Injection valve, HPLC

Automated sample injection systems and multiport injection valves (HPLC) have good reproducibility so that a series of injections can be made with a... 

Tubing outer diameter 1.59 mm Injection of further streams by HPLC-type sample injection valves... 

Before the actual reaction tube, a pre-heating tube is attached to bring the fluids close to reaction temperature [1], Injection of further streams is performed by HPLC-type sample injection valves. 

Figure4.62 Experimental set-up for liquid/liquid experiments (a) reservoir for the substrate in n-heptane (b) water reservoir (c, d) high-pressure liquid pumps (e) HPLC injection valve with sample loop for catalyst injection (f) micro mixer ...

A stream of ethylene is fed into the reactor by use of quaternary LC pumps and subsequently dissolved in a 1.90 ml h toluene stream [1]. Ethylene is handled at 60 °C, well above the critical temperature. Catalyst additions are fed via HPLC-type sample injection valves. Various combinations of precatalysts and activators were sampled and loaded by an autoinjector. Catalyst solutions typically were diluted 20-fold within the micro reactor. 

Figure 5.28 Schematic of the experimental set-up. Water/ethylene glycol/SDS reservoir (a) high-pressure liquid pumps (b) catalyst/ substrate HPLC injection valve with 200 pi sample loop (c) hydrogen supply, equipped with mass flow controller (d) micro mixer (e) heating jacket (f) tubular glass or quartz reactor (g) back-pressure regulator (h) [64],...

Sample preparation, injection, calibration, and data collection, must be automated for process analysis. Methods used for flow injection analysis (FLA) are also useful for reliable sampling for process LC systems.1 Dynamic dilution is a technique that is used extensively in FIA.13 In this technique, sample from a loop or slot of a valve is diluted as it is transferred to a HPLC injection valve for analysis. As the diluted sample plug passes through the HPLC valve it is switched and the sample is injected onto the HPLC column for separation. The sample transfer time typically is determined with a refractive index detector and valve switching, which can be controlled by an integrator or computer. The transfer time is very reproducible. Calibration is typically done by external standardization using normalization by response factor. Internal standardization has also been used. To detect upsets or for process optimization, absolute numbers are not always needed. An alternative to... 

The basic SFC system comprises a mobile phase delivery system, an injector (as in HPLC), oven, restrictor, detector and a control/data system. In SFC the mobile phase is supplied to the LC pump where the pressure of the fluid is raised above the critical pressure. Pressure control is the primary variable in SFC. In SFC temperature is also important, but more as a supplementary parameter to pressure programming. Samples are introduced into the fluid stream via an LC injection valve and separated on a column placed in a GC oven thermostatted above the critical temperature of the mobile phase. A postcolumn restrictor ensures that the fluid is maintained above its critical pressure throughout the separation process. Detectors positioned either before or after the postcolumn restrictor monitor analytes eluting from the column. The key feature differentiating SFC from conventional techniques is the use of the significantly elevated pressure at the column outlet. This allows not only to use mobile phases that are either impossible or impractical under conventional LC and GC conditions but also to use more ordinary... 

Principles and Characteristics Continuous-flow (or dynamic) FAB/FTB [102] and frit FAB/F1B [103] offer a means of introducing samples in solution into a continuous flow of solvent which terminates at the modified FAB/FIB probe tip, and they extend the applicability of FAB. Samples are injected through a conventional HPLC injection valve, or solutions are simply drawn in by the high vacuum in the ionisation source of the mass spectrometer. These very similar techniques are particularly amenable to coupling with HPLC columns, and ionisation of the sample is unchanged with respect to conventional FAB and FIB/LSIMS. 

Figure 7.5 Schematic representation of a coupled SFE-HPLC system employing a recirculating extraction manifold interfaced to HPLC via a sample injection valve. After Lynch [54]. Reprinted from T. Lynch, in Chromatography in the Petroleum Industry (E.R. Adlard, ed.), J. Chromatography Library, 56, 269-303, Copyright (1995), with permission from Elsevier...

A microparticulate hplc column is a very efficient filter, and if the mobile phase contains any particulate matter, or acquires it from the pump and/or the injection valve due to wear, it will collect at the top of the column. If this happens, the pressure drop across the column for a given flow will gradually increase, and the column may eventually become completely blocked. To prevent this happening, the mobile phase should always be filtered before use, preferably through a 0.5 p,m porosity filter, and guard and scavenger columns should be used as a matter of routine (see Section 5.3.2). 

The loop for the 2nd-D was loaded with the effluent of the 1 st-D at 50 pL/min for 1 min 58 s, and then the injection valve was turned to inject the 100 pL fraction for 2 s onto the 2nd-D HPLC. The flow rate was 5 mL/min, and the valve was turned back for the next loading, resulting in fractionation of the lst-D every 2 min. In this case less than 2% of the effluent from the 1 st-D was wasted during sample injection. The 2nd-D effluent eluted at 5 mL/min from the 2nd-D column, passed through a UV detector, and then was split by using a T-joint at approximately a 1/140 split ratio, resulting in a flow rate of ca. 36 pL/min going into the spray capillary for ESI-TOF-MS detection. 

Figure 12 Schematic representation of 2D chromatography using an eight-port injection valve and two storage loops. (A) In the first position of the valve the storage loop 1 is loaded with the HPLC eluent, while the content of the storage loop 2 is analyzed by SEC. (B) In the second valve position storage loop 2 is loaded with HPLC eluent and the content of loop 1 is analyzed according the molecular size of the solute.

Figure 10.1 shows a basic online SPE LC/MS/MS system, a column switching system (Kahlich et al. 2006) that includes a six-port switching valve, an injection valve, an SPE cartridge, an analytical column, SPE washing and HPLC pumps, and MS detector. The online process has three steps ... 

Samples that have low vapor pressure or extracts that are expected to contain components of low volatility can be analyzed by HPLC. The liquid sample is introduced via an injection valve and components separated by a chromatographic column. As components exit the column, they enter the MS where some of the eluent is stripped away and the remaining liquid enters the mass spectrometer. As with GC-MS, the mass spectrometer does not measure... 

Examine the HPLC instrument to which you are assigned. Find the inlet line to the pump and place the free end of this line in the reservoir containing the mobile phase with the 90/10 composition. Trace the path of the mobile phase from the reservoir, through the pump, injection valve, column, and detector, to the waste container so that you identify and recognize all components of the flow path. Turn on the pump and detector and begin pumping the mobile phase at a rate... 

A precision injection device is required to minimize sample dispersion and keep the sample volume and length of sample zone reproducible. This is normally a rotary valve similar to that used for injection in HPLC. Exact timing from sample injection to detection is critical because of rapidly occurring reactions which are monitored before they reach completion. This demands a constant flow rate with low amplitude pulsing, normally achieved by a peristaltic... 

Injectors introduce the sample into the mobile phase under high pressure. There are several approaches to injection in HPLC, such as syringe injection via septum, a combination of a septum and syringe or a valve injection. Valve injection is the method of preference in up-to-date HPLC instrumentation. 

Fig. 5.15 Analytical set-up for on-line label-free assay based on ESI-MS. MS instrument Ion-trap mass spectrometer (LCQ Deca, Thermo Electron). PI Carrier/HPLC pump. P2 HPLC pump delivering receptor solution. P3 HPLC pump delivering dissociation solution. PA HPLC pump for final LC-MS analysis of released ligands. 1 Mixing union. 2 Microcoil reactor. VI injection valve.

Apparatus. The major components in the HPLC system (Figure 2) include a Varian HPLC pump (model 5000, Varian Assoc., Walnut Creek, CA), Altex injection valve (model 210, Beckman Inst., Fullerton,... 

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 25-18 Injection valve tor HPLC. Replaceable sample loop comes in various fixed-volume sizes.

Fig. 2 Configuration used for postcolumn derivatization detection in HPLC. E = eluent P = HPLC pump IV = injection valve CC = chromatographic column R = pump reagent RC = reaction coil D = detector.

Fig. 2 Postcolumn derivatization scheme for aflatoxin analysis 1, mobile phase 2, HPLC pump 3, injection valve 4, precolumn 5. analytical column 6, derivatizing agent solution 7, auxiliary HPLC pump 8, T-valve 9, oil or water bath 10, reaction coil 11, fluorescence detector 12, waste 13, chromatographic data handling system.

These two very recent papers deal with a novel method of MISPE, the lab-on valve format. Here renewable portions of MIP are dosed into the loop of an injection valve. The full MISPE and HPLC process evolves automatically. Besides a detailed description of the technique used, these papers are also important from other aspects. 

HPLC The sample was injected on to an ACS Model LC750 chromatograph with dual pumps (Applied Chromatography Systems Ltd, Luton, Beds, U.K.) by means of a loop injection valve,... 

The basic components of an HPLC system are (1) a pump with a constant flow control (2) a high-pressure injection valve (3) a chromatographic column (4) a detector and (5) a strip-chart recorder or a data system for measuring peak areas and retention times. Calibration standards are prepared at various concentrations and the retention times and peak areas of the analytes are compared against the standard solutions of analytes for their identifications and quantitations. 

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