The present invention relates to a method for detecting or quantifying CTP in a cell sample comprising at least two nucleotide triphosphates by cationic ion pairing chromatography coupled to mass spectrometry, to a method for detecting or quantifying CTP synthase activity based on the method for detecting or quantifying CTP, and to their use in methods for screening potential immunosuppressive or anti-cancer compounds and in methods for determining the appropriate dose of an immunosuppressive or anti-cancer compound inhibiting CTP synthase activity for a treated subject.

The present disclosure relates to the determination of analytes in a sample using chromatography. The present disclosure provides methods of separating an analyte from a sample. The method includes introducing a sample comprising the analytes into a chromatographic system. The chromatographic system has a flow path disposed in an interior of the chromatographic system, at least a portion of the flow path having an active coating, and a chromatographic column having a stationary phase material in an interior of the chromatographic column that facilitates separation of the analytes in the sample through interaction with at least one analyte in the sample. The active coating is selected to interact with at least one analyte in the sample through (1) a repulsive force, (2) a secondary interaction, or (3) a retention mechanism distinct from the interaction with the stationary phase material.

A hetero type monodispersed polyethylene glycol containing a compound represented by the following formula (1):

NH.sub.2(CH.sub.2CH.sub.2O).sub.aCH.sub.2CH.sub.2COOH(1) (in the formula (1), a represents an integer from 6 to 40); wherein any of (A) a chromatogram detected by a differential refractometer when the hetero type monodispersed polyethylene glycol is separated using reverse phase chromatography, (B) a chromatogram detected by a differential refractometer when the hetero type monodispersed polyethylene glycol is separated using cation exchange chromatography, and (C) a chromatogram detected by a differential refractometer when the hetero type monodispersed polyethylene glycol containing a compound represented by the formula (1) shown above is derivatized and separated using anion exchange chromatography satisfy specific relational expressions, respectively.

The present invention relates to the detection and analysis of by-products, such as short RNA transcripts, in a process of RNA in vitro transcription by HPLC. It further relates to the use of this method for the quality control of RNA produced by in vitro transcription or for identifying suitable RNA purification conditions.