Rheodyne 7000 valve

The 1/16" x 0.02" i.d. transfer line also functioned as a sample dilution device in other applications, a stainless steel column packed with glass beads has been found to be useful for dilution. This simple dynamic dilution technique has been used extensively in flow injection analysis.3 A refractive index detector is typically used to measure the sample transfer time. As shown in Figure 4, approximately 5 minutes is required to transfer the sample plug to the Rheodyne valve. As the apex of the sample band passes though the Rheodyne valve, the valve is activated and 1 pi injected onto the liquid chromatographic column. The sample transfer time was checked periodically over 1 year of operation and found to be stable. 

The fluid leaves the sampling valve from port F and enters port 2 of a second switching valve (Rheodyne type 7010). The Rheodyne valve has six ports designated by Arabic numerals. The position of this valve determines the direction of flow from port 2 either through the core or through the capillary tube. These alternative paths are depicted in the second circle shown in the figure, by either dashed or solid lines. The capillary tube, Vc, has a volume of 0.50 cc. The core, which has been saturated with the 1% acidified brine, has a length of about 5 inches and is 1/2 inch in diameter. 

In this scenario, orthogonality between HILIC and reversed phase column can be successfully obtained using two LC pump and two 6-port Rheodyne valves, following the scheme reported in Figure 6. 

The strong alkaline solvents need some special efforts concerning materials. Capillaries and fittings should be of PEEK. The injection valve must be designated to be alkali resistant (e.g., Tefzel rotors of Rheodyne valves). Storage bottles for mobile solvents have to be of plastics and should be supplemented with a tube filled with caustic soda pellets. 

The assay was performed with a HPLC-system consisting of a Spectra-Physics (Spectra Physics, San Jose, CA 95134, USA) model SP8700 solvent delivery system used at a flow rate of l.Oml.min", a Kratos (Kratos Analytical Instruments, Ramsey, NJ 07446, USA) model 757 UV-detector, wavelength 260 nm, range 0.005 aufs, rise-time 1 second. Injections of extracts into a Zymark (Zymark Corporation Inc., Hopkinton, MA 01748, USA) Z 310 HPLC-injection station, equipped with an electrically controlled Rheodyne valve and a 20 pi sample loop, were performed by a Zymate II robot system. The Zymark Z 310 Analytical Instrument Interface was used to control the HPLC-injection station. 

Christie and Breckenridge (42) describe the application of this column to the isolation and determination of FAs containing trans double bonds in samples of natural and industrial origin. A column (250 X 4.6-mm ID) of NUCLEOSIL 5SA was flushed with 1% ammonium nitrate solution at a flow rate of 0.5 ml/min for 1 h, then with distilled water at 1 ml/min for 1 h. Silver nitrate (0.2 g) in water (1 ml) was injected onto column via the Rheodyne valve in 50-yu.l aliquots at 1-min intervals silver began to elute from the column after about 10 min, and 20 min after the last injection the column was washed with methanol for 1 h, then with 1,2-dichloroethane-dichloromethane (1 1 v/v) for 1 h. For most of the analytical work, the column temperature was maintained at 30°C in a thermostatted oven. 1,2-Dichloroethane-dichloromethane (1 1) (mixture A) at a flow rate of 1.5 ml/min was the mobile phase (detector operated at 242 nm) for the separation of isomeric monoenes, and the same solvents with the addition of 0.5% acetonitrile (mixture B) at a flow rate of 0.75 ml/min were employed for isomeric dienes and trienes. 

Prepare 500 pL of sample/AP-prog mixture (as for batch mode above) and inject into the cell from a syringe via the Rheodyne valve in the load position. 

The supercritical fluid is delivered by a syringe pump (model lOOD, Isco, Lincoln, NE). The modifier is added by means of a loop of 100 pL and a Rheodyne valve (model 7125) directly into the CO2. The extraction cell is heated to 110°C and the flow of supercritical fluid is adjusted to 1.1 to 1.2 mL/min. The extract is then recovered by trapping the decompressed fluid in a vial containing approximately 3.5 mL of methanol. 

The most common method of sample introduction in HPLC is via a rotary valve, e.g. a Rheodyne valve. A schematic diagram of a rotary valve is shown in Fig. 32.17. In the load position, the sample is introduced via a syringe to fill an external loop of volume 5, 10 or 20 L. While this occurs, the mobile phase passes through the valve to the column. In the inject position, the valve is rotated so that the mobile phase is diverted through the... 

The injection valve (e.g., Rheodyne valve) allows the sample to be injected onto the top of the column from a filled loop that is temporarily switched away from the flow of eluent while filling is taking place. The loop size vanes from approx 10 to 200 pL in the case of a typical analytical scale instrument and from approx Ito 10 mL for a benchtop preparative instrument. For sample introduction, the loop is switched back in series with the flow of eluent and the chromatographic run begins. 

Rheodyne valve fitted with 20 pi loop computing integrator. 

Injector system Rheodyne valve fitted with 10 pi loop. 

Chromatograph Perkin Elmer 410 ternary gradient system coupled to Perkin Elmer 1000 M Fluorimeter with 7 pi flow cell rheodyne valve with 10 pi loop. 

The eluent flow was provided by an Altex pump (Model 110A) and the samples were introduced into the eluent flow by a Rheodyne valve (Model 7125) fitted with a 100 1 loop. 

Evaluation of HA molar mass ehanges was performed with Shimadzu apparatus using a packed HEMA-BIO 1,000 colunm of dimensions 7.8 mm x 250 mm, the packing particle size was 10 pm. The mobile phase 100 mM phosphate buffer (pH 7.0) containing 0.15M NaCl was pumped by the LC-IOAD device at a flow rate of 0.5 ml/min. For catibration of the SEC system used reference HAs (M = 90.2-1380 kDa) with broader molar mass distributions (M /M = 1.60-1.88) were apphed. The samples of the volume of 20 pi with the polymer concentrations 1 mg/ml or lower were injected by a 7725i-type Rheodyne valve. The SEC analyses performance was monitored online by UV (SPD-IOAV, set at 206 run) and refractive index (RID-10) detectors. 

A portion (12 pi) of the sample is injected into the liquid chromatograph s Rheodyne valve and chromatographed under the following conditions - column Whatman PXS 10/25... 

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. 

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). 

Inject an aliquot (12 ul) of the sample into the liquid chromatographs Rheodyne valve and chromatograph under the following conditions column Whatman PXS 10/25 um PAC (250 x 4 mm i.d.) mobile phase, 0.01% v/v orthophosphoric acid in distilled water flow rate, 4 cm min pressure, 2000 lb in detector wavelength 195 nm chart speed, 0.5 cm min and absorbance scale 0.02. 

Recovery of the acetophenone from the carbon dioxide-methanol stream was attempted by simply flushing the Rheodyne valve with methanol and collecting the compound in a 100 mL volumetric flask. This method showed very poor recovery. 

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