Hardware injector

At present, micro-HPLC is not widely used despite its obvious advantages. For years, the lack of suitable instrumentation/hardware inhibited the use of micro-HPLC. Modification of conventional equipment helped kick-start the technique but the lack of suitable hardware (injectors/capillary columns) still prevented its widespread use. These issues have been addressed in the laboratories of micro-LC practitioners in academia and industry and by a few commercial suppliers. However, there still remains a perception that micro-LC is difficult to perform and therefore the exciting advantages of the technique go unrealized by many in the separation sciences. With... 

Hardware requirements — The system controller responsible for synchronizing the events is defined as LC System 1. It requires at least two time event outputs to trigger the injection of LC System 2 and start MS data collection. If MS fails, the injection of LC System 1 should be inhibited. Autosampler with ready-in, alarm-in, and stop inputs indicate capability to be stopped remotely. The autosampler of LC System 2 must be able to prepare a sample before the run from LC System 1 is finished and hold the sample in the injector loop until an injection signal is received. A manual injection input devices indicates that the autosampler can perform the required function. 

For the water analysis, automation is clearly best achieved with an auto-injector for the mechanical handhng of the samples coupled with on-hne data capture, using the computer to analyse the peak data. Serious consideration was given to employing the very considerable in house automation experience to construct a purpose-built auto-injector. However, in the interests of a speedy implementation of the automatic system, it was decided to purchase a commercially available auto-injector and to concentrate the laboratory s efforts on the area of on-hne data capture. Interfacing the complete system assembly via a data communications network required the development of a special control device (commhox), which allowed the LGC hardware to run unattended hut provided an audible warning in event of a fault condition. 

The retention equation allows us to understand the first major difference between the CCC solute retention and the retention obtained with any other chromatographic technique. Usually, in chromatography, the same solute mixture separated on the same column and using the same mobile phase produces the same chromatogram. If it is not the case, it is a sign of column wearing or problems in the hardware (pump, detector, or injector). 

The testing of the hardware should cover the functionality of the instrument expected during normal operation. For example, the testing for an HPLC system would include the operation of the pump, the injector, and the detector [15]. 

Sample introduction is a major hardware problem for SFC. The sample solvent composition and the injection pressure and temperature can all affect sample introduction. The high solute diffusion and lower viscosity which favor supercritical fluids over liquid mobile phases can cause problems in injection. Back-diffusion can occur, causing broad solvent peaks and poor solute peak shape. There can also be a complex phase behavior as well as a solubility phenomenon taking place due to the fact that one may have combinations of supercritical fluid (neat or mixed with sample solvent), a subcritical liquified gas, sample solvents, and solute present simultaneously in the injector and column head [2]. All of these can contribute individually to reproducibility problems in SFC. Both dynamic and timed split modes are used for sample introduction in capillary SFC. Dynamic split injectors have a microvalve and splitter assembly. The amount of injection is based on the size of a fused silica restrictor. In the timed split mode, the SFC column is directly connected to the injection valve. Highspeed pneumatics and electronics are used along with a standard injection valve and actuator. Rapid actuation of the valve from the load to the inject position and back occurs in milliseconds. In this mode, one can program the time of injection on a computer and thus control the amount of injection. In packed-column SFC, an injector similar to HPLC is used and whole loop is injected on the column. The valve is switched either manually or automatically through a remote injector port. The injection is done under pressure. 

Configuration files for hardware components are saved on the hard disks in directories in which names indicate the serial number of the particular component, for example, files for injector serial number 34 are located in the directory SI00034, files for column over serial number 7 are located in the directory 2G00007. The recent tuning parameters for... 

All detectors and injectors were connected to a PSS GPC 2000 Data Station. Data acquisition, timed events, and all calculations were done with 2D-CHROM hardware and software (V 2.0) from PSS. 

The use of ultra-high-pressure regimes and/or flow rates in the micro- or nanoliters per minute range imposes unique requirements on LC system hardware, such as pumps, valves, injectors, connecting tubing, column construction, stationary phases, column heating systems, detection flow cells, and the detector s data collecting speed. 

The review of data and evaluation of the run for acceptance based on the criteria established during method validation can be found in Section 10.5.3, but in this section the instance considered is that when the analytical run fails prior to completion of the inj ection sequence or upon inspection of the data and it is apparent that there was a hardware or software failure of some kind. For events of this kind the system will need to be checked for performance to determine the nature of the failure, and repaired if necessary prior to resumption of any additional analyses. Examples for reasons why a run could fail prior to completion include hardware or computer failure, intermittent software failures, clogged injectors or broken syringes. 

The initial instrument qualification process is detailed and comprehensive and includes both software (computer programs used in data acquisition, analysis, and archiving) and hardware (pumps, detectors, injectors, etc.). Once the instrument is qualified then methods themselves are developed and validated. The development process includes the initial evaluation of the appropriateness of the test, which is often determined by the ability of the method to meet targeted method requirements or mandates (linear range, linearity, accuracy, quantitation limits, resolution, etc.). Once these fundamental requirements are met, the cost effectiveness and overall efficiency are reviewed. Upon acceptance, a developed method then goes through a validation process. 

The basic coextrusion process consists of the generation of two or more melt streams and their confluence while in the melt phase. The number of separate extrusion systems is determined by the number of polymer types. This is typically 2, but occasionally 3 and exceptionally up to 10. Each polymer type to be incorporated in the structure is separately melted, pressimized, and (optionally) filtered in parallel extrusion systems before flowing into the coextrusion hardware. The optimum method of bringing the separate melts together depends primarily on their respective flow behaviors. The melt layers must remain distinct but well bonded in the process from the point(s) of confluence through to sohdification. There are basically two hardware configurations in use for common polymers the multi-manifold die and the injector block. Combinations of the two are also possible for complex structures (8,9). 

The injector assembly mounts to the frame as shown in figure 27. The four 1/2 inside diameter shaft collars shown in the drawing can be made or you can buy them at most hardware and farm supply stores. 

Not only are these tools important for injector development, they also provide critical information used as inputs for computational fluid dynamics (CFD) analysis. As mentioned previously, simulation plays a critical role in SCR system development. The more accurate the measurements are while quantifying an injector s spray quality, the more accurate the simulated spray quality will be which will in turn give better correlation between simulation and hardware testing. 

The column inlet (or injector) provides the means to introduce a sample into a continuous flow of carrier gas. The inlet is a piece of hardware attached to the column... 

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