Injection precision

Precision injection molding where feasible, gamma radiation resistant formulations, and improved production traceability and quality. 

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... 

Define the following terms instrument precision, injection precision, intra-assay precision, ruggedness, intermediate precision, and interlaboratory precision. 

Many LC users are curious about the precision they can expect from an analysis. This question is often answered with specifications concerning flow rate precision, injection volume precision, and so forth. However, the precision of the analysis is influenced by all of the variables in the HPLC system, including operator error. Often within a laboratory, the precision of the LC analysis is within 1%. However, the larger question concerns the between-laboratory reproducibility of analyses. 

Hydrodynamic loading is consistently reported to be the more precise injection method. Hettiarachchi and Cheung have concluded that hydrodynamic loading should always be used for high-precision quantitative applications because it is less dependent on the ionic concentration of the sample buffer (62), but running buffer is the recommended sample diluent. 

An alternative way to implement hydrodynamic injection is to use an injector—commutator [60]. With this strategy (Fig. 6.12), volumes as low as 600 nL can be precisely injected and the sample carrier stream is not stopped, resulting in a more stable flow. The other advantages of hydrodynamic injection are maintained. 

Samples can be injected via a sample loop using a valve (Figure 3.12). Once the sample has been introduced into the loop, the valve is switched (manually or by electric actuation) to deliver the sample plug onto the analytical column. Autosamplers allow more precise injection. In this case, a carousel or tray of sample vials can be left unattended for automatic injection (by compressed air or nitrogen) at predetermined intervals (Figure 3.13). The volumes injected are usually in the range 5-500)tL but lower and higher volumes can be injected under certain conditions if required. 

With the next example shown in Figure 2.20, the speed-up of a gradient separation performed on modern UHPLC-type columns and instrumentation is discussed. The attempted use of a narrow bore (2.1 mm) column packed with 2.2 pm particles requires an instrument with significantly reduced extra-colunm volume. This also includes the adaptation of the flow cell volume and the requirement of faster data handhng by the detector electronics (which was already a prerequisite in the example in Figure 2.19). Moreover, the instrument must be able to handle precise injection of 2 pi sample volume and withstand a column pressure of almost 600 bar. 

Kennedy PK, Zheng R (2006) Shrinkage of injection molded material. In Greener J, Wimberger-Friedl R (eds) Precision injection molding process, materials, and applications. Hanser, Munich... 

Finally test and burn in sockets must be able to survive the test conditions with a high degree of tolerance and dimensional stahility. ESD grades of PAEK are use together with precision injection moulding for fine connector arrays. Blends of PAEK with amorphous polymers, or less crystalline polymers such as PEKK, can offer a lower tendency to warp and higher dimensional tolerance. 

Oxygen lancing This is also used for enrichment, but is typically associated with more severe or complex conditions. Lancing involves the precise injection of oxygen at the point where it is most needed. Enrichment is not as accurate and is less efficient than selective lancing, which injects more total oxygen. 

A less flexible but simpler technique in comparison to the FIA system is BIA, which presents several advantages such as high reproducibility, elevated sampling rate, fast analysis time, and rapid response. BIA presents comparable sensitivity to FIA and does not require pumps, tubes, and commutators to introduce the samples. Moreover, motorized micropipettes provide very precise injections of small sample volumes at the constant rate due to the reproducible movement of the internal piston [40,102,103]. 

P. Thienel, Impact of Preparation on the Properties of Precision Injection Moulding Pieces, VDI Seminar Injection moulding of thermoplastic pieces . [In German]. 

Liu, L.T CM. Process studies in precision injection molding. I process parameters and precision. Polym Eng Sci Jan 1996 36 1-9. 

Last and not least, it is eqrtipped with bottom hole temperature and pressure gauges allowing a precise injection monitoring, and with a two zone selective completion. 

A repeatable volume of the specimen to be analyzed is precisely injected into a gas chromatograph equipped with a flame ionization detector (FID). The peak area of each impurity is measured. Concentration of each impurity is determined from the linear calibration curve of peak area versus concentration. Purity by gas chromatography (GC) is calculated by subtracting Ae sum of the impurities found from 100.00. Results are reported in weight percent... 

The PA12-based elastomer compounds offered are suitable both for precision injection molding and for high-performance extrusion processing, e.g., for making tubing and films. PA12 elastomer compounds and their typical applications are listed in Table 11. 

With the contained system , pressure may be applied to both sides of the injection piston. The actual pressme value of both piston chambers is measured by pressure gauges, the screw position is read by the position-sensing system. With the contained system, it is possible to define and regulate the position of the screw precisely. With this system, precise injection speed or holding pressure profiles may be followed, since there are now control commands for apply pressure injection side, withdraw pressure injection side, and also apply pressure retraction side and withdraw pressure retraction side. ... 

The MID is manufactured by two-shot molding. The metallizable material PC/ ABS (polycarbonate, acrylonitrile butadiene styrene) of the first shot is enciosed in the second shot of PC (polycarbonate). The PC/ABS forms what wiii become the conductors, and the PC is the package. The pins contact the PCB and have to be dimensionaiiy stable, so precision injection moiding is a must. The PC/ABS is chemicaiiy metaiiized with Cu-Ni-Au. 

Yoon, K., An Experimental Study on Precision Injection Molding of Center-Gated Disks, Korean Journal of Rheology, 7,19-27 (1995). 

Kazmer, D., Precision Injection Molding, Chapter 10, Precision Process Control of Precision Injection Molding. 265-297. 

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