| Summary: | 碩士 === 國立臺灣大學 === 化學研究所 === 103 === Part 1
Aminoglycosides are highly polar compounds. Usually, the analysis of aminoglycoside is performed by reversed phased liquid chromatography (RPLC) with haptafluorobutyric acid (HFBA) as ion pairing reagent. HFBA reagent can improve resolution, but it results in suppression of analytes by unstable spray and decreasing ionizing effect.
In this study, an integrated electrophoretic mobility control (EMC) device was developed to increase the sensitivity of aminoglycosides on the liquid chromatography-electrospray ionization mass spectrometry (LC-EMC-ESI-MS). By applying a positive electric field, HFBA anion is retained in the junction reservoir and aminoglycosides cation is able to move forward into mass spectrometry interface. A gap is between LC transfer and connecting capillary for retaining HFBA to avoid flowing into connecting capillary with the flow rate of 0.2 mL/min. The integrated electrophoretic mobility control device with a gap, 300 μm and the electric field , 1500 V/cm, is able to enhance S/N ratio without losing resolution. Therefore, EMC device successfully alleviate ion suppression caused by HFBA. The recoveries range from 86% to 105 %, and the limit of quantitation, LOQ, were found in the range of 2-4 ppb for milk sample.
Part 2
The particle size of ultra performance liquid chromatography (UPLC) column packing is 1.7 μm. According to the Van Deemter equation, it is able to work at higher flow rate (0.6 mL/min) with the 2.1 mm I.D. column. The flow rate is critical for high speed and separation efficiency. However, high flow rate will decrease the ionization efficiency.
In this study, seven β-agonists were analyzed by UPLC. The flow rate of mobile phase was 0.6 mL/min. Using post column splitting (split ratio3:1), a flow rate of 0.2 mL/min was introduced into the ESI-MS system for detection.
The elution flow rate of 0.6 mL/min was better than 0.2 mL/min by increasing sampling rate. UPLC-ESI-MS/MS with post column splitting (0.2 mL/min) provided better sensitivity that of the flow rate 0.6 mL/min without splitting. However, post column splitting did not achieve the sensitivity under 0.2 mL/min without splitting. One possible reason is the limitation in the rate of transferring the ions from ESI source to the mass spectrometer.
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