "modifier" results in improved response compared to conventional LC/MS [16].…”

SFC with evaporative light-scattering detection and atmospheric-pressure chemical-ionisation mass spectrometry for methylated glucoses and cyclodextrins analysis

“…Moreover, separations are often different from and complementary to those obtained in LC [3][4][5][6][7][8]. pSFC mainly uses LC-like detectors, such as UV, evaporative light-scattering detection (ELSD) [3][4][5][6][7][8][9][10], or atmospheric-pressure ionisation mass-spectrometry (API-MS) [2,9,[11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] including ionspray or electrospray (IS-MS) and atmospheric-pressure chemical-ionisation mass spectrometry (APCI-MS). ELSD and API-MS are low-pressure detectors especially appropriate to non-UV-absorbing analytes.…”

“…For pSFC, the transposition is more complex because of the necessity to regulate pressure. API-MS interfaces are commonly modified to incorporate the restrictor at the end of the MS source capillary [9,[11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27]. However, in the case of APCI-MS, an unmodified LC interface has recently been introduced for pSFC with pure-CO 2 mobile phase [2].…”