Optimization of a Stabinger Viscometric Method to Maximize Sample Throughput: Balancing the Competing Interests of Speed, Cost, and Data Quality

摘要

The U.S. Army Oil Analysis Program has sought to purchase automated viscometers (with autosamplers) for its centralized laboratories. The Army OAP has a sample throughput requirement of at least 40 samples per hour. In principle, this is within reach of the Anton Paar SVM3000 Stabinger viscometer. In addition, anecdotal evidence in our laboratory had led to disagreement regarding flush volume and measurement time requirements for optimal and sufficient performance of the SVM3000. Therefore, an investigation of the Stabinger viscometer was carried out to provide a scientific basis for parameter optimization while simultaneously balancing the competing requirements for speed, cost, and data quality. As a result of this investigation, it has been determined that the rigors of ASTM standard D 7042- 04 exceed the programmatic requirements of the Army OAP. The ASTM standard biases the golden triangle (good, fast, cheap) in favor of higher data quality and sacrifices the competing interests of cost and speed. It has been determined that measurement duration (stabilization time) can be set to 60 seconds while meeting Army OAP programmatic needs for data quality, but the extant firmware does not permit this. In addition, this study showed that flush volumes of 20.0 mL satisfactorily purge and recondition the densimeter and viscometer measuring chamber without external washes between the analyses. This practice yields data of sufficient quality for Army OAP decision-making. This flush volume requires the 24-position carousel for the autosampler, which uses 50 mL sample vials. A manually operated SVM series Stabinger viscometer can achieve or exceed the required Army OAP sample throughput when injecting with a 10 mL syringe, but an autosampler-equipped SVM series Stabinger viscometer is unable to do so with the current firmware configuration.