Micro-syringe pumps

Applied Biosystems has now developed a high sensitivity version of the Procise 494 N-terminal sequencer (Precise 494HS) which employs a capillary HPLC systems with Micro-Syringe Pumps. The 494HS facilitates the detection of PTH-amino acids at the subpicomole level. 

The channels, which had catalyzed electrodes on the surfaces, were covered with Nafion 112 (thickness 50 pm, equivalent weight 1,100 gmoF, ionic conductivity 0.083 S cm" ) to provide ionic conductivity between the anode and the cathode. The Nafion membrane was pressed with a glass plate to avoid solution leakage (Fig. 3.4a). Voltage-current measurements were performed at room temperature with a mass flow control system of fuel and oxidant as shown in Fig. 3.4b. The fuel and oxidant solutions were supplied to the electrodes with the micro-syringe pumps from the outlet of each channel. The flow rate of both the fuel and oxidant solutions was 80 pL miu". Composition of the fuel solution was 2M methanol solution... 

P 9] DL-l-Phenylethylamine and 4-amino-l-benzylpiperidine were dissolved in 0.1 M NaOH aqueous solution [23]. 3-Nitrobenzoyl chloride and 3,5-dinitrobenzoyl chloride were used as ethyl acetate solutions. The concentration of all reactants was set to 0.01 M. Syringe pumps served for liquid feed. The flow rate was 50 plmin and room-temperature processing was applied. No further temperature control was exerted as the reaction is only mildly exothermic. After having passed the micro reactor, the phases were settled in test-tubes and the organic phase was withdrawn for analysis. 

P 19] Two micro syringes were filled with 0.32 mM p-nitrophenyl-y9-D-galacto-pyranoside in phosphate buffer (pH 8) and /3-galactosidase (20 U) in 10 ml of the same buffer [26]. Both solutions were pumped into the micro channel at the same flow rate (a few pi min ). The reaction was carried out for 0-30 min at 37 °C using a hot-plate. The residence time was set by adjusting the flow rate. After passing the micro channel, the reaction mixture was dropped into hot water to inactivate the enzyme. 

P 32] Pyrene (20 mM), 1,4-dicyanobenzene (40 mM) and sodium cyanide (1 M) were reacted in propylene carbonate and water. A 100 pi solution of pyrene (20 mM), 1.4-dicyanobenzene (40 mM) in propylene carbonate and a 100 pi solution of sodium cyanide (1 M) in water were fed by programmable dual-syringe pumps via fused-silica capillary tubes into a micro-channel chip [29]. Both solutions were fed with equal flow velocity. A 300 W high-pressure mercury lamp was used as light source. After passing an optical filter made of a CUSO4 solution, the whole chip was irradiated after formation of a stable oil/water interface inside. The oil phase was collected at the exit. 

P 60] The dehydration of 1-hexanol to hexane and of ethanol to ethane were conducted at 155 °C. Heating was accomplished by a heating wire inserted in the micro reactor s top plate. This wire was connected to a potentiostat (0-270 V) temperature was monitored by a digital thermometer with the probe close to the reaction channel. A syringe pump was applied for liquid transport [19]. A flow rate of 3 pi min was applied. The alcohols were purged with nitrogen directly prior to reaction to minimize coke formation. 

P 14] A solution containing p-chlorophenol was fed from a 250 ml flask to the micro reactor by a syringe pump [20]. Flow rates from 10 to 65 ml min were applied. The reaction temperature was set to either 20 or 40 °C. 

Another advantage of the micro-LC approach is that the required sample size is minimal, so the sample can be drawn from a 1-1 laboratory scale reactor without influencing the reactor composition. The ISCO pLC-500 microflow syringe pump has proven to be reliable and reproducible in evaluations in our laboratory. Capillary liquid columns have been fabricated on planar devices such as silicon to form a miniaturized separation device.19... 

The concept of an integrated micro-fluidic-based system has now been developed (Zhang et al. 2006), with an example shown in Fig. 7. This particular system is based on conventional chromatographic instrumentation and employs a multi-valving system, located between two syringe pumps, shown in the foreground, to enable the introduction of multiple reagents from an auto-sampler to be loaded onto the micro-reactor. Because of the low diffussional distances obtained in this sys-... 

Schwartz and Brownlee introduced a syringe pump for micro LC applications in early 1984.23 It exhibits a number of advantages over a conventional reciprocating pump ... 

In addition to the commercially available systems, several authors have described laboratory-built systems using commercially available components from companies such as Upchurch Scientific (Oak Harbor, WA). One of the first reported laboratory-built micro-bore HPLC systems was described by Simpson and Brown, which was a simple adaptation of a standard HPLC system to accept micro-bore columns built from guard columns. A complete system has been described based on dual microdialysis syringe pumps (CMA Microdialysis, Chelmsford, M A) or dual syringe pumps (Harvard Apparatus, Inc., Holliston, MA), a microinjection port, and a micro-column the latter components being obtained from Upchurch scientific (Figure 3.5). This system was coupled with a laser-induced fluorescence (LIF) detector and used to measure neuropeptides in sub-microliter samples. A further modification of this system was built to perform immunoaffinity isolations of biomedically important analytes from clinical samples. ... 

Controlled by the MS-MS software, the PE Series 200-micro LC pump operates iso-cratically using 80% acetonitrileiwater at 40 pl/min. A 50 x 1 mm C18 column (Keystone) is used between the pump and autosampler to provide back-pressure. The syringe/system flush solution is the 80% acetonitrileiwater used as the mobile phase. The autosampler is connected directly to the MS-MS Turboion Spray source. The injected sample volume is 20 pi. 

In the syringe-type pump the liquid is enclosed in a cylinder. A piston moves at a constant speed to push the liquid. Eluent compressibility induces time-consuming flow equilibrium. Nevertheless, the flow from a syringe pump is pulse free. For micro LC, flow rates of 50 yuL/min are utilized in spite of the drawback of column pressurization. With very low flow rates (in the nanoliter range) the use of pumps is tedious, and split-flow techniques are required. 

Syringe Pump—A pulseless pump made up of a motor-driven piston or plunger in a solvent-filled cylinder. Useful only when small solvent volumes are to be pumped often used in micro-flow or nano-flow HPLC systems. 

For liquid feed, a double-channel syringe pump with two 500 pi syringes, a highspeed pneumatic switching valve and PTFE tubing with an inner diameter of254 pm was used [110] 0.5 pm PTFE microfilters were set in front of the micro mixer to remove particles. The flow rate was set to 6 ml h-1. 

P 86] A solution with a commercial fluorescent dye (1.2 mM) and deionized water were fed by syringe pumps into the micro mixer [54], A mercury lamp illuminated the mixing chamber. Filters were used to select between the emission light and the reflected light A microscope with a digital camera was used for flow monitoring. 

Peak identification and interpretation of mass spectra Mobile phases for proanthocyanidins contain 2% (v/v) of acetic acid, and it suppresses electrospray ionization at negative mode. This can be overcome by adding ammonia acetate as an ionization enhancer. The ammonia acetate (lOmM in methanol, 0.1 mL/min flow rate) can be added into the flow via a three-way micro-splitter ( P-445, Upchurch Scientific, WA) just before the mass spectrometry. It can be delivered by a separate HPLC pump or by a syringe pump. 

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