# US 10,309,972 B1 · C peptide detection by mass spectrometry > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,309,972 B1 - Document ID: US10309972B1 - Status: Granted - Kind: B1 - Application number: 16/259,606 - Filed: 2019-01-28 - Published: 2019-05-23 - Granted: 2019-06-04 - Earliest claimed: 2012-12-26 - Assignees: Quest Diagnostics Investments Incorporated - Applicants: Quest Diagnostics Investments Incorporated - Inventors: Nigel Clarke; Zhaohui Chen - Web page: https://patentgrep.com/patent/US10309972B1 ## CPC - G01N 33/6848: {Methods of protein analysis involving mass spectrometry} - G01N 30/7266: {by electric field, e.g. electrospray} - G01N 33/487: of liquid biological material - G01N 33/6851: {Methods of protein analysis involving laser desorption ionisation mass spectrometry} - G01N 33/74: involving hormones {or other non-cytokine intercellular protein regulatory factors such as growth factors, including receptors to hormones and growth factors} - H01J 49/0431: {for liquid samples (interfaces to liquid chromatographs G01N30/7233)} - G01N 2030/027: {Liquid chromatography} - G01N 2030/8831: {involving peptides or proteins} - G01N 2333/62: Insulins - G01N 2560/00: Chemical aspects of mass spectrometric analysis of biological material - H01J 49/005: {by collision with gas, e.g. by introducing gas or by accelerating ions with an electric field} - H01J 49/165: {Electrospray ionisation} - H01J 49/40: Time-of-flight spectrometers (H01J49/36 takes precedence) - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) - H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H) ## Abstract Methods are described for measuring the amount of C peptide in a sample. More specifically, mass spectrometric methods are described for detecting and quantifying C peptide in a sample utilizing on-line extraction methods coupled with tandem mass spectrometric or high resolution/high accuracy mass spectrometric techniques. ## Claims ### Claim 1 A method for determining the amount of C peptide in a sample by tandem mass spectrometry, the method comprising: (a) subjecting a sample suspected of containing C peptide to high performance liquid chromatography (HPLC) to obtain a fraction enriched in C peptide; (b) subjecting the enriched C peptide to an ionization source under conditions suitable to generate one or more C peptide ions detectable by mass spectrometry; (c) determining the amount of one or more C peptide ions by tandem mass spectrometry, wherein said determined ions comprise one or more fragment ions selected from the group of ions with mass to charge ratios consisting of 785.4±0.5 and 646.1±0.5; wherein the amount of ions determined in step (c) is related to the amount of a C peptide in said sample. ### Claim 2 (depends on 1) The method of claim 1, wherein said HPLC is 1-D HPLC. ### Claim 3 (depends on 1) The method of claim 1, wherein said ionization source is an electrospray (ESI) ionization source. ### Claim 4 (depends on 1) The method of claim 1, wherein further comprising subjecting the sample suspected of containing C peptide to solid phase extraction (SPE). ### Claim 5 (depends on 1) The method of claim 1, wherein said sample comprises a biological sample. ### Claim 6 (depends on 1) The method of claim 1, wherein said sample is from a human. ### Claim 7 (depends on 1) The method of claim 1, wherein said sample comprises a body fluid sample. ### Claim 8 (depends on 1) The method of claim 1, wherein said sample comprises plasma or serum. ### Claim 9 A method for determining the amount of C peptide in a sample by tandem mass spectrometry, the method comprising: (a) subjecting a sample suspected of containing C peptide to solid phase extraction (SPE) and 1-D high performance liquid chromatography (1-D HPLC) to obtain a fraction enriched in C peptide; (b) subjecting the fraction enriched C peptide to an ionization source under conditions suitable to generate one or more C peptide ions detectable by mass spectrometry; (c) determining the amount of one or more C peptide ions by tandem mass spectrometry, wherein said determined ions comprise one or more fragment ions selected from the group of ions with mass to charge ratios consisting of 785.4±0.5 and 646.1±0.5; wherein the amount of ions determined in step (c) is related to the amount of a C peptide in said sample. ### Claim 10 (depends on 9) The method of claim 9, wherein relating said ions determined in step (c) to the amount of C peptide in the sample comprises summing the amount of said two or more fragment ions. ### Claim 11 (depends on 9) The method of claim 9, wherein said ionization source is an electrospray (ESI) ionization source. ### Claim 12 (depends on 9) The method of claim 9, wherein said SPE and 1-D HPLC are conducted with on-line processing. ### Claim 13 (depends on 9) The method of claim 9, wherein said sample comprises a biological sample. ### Claim 14 (depends on 9) The method of claim 9, wherein said sample is from a human. ### Claim 15 (depends on 9) The method of claim 9, wherein said sample comprises a body fluid sample. ### Claim 16 (depends on 9) The method of claim 9, wherein said sample comprises plasma or serum. ### Claim 17 (depends on 9) The method of claim 9, wherein said mass spectrometry is high resolution/high accuracy mass spectrometry. ### Claim 18 (depends on 17) The method of claim 17, wherein said high resolution/high accuracy mass spectrometry is conducted at a FWHM of 10,000 and a mass accuracy of 50 ppm. ### Claim 19 (depends on 17) The method of claim 17, wherein said high resolution/high accuracy mass spectrometer is a high resolution/high accuracy time-of-flight (TOF) mass spectrometer.