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Ye D, Wang W, Moline D, Islam MS, Chen F, Wang P. A Microwave Flow Detector for Gradient Elution Liquid Chromatography. Anal Chem 2017; 89:10761-10768. [PMID: 28936868 DOI: 10.1021/acs.analchem.7b01924] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
This study presents a microwave flow detector technique for liquid chromatography (LC) application. The detector is based on a tunable microwave interferometer (MIM) with a vector network analyzer (VNA) for signal measurement and a computer for system control. A microstrip-line-based 0.3 μL flow cell is built and incorporated into the MIM. With syringe pump injection, the detector is evaluated by measuring a few common chemicals in DI water at multiple frequencies from 0.98 to 7.09 GHz. Less than 30 ng minimum detectable quantity (MDQ) is demonstrated. An algorithm is provided and used to obtain sample dielectric permittivity at each frequency point. When connected to a commercial HPLC system and injected with a 10 μL aliquot of 10 000 ppm caffeine DI-water solution, the microwave detector yields a signal-to-noise ratio (SNR) up to 10 under isocratic and gradient elution operations. The maximum sampling rate is 20 Hz. The measurements show that MIM tuning, aided by a digital tunable attenuator (DTA), can automatically adjust MIM operation to retain detector sensitivity when mobile phase changes. Furthermore, the detector demonstrates a capability to quantify coeluted vitamin E succinate (VES) and vitamin D3 (VD3).
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Affiliation(s)
- Duye Ye
- Department of Electrical and Computer Engineering, ‡Department of Food, Nutrition, and Packaging Sciences, Clemson University , Clemson, South Carolina 29634, United States
| | - Weizheng Wang
- Department of Electrical and Computer Engineering, ‡Department of Food, Nutrition, and Packaging Sciences, Clemson University , Clemson, South Carolina 29634, United States
| | - David Moline
- Department of Electrical and Computer Engineering, ‡Department of Food, Nutrition, and Packaging Sciences, Clemson University , Clemson, South Carolina 29634, United States
| | - Md Saiful Islam
- Department of Electrical and Computer Engineering, ‡Department of Food, Nutrition, and Packaging Sciences, Clemson University , Clemson, South Carolina 29634, United States
| | - Feng Chen
- Department of Electrical and Computer Engineering, ‡Department of Food, Nutrition, and Packaging Sciences, Clemson University , Clemson, South Carolina 29634, United States
| | - Pingshan Wang
- Department of Electrical and Computer Engineering, ‡Department of Food, Nutrition, and Packaging Sciences, Clemson University , Clemson, South Carolina 29634, United States
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