The present invention generally pertains to methods of characterizing charge variants of a protein. In particular, the present invention pertains to the use of anion exchange chromatography-mass spectrometry (AEX-MS) methods using a salt-gradient. The present invention is particularly useful for charge variant analysis of IgG4 subclasses.

A method of processing of a biological sample containing multiple metabolites is described The method comprising the steps of pre-treating the biological sample with a metabolite extraction solvent to provide a pre-treated sample, separating a first aliquot of the pretreated sample by reverse phase liquid chromatography (RPLC) to provide a first eluent containing resolved hydrophobic metabolites, and separating a second aliquot of the pre-treated sample by hydrophilic interaction liquid interaction chromatography (HILIC) to provide a second eluent containing resolved hydrophilic metabolites. The first and second eluents are assayed using targeted tandem mass spectroscopy operated in multiple reaction monitoring mode. Each liquid chromatography step (LC) is directly hyphenated with the tandem mass spectrometry (MS/MS) into a single LC-MS/MS analysis. The extraction solvent typically comprises methanol, isopropanol and an acetate buffer.

A method of processing of a biological sample containing multiple metabolites is described The method comprising the steps of pre-treating the biological sample with a metabolite extraction solvent to provide a pre-treated sample, separating a first aliquot of the pretreated sample by reverse phase liquid chromatography (RPLC) to provide a first eluent containing resolved hydrophobic metabolites, and separating a second aliquot of the pre-treated sample by hydrophilic interaction liquid interaction chromatography (HILIC) to provide a second eluent containing resolved hydrophilic metabolites. The first and second eluents are assayed using targeted tandem mass spectroscopy operated in multiple reaction monitoring mode. Each liquid chromatography step (LC) is directly hyphenated with the tandem mass spectrometry (MS/MS) into a single LC-MS/MS analysis. The extraction solvent typically comprises methanol, isopropanol and an acetate buffer.

This disclosure provides liquid chromatography tandem mass spectrometer (LC-MS/MS) methods and systems for detecting low levels of pesticides in a test sample. In the disclosed methods and systems, an ammonium salt is added to a mobile phase added to a liquid chromatography column or to the eluant from a liquid chromatography column. This addition improves the signal for certain pesticides by a factor of from 2 to 20, improving their detection limits in a variety of test samples.

The present disclosure discusses a method of separating and/or purifying acidic peptides by the use of a mobile phase having a pH greater than or about equal to the isoelectric point of one or more of the metal oxides in the flow path.

The measurement of glutaraldehyde-based biocides in seawater without the use of a derivatization agent. The measurement of glutaraldehyde-based biocides in seawater may be performed without additional components to reduce background interferences. The concentration of a glutaraldehyde-based biocides in a seawater sample is determined using reversed phase liquid chromatography and a gradient mobile phase of acetonitrile and deionized water. Systems for determining the concentration of glutaraldehyde-based biocide in a seawater injection system are also provided.

When a liquid in the column is replaced by carbon dioxide in a supercritical state in the chromatograph, an operation of a first pump is controlled by a flow rate control unit, and the carbon dioxide in the supercritical state is supplied at a constant pressure. Moreover, when a flow rate of the carbon dioxide in the supercritical state reaches a predetermined flow rate thereafter, the flow rate control unit controls an operation of the first pump so that the carbon dioxide in the supercritical state is supplied at a constant flow rate.

When a liquid in the column is replaced by carbon dioxide in a supercritical state in the chromatograph, an operation of a first pump is controlled by a flow rate control unit, and the carbon dioxide in the supercritical state is supplied at a constant pressure. Moreover, when a flow rate of the carbon dioxide in the supercritical state reaches a predetermined flow rate thereafter, the flow rate control unit controls an operation of the first pump so that the carbon dioxide in the supercritical state is supplied at a constant flow rate.

The present invention relates to a method for increasing antibody yield during antibody purification from a sample by ion exchange chromatography in flow-through mode by pre-conditioning the sample with Tris without the use of NaCl to adjust the conductivity.

The present invention relates to a method for increasing antibody yield during antibody purification from a sample by ion exchange chromatography in flow-through mode by pre-conditioning the sample with Tris without the use of NaCl to adjust the conductivity.