title: Instrumentation for hand-portable liquid chromatography.
abstract: Liquid chromatography (LC) has lagged behind gas chromatography (GC) in developments related to hand-portable instrumentation. In this work, a new battery-operated (24V DC) nano-flow pumping system with a stop-flow injector was developed and integrated with an on-column UV-absorption detector (254nm) that was reduced in size to an acceptable weight and power usage for field operation. The pumping system, which includes nano-flow pump, stepper motor and high-pressure valve weighs only 1.372kg (3lbs) and can generate up to 110.32MPa (16,000psi) pressure. A major advantage of this pump is that it does not employ a splitter, since it was specifically designed for capillary column use. The volume capacity of the pump is 24μL, and a sample volume as low as 10nL can be injected. Flow rate calibration (300nL to 6.12μL per min) was performed, and an accuracy >99.94% was obtained. The percent injection carry-over was found to be low (RSD 0.31%), which makes it practical for quantitative analysis. The detector linear range and limit of detection (LOD) were determined using sodium anthraquinone-2-sulfonate. A linear regression coefficient (R) of 0.9996 was obtained for a plot of log peak area versus log concentration over the range of 3.2μM to 6.5mM, and the LOD (S/N=3) was found to be 7.8fmol (0.13μM). The short term noise of the detector is comparable to commercially available detectors (∼10(-5)AU). In this work, the system was tested in the laboratory using regular line power (120V AC) with an AC to DC adapter. Reversed-phase isocratic separations were performed using a 15.5cm×75μm i.d. fused silica capillary column containing a monolithic stationary phase synthesized from 1,6-hexanediol dimethacrylate. Good retention time repeatability (RSD 0.09-0.74%) was obtained for a mixture containing an unretained marker (i.e., uracil) and a homologous series of alkyl benzenes.
authors.affiliation: Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602, USA.
authors.forename: Sonika
authors.initials: S
authors.lastname: Sharma
authors.affiliation: VICI Valco Instruments, Houston, TX 77255, USA.
authors.forename: Alex
authors.initials: A
authors.lastname: Plistil
authors.affiliation: VICI Valco Instruments, Houston, TX 77255, USA.
authors.forename: Robert S
authors.initials: RS
authors.lastname: Simpson
authors.affiliation: Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602, USA.
authors.forename: Kun
authors.initials: K
authors.lastname: Liu
authors.affiliation: Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602, USA.
authors.forename: Paul B
authors.initials: PB
authors.lastname: Farnsworth
authors.affiliation: VICI Valco Instruments, Houston, TX 77255, USA.
authors.forename: Stanley D
authors.initials: SD
authors.lastname: Stearns
authors.affiliation: Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602, USA. Electronic address: milton_lee@byu.edu.
authors.forename: Milton L
authors.initials: ML
authors.lastname: Lee
mesh_terms: D001555:Benzene Derivatives / Q000032:analysis; D002138:Calibration; D002853:Chromatography, Liquid / Q000295:instrumentation* / Q000379:methods; D056148:Chromatography, Reverse-Phase / Q000295:instrumentation / Q000379:methods; D057230:Limit of Detection; D036103:Nanotechnology; D012822:Silicon Dioxide; D014498:Uracil / Q000032:analysis
chemical_list: D001555:Benzene Derivatives; D014498:Uracil; D012822:Silicon Dioxide
keywords: Capillary column; Hand-portable; Liquid chromatography; Nano-flow pump; On-column detection; UV-absorption