| 1. |
- Alwis, KU, et al.
(författare)
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Suppression of ionization and optimization of assay for 3-hydroxy fatty acids in house dust using ion-trap mass spectrometry
- 2006
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Ingår i: American Journal of Industrial Medicine. - : Wiley. - 0271-3586 .- 1097-0274. ; 49:4, s. 286-295
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Tidskriftsartikel (refereegranskat)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.
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| 2. |
- Chun, DTW, et al.
(författare)
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History and results of the two inter-laboratory round robin endotoxin assay studies on cotton dust
- 2006
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Ingår i: American Journal of Industrial Medicine. - : Wiley. - 0271-3586 .- 1097-0274. ; 49:4, s. 301-306
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Konferensbidrag (refereegranskat)abstract
- Background In the US cotton industry, airborne cotton dust levels are regulated, and other countries are moving to specify safety limits for airborne endotoxins. There is concern about potential respiratory health hazards associated with agricultural and otherorganic dusts. In laboratories, ranking which samples have high and low levels of endotoxin is usually in good agreement between laboratories. When different laboratories assay identical samples, the levels differ The objective of this research was to evaluate the intra- and inter-laboratory variability for 13 laboratories measuring endotoxin in cotton dust. Method Two inter-laboratory round robin endotoxin assay studies were conducted using cotton dust. In the first round robin, each laboratory used their normal in-house assay method and then used a common extraction protocol. In the second round robin, a common extraction protocol and endotoxin assay, kit was used. Results The inter-laboratory, results using a common extraction protocol showed reduced differences. Using the same extraction protocol and endotoxin assay kit, the intra-laboratory variation was small and inter-laboratory variation was reduced but not enough for inter-laboratory agreement. Most of the laboratories were able to discern between the high and low endotoxin concentration dusts. Conclusions Standardization has reduced the differences in results between laboratories and possibly further standardization may bring closer inter-laboratory agreement.
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| 3. |
- Reynolds, SJ, et al.
(författare)
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Comparison of endotoxin assays using agricultural dusts
- 2002
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Ingår i: AIHA journal : a journal for the science of occupational and environmental health and safety. - : Informa UK Limited. - 1542-8117. ; 63:4, s. 430-438
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Tidskriftsartikel (refereegranskat)
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| 4. |
- Reynolds, SJ, et al.
(författare)
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Interlaboratory evaluation of endotoxin analyses in agricultural dusts - comparison of LAL assay and mass spectrometry
- 2005
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Ingår i: Journal of Environmental Monitoring. - : Royal Society of Chemistry (RSC). - 1464-0325 .- 1464-0333. ; 7:12, s. 1371-1377
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Tidskriftsartikel (refereegranskat)abstract
- Endotoxin exposure is associated with wheeze and asthma morbidity, while early life exposure may reduce risk of allergy and asthma. Unfortunately, it is difficult to compare endotoxin results from different laboratories and environments. We undertook this study to determine if lipopolysaccharide ( LPS) extraction efficiency could account for differences among laboratories. We generated and collected aerosols from chicken and swine barns, and corn processing. We randomly allocated side-by-side filter samples to five laboratories for Limulus assay of endotoxin. Lyophilized aliquots of filter extracts were analyzed for 3-hydroxy fatty acids ( 3-OHFAs) as a marker of LPS using gas chromatography-mass spectrometry. There were significant differences in endotoxin assay and GC-MS ( LPS) results between laboratories for all dust types ( p < 0.01). Patterns of differences between labs varied by dust type. Relationships between assay and GC/MS results also depended on dust type. The percentages of individual 3-OHFA chain lengths varied across labs ( p < 0.0001) suggesting that each lab recovered a different fraction of the LPS available. The presence of large amounts of particle associated LPS and absence of a freezing thawing cycle were associated with lower correlations between LPS and bioactivity, consistent with an absence of Limulus response to cell-bound endotoxin. These data suggest that extraction methods affect endotoxin measurements. The LAL methods may be most suitable when comparing exposures within similar environments; GC-MS offers additional information helpful in optimizing sample treatment and extraction. GC-MS may be of use when comparing across heterogeneous environments and should be considered for inclusion in future studies of human health outcomes.
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