Autosampler Operation

P 53] Before operation, a start-up time of about 10 min was applied to stabilize pressure in the chip micro reactor ([R 6]) [20]. As a result, a stable flow pattern was achieved. The reactant solutions were filled into vials. Slugs from the reactant solutions were introduced sequentially into the micro chip reactor with the autosampler and propelled through the chip with methanol as driving solvent. The flow rates were set to 1 pi min The slug volume was reduced to 2.5 pi. 

The Benchmate program is started. After unattended operation, the vials are removed from the EasyFill module and placed on the LC/MS/MS autosampler tray for analysis. Each Benchmate Workstation will process up to 50 samples in less than a 24-h period. 

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. 

Cool on-column >250 pm column (i.d.) 1 ppm (FID) Reduced thermal degradation and discrimination Wide range of analyte concentrations High sample capacity (LVI) Autosamplers Direct quantification Excellent precision Control of operational conditions (initial oven temperature) Optimisation required Not applicable for polar solvents Column contamination by dirty matrices Poor long term stability... 

In our system the data collection process is essentially a passive slave to the chromatograph, which is controlled by its own internal microprocessor. An amplifier matches the voltage output from the strip chart recorder terminals on the chromatograph to the A/D converter input. The data collection program uses the "Equilibration Pulse" and "Injection Pulse" relay closures shown in Figure 1 to synchronize the data collection process with the operation of the autosampler on the chromatograph. 

Computer hardware and software used in 2DLC generally take care of three critical operations. These include real-time control of valves and sequencing functions such as autosampler control, formatting the time series data into a 2D data matrix, and analyzing the data. These will be described in some detail. 

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. 

Unattended operation possible, loop-sampler option autosampler printer, option inorganic, carbon, purgeable carbon, total carbon and total organic carbon measurements possible... 

In general, gas chromatography will undoubtedly continue to be the method of choice for characterization of light hydrocarbon materials. New and improved detection devices and techniques, such as chemiluminescence, atomic emission, and mass spectroscopy, will enhance selectivity, detection limits, and analytical productivity. Laboratory automation through autosampling, computer control, and data handling will provide improved precision and productivity, as well as simplified method operation. 

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. 

FIGURE 10 A schematic of a push-loop autosampler which mimics the operation of a manual injection. 

FIGURE II A schematic of an integrated-loop autosampler under various operational cycles (a) flush, (b) sample fill, (c) inject. Reprinted with permission from Reference 16. 

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