Rheodyne sampling valve injector

The high-pressure switching valve is the most important part of the instrumentation in this technique. It must work reliably even after several thousand switches under high pressure, must have a very small dwell volume, and must be chemically inert to both the sample and the mobile phase. Normal switching valves have six ports, but four- and up to ten-port valves are commercially available as well. Their setup is very similar to the usual sample valve injectors, e.g., rheodyne valves (Section 12.2.4.2). They can be driven by hand or automatically either by pneumatic force or electronically. Pneumatically or electronically driven valves have the advantage that the entire analysis can be automated. 

One system we used for this work was comprised of four 30-cm 100-A /x-Styragel columns (from Waters Associates) connected in series with a Rheodyne Model 7105 injector valve and a Varian 4200 syringe pump that maintained a constant flow of either 1 or 2 mL/min. At 1 mL/min the overall resolution efficiency was about 15,000 theoretical plates and the run time was about 50 min. By doubling the flow rate, the run time was cut in half with only a slight loss of column efficiency. The pressure required for a flow rate of 2 mL/min was usually about 1200 psi. Tetrahydrofuran (UV grade from Burdick and Jackson Laboratories) was used as the eluting solvent. The amount of sample solution injected into the system varied from 10 /xL to 500 /xL. 

Sample introduction was by means of a Hamilton 701N syringe in combination with a septum injector (HETP Components, Macclesfield, Great Britain) or alternatively a Rheodyne valve injector with 20 pi sample loop was used (HPLC Technology Ltd., Macclesfield, Great Britain). 

An HPTC injector allows the introduction of a precise sample volume onto the column. A typical manual injector consists of a 6-port valve with a rotor, a sample loop and a needle port (Eigure 9). A sample solution is introduced into the sample loop using a 22-gauge blunt tip syringe in the TOAD position. The sample is then injected into the column by switching the valve to INJECT. The typical external sample loop size ranges from 6 pT to 2 mT. For many years, the Rheodyne 7125 injector was the industry-standard. In the early 1990s, it was replaced by the Rheodyne 7725 injector, which injects samples without momentary flow disruptions. ... 

Electrospray (ES) mass spectrometry was carried out with a Fisons platform quadrupole mass specfrometer coupled fo a VG Masslynx data system. The samples were introduced into the source by direct injection via a valve loop system. Loop injection was accomplished with a Rheodyne 7125 injector valve, placing a 10-pl loop in the acetoni-trile/water stream. 

Figure 3.5—The two positions of a loop injector, a) Load sample b) Inject sample. Schematic of the model 7125 valve from Rheodyne Inc. Injection valves can be manual, pneumatic or electrical (reproduced with...

The continuous-stream flow-injection system (Figure 2) consisted of a gravity-feed electrolyte reservoir, a sample injection valve (Rheodyne, Model 50) fitted with a 30 /xL-sample loop, and a flow-through electrochemical detector cell. The channel diameter of the Teflon tubing for the stream was 0.8 mm. The tubing length from injector to detector was 10 cm. 

The D4 content of the samples was determined by reverse-phase high-pressure liquid chromatography (HPLC) with a Varian 5500 liquid chromatograph. A DuPont Zorbax ODS (Cis) column was used with a Wilmad infrared detector set at 12.45 xm to monitor the Si-CHa vibration. The mobile phase was an 83 17 mixture of acetonitrile and acetone at a flow rate of 0.8 mL/min. A Rheodyne injector valve operating on compressed air was used with a 10-p,L sample loop for reproducible injection volumes. Ethyl acetate was used to dissolve the samples for analysis. 

Sample introduction is done either with a hand injector or a manual valve (in many cases supplied by Valeo or Rheodyne) or with an autosampler. 

The HPLC analysis was performed on an Agilent 1100 series LC (Santa Clara, CA), equipped with a quaternary pump (G1311A) and a UV multiwave length detector (G1365B), set at 220 and 280nm. The injector was a Rheodyne manual injector valve, model 77251 (Santa Clara, CA), equipped with a 20-1 sample loop. The column temperature was controlled using a ThermaSphere TS-130 oven from Phenomenex set at 40 °C. 

The flow FFF systems are characterized by the use of a second pump to drive carrier across the channel thickness this setup provides the field that induces migration of sample toward the accumulation wall. The Flow I system was operated with an Isochrom EC pump (Spectra-Physics Inc., San Jose, CA) as the channel flow pump and a pulseless syringe pump (built in-house) as the cross-flow pump. Sample was injected via a Valeo injector (Valeo Instruments co., Houston, TX) with a 20-pL loop, and the eluted sample was detected at 254 nm with a UV-visible detector (UV-106, Linear Instruments, Reno, NV). The peripheral equipment employed in How II and ni consisted of a Kontron model 410 channel flow pump, a syringe pump serving as the cross-flow pump, a Rheodyne (Cotati, CA) model 7010 pneumatic-actuated injection valve, and a model 757 Spectroflow UV-vis detector from Applied Biosystems (Ramsey, NJ) operated at 254 nm. 

Figure 2.4 (a) Diagram of a six-port loop injector being filled by injection of the analyte solution from a syringe. In this mode the loop is bypassed and the mobile phase flows directly from pump to column through the injector valve via ports 2 and 3. In order to inject the sample in the loop onto the column the valve is rotated so that internal connections are now made between ports 1 and 2, and between ports 3 and 4. Reproduced from literature of Rheodyne Corporation, Technical Note 5 (2001), Achieving Accuracy and Precision with Rheodyne Manual Sample Injectors, with permission (www.rheodyne.com). 

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