Instrument, autosampler

Force the solution through the Alter cartridge into a clean glass vial with a TeAon-lined lid for storage. Just prior to analysis, this Altered extract is diluted 1 1 (v/v) with internal standard solution. The combination of exAact with internal standard solution may be made directly into the instrument autosampler vial. 

Attach a 25-mm Acrodisc nylon Alter carAidge to the LuerLok Atting of a 10-mL disposable syringe, and transfer approximately 1.5 mL of extract to the syringe barrel. Force the solution through the Alter carAidge directly into a clean instrument autosampler vial. 

Fig. 9.6 Different mechanisms for placement of the final analytical solution in the measuring instrument. Indirectly, via the instrument autosampler, which can receive either a vial (A) or a sample aliquot to be held in cups (B). Directly, by means of a sensor (C) or by aspiration (D) at a fixed point where the tube is taken or with the aid of a moving aspiration tube, which is inserted by the robot arm (RA) in each tube in the rack in turn.

Figure 3 LC-GC instrument autosampler, two syringe pumps (main pump and slave pump), LC-switching box with injection valve, valve with first LC column and backflush loop (filled from pressurized bottle, not shown), second LC column on heart cutting valve, LC detector (mostly UV), transfer valve directing to waste or into GC, on-column injector or other inlet device, precolumn (coated or uncoated) ending on T-piece directing to solvent vapor exit or separation column.

The use of "fixed" automation, automation designed to perform a specific task, is already widespread ia the analytical laboratory as exemplified by autosamplers and microprocessors for sample processiag and instmment control (see also Automated instrumentation) (1). The laboratory robot origiaated ia devices coastmcted to perform specific and generally repetitive mechanical tasks ia the laboratory. Examples of automatioa employing robotics iaclude automatic titrators, sample preparatioa devices, and autoanalyzers. These devices have a place within the quality control (qv) laboratory, because they can be optimized for a specific repetitive task. AppHcation of fixed automation within the analytical research function, however, is limited. These devices can only perform the specific tasks for which they were designed (2). 

In principle, on-line SPE-LC can be automated quite easily as well, for instance, by using Such programmable on-line SPE instrumentation as the Prospekt (Spark Holland) or the OSP-2 (Merck) which have the capability to switch to a fresh disposable pre-column for every sample. Several relevant applications in the biomedical field have been described in which these devices have been used. Eor example, a fully automated system comprising an autosampler, a Prospekt and an LC with a UV... 

Sample solution instability or incomplete extraction/separation would show up if several aliquots from the same sample work-up were put in a series of vials that would be run in sequence that would cover at least the duration of the longest sequence that could be accommodated on the autosample/instrument configuration. For example, if an individual chromatogram is acquired for 5.5 minutes, postrun reequilibration and injection take another 2.75 minutes, and 10 repeat injections are performed for each sample vial in the autosampler, then at least 15 60/(5.5 -I- 2.75)/10 = 11 vials would have to be prepared for a 5 P.M. to 8 A.M. (=15 hour) overnight run. If there is any appreciable trend, then the method will have to be modified or the allowable standing time limited. 

In the last several years, on-line extraction systems have become a popular way to deal with the analysis of large numbers of water samples. Vacuum manifolds and computerized SPE stations were all considered to be off-line systems, i.e., the tubes had to be placed in the system rack and the sample eluate collected in a test-tube or other appropriate vessel. Then, the eluted sample had to be collected and the extract concentrated and eventually transferred to an autosampler vial for instrumental analyses. Robotics systems were designed to aid in these steps of sample preparation, but some manual sample manipulation was still required. Operation and programming of the robotic system could be cumbersome and time consuming when changing methods. 

Instrumentation — The parallel LC/MS/MS system for this application was operated under the dual online SPE mode. Figure 2.7 is a flow diagram for the dual stream and Figure 2.8 depicts the staggered timing scheme. Figure 2.9 shows the autosampler setup in action. 

This level of control requires a controlling script from the instrument vendor and is for more serious programmers. Direct HPLC control by the MS and multiple staggered LC capabilities provided by several autosampler and instrument vendors fulfill the function but may limit the hardware used or require purchase of software/hardware. 

As with any analytical instrumentation that incorporates an autosampler, it is essential to evaluate the percent carryover obtained for a particular analyte under particular rinsing conditions. For these evaluations, a cartridge packed with a C18 stationary phase (80 x 0.5 mm/column) was employed. Gradient and detection conditions were the same as those described for the evaluation of retention time and peak area reproducibility (see Section 6.3.2). 

A simple system is comprised of an isocratic pump, a manual injector, a UV detector, and a strip-chart recorder. A schematic diagram of an HPLC instrument is shown in Fig. 15.4. This simple configuration is rarely used in most modern laboratories. A typical HPLC system is likely to consist of a multi-solvent pump, an autosampler, an on-line degasser, a column oven, and a UV/Vis or photodiode array detector all connected to and controlled by a data-handling workstation. Examples of modular and integrated systems are shown in Fig. 15.5. Some of the important instrumental requirements are summarized in Table 15.2. 

The lncos-50 is a relatively low-cost benchtop instrument as opposed to the research grade instruments discussed earlier. The gas chromatography-mass spectrometer transfer lines allow it to be used with either the Hewlett Packard 5890 or the Varian 3400 gas chromatographs. The Incos 50 provides data system control of the gas chromatography and accessories such as autosampler or liquid sample concentration. It can be used with capillary, wide-bore or packed columns. It performs electron ionization or chemical ionization with positive or negative detection. It also accepts desorption or other solids controls. 

OIC Analytical Instrument supply the 4460A purge and trap concentrator. This is a microprocessor-based instrument with capillary column capability. It is supplied with an autosampler capable of handling 76 sample vials. Two automatic rinses of sample lines and vessel purge are carried out between sample analyses to minimize carry-over. 

In this instrument the sample is first oxidized in a pure oxygen environment. The resulting combustion gases are then controlled to exact conditions of pressure, temperature and volume. Finally the product gases are separated under steady-state conditions and swept by helium or argon into a gas chromatography for analysis of the components. The equipment is supplied with a 60 position autosampler and microprocessor controller... 

Let us dwell on Figure 6.4 for a moment. The standards and sample solutions are introduced to the instrument in a variety of ways. In the case of a pH meter and other electroanalytical instruments, the tips of one or two probes are immersed in the solution. In the case of an automatic digital Abbe refractometer (Chapter 15), a small quantity of the solution is placed on a prism at the bottom of a sample well inside the instrument. In an ordinary spectrophotometer (Chapters 7 and 8), the solution is held in a round (like a test tube) or square container called a cuvette, which fits in a holder inside the instrument. In an atomic absorption spectrophotometer (Chapter 9), or in instruments utilizing an autosampler, the solution is sucked or aspirated into the instrument from an external container. In a chromatograph (Chapters 12 and 13), the solution is injected into the instrument with the use of a small-volume syringe. Once inside, or otherwise in contact with the instrument, the instrument is designed to act on the solution. We now address the processes that occur inside the instrument in order to produce the electrical signal that is seen at the readout. 

This chapter presents an overview of current trends in high-pressure liquid chromatography (HPLC) instrumentation focusing on recent advances and features relevant to pharmaceutical analysis. Operating principles of HPLC modules (pump, detectors, autosampler) are discussed with future trends. 

The IBW of a standard system can be reduced to 30-40 jL by using shorter lengths of 0.005-0.007" i.d. tubing and a semi-micro flow cell (2-3 tL).i° Further reduction might involve a low dispersion micro-injector or a redesign of the autosampler. Table 4 summarizes the typical IBW and other instrumental requirements of various column types from conventional (4.6 mm), Fast TC, minibore (3 mm), narrowbore (2 mm) and microbore (1mm) to micro TC (<0.5mm) columns. Note that the dispersion... 

A system is typically comprised of multiple instrument components. Therefore, there is usually an individual IQ for each of these instruments and for any corresponding instrument control/data-handling software. The typical instrument components making up an HPLC system include a binary or quaternary HPLC pump, an autosampler supporting multiple vials or microtiter plates (autosamplers often include cooled Peltier trays for sample stability), a column oven, and a UV-Vis or photodiode array (PDA) detector. 

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