title: Hand-Portable Gradient Capillary Liquid Chromatography Pumping System.
abstract: In this work, a novel splitless nanoflow gradient generator integrated with a stop-flow injector was developed and evaluated using an on-column UV-absorption detector. The gradient pumping system consisted of two nanoflow pumps controlled by micro stepper motors, a mixer connected to a serpentine tube, and a high-pressure valve. The gradient system weighed only 4 kg (9 lbs) and could generate up to 55 MPa (8000 psi) pressure. The system could operate using a 24 V DC battery and required 1.2 A for operation. The total volume capacity of the pump was 74 μL, and a sample volume of 60 nL could be injected. The system provided accurate nanoflow rates as low as 10 nL/min without employing a splitter, making it ideal for capillary column use. The gradient dwell volume was calculated to be 1.3 μL, which created a delay of approximately 4 min with a typical flow rate of 350 nL/min. Gradient performance was evaluated for gradient step accuracy, and excellent reproducibility was obtained in day-to-day experiments (RSD < 1.2%, n = 4). Linear gradient reproducibility was tested by separating a three-component pesticide mixture on a poly(ethylene glycol) diacrylate (PEGDA) monolithic column. The retention time reproducibility was very good in run-to-run experiments (RSD < 1.42%, n = 4). Finally, excellent separation of five phenols was demonstrated using the nanoflow gradient system.
authors.forename: Sonika
authors.initials: S
authors.lastname: Sharma
authors.affiliation: VICI Valco Instruments , Houston, Texas 77055, United States.
authors.forename: Alex
authors.initials: A
authors.lastname: Plistil
authors.affiliation: VICI Valco Instruments , Houston, Texas 77055, United States.
authors.forename: Hal E
authors.initials: HE
authors.lastname: Barnett
authors.forename: H Dennis
authors.initials: HD
authors.lastname: Tolley
authors.forename: Paul B
authors.initials: PB
authors.lastname: Farnsworth
authors.affiliation: VICI Valco Instruments , Houston, Texas 77055, United States.
authors.forename: Stanley D
authors.initials: SD
authors.lastname: Stearns
authors.forename: Milton L
authors.initials: ML
authors.lastname: Lee
mesh_terms: D002853:Chromatography, Liquid / Q000295:instrumentation*; D036103:Nanotechnology / Q000295:instrumentation*; D013056:Spectrophotometry, Ultraviolet / Q000295:instrumentation