This invention employs columns and methods to apply external and internal standards and compounds. Analytical standard or compounds are adsorbed to a solid phase extraction media and are stored indefinitely. The standards or compounds remain stable on the solid phase extraction media without decomposing. The standards or compounds may be removed from the solid phase extraction media with a solvent.

The teachings herein provide for a method of analyzing testosterone using mass spectrometry. The method entails combining in a vial or well, a tagging reagent that is reactive with testosterone, an aqueous precipitation agent that precipitate proteins from solution, and an internal standard solution, the internal standard solution containing a known concentration of an isotopically enriched testosterone and then adding to the vial or well, a sample containing or suspected to contain testosterone. The vial can then be mixed to cause simultaneous precipitation of proteins and reaction of any testosterone present with the tagging reagent to form a mixture of a precipitate and a liquid solution. The liquid solution can then be separated from any precipitate and then analyzed for testosterone using liquid chromatography tandem mass spectrometry.

Methods, compositions, kits, and apparatuses for MS-based quantification of a target analyte (e.g., a peptide, a hormone) in a sample are provided for increasing the productivity and/or throughput of samples by reducing the time and/or cost associated with conventional techniques for external instrument calibration that typically utilize a series of calibrators that are sequentially run through the same analytical process as a batch of samples. In various aspects, calibration mixtures are provided containing a known quantity of a plurality of calibrants for a target analyte of interest, with each calibrant being distinguishable in the calibration mixture by mass spectrometry such that a complete calibration curve can be generated from a single external calibration run.

Methods, compositions, kits, and apparatuses for MS-based quantification of a target analyte (e.g., a peptide, a hormone) in a sample are provided for increasing the productivity and/or throughput of samples by reducing the time and/or cost associated with conventional techniques for external instrument calibration that typically utilize a series of calibrators that are sequentially run through the same analytical process as a batch of samples. In various aspects, calibration mixtures are provided containing a known quantity of a plurality of calibrants for a target analyte of interest, with each calibrant being distinguishable in the calibration mixture by mass spectrometry such that a complete calibration curve can be generated from a single external calibration run.

Disclosed is a method of measuring tacrolimus levels in a subject. In exemplary embodiments, the method comprises the steps of: collecting oral fluid from the subject; homogenizing the oral fluid; combining the homogenized oral fluid with a precipitating solvent; separating oral fluid components on a liquid chromatography column by gradient elution with a mixture of a solvent A and a solvent B, wherein the solvent A is about 2 mM ammonium acetate/0.1% (v/v) formic acid in water and solvent B is about 2 mM ammonium acetate/0.1% (v/v) formic acid in MeOH and wherein the amount of solvent B is increased from about 50% (v/v) to about 98% (v/v); and determining amount of tacrolimus in the oral fluid by mass spectrometry.

An automated method of monitoring a state of an analyzer is provided including a mass spectrometer (MS) with an electrospray ionization (ESI) source coupled to a liquid chromatography (LC) stream, including monitoring an electrospray ionization current of the ESI source and identifying a condition of multiple conditions of the analyzer based on the monitored ionization current of the ESI source, one of the conditions being a presence of a dead volume in a liquid chromatography stream of the analyzer downstream of an LC column of the LC stream.

A method of quantifying a target analyte by mass spectrometry includes obtaining a mass spectrometer signal comprising a first calibrator signal, comprising a second calibrator signal, and potentially comprising a target analyte signal from a single sample comprising a first known quantity of a first calibrator, comprising a second known quantity of a second calibrator, and potentially comprising a target analyte. The first known quantity and the second known quantity are different, and wherein the first calibrator, the second calibrator, and the target analyte are each distinguishable in the single sample by mass spectrometry. The method also includes quantifying the target analyte in the single sample using the first calibrator signal, the second calibrator signal, and the target analyte signal.

Provided are a novel internal standard useful in the measurement of androgens, a method capable of measuring the androgen in a highly selective and highly sensitive (accurate) manner using liquid chromatography mass spectrometry with simplified pretreatments, and a method for diagnosis of a disease using the androgen measurement method. The novel stable isotope-labeled compound is synthesized by performing reduction reaction in a specific solvent. An androgen is measured using this novel stable isotope-labeled compound as an IS.

A sensitive method for quantitating curcuminoids in biological and other samples is described wherein curcuminoids in the sample are derivatized to boron difluoride curcuminoid complexes then analyzed by liquid chromatography-mass spectroscopy.

Provided are methods for detecting chromogranin A by mass spectrometry. In another aspect, provided herein are methods for quantitating chromogranin A by mass spectrometry. In another aspect, provided herein are methods for prognosis of or measuring the size of neuroendocrine tumors by mass spectrometry.