Research Of Lung Cancer Markers In Pleural Effusions By Cryo Trap Combined With Solid Phase Microextraction-Gas Chromatography/Mass Spectrometry

Lung cancer?LC?is one of the malignant tumors that seriously threat to people's health and lives in the world.It has become the first cause of cancer death in China.Lung cancer markers have a clinical certain value in the diagnosis of lung cancer,but their sensitivity and specificity are not high that can often lead to misdiagnosis and missed cases.And most of the research objects are exhaled breath,blood,urine,cells and tissue samples.Pleural effusion,usually directly from the lungs,is closely related to the occurrence of lung disease and can be divided into malignant and benigneffusions.Lung cancer is a common cause of malignant pleural effusion.So the differential diagnosis of malignant pleural effusion is very important to the early lung cancer treatment.Studies have shown that pleural effusion contains many volatile organic compounds.Their exists and content in pleural effusions are important information for human health,and may be related to disease progression.Some VOCs have been reported to be potential lung cancer markers which present in exhaled breath,blood,urine and other biological samples.So it is important for the analysis of such substances.Preliminary studies suggest that low-boiling VOCs in pleural effusions can not be well separated using conventional SPME-GC/MS method which can cause band broadening.So in this paper,cryo trap combined with headspace solid phase microextraction-gas chromatography/mass spectrometry method was established for analysis of volatile organic compounds in pleural effusions.Cryo trap divice was self-made and experiment conditions were further improved.Dozens of low-boiling compounds were separated successfully.The results of repeatability examin were obtained with the RSDs from 1.35%to 13.37%of all compounds.Then 50 cases of pleural effusion samples?20 malignant and 30 benign?were analyzed.76 compounds with high degree of matching were identified using MS NIST library combined with artificial analysis.The major substances in pleural effusions were alkanes olefins,aldehydes,ketones and benzene derivatives.Among them,24 substances with high occurrence frequencies were selected,and their differences of average peak areas obtained by selscted ions between benign and malignant groups were preliminary compared.Six compounds were screened with significant larger average peak areas in malignant effusions than in benign effusions(R_m/b>2.5).In addition,the samples were collected over several months that can be affected by the sensitivity of the instrument.Therefore,0.2 mg/L cyclopentanone was added as internal standard in 26 pleural effusion samples?10 lung cancer and 16 benign diseases?for analysis of relative peak areas.27 compounds with occurrence frequencies larger than 40%were identified.The relative peak areas of 27 compounds were obtained,and their average value in the two groups were compared.Further analysis was made by box-plot.The results showed that seven ocompounds of2-pentanone,ethylbenzene,xylene,cyclohexanol,cyclohexanone,2-ethyl-1-hexanol and tetramethylbenzene were quite different between lung cancer and benign pleural effusions.These results suggest that cryo trap combined with SPME-GC/MS method developed in this paper is suitable for the analysis of VOCs in pleural effusions,and provide a reference for the screening of potential lung cancer biomarkers.