Methods and systems for measuring serotonin in a sample

1. A method for determining amount of serotonin released by a biological sample, the method comprising:

incubating at least one sample comprising the biological sample, heparin and donor platelets for a period of time to release serotonin from the donor platelets, thereby generating at least one incubated sample;

chromatographically separating serotonin from other components in the at least one incubated sample using liquid chromatography; and

analyzing the chromatographically separated serotonin by tandem mass spectrometry to determine the amount of released serotonin in the at least one sample relative to a total amount of serotonin available in the donor platelets.

2. The method of claim 1 , wherein the analyzing includes ionizing the chromatographically separated serotonin using electrospray ionization, atmospheric pressure chemical ionization, or atmospheric pressure photoionization.

3. The method of claim 1 , wherein the tandem mass spectrometry uses a quadrupole mass spectrometer.

4. The method of claim 3 , wherein the quadrupole mass spectrometer is a triple quadrupole mass spectrometer.

5. The method of claim 4 , wherein the analyzing includes:

detecting intact serotonin ion in first quadrupole;

fragmenting the intact serotonin ion in second quadrupole to yield one or more serotonin fragment ions; and,

detecting the one or more serotonin fragment ions in third quadrupole.

6. The method of claim 1 , wherein the analyzing comprises ionizing the chromatographically separated serotonin to produce one or more serotonin ions, comprising at least one of a precursor ion of 160.1±0.5 mass-to-charge ratio, or a product ion of 115.1±0.5, 132.1±0.5, 105.1±0.5, or 89.1±0.5 mass-to-charge ratio.

7. The method of claim 1 , wherein the at least one sample is at least two samples, wherein a first one or more of the at least two samples comprises heparin at a first concentration, and a second one or more of the at least two samples comprises heparin at a second concentration different from the first concentration.

8. The method of claim 7 , wherein the first concentration of heparin is 0.001 to 1 U/mL, and the second concentration of heparin is 50 to 1000 U/mL.

9. The method of claim 1 , wherein the biological sample is a serum sample or a plasma sample.

10. The method of claim 9 , wherein the serum sample or the plasma sample is obtained from a heparin-treated subject, or a subject suspected of having heparin-induced thrombocytopenia (HIT).

11. The method of claim 1 , wherein the donor platelets are washed and partially purified prior to the incubating the at least one sample.

12. The method of claim 1 , wherein the donor platelets are serotonin-incubated donor platelets.

13. The method of claim 12 , wherein the serotonin-incubated donor platelets are incubated with serotonin prior to the incubating the at least one sample.

14. The method of claim 12 , wherein the serotonin-incubated donor platelets are incubated with stable isotopically-labeled serotonin prior to the incubating the at least one sample.

15. The method of claim 1 , further comprising partially purifying the at least one incubated sample prior to the chromatographically separating serotonin from the other components in the at least one incubated sample.

16. The method of claim 1 , wherein the liquid chromatography includes reverse phase column chromatography.

17. The method of claim 1 , wherein the liquid chromatography includes using two or more liquid chromatography columns in parallel, where the two or more liquid chromatography columns are connected inline to a single mass spectrometer.

18. A system for determining amount of serotonin released by a biological sample, the system comprising:

a station for incubating at least-one sample comprising the biological sample, heparin and donor platelets for a period of time to release serotonin from the donor platelets, thereby generating at least one incubated sample;

a station for chromatographically separating serotonin from other components in the at least one incubated sample using liquid chromatography; and

a station for analyzing the chromatographically separated serotonin by tandem mass spectrometry to determine amount of released serotonin in the at least one sample relative to a total amount of serotonin available within the donor platelets.

19. The system of claim 18 , wherein the station for analyzing the chromatographically separated serotonin by tandem mass spectrometry comprises a quadrupole mass spectrometer.

20. The system of claim 19 , wherein the quadrupole mass spectrometer is a triple quadrupole mass spectrometer.

21. The system of claim 18 , wherein the station for chromatographically separating serotonin comprises at least one reverse phase column.

22. The system of claim 18 , wherein the station for chromatographically separating serotonin comprises two or more liquid chromatography columns in parallel, wherein the two or more liquid chromatography columns are connected inline to a single mass spectrometer.

23. The system of claim 18 , further comprising a station for partially purifying the at least one incubated sample prior to chromatographically separating serotonin from other components in the at least one incubated sample.

24. The system of claim 18 , wherein the at least one sample is at least two samples, wherein a first one or more of the at least two samples comprises heparin at a first concentration, and a second one or more of the at least two samples comprises heparin at a second concentration different from the first concentration.

25. The system of claim 24 , wherein the first concentration of heparin is 0.001 to 1 U/mL, and the second concentration of heparin is 50 to 1000 U/mL.