How are detector baseline variations addressed? - WKB201951

ENVIRONMENT

• 2487 Dual-Wavelength Absorbance Detector
• 2488 Multichannel Absorbance Detector
• 2489 UV/Vis Detector
• 2996 PDA Detector
• 2998 Photodiode Array Detector
• ACQUITY UPLC Tunable UV Detector
• ACQUITY UPLC PDA Detector
• ACQUITY UPLC PDA eλ Detector 

ANSWER

Qualification is intended to demonstrate that the equipment operates as expected. Slight variations among instruments are acceptable and it would be realistically impossible to expect them to perform 100% the same.

The baseline variations of the detector can be affected by the following, including but not limited to:

• Overall system pressure, movements of pumps and valves
• State of system cleanliness
• Lamp energy
• Environment differences such as temperature, humidity, voltages, sources of mechanical vibrations close to the detector, and so on
• Movements such as knocking, opening, or closing the front door
• Grade of the material, batch and lot of the electronic components used during manufacture

Our advice to customers is that zooming in so much on the baseline is not necessary, and there is often no need to do so. Customers do not get to make up the detector specifications. The baseline variations are considered acceptable if they meet the Waters specifications for the Noise and Drift test.

ADDITIONAL INFORMATION

Standardized procedures for qualification that are under revision control are the normal situation and encouraged. Occasionally, a customer prefers a different test or specification and is willing to pay for any additional work required. Although we want to be flexible in working with the customer in such situations, we must advise customers against designing tests that are unlikely to pass.

Although the customer may have the end decision on the pass/fail criteria used, it is important to note that customers own the responsibility for validating and determining suitable pass/fail criteria for any nonstandard test. For its part, Waters agrees to perform the customer's test on a best effort basis, but we do not guarantee that tests not validated by Waters will pass.

Waters' tests are developed with an appropriate safety margin. While they will pick out a faulty system, they will not fail a functional system that merely has items that have a little wear on them. In the situation where a system fails the customer's version of a test using their configuration and/or specifications, this does not necessarily mean that it would fail the Waters approved version of the test. As such, repairs required to allow the system to pass the customer's pass/fail criteria may be billable even if the customer is under warranty or plan.

The customer should be advised to review and, if necessary, revise (under their change control system) their pass/fail criteria to avoid additional future expense.