Main PageENVIRONMENTAL CONSULTINGPosition PaperBLANKSSPIKESDUPLICATE

SUGGESTIONS FOR REDUCTION
OF ANALYTICAL COSTS BY
ELIMINATION OF UNNECESSARY
2ND COLUMN CONFIRMATIONS

by Douglas M. Chatham
Senior Chemist

SUMMARY

Many projects have specified that all positive results for GC methods will be confirmed by second column confirmation only because the SW846 method provides for it. Many more projects have suffered from inflated analytical costs because second column confirmations were not discussed in the work plan or the QAPP and the laboratory performed these analyses because they were called for by the SW846 method. The large number of confirmations resulting from this protocol is excessive and often results in an unnecessary inflation of the analytical cost. If good historical data exist, the only analytes requiring confirmation are compounds not previously detected and confirmed. For example, if benzene was detected and confirmed by method SW8240 (a GC/MS method) or by method SW8020 with second column confirmation during Superfund investigations, a positive result for benzene in the RI/FS investigation does not need to be confirmed. Positive results less than Quantitation Limits, MCLs, ARARs, or cleanup levels should not be confirmed. Sampling efforts involving numerous samples at each site, e.g. grid sampling, should include only enough confirmations to confirm the identity of each analyte found at the site. Thorough evaluation of the need for 2nd column confirmations during planning stages and frequent communication with laboratory personnel could reduce analytical costs for GC methods as much as 50%.

RECOMMENDATIONS

If historical data exist, the laboratory should be directed to conduct second-column confirmations only for compounds not previously detected. When second-column confirmations are deemed necessary, the laboratory should confer with the PM or the QAPO.
Positive results less than Quantitation Limits, MCLs, ARARs, or cleanup levels should not be confirmed.
Sampling efforts involving numerous samples at each site, e.g. grid sampling, should have a limited number of confirmations.

DISCUSSION

Second column confirmations apply to organic analyses using GC methods , such as SW846 methods SW8010, SW8020, SW8021, SW8080, SW8081 and SW8280. A second column confirmation often is billed by the laboratory as a separate sample analysis. Method 8000A of SW846 states in Paragraph 7.6.9.1 ";Tentative identification of an analyte occurs when a peak from a sample extract falls within the daily retention time window. Normally, confirmation is required: on a second GC column, by GC/MS if concentration permits, or by other recognized confirmation techniques. Confirmation may not be necessary if the composition of the sample matrix is well established by prior analyses.";(1) Methods SW8010B, SW8011, SW8015A, SW8020B, SW8021A, and SW8030A, include the statement"; If analytical interferences are suspected, or for the purpose of confirmation, analysis using the second GC column is recommended.";
For example, a sampling grid of 100 sampling points with positive results for benzene, toluene, ethylbenzene, and xylenes (BTEX) in each sample would result in 200 analyses for BTEX if every positive result is confirmed. At an analytical cost of $100/sample for BTEX, the result analytical cost is $20,000. This example should require no more than five confirming samples which would be 105 analyses for BTEX and an analytical cost of $10,500. One investigation submitted 107 samples for an organic GC analysis costing $176 each. The site had been investigated several times before, providing adequate historical data to eliminate the need for 2nd column confirmations. There were 70 2nd column confirmations resulting in 177 analyses for a total analytical cost of $31,152 (not including other QA/QC samples). These 70 additional analyses were performed because SW846 method SW8150 provided for them and they were not specifically addressed by the work plan or the QAPP. Elimination of the unnecessary 2nd column confirmations would have saved the project $12,320.
The only confirmations required for initial site investigations conducted under CLP protocols are GC/MS confirmations of Pesticide/PCB analyses since the volatiles and semi-volatiles are analyzed by GC/MS methods. Cost reductions by limitation of 2nd column confirmations could be realized for any sampling investigation utilizing GC methods.

Types of Investigations

The CERCLA preliminary assessment (PA) and the RCRA facility assessment (RFA) are used to identify any releases or migration from a facility based on the existing information and apparent visual evidence. The PA or RFA are typically the first step in the CERCLA or RCRA process. Samples are not usually taken during these assessments.
The CERCLA Site Investigation (SI) and the RCRA Confirmation Sampling Process (CS) are used to confirm or disprove suspected releases to an environmental medium based on information obtained during the PA or RFA. The SI or CS process is generally limited in scope; the goal is to gather sufficient data to confirm the presence or absence of contamination at Potential Release Locations (PRLs), and to provide a basis for the scope of the CERCLA Remedial Investigation (RI) or the RCRA Facility Investigation (RFI) process or a No Further Action decision. The data quality levels for SIs or CSs are generally required to be Level IV (CLP) or Definitive data (2) since the data is required to be litigation quality. These investigations are usually the first ones conducted at most sites and historical data will be limited or non-existent. The only CLP or Definitive data requiring confirmation analyses are Pesticide/PCB analyses. If on-site, Level II, or Level III analyses are conducted, especially with grid sampling, some limitations of 2nd column confirmations are justified.
The CERCLA Remedial Investigation (RI) and the RCRA Facility Investigation (RFI) are used to evaluate the nature and extent of the releases of hazardous waste and hazardous constituents and to gather sufficient data to support the preparation of a risk assessment and Feasibility Study (FS) or Corrective Measures Study (CMS). RI/RFI studies could be screening data with definitive confirmation. These studies are much more extensive than SI/CS investigations. The screening data could be on-site and/or Level II fixed laboratory analyses with 10% Level III or CLP definitive confirmations. Limitations on second column confirmations could be based on historical data and grid sampling limitations as discussed above.
The CERCLA Feasibility Study (FS) and the RCRA Corrective Measures Study (CMS) are used to develop and evaluate a remediation plan or corrective measures alternatives and to recommend the appropriate corrective measure for the facility. FS/CMS studies could be screening data with definitive confirmation. These studies can be as extensive as RI/RFI investigations, but FS/CMS studies are much more focused. The analyses are limited to the analytes of concern which have been well documented in prior investigations. The screening data could be on-site and/or Level II fixed laboratory analyses with 10% Level III or CLP definitive confirmations. Limitations on second column confirmations could be based on historical data and grid sampling limitations as discussed above. It is likely that second column confirmations would not be needed for these studies.
The CERCLA Remedial Design/Remedial Action (RD/RA) and the RCRA Corrective Measures Implementation (CMI) are used to design, construct, operate, maintain, and monitor the performance of the remedial action or corrective measure selected. These studies can be as extensive and focused as FS/CMS investigations. The analyses are limited to the analytes of concern which have been well documented in prior investigations. The screening data could be on-site and/or Level II fixed laboratory analyses with 10% Level III or CLP definitive confirmations. Second column confirmations are not needed for these studies.
The basic purpose of cleanup verifications and long-term monitoring is to demonstrate that the concentrations of contaminants are below a mandated level. Second column confirmations are not needed for these studies.

LIST OF REFERENCES

1. EPA, Test Methods for Evaluating Solid Waste, Physical/Chemical Methods, SW-846, 3rd Edition, Final Update 1, November 1990.
2. EPA, Data Quality Objectives Process for Superfund, Interim Final Guidance, p. 42, EPA540-R-93-071, September 1993.