Fast derivatization of aliphatic aldehydes followed by gas chromatographic analysis Application: for human exhaled breath analysis

Aliphatic aldehydes which have unpleasant pungent odors are usually present at trace amount in various complex material such as food, air and water pollution samples, car exhaust, cigarette smoke, physiological fluid and exhaled breath (EB) [1]. These compounds in EB are divided into two groups, namely exogenous volatiles and endogenously produced compounds. Exogenous volatiles include those inhaled from the environment, the oral ingestion of food, and smoking cigarettes. Endogenously produced volatiles include materials newly made from cells in the body and those made by intestinal bacteria. Aliphatic aldehydes present in very low concentrations from malignant cells of human organs, e.g. lung diseases [2]. Breath analysis is a promising non-invasive approach that allows the identification of the various respiratory conditions such as breath cancer.Exhaled C1-C10 aldehydes have been detected in all healthy volunteers, smokers and lung cancer patients. Exhaled pentanal, hexanal, octanal and nonanal concentrations were significantly higher in lung cancer patients than in smokers and healthy controls. Lung cancer patients could be therefore screened by means of exhaled pentanal, hexanal, octanal and nonanal concentrations [1].C1-C10 aldehydes analysis in EB present certain difficulties because of their high volatility and polarity. Therefore, derivatization and enrichment procedures are usually required for GC analysis [3]. The proposed method is based on co-liquefaction of the analytes existing in human EB followed by air assisted dispersive microextraction (AADME) with small volume of extraction solvent. In this work 1000mL of smoker exhaled breath sample was taken in the specially fabricated extraction device. 1.4mL of methanol was added. The extraction device was exposed to ultrasonic bath for the evaporation of solvent and then co-liquefaction at -18ºC with any VOCs present in exhaled breath. 0.4 mL of 3-Methyl-2-benzothiazolinone hydrazone hydrochloride hydrate (MBTH) solution, 0.4mL of phosphate buffer (pH=5.5) and 0.2mL H2O was added into collected metanolic solution. The extraction of derivatized aldehydes was performed using AADME with 0.1mL hexane for 5 min. 2 µL of extract was analysed. Under optimal conditions, the method displayed good linearity for the studied aldehydes within a range of 0.1-10 ng.mL-1, with correlation coefficients 0.9975. The limits of detection (LODs) and the limits of quantitation (LOQs) were ranged from 0.04 to 0.11ng.mL-1 and 0.1 to 0.3ng.mL-1, respectively. The relative standard deviations were less than 8.8%. Moreover, enrichment factors (EFs) were in the ranges of 8100 to 9100-fold.The overall time for sampling and extraction is 40 minutes.