Microchip Atmospheric Pressure Chemical Ionization Source for Mass Spectrometry

Abstract

A novel microchip heated nebulizer for atmospheric pressure chemical ionization mass spectrometry is presented. Anisotropic wet etching is used to fabricate the flow channels, inlet, and nozzle on a silicon wafer. An integrated heater of aluminum is sputtered on a glass wafer. The two wafers are jointed by anodic bonding, creating a two-dimensional version of an APCI source with a sample channel in the middle and gas channels symmetrically on both sides. The ionization is initiated with an external corona-discharge needle positioned 2 mm in front of the microchip heated nebulizer. The microchip APCI source provides flow rates down to 50 nL/min, stable long-term analysis with chip lifetime of weeks, good quantitative repeatability (RSD < 10%) and linearity (r(2) > 0.995) with linear dynamic rage of at least 4 orders of magnitude, and cost-efficient manufacturing. The limit of detection (LOD) for acridine measured with microchip APCI at flow rate of 6.2 muL/min was 5 nM, corresponding to a mass flow of 0.52 fmol/s. The LOD with commercial macro-APCI at a flow rate of 1 mL/min for acridine was the same, 5 nM, corresponding to a significantly worse mass flow sensitivity (83 fmol/s) than measured with microchip APCI. The advantages of microchip APCI makes it a very attractive new microfluidic detector.

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

“…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].…”

“…8 [86]. 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.…”

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).…”

Integrated liquid chromatography–heated nebulizer microchip for mass spectrometry

“…The microchips can be used with APCI [21], APPI [22], sonic spray ionization (SSI) [23], atmospheric pressure thermospray ionization (APTSI) [24], or ionspray [25] and combined with any mass spectrometer used for LC-MS. Heated nebulizer microchips have been combined with traditional capillary LC [26,27] and gas chromatography [27,28] for the determination of various compounds.…”