The benefits continue in the laboratory, where the environmental footprint from testing is reduced with lower chemical, consumable and energy requirements. In many cases the research and development that has resulted in lower volume requirements has also led to the additional benefit of improved test method performance.
The implementation of a NEW low-level Organochlorine Pesticide (OCP) and Polychlorinated Biphenyls (PCB) method that allows a reduced sample size is no exception; and the data quality benefits are significant for this accredited(a) method, now offered by ALS Waterloo, Canada.
General Quality Implications
The required detection levels for OCP in water for various regulations in Canada are quite low. To achieve these levels by either GC/MS or GC/ ECD, sensitive instrumentation and sample extracts free from interfering compounds are essential. ALS has focused on both of these aspects, working to overcome the sensitivity limitations of GC/MS through optimization of new technology, and modifying sample preparation methodologies to virtually eliminate background interference and carryover risk.
The end result is data that meet stringent detection limit criteria, while at the same time significantly reducing the risk of false positives when analyzing a range of ultra-clean and dirty samples – a challenge for any lab.
What This Means For ALS Clients
Ontario Reg. 153/04, BC Contaminated Sites Regulation (CSR), Alberta Tier 1 (ABT1), and CCME each have specific criteria for Organochlorine Pesticides. ALS Canada has developed a Routine Method that meets O.Reg. 153/04 and the lowest BC CSR criteria with a 100 mL sample size.
To meet the lowest ABT1 and CCME levels, a Trace Method using a 500 mL sample is required. The table on Page 2 shows reporting limits, applicable regulatory standards, and current method performance for the 100 mL Routine Method at or near the detection limit.
In addition, the reporting limits for the 500 mL Trace Method are provided, along with associated regulatory limits that require this method. The Limits of Reporting (LORs) of the Routine and Trace methods meet or surpass routine LORs previously offered by ALS Canada, and require less sample volume.
Routine vs. Trace
Precision and Accuracy Implications
In addition to other benefits, these new methods have resulted in improvements to data quality for both precision and accuracy, which means any trending of pesticide positives will be more accurate, with less ‘noise.’ The previous OCP method (using 500 mL samples) yielded average precision of 12.5% RSD at 0.010 ug/L. The new Routine OCP Method (using 100 mL samples) shows notable improvement, with average precision of 5.4% RSD at 0.010 ug/L.
This method is also validated and accredited(a) for PCB Aroclors with similar improvements in performance. The Routine method easily meets any of the indicated regulatory requirements for Aroclors in water. The table below shows the 100 mL Routine Method performance at the Limit of Reporting.
Sampling Considerations and Sample Containers
When testing to trace levels, exclusion of sediment in the sampling procedure is particularly important. Sediment may provide high bias to water sample results when testing for hydrophobic compounds such as OCPs and PCBs. Groundwater samples should be taken using lowflow techniques to minimize disturbance which can result in uptake of sediment into the sample. Samples may not be filtered for OCP or PCB, as the filtering step will potentially result in low bias through adsorption.
These new ALS methods should only be applied using ALS proofed and validated 100 mL or 500 mL amber glass bottles.
In order to meet applicable criteria, the test method required (Routine or Trace) should be indicated when ordering sample bottles.