Design And Research Of The Automatic Micro-injection System For Surface Desorption Atmospheric Pressure Ionization

Mass spectrometry(MS), as a detection method with high sensitivity, fast response and good specificity,etc., has already become an important method in the field of analytical chemistry. Surface desorption atmospheric pressure chemical ionization mass spectrometry(DAPCI-MS) is a new technique of ambient mass spectrometry, which requires no sample pre-treatment, and of high speed without pollution. Based on DAPCI, trace sampling DAPCI improves the sample consumption to less than 0.11 nL. DAPCI-MS has been widely used in the field of food, medicine and medical science. However, there are no stable devices with automatic system for the trace sampling DAPCI-MS, leading to the limit of its application. Herein, this thesis proposed two automatic micro-injection systems for DAPCI-MS and the precision control of the system was reseatched. The main content of this thesis includes:1. Relevant literature was reviewed and the research status of DAPCI-MS was summarized. According to the weakness of micto-sampling DAPCI-MS method currently, the requirement of designing a micro-injection system was raised.2. The mechanic structure of micro-injection system was designed and was divided into three structures with sampler, driver and transmission part. Based on the real need in experiments, a high-throughput structure and a high-precision structure was designed respectively. The main driving component, stepper motor was chosen to fit the design. The mechanic structure design is the basis for the micro-injection system, which points out the direction to the hardware and software design.3. The hardware of micro-injection system was designed and was divided into five modules. The main control module, based on STC12C5410 AD, was designed to achieve communication and control among all modules. The power module mainly work with UC3842. The stepper motor and its driving circuit with THB6128 as execution module. The clean module was made by a coreless vibration motor and a soft brush.And the correlation photoelectric sensor was used to calibrate zero.4. The hardware of micro-injection system was designed and was divided into two parts. The upper computer software was written with LabVIEW to connect people and the machine. The lower-computer software was written to coordinate the hardware modules. Then the subdivision drive was achieved to reduce the step angle of HSM. Thus can improve the accuracy of the whole system.5. The repeation position error was tested to measure the accuracy of the micro-injetion system. The system was tested respectively with the high-throughput structure and a high-precision structure. The result shows that, the epeation position error was below 0.052 mm and 0.09 mm, furthermore, the later one can reduce the error down to 0.005625 mm by using the subdivision drive at a number of 16.