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Quantification of triacylglycerol regioisomers in oils and fat using different mass spectrometric and liquid chromatographic methods
Author(s) -
Leskinen Heidi,
Suomela JukkaPekka,
Kallio Heikki
Publication year - 2007
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.3090
Subject(s) - chemistry , atmospheric pressure chemical ionization , chromatography , mass spectrometry , chemical ionization , electrospray ionization , ion , analytical chemistry (journal) , structural isomer , collision induced dissociation , ionization , ion source , tandem mass spectrometry , organic chemistry
The regioisomers ( sn‐ ABA/ sn‐ AAB) of four triacylglycerols (TAGs), 18:2/18:2/18:1 (LLO), 18:2/18:1/18:1 (LOO), 16:0/18:1/18:1 (POO), and 16:0/16:0/18:1 (PPO), were quantified in lard, rapeseed oil, and sunflower seed oil by three different mass spectrometric methods using liquid chromatography (LC) and two different mass spectrometers. The ionization methods used were positive ion atmospheric pressure chemical ionization (APCI), positive ion electrospray ionization (ESI), and negative ion chemical ionization (NICI) with ammonia as the reagent gas. The LC/APCI‐MS results with two different instrumentation types, LC/ESI‐MS/MS and direct inlet ammonia NICI‐MS/MS, were compared. The LC/APCI‐MS method is based on the preferential formation of diacylglycerol (DAG) fragment ions during ionization by loss of sn ‐1/3 fatty acids from [M+H] + ions. Similar formation of the DAG ions from [M+NH 4 ] + ions by collision‐induced dissociation (CID) in the LC/ESI‐MS/MS method and the [M−HRCOOH−100] − ions from [M−H] − ions by CID in the direct inlet ammonia NICI‐MS/MS method is observed. These methods were found to be useful and reliable in determining the regioisomeric structure of TAGs. No statistically significant differences were found between the results obtained with these methods. For LLO, LOO, and POO the proportions of sn‐ ABA isomer calculated from the results from all four methods were in rapeseed oil 7.7 ± 6.5, 57.9 ± 3.3, and 4.5 ± 6.1%, respectively, and in sunflower seed oil 12.2 ± 6.9, 34.0 ± 5.2, and 1.4 ± 2.8%, respectively. The proportions of ABA of POO and PPO in lard were 95.3 ± 3.2 and 4.9 ± 5.6%, respectively. This study also proved that the LC/APCI‐MS/MS method examined is not applicable in the quantification of TAG regioisomers because the formation of DAG ions is not clearly dependent on the positional distribution of the fatty acids. Copyright © 2007 John Wiley & Sons, Ltd.