Rheodyne loop valve

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. 

The analytical HPLC column used for analysis was packed in 300 x 3.9 nin stainless column with Lichrospher lOORP-18 packing(lS urn, Merck Co.). The HPLC used for analysis consists of a M930 Solvent Delivery Pump, a 486 detector (M 7200 Absorbance Detector) from Young-ln Scientific Co, and a Rheodyne injection valve (20 pi sample loop). Autochrowin (ver. 1.42, Young-ln Scientific Co.) connected to PC was used as data acquisition system. 

Preparative Recycle HPLC column was a JAIGEL-ODS-AP column(13 /an, 21.5 x 300 DU, JAl Korea). The Preparative Recycle HPLC consists of a Pl-SOF Pump(JAl Korea), a UV-310B detector(JAl Korea), a Rl-50 detector(JAl Korea), a Rheodyne injection valve(3 sample loop), and a SS-2S0F2 recorder(JAl Korea). 

The remaindCT of the mixture was separated by RP-HPLC on a Vydac CIS 530pm ID fused silica capillary column. Capillary LC was carried out using a model MOB Applied Biosystem HPLC and a Rheodyne injection valve with a 100 pi injection loop. A linear gradient of 2% B to 70% B in 60 minutes using solvent A (0.1% TFA) and solvent B (90% acetonitrile, 0.07% TFA) was used with a flow rate of 20 pl/min. Fractions corresponding to all UV-absorbing peaks were hand collected. 

The disadvantage of internal loops is that they are fixed and can only be altered by changing the rotor. This has led to the development of external interchangeable loop valves of the type marketed by Valeo and Rheodyne. Here dead volumes are minimised and the loop can readily be exchanged for other desired sample sizes, e.g. 5 pi, 10 pi, 20 pi and 50 pi. Microsample injection valves capable of delivering 0.5-5 pi are also available. Operation of the valve is similar to those with internal loops, i.e. a load position and an inject position (Figure 6.16). 

Automatic inlet systems are desirable and are a necessity in the automatic batch systems described later. Such systems are pneumatic loop-valve systems and are supplied by Hamilton, Valeo, Rheodyne and Siemens. These valves can be used at pressures up to ZOO bar. The loop tubes are interchangeable and the volume... 

In the FIA system, peristaltic pnimp (ISMATEC ITC, Switzerland) 0.50 mm i.d. PFTE tubing was used to propel the samples and reagent solutions. Samples were injected into the carrier stream by a 7125 model stainless steel high pressure Rheodyne injection valve provided with a 20 )xL loop. The absorbance of the coloured complex formed (Xmax 415 nm) was measured with a UV-Visible spectrophotometer equip>p)ed with a flow-through micro cell (Spectra SYSTEM UV 3000 HR, Thermo Separation Products, USA), and connected to a compniter incorporated with a PCI000 software programme. 

HPLC experiments were carried out using a Model 510 Liquid Chromatograph equipped with a Model 481 UV detector (Waters Associates, Milford, Massachusetts, U.S.A.). The chromatograms were processed by means of a chromatographic workstation (Baseline 810). Separation was performed on a reversed-phase Supelcosil LC-18 column (250 x 4.6 mm I.D., 5 jim particle size) (Supelco, St. Louis, Missouri, U.S.A.). The samples were injected into a 50 jl1 loop using a Rheodyne 7125 valve (Rheodyne, Cotati, California, U.S.A.). 

Fig. 2 Different construction types of external sample loop valves a, Rheodyne b, Valeo c, Beckman.

Rheodyne injection valve With 250 pL loop capacity. 

The equipment consisted of two Waters (Waters Corp. Milford, MA) M-45 pumps, a Waters 481 UV detector, a six-port Valeo sampling valve (A2L6P) with 0.08" holes in the valve body and rotor, a Rheodyne Model 7413 injection valve with a 1-pl loop, a valve interface box, and a Digital Equipment LSI-11/23-based microcomputer system. The microcomputer was used to control all valves, collect raw data from the UV detector, integrate the chromatogram, and store and plot results. 

The equipment used in this application included two Waters M-45 pumps, a Waters 481 UV detector with microbore cell, an air-actuated Rheodyne 7413 injection valve with a 1-pl injection loop, an air-actuated Valeo four-port sampling valve (A2CI4UW2) with no groove in the injection entry ports, an air-actuated Valeo three-port switching valve (AC3W), and a Digital Equipment LSI-11/23 microcomputer. The LC system was located in a purged cabinet suitable for use in Class I, division 2 areas. The cabinet was in a heated room about 40 feet from the reactor column. The two Valeo valves were mounted next to the reactor column, while the microcomputer was located in the control room. 

C. The Rheodyne Model 7010 injection valve, equipped with a 20-pl loop, was switched to injection at the apex of the sample band, as observed on the refractive index detector. The complex kinetics of the production of mono-, di-, and tri-brominated glycols is shown in Figure 14. Optimization of parameters such as the flow rate of acid resulted in a 15% reduction in batch cycle time and eliminated the need for manual analysis and intervention to obtain a desired endpoint composition. 

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. 

Apparatus Pumping systems used in these studies for high-performance columns were a Varian 8500 syringe pump and a Varian 5000 isocratic pump. An Altex IlOA was employed for the con-trolled-pore glass (CPG) columns. Waters Associates model 401 refractometers were used on all instruments. Stagnant mobile phase was kept in the reference side of the refractometer. Samples were injected with a Rheodyne 70-10 injection valve using a 20yl loop (lOOyl for CPG columns). 

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. 

Equipment. A LDC (Laboratory Data Control) Constametric III pump was used together with a Rheodyne 7120 20 yl loop injection valve and two LDC Spectromonitor III, variable wavelength UV-detectors. A Stanstead constant pressure pump was used for packing the columns. 

Figure 3.4—HPLC injection valve and assorted loops. Rear view of the valve showing six entries/exits and a series of loops with different volumes (reproduced by permission of Rheodyne Inc.).

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. 

A Perkin-Elmer MPF-2A Fluorescence Spectrophotometer was used to determine the excitation and emission wavelengths required for achieving maximum fluorescence intensity for the pesticides studied. The MPF-2A contained a 150 watt xenon arc and an excitation monochromator with a grating blazed at 300 nm as the excitation unit a Hamamatsu R 777 photomultiplier tube (sensitivity range 185 - 850 nm) and an emission monochromator grating blazed at 300 nm as the emission detection unit. A DuPont Model 848 Liquid Chromatograph was used for HPLC (Figure 2). The accessory injection device included a Rheodyne Model 70-10 six-port sample injection valve fitted with a 20 y liter sample loop. A Whatman HPLC column 4.6 mm x 25 cm that contained Partisil PXS 1025 PAC (a bonded cyano-amino polar phase unspecified by the manufacturer) was used with various mobile phases at ambient temperature and a flowrate of 1.25 ml/minute. 

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. 

Figure 11.24 Rheodyne Type SO mplc injection valve the vent (green). Thus with the solvent flow by-passing the load loop, sample can be injected from a syringe onto the loop, displacing any residual solvent out of the vent. On switching the valve clockwise to the alternative inject position, the solvent stream is diverted through the load loop, introducing the sample onto the column (Fig. 11.25).

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... 

With the exception of on-line trace enrichment and/or derivatisation systems, the form of injection is almost exclusively by use of a sample loop with rotary valve (Rheodyne or similar). Normally the size of sample loop is used to decide sample size rather than injection volume. As in other types of laboratory, septum type injection systems in environmental laboratories have long been superseded. 

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