Autosampler test

The autosampler is switched on and the displays and connections are checked visually. In the case of complaint the necessary measures are planned and documented. 

For the determination of repeatability injections 8-13 of the test sequence are evaluated. The precision (in %) is calculated from the peak areas (Section 25.8). 

The carry over of the autosampler is calculated from injections 13 and 14 of the test sequence. 

0 Carry over 0.1% or less for autosamplers with flushing, 0.2 % or less for autosamplers without flushing. 

Remark The injection volume and the number of flushing cycles is to be noted in the documentation. 

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Flow precision Determine retention time RSD of six 10-pL injections of ethylparaben (same as in autosampler test) RSD <+0.5%... 

For the determination of the dynamic detector noise it is necessary to equilibrate the whole HPLC system for at least 30 min according to the conditions described in the autosampler test. The recording unit is set to 0.5-1.5 X 10 AU and the detector signal is recorded during 10 min. The detector noise is determined graphically (peak-to-peak) and documented. Note that this is only a test of short-time noise. A possible drift (long-time noise) is not included. 

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. 

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. 

System test—turn off all modules and power-up to perform startup diagnostics. Perform static leak test of the pump and compression test of the autosampler as suggested by the manufacturer. 

For autosampler precision, 10 consecutive lO-pL injections of an eth-ylparaben solution (20 J,g/mL) are used (Figure 6). A Waters Symmetry column packed with 5- J,m particles is used. The manufacturer s specification for peak area precision at 0.5% RSD is adopted as the acceptance criterion. This stringent precision criterion is required for precise assay testing of drug substances typically specified at 98-102% purity. The linearity test is performed by single injections of 5, 10, 40, and 80 pL of the... 

FIGURE 7 Waters Millennium report showing the linearity verification for the autosampler.This test also verifies the combined linearity of the system including the autosampler, detector, and the data system. 

The autosampler injection accuracy test involves the gravimetric determination of the average volume of water withdrawn from a tared vial filled with water after six 50- uL injections. The procedure, adopted from a manufacturer s OQ, takes less than 10 min and has an acceptance criterion of 50 2 J,L (Figure 9). 

This test is then repeated at various injection volumes, typically 3-4 volumes in all. Common volumes that are chosen are 5, 10, 25 and 50 uL, but will depend on the range of the particular autosampler, capacity of the test column and the user s intended injection range. Within the 5-20 uL range, the typical %RSD specification is <0.5%. 

Experiments 10-27 are designed to check the autosampler injection precision, pump repeatability and detector/system linearity. One programs the system to automatically inject multiple replicate volumes of a certified test standard. One typically injects 6-10 replicates per volume. The standard component s peak areas are used for calculated injection precision (reproducibility) and system linearity whereas, the retention times are used to calculate pump repeatability. 

Eor injection precision test details and calculations, refer to the procedure described earlier under Autosampler in section (j) of the OQ guidelines. 

To test the autosampler s performance independence of vial location, it would be recommended that standards are injected out of various locations in the autosampler tray. This is shown in the Vial colnmn for experiments 10-27 in Figure 10. It should be noted that the higher vial positions may have to be tailored to the capacity of the actual autosampler tray. 

Finally, Experiment 28 is used to check for any autosampler/ system sample carryover. A blank water sample is injected immediately following the highest injected volume of the preceding precision/repeatability/linearity test. Any carryover is then calculated as in the procedure described earlier under Autosampler in section (j) of the OQ guidelines. 

It is recommended that OQ test the following on an HPLC system flow accuracy, pump compositional accuracy, pressure pulsations, column oven temperature accuracy/stability, detector noise/drift and wavelength accuracy, autosampler injection precision and carryover. 

The autosampling device is critical to the integrity of automated dissolution testing systems as it serves as the interface between the dissolution apparatus and the sample analysis systems. The autosampler takes... 

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