Gas Chromatography-Microchip Atmospheric Pressure Chemical Ionization-Mass Spectrometry

Abstract

An atmospheric pressure chemical ionization (APCI) microchip is presented for combining a gas chromatograph (GC) to a mass spectrometer (MS). The chip includes capillary insertion channel, stopper, vaporizer channel, nozzle and nebulizer gas inlet fabricated on the silicon wafer, and a platinum heater sputtered on a glass wafer. These two wafers are joined by anodic bonding creating a two-dimensional version of an APCI microchip. The sample from GC is directed via heated transfer line capillary to the vaporizer channel of the APCI chip. The etched nozzle forms narrow sample plume, which is ionized by an external corona discharge needle, and the ions are analyzed by a mass spectrometer. The GC-microchip APCI-MS combination provides an efficient method for qualitative and quantitative analysis. The spectra produced by microchip APCI show intensive protonated molecule and some fragmentation products as in classical chemical ionization for structure elucidation. In quantitative analysis the GC-microchip APCI-MS showed good linearity (r(2) = 0.9989) and repeatability (relative standard deviation 4.4%). The limits of detection with signal-to-noise ratio of three were between 0.5 and 2 micromol/L with MS mode using selected ion monitoring and 0.05 micromol/L with MS/MS using multiple reaction monitoring.

Gas chromatography coupled to atmospheric pressure ionization mass spectrometry (GC-API-MS): Review

“…Moreover, there are several advantages behind the growing interest in the miniaturization of analytical devices. These include higher sensitivity, faster analysis, reduced sample and solvent consumption, and lower manufacturing cost [13,84]. For these reasons, miniaturized heated nebulizers were developed for microchip-based APPI [85] and APCI [86] for LC and also GC [13,50].…”

“…The sample from GC is In microchip APCI (µAPCI), an external corona-discharge needle is positioned in front of the nozzle of the heated nebulizer microchip. The microchip APCI was positioned 1 cm away from the mass spectrometer orifice in orthogonal position [13]. In APPI studies, a 10 eV krypton discharge VUV lamp was attached to an APPI power source [50].…”

“…The sensitivity of the μAPCI was comparable to that of conventional APCI in terms of sample concentration, but the mass flow sensitivity was 100-200 times better with μAPCI [86][87]. A likely reason for the more efficient ionization in μAPCI as compared with conventional APCI is the narrower plume generated by the heated nebulizer microchip, which allows a larger proportion of the neutral analytes to be ionized with the corona discharge [13]. The analytical performance of GC-μAPPI-MS was evaluated with some polycyclic aromatic hydrocarbons, amphetamines, and steroids.…”

“…Ionization in LC/MS can be realized by electrospray ionization (ESI) [5], atmospheric pressure chemical ionization (APCI) [6] , photo ionization (APPI) [7,8], atmospheric pressure laser ionization (APLI) [9,10] and others [11,12]. In GC-MS and LC-MS different instruments are used, since in GC-MS compounds are ionized at vacuum (EI and CI) and in LC/MS at atmospheric pressure [13]. But GC/MS can also be used under atmospheric pressure ionization conditions.…”

APCI/APPI for synthetic polymer analysis

“…Miniaturized APCI nebulizers that connect capillary LC with MS with flow rates in the mL min À1 range have been described (Nyholm, Sjoberg, & Markides, 1996;Ostman et al, 2006a). One of them that uses microchip technology (Ostman et al, 2004(Ostman et al, , 2006a has recently allowed the coupling of gas chromatography with MS (Ostman et al, 2006b). Other authors have previously presented a capillary electrophoresis-MS coupling with a miniaturized APCI source by modifying a commercial source (Tanaka, Otsuka, & Terabe, 2003).…”