Atmospheric pressure chemical ionization voltage

In atmospheric pressure chemical ionization, heat and a coaxial flow of N2 convert eluate into a fine mist from which solvent and analyte evaporate (Figure 22-19). Like chemical ionization in the ion source of a mass spectrometer, atmospheric pressure chemical ionization creates new ions from gas-phase reactions between ions and molecules. The distinguishing feature of this technique is that a high voltage is applied to a metal needle in the path of the aerosol. An electric corona (a plasma containing charged particles) forms around the needle,... 

Gas emerging from a capillary gas chromatography column can go directly into the ion source of a well-pumped mass spectrometer to provide qualitative and quantitative information about the components of a mixture. For liquid chromatography, atmospheric pressure chemical ionization utilizes a corona discharge needle to create a variety of gaseous ions. Alternatively, electrospray employs high voltage at the exit of the column, combined... 

S Lacorte, C Molina, D Barcelo. Temperature and extraction voltage effect on fragmentation of organophosphorus pesticides in liquid chromatography atmospheric pressure chemical ionization mass spectrometry. J Chromatogr A 795 13-26, 1998. 

Methods Ambient ionization methods, of which there are now over 20, e.g., desorption electrospray ionization (DESI), desorption atmospheric pressure chemical ionization (DAPC), desorption atmospheric pressme photo-ionization (DAPPI), and direct analysis in real time (DART), are now joined by paper spray, a method where ESI is initiated at the pointed tip of a piece of filter paper. A drop of blood ( 15 pi) is dried on the paper, and then the paper is moistened with 25 pi of a solvent suited to both the extraction of the analytes from the blood and the ESI process (e.g., 90% methanol 10% water with either 100 ppm acetic acid or 200 ppm sodium acetate). When the paper is exposed to high voltage (3-5 kV) while held close ( 5 mm) to the entrance of the mass analyzer, a spray (similar to electrospray) is induced at the tip of the paper as capillary action carries extracted compounds through the paper (Figure 4.5). The spray is maintained for 30-90 s at a flow rate comparable to that used in nano-electrospray. 

Five mutagenic heterocyclic aromatic amines (2-amino-3-methyl-, 2-amino-3,8-dimethyl-, 2-amino-3,4,8-trimethyI-, 2-amino-l,7 -trimethylimidazo[4,5/]-quin-oxaline, 2-amino-l-methy]-6-phenylimidazo[4,56]pyiidine) were isolated from cooked meat and separated on a C g column (A = 265 nm, atmospheric pressure chemical ionization MS capillary T = 250 C, vaporizer T = 500°C, N2 sheath gas pressure 20psi, collision voltage 13 eV). A complex 16-min 90/10 0/100 (95/5... 

Most mass spectrometers equipped for electrospray ionization can be converted to atmospheric pressure chemical ionization (APCI), and many commercial LC-APCI-MS instruments are equipped with both ionization techniques. During APCI, ionization takes place in an atmospheric pressure chamber when the sample molecules collide with solvent irais formed in a continuous corona discharge. Unlike electrospray, the needle used to spray the HPLC effluent is not at high voltage. 

Detector MS, Finnigan MAT TSQ-7000 quadrupole, atmospheric pressure chemical ionization, m/z 190, corona voltage 1.8 kV, corona current 5.0 gA, capillary temperature 220°, electron multiplier 1400 V, vaporizer temperature 400°... 

The MS-Nose consists of an atmospheric pressure chemical ionization gas phase analyzer (APCI-GPA) attached to a VG Quattro II MS mass spectrometer [5] the cone voltage was 20 V. The ions monitored (MH+, M H2O + H+) were 58 (acetone in the panelists breath), 71 (amyl acetate fragment), 83 (cit-3-hexenol), 117 (ethyl butyrate), 131 (amyl acetate), 137 (linalool), and 163 (methyl cinnamate). 

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