Method and device for separating metabolites or stereoisomers
A method of quantifying the amount of at least two analytes A1 and A2 involving (a) adding at least one salt (S) to at least a portion (P1) of the sample comprising the at least two analytes A1 and A2, (b) ionizing at least a portion of the sample according to (a) thereby forming an analyte flow comprising the analytes A1 and A2 in ionized form, (c) separating the ionized analytes A1 and A2 from each other by using at least one ion mobility separator ( 124 ), wherein the analyte flow according to (b) at least partially passes through the ion mobility separator ( 124 ), and (d) quantifying the amount of the separated ionized analytes obtained according to (c), wherein A1 is a pharmaceutically active compound C or derivative thereof and A2 is a metabolite or stereoisomer of C.
1. A method of quantifying the amount of at least two analytes A1 and A2 comprised in a sample, comprising:
(a) adding at least one salt (S) being a monovalent cation of an alkaline metal or a transition metal or of an organic compound, and wherein, when the salt is a monovalent cation of an organic compound, the cation is selected from the group consisting of pyridine, pyrrolindin, imidazole and morpholin to at least a portion (P1) of the sample comprising the at least two analytes A1 and A2,
(b) ionizing in the presence of the at least one salt (S) at least a portion of the sample according to (a) thereby forming an analyte flow comprising the analytes A1 and A2 in ionized form,
(c) separating the ionized analytes A1 and A2 from each other by using at least one ion mobility separator, wherein the analyte flow according to (b) at least partially passes through the ion mobility separator, and
(d) quantifying the amount of the separated ionized analytes obtained according to (c), wherein A1 is a pharmaceutically active compound C or derivative thereof and A2 is an epimer of C, and wherein A1 has a log P value of greater than 0.
2. The method according to claim 1 , wherein said log P value of A1 is the octanol/water partitioning coefficient of A1.
3. The method according to claim 1 , wherein A1 is a vitamin D and wherein A2 is 3-epi-25-hydroxy vitamin D3.
4. The method according to claim 1 , wherein the sample is a blood, plasma or serum sample derived from a raw sample comprising the analytes A1 and A2 and matrix constituents, and wherein the method further comprises removing at least part of the matrix constituents before performing step (a) to give the sample according to (a).
5. The method according to claim 1 , wherein the salt (S) is a salt of a monovalent cation selected from the group consisting of Li+, Na+, K+, Rb+, Cs+, Ag+, Cu+, Ni+, Mn+, pyridinium and mixtures of two or more thereof.
6. The method according to claim 1 , wherein the sample according to (a) comprises the added salt (S) in a concentration in the range of from 25 micromol/L to 2 mmol/L.
7. The method according to claim 1 , wherein in (a) at least one further additive is added.
8. The method according to claim 1 , wherein in (a) at least one acid is additionally added.
9. The method according to claim 1 , wherein step (b) comprises using at least one ionizer, wherein the ionizer is used for at least partially ionizing the sample and thereby generating the analyte flow before or during entering the ion mobility separator.
10. The method according to claim 1 , wherein the ion mobility separator is a field-asymmetric waveform ion mobility separator.
11. The method according to claim 1 , wherein the ion mobility separator comprises at least one ion mobility spectrometer or wherein the ion mobility separator is part of at least one ion mobility spectrum spectrometer, wherein the ion mobility spectrum spectrometer comprises at least one field-asymmetric waveform ion mobility spectrometer.
12. The method according to claim 1 , wherein step (c) further comprises using at least one mass spectrometer for analyzing an output flow of the ion mobility separator.
13. The method according to claim 12 , wherein the mass spectrometer comprises one or more of: a tandem mass spectrometer, an ion trap mass spectrometer, a time-of-flight mass spectrometer, a Fourier transformation mass spectrometer, an orbitrap mass spectrometer, a quadrupole mass spectrometer.
14. A method of using at least one salt (S) as a modifier in a process for quantifying the amount of at least two analytes A1 and A2 comprised in a sample by ion mobility spectrometry, the method comprising ionizing the sample in the presence of the at least one salt (S), wherein the salt is a monovalent cation of an alkaline metal or a transition metal or of an organic compound, and wherein, when the salt is a monovalent cation of an organic compound, the cation is selected from the group consisting of pyridine, pyrrolindin, imidazole and morpholin, wherein A1 is a pharmaceutically active compound C or a derivative thereof and A2 is an epimer of C, and wherein A1 has a log P value of greater than 0.
15. The method according to claim 1 , wherein A1 has a log P value of greater than 2.
16. The method according to claim 1 , wherein A1 is 25-hydroxy-vitamin D3 and wherein A2 is 3-epi-25-hydroxy vitamin D3.
17. The method according to claim 1 , wherein in (a) at least one further additive is added selected from the group consisting of acetonitrile, methanol, ethanol, propanol and butanol.
18. The method according to claim 1 , wherein in (a) at least formic acid is additionally added.
19. The method according to claim 1 , wherein A1 is a vitamin D and wherein A2 is 3-epi-25-hydroxy vitamin D3, and wherein the salt (S) is a salt of a monovalent cation selected from the group consisting of Li+, Na+, K+, Rb+, Cs+, Ag+, Cu+, Ni+, Mn+, pyridinium and mixtures of two or more thereof.
20. The method according to claim 14 , wherein A1 has a log P value of greater than 2.
21. A method of quantifying the amount of at least two analytes A1 and A2 comprised in a sample, comprising:
(a) adding at least one salt (S) being a monovalent cation selected from the group consisting of Li+, Na+, K+, Rb+, Cs+, Ag+, Cu+, Ni+, Mn+, pyridinium and combinations thereof to at least a portion (P1) of the sample comprising the at least two analytes A1 and A2,
(b) ionizing in the presence of the at least one salt (S) at least a portion of the sample according to (a) thereby forming an analyte flow comprising the analytes A1 and A2 in ionized form,
(c) separating the ionized analytes A1 and A2 from each other by using at least one ion mobility separator, wherein the analyte flow according to (b) at least partially passes through the ion mobility separator,
(d) quantifying the amount of the separated ionized analytes obtained according to (c), wherein A1 is a pharmaceutically active compound C or derivative thereof and A2 is an epimer of C, and wherein A1 has a log P value in the range of from 0 to 12.