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Suppression of ionization and optimization of assay for 3-hydroxy fatty acids in house dust using ion-trap mass spectrometry

Alwis, KU ; Larsson, Lennart LU and Milton, DK (2006) In American Journal of Industrial Medicine 49(4). p.286-295
Abstract
Background 3-Hydroxy fatty acids (3-OHFAs), components of lipid A of gram-negative bacteria are useful chemical markers of endotoxin. Methods We analyzed 3-OHFAs in house dust as trimethylsilyl (TMS) methyl ester derivatives in the electron impact ionization mode using gas chromatography ion-trap mass spectrometry. Linear calibrations with r > 0.995 were observed for all the 3-OHFA methyl ester external standards. Results Recovery efficiency experiments with house dust demonstrated that accurate quantification requires calibration curves to be subjected to phase separation and solid phase extraction (SPE) because of differing clean-up losses according to chain length of 3-OHFAs. Recovery experiments also demonstrated interference with... (More)
Background 3-Hydroxy fatty acids (3-OHFAs), components of lipid A of gram-negative bacteria are useful chemical markers of endotoxin. Methods We analyzed 3-OHFAs in house dust as trimethylsilyl (TMS) methyl ester derivatives in the electron impact ionization mode using gas chromatography ion-trap mass spectrometry. Linear calibrations with r > 0.995 were observed for all the 3-OHFA methyl ester external standards. Results Recovery efficiency experiments with house dust demonstrated that accurate quantification requires calibration curves to be subjected to phase separation and solid phase extraction (SPE) because of differing clean-up losses according to chain length of 3-OHFAs. Recovery experiments also demonstrated interference with detection of C16:0 by the ion trap, which may be due to suppression of ionization by a constituent in house dust. Interference was overcome by injecting 1:4 dilutions of derivatized samples. The range of recoveries was 89.3%-111.5%.for 3-OHFAs added to house dust. The reproducibility of injections was high (CV for C14:0 = 2.36%). The limit of detection (LOD) was 0.15 ng/mg for each 3-OHFA. Conclusions The modifications we made included: use of 3-hydroxy C11:0 and C13:0 methyl esters as internal standards, subjecting calibration standards to phase separation and SPE; addition of water to phase separation; addition of 1-pentadecanol as a carrier; injecting 1:4 diluted TMS derivatives of 3-OHFAs; and monitoring both m/z 131 and 133 ions to improve stability of area measurements for product ions. This method of optimization establishes an appropriate technique for quantification of 3-OHFAs in house dust. (Less)
Please use this url to cite or link to this publication:
author
; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
recovery, GCMSMS, house dust, 3-hydroxy fatty acids, endotoxin, suppression of ionization, efficiency
in
American Journal of Industrial Medicine
volume
49
issue
4
pages
286 - 295
publisher
John Wiley and Sons
external identifiers
  • wos:000236824900008
  • pmid:16550567
  • scopus:33646032361
ISSN
0271-3586
DOI
10.1002/ajim.20263
language
English
LU publication?
yes
id
ee116c33-c6d7-4bcf-84ee-8be34c58392e (old id 414241)
date added to LUP
2016-04-01 12:03:03
date last changed
2021-01-06 03:50:53
@article{ee116c33-c6d7-4bcf-84ee-8be34c58392e,
  abstract     = {Background 3-Hydroxy fatty acids (3-OHFAs), components of lipid A of gram-negative bacteria are useful chemical markers of endotoxin. Methods We analyzed 3-OHFAs in house dust as trimethylsilyl (TMS) methyl ester derivatives in the electron impact ionization mode using gas chromatography ion-trap mass spectrometry. Linear calibrations with r > 0.995 were observed for all the 3-OHFA methyl ester external standards. Results Recovery efficiency experiments with house dust demonstrated that accurate quantification requires calibration curves to be subjected to phase separation and solid phase extraction (SPE) because of differing clean-up losses according to chain length of 3-OHFAs. Recovery experiments also demonstrated interference with detection of C16:0 by the ion trap, which may be due to suppression of ionization by a constituent in house dust. Interference was overcome by injecting 1:4 dilutions of derivatized samples. The range of recoveries was 89.3%-111.5%.for 3-OHFAs added to house dust. The reproducibility of injections was high (CV for C14:0 = 2.36%). The limit of detection (LOD) was 0.15 ng/mg for each 3-OHFA. Conclusions The modifications we made included: use of 3-hydroxy C11:0 and C13:0 methyl esters as internal standards, subjecting calibration standards to phase separation and SPE; addition of water to phase separation; addition of 1-pentadecanol as a carrier; injecting 1:4 diluted TMS derivatives of 3-OHFAs; and monitoring both m/z 131 and 133 ions to improve stability of area measurements for product ions. This method of optimization establishes an appropriate technique for quantification of 3-OHFAs in house dust.},
  author       = {Alwis, KU and Larsson, Lennart and Milton, DK},
  issn         = {0271-3586},
  language     = {eng},
  number       = {4},
  pages        = {286--295},
  publisher    = {John Wiley and Sons},
  series       = {American Journal of Industrial Medicine},
  title        = {Suppression of ionization and optimization of assay for 3-hydroxy fatty acids in house dust using ion-trap mass spectrometry},
  url          = {http://dx.doi.org/10.1002/ajim.20263},
  doi          = {10.1002/ajim.20263},
  volume       = {49},
  year         = {2006},
}