The invention generally relates to systems and methods for quantifying an analyte extracted from a sample. In certain embodiments, the invention provides methods that involve introducing a solvent into a capillary, introducing the capillary into a vessel including a sample such that a portion of the sample is introduced into the capillary, moving the sample and the solvent within the capillary to induce circulation within the sample and the solvent, thereby causing the analyte to be extracted from the sample and into the solvent, analyzing the analyte that has been extracted from the sample, and quantifying the analyte. In certain embodiments, the quantifying step is performed without knowledge of a volume of the sample and/or solvent.

A method of mass and/or ion mobility spectrometry is disclosed that includes ionising analyte from a sample so as to generate a plurality of ions, separating precursor ions from first fragment and/or other ions of the plurality of ions, fragmenting or reacting at least some of the precursor ions using a fragmentation, reaction or collision device so as to generate second fragment ions, and then analysing at least some ions that emerge from the fragmentation, reaction or collision device. The sample is classified and/or identified based on the analysis of the second fragment ions.

Provided are methods for determining the amount of tamoxifen and its metabolites in a sample by mass spectrometry. In some aspects, the methods provided herein determine the amount of N-Desmethyl Tamoxifen. In some aspects, the methods provided herein determine the amount of N-Desmethyl Tamoxifen and other tamoxifen metabolites. In some aspects, the methods provided herein determine the amount of tamoxifen, N-Desmethyl Tamoxifen, and other tamoxifen metabolites.

Provided are methods for determining the amount of lacosamide in a sample using mass spectrometry. The methods generally involve ionizing lacosamide in a sample and detecting and quantifying the amount of the ion to determine the amount of lacosamide in the sample.

A method for the in situ derivatization of at least one biogenic amine, precursor, or metabolite thereof in an isolated aqueous sample includes the steps of: (i) contacting the sample with a propionic anhydride/acetonitrile solution in the presence of a phosphate buffer having a pH in the range of 7.0 to 9.0 and allowing the conversion of amine and/or hydroxyl moieties of the biogenic amine, precursor, or metabolite thereof to form a propionyl derivative of the biogenic amine; followed by (ii) adding to the reaction mixture obtained in step (i) a carbodiimide compound and an electrophilic amine-containing compound, and allowing the carbodiimide-mediated derivatization of carboxylic acid moieties of the biogenic amine, precursor, or metabolite thereof.

Provided are methods of detecting the presence or amount of a dihydroxyvitamin D metabolite in a sample using mass spectrometry. The methods generally comprise ionizing a dihydorxyvitamin D metabolite in a sample and detecting the amount of the ion to determine the presence or amount of the vitamin D metabolite in the sample. In certain preferred embodiments the methods include immunopurifying the dihydroxyvitamin D metabolites prior to mass spectrometry. Also provided are methods to detect the presence or amount of two or more dihydroxyvitamin D metabolites in a single assay.

Provided are methods of detecting the presence or amount of a vitamin D metabolite in a sample using mass spectrometry. The methods generally directed to ionizing a vitamin D metabolite in a sample and detecting the amount of the ion to determine the presence or amount of the vitamin D metabolite in the sample. Also provided are methods to detect the presence or amount of two or more vitamin D metabolites in a single assay.

A process of determining whether a patient with a disease or disorder will be responsive to a drug, used to treat the disease or disorder, including obtaining a test spectrum produced by a mass spectrometer from a serum produced from the patient. The test spectrum may be processed to determine a relation to a group of class labeled spectra produced from respective serum from other patients having the or similar clinical stage same disease or disorder and known to have responded or not responded to the drug. Based on the relation of the test spectrum to the group of class labeled spectra, a determination may be made as to whether the patient will be responsive to the drug.

A method for analyzing aromatic compounds, and a reagent kit for LC-MS analysis of aromatic compounds. The method includes preparing a diazonium reagent, contacting aromatic compounds in a sample with the diazonium reagent to form an analyte; and measuring an amount or ratio of the analyte. The reagent kit includes a diazonium reagent, wherein the diazonium reagent includes (i) a diazonium salt that contains a diazonium ion; (ii) an amine and nitrous acid; and/or (iii) a nitrite and an acid.

The present invention relates to a metabolic biomarker set for use in assessing breast cancer in a mammalian subject. In particular, the invention relates to a metabolic biomarker set for screening and/or diagnosing breast cancer, the metabolic biomarker set comprising at least (a) one amino acid selected from glutamine, glutamate and serine, and one lipid, or (b) glutamine and glutamate. Further, the invention relates to a metabolic biomarker set for prediction of therapeutic response to breast cancer neoadjuvant chemotherapy. Further, the invention relates to a metabolic biomarker set for assessing biochemical reflection of breast cancer tumor activity. Further, the invention relates to a metabolic biomarker set for subclassification between intrinsic breast cancer tumor subtypes. Moreover, the present invention relates to a method for assessing breast cancer, which comprises obtaining a biological sample, preferably blood, from a mammalian subject and measuring in the biological sample the amount and/or ratios of metabolites. By employing the specific biomarkers and the method according to the present invention it becomes possible to more properly and reliably assess breast cancer.