TY - JOUR
T1 - Comparison of reversed-phase liquid chromatography-mass spectrometry with electrospray and atmospheric pressure chemical ionization for analysis of dietary tocopherols
AU - Lanina, Svetlana A.
AU - Toledo, Patricia
AU - Sampels, Sabine
AU - Kamal-Eldin, Afaf
AU - Jastrebova, Jelena A.
N1 - Funding Information:
We thank Kumari Ubhayasekera (SLU, Uppsala, Sweden) for her helpful assistance with the equipment for the experimental work. We are also grateful to Prof. Margaretha Jägerstad and Sodeif Azadmard Damirchi (SLU, Uppsala, Sweden) for their comments and valuable discussions on the manuscript. The sponsorship of Dr. Svetlana Lanina by the Swedish Institute, Dr. Afaf Kamal-Eldin by the Swedish Research Council, and financial support of the LC–MS equipment by the Knut and Alice Wallenberg Foundation are also acknowledged.
PY - 2007/7/20
Y1 - 2007/7/20
N2 - ESI and APCI ionization techniques in both negative and positive ion modes were evaluated for simultaneous LC-MS analysis of the four tocopherol homologues (α, β, γ and δ). The ESI and APCI ionization of tocopherols in positive ion mode was not efficient and proceeded via two competitive mechanisms, with the formation of protonated pseudo-molecular ions and molecular ions, which adversely influenced the repeatability of MS signal. Ionization in negative ion mode in both ESI and APCI was more efficient as it only produced target deprotonated pseudo-molecular ions. The APCI in negative ion mode showed larger linearity range, lower detection limits and was less sensitive to the differences in chemical structure of analytes and nature of applied solvents than negative ion ESI. Negative ion APCI was, therefore, chosen for the development of LC-MS method for simultaneous determination of the four tocopherols in foods. A baseline separation of the tocopherols was achieved on novel pentafluorophenyl silica-based column Fluophase PFP. The use of methanol-water (95:5, v/v) as a mobile phase was preferable to the use of acetonitrile-water due to considerable gain in MS signal. The limits of quantifications were 9 ng/mL for α-tocopherol, 8 ng/mL for β- and γ- and 7.5 ng/mL for δ-tocopherol when 2 μL was injected. This method was successfully applied to determination of tocopherols in sunflower oil and milk.
AB - ESI and APCI ionization techniques in both negative and positive ion modes were evaluated for simultaneous LC-MS analysis of the four tocopherol homologues (α, β, γ and δ). The ESI and APCI ionization of tocopherols in positive ion mode was not efficient and proceeded via two competitive mechanisms, with the formation of protonated pseudo-molecular ions and molecular ions, which adversely influenced the repeatability of MS signal. Ionization in negative ion mode in both ESI and APCI was more efficient as it only produced target deprotonated pseudo-molecular ions. The APCI in negative ion mode showed larger linearity range, lower detection limits and was less sensitive to the differences in chemical structure of analytes and nature of applied solvents than negative ion ESI. Negative ion APCI was, therefore, chosen for the development of LC-MS method for simultaneous determination of the four tocopherols in foods. A baseline separation of the tocopherols was achieved on novel pentafluorophenyl silica-based column Fluophase PFP. The use of methanol-water (95:5, v/v) as a mobile phase was preferable to the use of acetonitrile-water due to considerable gain in MS signal. The limits of quantifications were 9 ng/mL for α-tocopherol, 8 ng/mL for β- and γ- and 7.5 ng/mL for δ-tocopherol when 2 μL was injected. This method was successfully applied to determination of tocopherols in sunflower oil and milk.
KW - APCI
KW - ESI
KW - Fluorinated stationary phases
KW - LC-MS
KW - Tocopherols
UR - http://www.scopus.com/inward/record.url?scp=34250693717&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=34250693717&partnerID=8YFLogxK
U2 - 10.1016/j.chroma.2007.04.058
DO - 10.1016/j.chroma.2007.04.058
M3 - Article
C2 - 17512939
AN - SCOPUS:34250693717
SN - 0021-9673
VL - 1157
SP - 159
EP - 170
JO - Journal of Chromatography A
JF - Journal of Chromatography A
IS - 1-2
ER -