Introducing Quality Control in the Chemistry Teaching Laboratory Using Control Charts

Abstract

In subsequent years the QC chart archive will grow allowing for the optimization of the limits set at the start of each year. Limits set must not be too strict or too lenient but rather should allow for a reasonable compromise between allowing progress with laboratory teaching, yet providing regular incidences where trouble shooting is required. The detection and rectification of errors must be possible with reasonable extra care, within the time constraints of a laboratory teaching session and respecting student ability. Because of high incidences of calculation errors where results were calculated manually, we have opted for computer-assisted calculations (templates) allowing the focus to be on laboratory error in future. In the first year we were surprised to find that virtually all QC data points were outside the control limits for the simpler UV-vis experiment for master's and undergraduate students. We believe that feedback and student discussion prior to the start of the second year contributed to improved quality of results and better compliance for undergraduate students although most data points were still outside the staff-generated limits. Total compliance was achieved in the second year based on limits calculated using the first-year student data. For subsequent years we shall continue to use and fine tune student-generated limits for this experiment. For the HPLC experiment in the first year, total compliance for k and a 20% failure rate for N was achieved by master's students. The undergraduate class had a 30% failure rate for N and a 35% failure rate for k. These dramatically higher failure rates perhaps reflects the less experience of the undergraduate students. A marked improvement in quality of results was again observed for the second year. Undergraduates achieved total compliance with staff-generated limits of k and improved compliance in the QC test for N, with about 7% results outside the control limits of N, requiring troubleshooting and repeat analysis. For the HPLC experiment we intend to continue using staff-generated QC chart limits. Unlike for the UV-vis experiment, the wider student data-based limits are perhaps too lenient, not providing enough incidences where student action is required. We have found that the quality of results does not necessarily follow the perceived simplicity of an experiment. Each experiment is clearly unique and the process of establishing an appropriate mean and limits varies. The goal is the same in all cases, where adequate progress learning laboratory skills must be balanced with the provision of enough realistic troubleshooting scenarios (occasional quality failures). With time and a growing archive of QC data, the instructor can get a better feel for the level of performance that can be reasonably expected from students. An additional step in the future may be that a student or a small group of students could take charge of a particular QC chart, collecting data from other groups over consecutive weeks. By communicating with teachers and colleagues, they could help manage the quality and troubleshooting for their experiment, thereby taking responsibility and developing a greater sense of involvement with the laboratory function. Interestingly the QC components in the experiments, besides motivating the individual, were found to nurture a healthy element of competition between students helping to achieve better quality results. Students were shown the real-world fact that improving quality control is a dynamic never-ending yet essential task. Both the QC tolerances and achieved quality continually vary with changing technology, market expectations, and caliber of laboratory personnel. © Division of Chemical Education.