Mass spectrometric determination of fatty acids
The invention relates to the detection of fatty acids. In a particular aspect, the invention relates to methods for detecting very long chain fatty acids and branched chain fatty acids by mass spectrometry.
1. A method for determining an amount of one or more very long chain fatty acids (VLCFA) and/or branched chain fatty acids (BCFA) in a sample by mass spectrometry, the method comprising:
(a) subjecting the sample to an atmospheric pressure chemical ionization (APCI) source to generate one or more VLCFA and/or BCFA ions detectable by mass spectrometry;
(b) determining the amount of the one or more VLCFA and/or BCFA ions by mass spectrometry; and
(c) relating the amount of the one or more VLCFA and/or BCFA ions determined in step (b) to the amount of the VLCFA and/or BCFA in the sample;
wherein the VLCFA and/or BCFA are underivatized prior to ionization.
2. The method of claim 1 , wherein said one or more VLCFA are selected from the group consisting of docosanoic acid, tetracosanoic acid, and hexacosanoic acid.
3. The method of claim 2 , wherein said one or more VLCFA ions comprise ions with a mass to charge ratio (m/z) of 339.3±0.5.
4. The method of claim 2 , wherein said one or more VLCFA ions comprise ions with a mass to charge ratio (m/z) of 367.3±0.5.
5. The method of claim 2 , wherein said one or more VLCFA ions comprise ions with a mass to charge ratio (m/z) of 395.4±0.5.
6. The method of claim 1 , wherein said one or more BCFA are selected from the group consisting of pristanic acid and phytanic acid.
7. The method of claim 6 , wherein said one or more BCFA ions comprise ions with a mass to charge ratio (m/z) of 297.3±0.5.
8. The method of claim 6 , wherein said one or more BCFA ions comprise ions with a mass to charge ratio (m/z) of 311.2±0.5.
9. The method of claim 1 , wherein the APCI source is operating in negative ionization mode.
10. The method of claim 1 , wherein the amounts of one or more VLCFA and one or more BCFA are separately determined.
11. The method of claim 10 , wherein said one or more VLCFA are selected from the group consisting of docosanoic acid, tetracosanoic acid, and hexacosanoic acid, and wherein said one or more BCFA are selected from the group consisting of pristanic acid and phytanic acid.
12. The method of claim 1 , wherein said sample comprises a human sample comprising plasma or serum.
13. The method of claim 1 , wherein said sample is subjected to a hydrolyzing agent prior to ionization.
14. The method of claim 1 , wherein the sample is subjected to liquid/liquid extraction prior to ionization.
15. The method of claim 1 , wherein the one or more VLCFA and/or BCFA are subjected to a liquid chromatography column prior to ionization.
16. A method of determining an amount of one or more very long chain fatty acids (VLCFA) and/or branched chain fatty acids (BCFA) in a plasma or serum sample from a human patient comprising:
(a) subjecting the sample to a hydrolyzing agent to generate a hydrolyzed sample;
(b) purifying the hydrolyzed sample to generate a purified sample;
(c) subjecting the purified sample to an atmospheric pressure chemical ionization (APCI) source to generate one or more VLCFA and/or BCFA ions detectable by mass spectrometry;
(d) determining the amount of the one or more VLCFA and/or BCFA ions by mass spectrometry; and
(e) relating the amount of the one or more VLCFA VLCFA and/or BCFA ions determined in step (d) to the amount of the VLCFA and/or BCFA in the sample;
wherein the VLCFA and/or BCFA are underivatized prior to ionization.
17. The method of claim 16 , wherein said one or more VLCFA are selected from the group consisting of docosanoic acid, tetracosanoic acid, and hexacosanoic acid.
18. The method of claim 17 , wherein said one or more VLCFA ions comprise ions with a mass to charge ratio (m/z) of 339.3±0.5.
19. The method of claim 17 , wherein said one or more VLCFA ions comprise ions with a mass to charge ratio (m/z) of 367.3±0.5.
20. The method of claim 17 , wherein said one or more VLCFA ions comprise ions with a mass to charge ratio (m/z) of 395.4±0.5.
21. The method of claim 16 , wherein said one or more BCFA are selected from the group consisting of pristanic acid, and phytanic acid.
22. The method of claim 21 , wherein said one or more BCFA ions comprise ions with a mass to charge ratio (m/z) of 297.3±0.5.
23. The method of claim 21 , wherein said one or more BCFA ions comprise ions with a mass to charge ratio (m/z) of 311.2±0.5.
24. The method of claim 16 , wherein the APCI source is operating in negative ionization mode.
25. The method of claim 16 , wherein the amounts of one or more VLCFA and one or more BCFA are separately determined.
26. The method of claim 25 , wherein said one or more VLCFA are selected from the group consisting of docosanoic acid, tetracosanoic acid, and hexacosanoic acid, and wherein said one or more BCFA are selected from the group consisting of pristanic acid and phytanic acid.
27. The method of claim 16 , wherein said sample comprises plasma or serum.
28. The method of claim 16 , wherein said sample is subjected to a hydrolyzing agent prior to ionization.
29. The method of claim 16 , wherein the sample is subjected to liquid/liquid extraction prior to ionization.
30. The method of claim 16 , wherein the one or more VLCFA and/or BCFA are subjected to a liquid chromatography column prior to ionization.
31. The method of claim 16 , wherein the human patient is suspected of having a peroxisomal disorder.