To check accuracy of standard in HPLC analysis, 2 standard are prepared (std 1 for system suitability and Standard 2 to checking). They are prepared by separately weighing but the preparation is identical. They should have an area ratio between 98% to 102%. We ran 4 analysis on 4 different days and this ratio only met in 2 analysis (days 2 and 4). The HPLC and the column is the same, the stability of the standard is 5 days. New standars have been prepared and the same problem was found, only met specifications in some analysis despite of the standard, HPLC and column is the same. What could be the cause of this problem?
Your observation is unusual. Please investigate as follows,
- The reason could be system suitability requirements are not met. Hence, please ensure that system suitability meets the requirements as per your internal SOP.
- Another reason could be the stability of the mobile phase. Please ensure that the mobile phase is stable over 4 days. If not, then either degas the mobile phase before use or prepare a fresh mobile phase each time.
- Please use another column of the same make and composition with the same particle size of the packing material to verify this aspect.
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