Table of Contents
Overview
The Merlin AutoGC Xplorer (MAX) is a cloud-based database designed to ingest data generated by chromatographic equipment deployed into EPA Photochemical Assessment Monitoring Sites (PAMS) which are collecting and analyzing hourly concentrations of up to 60 volatile organic compounds (VOC). MAX is a Structured Query Language (SQL) database of the data which includes the necessary information to allow users to view and graphically evaluate the hourly concentration data from these sites.
Orsat, LLC has developed and designed MAX to accommodate data originating from either PerkinElmer Ozone Precursor systems or Agilent systems using Markes International pre-concentration sampling system. These analytical systems incorporate a thermal desorption sampling system, a gas chromatographic system capable of separating the VOCs of interest and an chromatographic data system to integrate and quantitate the resulting chromatographic output. The format of the data from the chromatographic data system is generally an ASCII text output which has been formatted specifically for ingestion into the MAX system. Currently data formats for ingestion into MAX are available for the PerkinElmer Totalchom and Agilent OpenLab EZChrom edition chromatographic data systems.
Features
The PAMS AutoGC systems collect not only hourly ambient air data but also have Quality Control samples which are outlined in the EPA PAMS Technical Assistance Guidance document (TAD). While most agencies have large databases capable of accumulating ambient data for review by policy makers, they do not always have the ability to review large amounts of quality control data associated with these highly technical systems. MAX was designed specifically to allow program managers, operators and data validators to review both the ambient data and the quality control samples to evaluate in near real-time the performance of their systems. Multiple QC sample types are specified by the EPA TAD to reconcile the performance of each analyzer.
Quality Control Sample Types
- Calibration Verification Standard (CVS) or Continuing Calibration Verification (CCV) Standard
- Required daily
- Used to confirm system response daily; recoveries generally ± 30% specified in the Network configuration
- System Blank (SB) or Method Blank
- Required daily
- Used to determine concentrations of target compounds which may be contributed by the analytical system
- Laboratory Calibration Standard (LCS) or Second Source Calibration Verification (SSCV) Standard
- Required weekly
- Used to confirm original calibration by reference.
- Retention Time Standard (RTS)
- Required weekly
- Used to verify correct target identification by retention time windows in method.
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Format for Incoming Data - ASCII Text
The output format for data generated by the analytical data system must adhere to a specific ASCII text format to enable MAX to be able to correctly interpret and store the data. Orsat has generated output formats for both the Totalchrom and EZChrom data systems. The user will not only need this format for the output but will need their analytical method to adhere to specific requirements such as target names, response factor format and calibration units. Orsat can assist by supplying methods for each analytical and help the user to implement any necessary changes that might be required.
- Instrument Name - (Format “SITE-x”)
- Filename - specific format (see File Naming)
- Acquisition Time - the time the analytical data collection started.
- Process Date and time- the time the data file was generated
- Sample Name, generally Blank, Standard, Ambient Air, IQ-RTS, CS-LCS
- Instrument Name
- Instrument method filename
- Sequence filename
- Peak Details
- Component Name
- Amount in ppbC
- Retention time
- Peak Area
MAX was designed to identify the QC control samples by using a specific file naming paradigm. Thus filenames must be specific to the sample type. Filenames are generated using a sequence generator which assigns filenames and schedules the necessary QC samples in the analytical system. This requires specific automation not generally provided as part of the original manufacturers product. Orsat offers the necessary hardware and software to generate not only the sequences with descriptive filenames but also the hardware to automate the introduction of the necessary QC samples for both the PerkinElmer and Agilent systems.
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Network and Site Configuration
In order to allow the evaluation of these QC samples each data set or Site has a definition which incorporates configuration parameters for the Network which defines information about incoming data such as a list of target VOCs, which targets will be in the QC samples and their concentrations and control limits. These parameters will be used by the system to calculate and display QC recoveries and threshold exceedances. A Network may have multiple sites or a single site depending on the agency and the number of PAMS sites they operate. The Network configuration also includes information about the site which is required to generate the EPA required Air Quality System (AQS) data file which is submitted for each site to incorporate the ambient data into the EPA AQS system.
Information Required for Network Configuration
- Units (default is ppbC)
- How Lost data will be displayed
- How zero values will be displayed
- Total Blank Maximum value
- List of Target Compounds by Channel
- List of Target Compounds in each of the required QC samples (LCS, CVS, RTS, Blank and MDL) including required control limits
- List of applicable Null, Qualifier and Inform Flags available for use in AQS files.
Each Site also has unique information to identify it in the database. In addition to a unique site name other information is required to generate a site-specific AQS data file which will be submitted to the EPA AQS Database.
Information Required for Site Configuration
- Site name (defined in the incoming ASCII text file as “SITE-x” where x can be from 1-3 characters)
- Type - designation of data system generating the data, PerkinElmer or EZChrom
- Minimum display value - generally 0
- Network assigned to the site
- AQS number assigned to the site
- POC if necessary
- Short name - user entered text field
- Formal name - user entered text field
- Address, City and Zipcode
- Latitude and Longitude
- UTC offset
- CAMS code (if available)
- Interval, units code and method codes required for AQS file generation
- Operator
These rights are given to operators and do not include some features
- Validator
References
EPA Technical Assistance Document (TAD)
