| Currently, the morbidity rate of lung cancer tends to increase and becomes higher than other malignant tumors, which is often diagnosed at an advanced stage. Therefore, there is an increasing demand for the early diagnosis for lung cancer. A novel, non-invasive diagnostic method of breath analysis has become a promising early detection means. Human breath gas is composed of many different elements, it may contain more than 200 kinds of compositions in a sampling of an individual. However, the concentrations of the volatile substances in the breath gas are too low to analyze by routine analytical methods. Therefore, it is necessary to develop an appropriate pretreatment method to concentrate the volatile substances prior to chromatographic analysis.In the 1990's, a new solid-phase microextraction method (SPME) was proposed by Pawliszyn, it is considered as one of the greatest discoveries in analytical chemistry. In this method, the quartz fiber was coated with a small amount of extraction phase. SPME can be applied in many fields, such as water and gas extraction. It has attracted extensive attention because it is simple, solvent-free, fast and easily to operate. However, due to its thin coating thickness and low specific surface area, this sample pretreatment method has a low extraction capacity, and it need a long time to reach extraction equilibrium.Electrospinning is a novel method of making one or more polymer solution to form three dimensional porous micro or nano fiber materials under high voltage electric field. These nanofibers possess a well-defined three-dimensional structure, large specific surface area-to-volume ratio, and strong hydrophobicity. Due to its excellent physical and chemical properties, it has aroused more and more attention in the field of extraction and separation as well as in many reseach fields.In this work, two kinds of new composite fiber extraction materials were prepared by a simple electrostatic spinning method. And two extraction methods—thin film microextraction (TFME) and solid-phase microextraction (SPME) were developed and coupled with high performance liquid chromatography (HPLC) and gas chromatography mass spectrometry (GC-MS), for the breath analysis. These methods were applied successfully to determine volatile organic compounds in human exhaled breath (condensate and vapor). The research contents are as follows:1. In the current study, polystyrene/graphene (PS/G) composite nanofibers with three-dimensional network structure were prepared by electrospinning. Due to porous fibrous structure, large surface area and strong hydrophobicity, PS/G nanofiber film was first applied as a novel adsorbent of thin film microextraction (TFME). And an electrospun nanofiber-based thin film microextraction was developed and coupled to high performance liquid chromatography for the determination of six aldehydes in human exhaled breath condensates. Excellent extraction efficiency and fast extraction were obtained toward analytes. In addition, some important extraction parameters including sampling rate, desorption solvent and volume were investigated. Based on the optimal conditions, the linear range was in the range of 0.02-30 ?mol L-1 with a correlation coefficient of 0.9938, and the recoveries were between 79.8% to 105.6% with the relative standard deviation of 16.3% (n= 5). The limits of quantification of six aldehydes ranged from 13.8 to 64.6 nmol L-1. Taken together, the developed method provides a simple, rapid, cost-effective, non-invasion approach for the analysis of linear aliphatic aldehydes in exhaled breath condensates.2. Polystyrene/graphene oxide (PS/GO) fiber coating was fabricated for the first time on the outside of a stainless steel wire by an electrostatic spinning strategy. Based on the material, a simple, fast, low cost and high sensitivity solid-phase microextraction method was established. And it was applied in the analysis of volatile organic compounds in human breath vapor by coupling wtih gas chromatography/mass spectrometry (SPME/GC/MS). The features of the electrostatic spinning fiber coating were characterized, including composition, morphology, thermal stability and lifetime. In addition, the parameters which influence extraction and thermal desorption performance were optimized. The limits of detection (LOD) were in the range of 1.2-3.5 ng L-1.The relative standard deviation (RSD) of the same fiber was 1.4-16.4%, and inter-day RSD ranged from 5.7% to 20.0%. The recoveries were between 87-108%. Therefore, the method possesses numerous advantages, including simple, cost-effective and efficient. It has the potential to be used in the clinical analysis of volatile organic compounds in exhaled breath of lung cancer patitents and healthy people. |
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