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Determination of Isotopic Ratios of L ‐Leucine and L ‐Phenylalanine and their Stable Isotope Labeled Analogues in Biological Samples by Gas Chromatography/Triple‐stage Quadrupole Mass Spectrometry
Author(s) -
Schweer Horst,
Watzer Bernhard,
Seyberth Hannsjörg W.,
Steinmetz Armin,
Schaefer Juergen R.
Publication year - 1996
Publication title -
journal of mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 1076-5174
DOI - 10.1002/(sici)1096-9888(199607)31:7<727::aid-jms347>3.0.co;2-o
Subject(s) - chemistry , phenylalanine , chromatography , mass spectrometry , chemical ionization , gas chromatography , detection limit , leucine , gas chromatography–mass spectrometry , selected ion monitoring , isotope dilution , triple quadrupole mass spectrometer , tandem mass spectrometry , ion , selected reaction monitoring , analytical chemistry (journal) , amino acid , ionization , organic chemistry , biochemistry
A gas chromatographic/triple‐stage quadrupole mass spectrometric (GC/MS/MS) method for measuring very low levels of enrichment of [5,5,5‐ 2 H 3 ]‐ L ‐leucine and [ ring ‐ 13 C 6 ]‐ L ‐phenylalanine in plasma and lipoprotein hydrolysates is described. The amino acids were derivatized to their N ‐heptafluorobutyryl isobutyl ester derivatives and the isotope ratio was determined by GC/MS/MS in the negative‐ion chemical ionization mode. Parent ions were the [M‐HF] ‐ ions and fragment ions used for quantification were [P‐2HF‐C 3 H 7 ] ‐ (leucine) and [P‐HF‐OC 4 H 9 ] ‐ (phenylalanine), respectively. The limit of quantification was about 10 pg of the labeled compound co‐eluting with 20 ng of the endogenous compound. The calibration curves were linear in the investigated range from 0.1% to 100% of the labeled compound. In biological samples, the higher selectivity of GC/MS/MS compared with GC/MS was demonstrated.