Most analytic methods are subject to drift. Describe a system which could be used to determine the rate of drift of an analytic method.

To determine the rate of drift of an analytic method, you can set up a system that involves comparing the results of the method over time. Here's a description of one possible system:

1. Data Collection: Start by collecting a set of samples or test materials that represent the target analyte. Ideally, these samples should cover a wide range of concentrations or values.

2. Initial Calibration: Calibrate the analytic method using the samples collected in step 1. The calibration establishes a relationship between the measured signal and the known concentration or value of the analyte.

3. Regular Measurements: Perform measurements using the calibrated analytic method on a regular basis. The frequency of measurements depends on the expected rate of drift and the importance of accurate results. For example, you may choose to measure daily, weekly, or monthly.

4. Reference Standard: Alongside the regular measurements, maintain a reference standard with a known concentration or value of the analyte. This reference standard should be stable and traceable to a recognized standard if possible.

5. Comparative Analysis: Periodically, analyze the reference standard using both the regular analytic method and an independent, highly accurate method. This is known as the "reference method." The reference method should have minimal or no drift. The results from the reference method will serve as a benchmark to compare the regular method's performance.

6. Drift Analysis: Compare the results obtained from the regular method with those of the reference method. Calculate the difference between the two sets of results. This difference will indicate any drift in the regular method.

7. Trend Monitoring: Track the drift over time by monitoring the differences calculated in step 6. Plotting these differences on a graph or chart will help visualize the rate of drift. You can also calculate statistical parameters such as the slope or rate of change to quantify the drift.

By following this system, you can assess the rate of drift of an analytic method and take corrective actions accordingly. Regular calibration, reference standard analysis, and trend monitoring are key components for accurate drift determination.