Case Study 4 Equipment Malfunctioning

Case study 4 shows several examples of problems caused by equipment malfunctions and their subsequent diagnosis and solution. The first one involved a situation of poor retention time reproducibility of a gradient assay. It involved the analysis of a complex natural product, using a narrowbore column (2-mm i.d.) at 0.5 mL/min. System suitability test showed retention times to be erratic and could vary by 1-2 minutes without any obvious trends. Flow rate accuracy was found to be acceptable, however, the compositional accuracy test failed (see Chapter 9 on HPLC calibration). The tentative diagnosis was that of a malfunctioning of the proportioning valve. After its replacement, the retention time precision performance was re-established. 

The last example showed a case of a mysterious baseline rise occurring at exactly 30 min (encountered repeatedly like clockwork) during a long 

Data performance Retention time Degassing, column, temperature changes 

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