title: [Analysis of meibum by gas chromatography-mass spectrometry].
abstract: OBJECTIVE
  To analyze and identify the meibum from healthy individuals and patients with meibomian gland dysfunction (MGD) by gas chromatography-mass spectrometry (GC-MS).
  
  
  METHODS
  Case-control study. The meibum from twenty healthy persons and nineteen MGD patients was separated and analyzed by GC-MS. GC conditions were: column: DB-5 MS (30 m × 0.25 mm × 0.25 µm) capillary column, carrier gas: He, flow rate: 1.0 ml/min, injection amount: 1 ml. MS conditions were: MS ionization mode: EI, electron impact source electron energy: 70 eV, ion source temperature: 200 °C, electron multiplier voltage of 1.10 kV, solvent delay time: 1.00 min, scanning mode: San, scanning range m/z 20-500 aum. The components of meibum were identified by El mass fragmentation and the standard substance in the database. The relative content of the components was calculated by the method of chromatographic peak area normalization.
  
  
  RESULTS
  In the 39 samples that were analyzed by GC-MS, 102 chromatography peaks were separated, and 23 compounds were identified, including 3 alkanes, 4 alkenes, 2 alcohols, 1 aromatic hydrocarbon, 7 esters, 4 fatty acids, 1 amide, and 1 phenol. However, there was no corresponding physical mass library information in the remaining 79 GC peaks, and no identification could be performed. The relative concentration level of palmitic acid, stearic acid, and squalene in the MGD group was significantly lower than that in the healthy controls (U = -2.086, -2.027, -2.866, P < 0.05).
  
  
  CONCLUSIONS
  Meibum has a wide variety of components, the structures are complex, and the components in different individuals vary greatly. Palmitic acid, stearic acid, and squalene levels were significantly decreased in MGD patients compared to the healthy group, suggesting that MGD is related to changes of the meibum components.
authors.affiliation: Department of Ophthalmology, Second Affiliated Hospital of Fu jian Medical University, Fuzhou 362000, China.
authors.forename: Xueqing
authors.initials: X
authors.lastname: Dong
authors.affiliation: Email: gaoyingying1968@163. com.
authors.forename: Yingying
authors.initials: Y
authors.lastname: Gao
authors.forename: Mingfan
authors.initials: M
authors.lastname: Zeng
authors.forename: Mu
authors.initials: M
authors.lastname: Liu
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.forename: Qian
authors.initials: Q
authors.lastname: Liu
authors.forename: Bo
authors.initials: B
authors.lastname: Wang
mesh_terms: D016022:Case-Control Studies; D005141:Eyelid Diseases / Q000175:diagnosis*; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D019308:Palmitic Acid / Q000737:chemistry*; D013185:Squalene / Q000737:chemistry*; D013229:Stearic Acids / Q000737:chemistry*
chemical_list: D013229:Stearic Acids; D019308:Palmitic Acid; C031183:stearic acid; D013185:Squalene