Ammonium acetate

The following chemicals and reagents were used for the analyses: methanol (99.95%), acetonitrile (99.99%), and ammonium acetate, purchased from Carl Roth GmbH and Co. KG (Germany); tetrahydrofuran (99.7%) from VWR International GmbH (Germany); methyl tert-butyl ether (99.8%) from Geyer GmbH & Co. KG (Germany); formic acid (98-100%), dichloromethane (99.9%), isopropanol (99.95%), Tween 20 from Serva Electrophoresis GmbH (Germany); methyl salicylate (MeSA) and methyl jasmonate (MeJA) from Merck AG (Germany); C7-C40 alkanes (Supelco-49452-U), terpinenes (α, δ, ɣ), trans-β-ocimene, n-hexanal, nonanal, nerolidol, β-pinene, myrcene, sabinene, phellandrenes (α, β), β-caryophyllene and β-carotene from Sigma-Aldrich Chemie GmbH (Germany); α-carotene, (9Z)-neoxanthin, zeaxanthin, violaxanthin from CaroteNature GmbH (Switzerland). Lutein was isolated from Tagetes erecta by flash chromatography. After saponification, the lutein was purified and crystallized. Its structure was elucidated by NMR and high-resolution mass spectrometry (Baldermann, 2008 ), and compared to the authentic reference compound purchased from Sigma-Aldrich Chemie GmbH (Germany).

Dry powder of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) was from Avanti Polar Lipids (Alabaster, AL). Ubiquinone-10 (Q10), methyl-tert-buthylether (MTBE), chloroform, 2,2,6,6-tetramethyl-4-piperidone hydrochloride (TEMPD–HCl, purity 98.4%), HEPES buffer, and Ammonium formate (MS-grade) were purchased from Sigma-Aldrich. Potassium ferrocyanide (K₄[Fe(CN)₆]), disodium hydrogen phosphate (Na₂HPO₄), and sodium dihydrogen phosphate (NaH₂PO₄) were obtained from Merck. Ammonium acetate was purchased from Roth. Sodium sulfate was purchased from VWR. Formic acid (MS grade) was obtained from Fluka. 5-tert-Butoxycarbonyl-5-methyl-1-pyrroline-N-oxide (BMPO, purity 99.9%) was purchased from Dojindo Laboratoire. Water, methanol, isopropanol (all from ChemSolute) were of MS grade. All chemicals employed were used without further purification.

Solvents for LC–MS/MS, such as acetonitrile (ACN), methanol, and water were HPLC or MS grade and were obtained from Carl Roth (Karlsruhe, Germany). All other chemicals used were HPLC or analytical grade (p.a.). The solvent additives ammonium hydroxide and ammonium acetate were purchased from Carl Roth and Honeywell Riedel-de Haën (Seelze, Germany), respectively. Matrices for MALDI-TOF MS, such as DAN, 9-aminoacridine (AA), α-cyano-4-hydroxycinnamic acid (CHCA), 2,4,6-trihydroxyacetophenone (THAP), and multiwalled carbon nanotubes, as well as standard explosive solutions of 2-amino-4,6-dinitrotoluene (2-ADNT), 4-amino-2,6-dinitrotoluene (4-ADNT), 1,3,5-trinitrobenzene (TNB), 1,3-dinitrobenzene (DNB), 2-nitrotoluene (NT), and 5-chloro-2,4-dinitrotoluene (CDNT) were obtained from Sigma-Aldrich (St Louis, MO, USA). TNT, 2,4-dinitrotoluene (2,4-DNT), and 2,6-dinitrotoluene (2,6-DNT) were provided by terracon (Jüterbog, Germany). Mefenamic acid and chlorogenic acid were from Sigma-Aldrich. Citric acid was purchased from Merck (Darmstadt, Germany). Standard stock solutions were prepared as a mixture of each explosive at 50 ng/μL (TNT, 2-ADNT, 4-ADNT, 2,4-DNT, 2,6-DNT, TNB, DNB, NT) in ACN for LC–MS/MS measurements. For MALDI-TOF MS, a stock solution consisting of TNT, TNB, DNB, NT, 1:10 2-ADNT/4-ADNT, and 1:1 2,4-DNT/2,6-DNT each at 100 ng/μL in ACN was used.