Sheath liquid effects in capillary high-performance liquid chromatography–electrospray mass spectrometry of oligonucleotides

Mutation scanning by ion-pair reversed-phase high-performance liquid chromatography-electrospray ionization mass spectrometry (ICEMS)

“…Recent changes in experimental conditions have led to successive improvements in electrospray ionization efficiency and, hence, detection sensitivity-enabling today the direct analysis of PCR products in the upper attomole to lower femtomole range. Modifications made included the reduction in the concentration of ion-pair reagent in the mobile phase [Apffel et al, 1997], the use of capillary columns with an internal diameter of 200 mm [Huber and Krajete, 1999;Premstaller et al, 2000], the post-column addition of acetonitrile to the column effluent [Huber and Krajete, 2000], and the replacement of triethylammonium bicarbonate with butyldimethylammonium bicarbonate [Oberacher et al, 2001a]. The latter ionpair reagent improved the signal-to-noise ratio, as demonstrated in direct-infusion experiments, and caused an increase in the concentration of acetonitrile necessary to elute the nucleic acids from the column.…”

“…Eluting nucleic acids were detected and mass analyzed by ESI-MS using a quadrupole ion trap mass spectrometer (LCQt, Thermo Finnigan, San Jose, CA). To enhance detection sensitivity, acetonitrile was added post-column to the column effluent at a flow rate of 2.0 ml/min using a syringe pump and a tee-piece [Huber and Krajete, 2000;Oberacher et al, 2002a]. Electrospray voltage was set at 4.5 kV and a nitrogen sheath gas flow of 100 arbitrary units was employed.…”

Optimized suppression of adducts in polymerase chain reaction products for semi-quantitative SNP genotyping by liquid chromatography-mass spectrometry

“…The capillary column was connected directly to the spray capillary (fused silica, 90 m o.d., 20 m i.d., Polymicro Technologies, Phoenix, AZ) by means of a microtight union (Upchurch Scientific, Oak Harbor, WA). In order to enhance detection sensitivity, acetonitrile was added post-column to the column effluent at a flow rate of 2.0 l/min using a syringe pump and a tee-piece [34]. 5, and 6) was employed.…”

“…Eluents of low electric conductivity and high content of volatile organic solvent are most suitable for nucleic acid analysis by ESI-MS [27,28,34,40,41]. In ion-pair reversed-phase HPLC of nucleic acids, an ion-pair reagent such as triethylammonium acetate or butyldimethylammonium acetate is added to the mobile phase to ensure chromatographic retention of nucleic acids on a nonpolar stationary phase [42].…”

Enhancing the response of alkyl methylphosphonic acids in negative electrospray ionization liquid chromatography tandem mass spectrometry by post-column addition of organic solvents

“…In negative ionization, in the case where the ion forms as a result of a loss of a proton (or loss of charge balancing cation, if present as a salt), the addition of fluorinated alcohols has been shown to enhance the signal of oligonucleotides, which has been attributed to volatility [15] and solution phase chemistry [16]. Huber and Krajete have shown the effects of volatile acids, bases, and solvents added via sheath flow on the response of oligonucleotides [17], where the addition isopropyl alcohol, methanol, and acetonitrile enhanced the analyte S/N.…”