Review and Validation of Hourly VOC Data Collected by PAMS AutoGC Systems

Best Practices in Indoor and Outdoor Air Monitoring
Oral Presentation

Prepared by C. Meyer
Orsat, LLC, 1416 E Southmore, Pasadena, Texas, 77502, United States


Contact Information: carol@orsat.com; 281-652-6423


ABSTRACT

Unlike other types of automated gas chromatographic systems used for process control the VOC data collected by AutoGC systems used at Photochemical Assessment Monitoring Sites (PAMS) is collected for use in ambient air modeling. In the process control and often in the regulatory world chromatographic data is used as a snapshot on which an immediate or relatively immediate decision will be made. Although most systems have quality controls in place to insure that the data is accurate, when issues do arise the remedies are often quite different from those used in continuous ambient monitoring where the data is collected for archival purposes. Often a second analysis is done or even analysis with a different analyzer is completed to arrive at the necessary snapshot of the stream being monitored. Data collected for ambient air modeling requires that every analysis meet minimum requirements for quality in order to develop the necessary population of data to allow modelers to adequately represent the spacial and temporal data necessary for sophisticated models.
Since these automated systems generate large amounts of data, some strategy must be developed for insuring that the data is accurate. Like data collected in a laboratory, data must be reviewed and validated to achieve this. The best chromatographic systems are capable of repeatable, accurate analysis but when systems are unattended it is not always clear when problems arise. Some systematic review of this large amount of data must be achieved to validate results. Some problems which occur can be corrected by simply reprocessing some data. Changes in flows, temperatures, humidity may case analytes to shift slightly and become miss identified. Equipment failures or power interruptions occur and data must be reviewed to determine accuracy and ultimately some will be lost. While fully automated systems can collect a large amount of quality data, they can also collect a large amount of poor quality data as well. Identifying problems, implementing corrective actions and determining what is valid or invalid is still a challenge. This presentation will address a comprehensive plan for the review and validation of hourly VOC data generated from AutoGC sites based on 20 years of experience and operation of over 30 sites year-round in Texas.