Abstract: In a mass spectrometer or gas chromatograph/mass spectrometer system, a conditioning gas such as, for example, hydrogen is added to condition or clean one or more components or regions of the mass spectrometer such as the ion source. The conditioning gas may be added upstream of the mass spectrometer such as, for example, into a sample inlet or a chromatographic column, or may be added directly into the mass spectrometer. The conditioning gas may be added off-line, when the mass spectrometer is not analyzing a sample, or on-line during sample analysis. When added on-line, the conditioning gas may be mixed with a carrier gas such as, for example, helium. In another embodiment, the conditioning gas also serves as the carrier gas through the column; another gas such as, for example, helium may be added to the carrier gas stream.

Abstract: A method for operating a mass spectrometer (MS) includes establishing a pressure differential across a membrane wherein an upstream pressure in a calibrant gas inlet line on an upstream side of the membrane is greater than a downstream pressure in an ion source on a downstream side of the membrane; flowing a calibrant gas from the calibrant gas inlet line, through a nano-scale orifice of the membrane, and into the ion source; and maintaining the upstream pressure at a constant value. The calibrant may be flowed at a low flow rate. An MS system includes a membrane interposed between a calibrant gas introduction system and a mass spectrometer. The membrane may include an orifice of nano-scale diameter.

Abstract: A method and compositions for sulfurizing at least one phosphite or thiophosphite linkage in an oligonucleotide. The addition of N-alkyl imidazole to the acetyldisulfide sulfurization solution enables the use of industrially preferred solvents or solvents that are derived from renewable resources.