Enhanced QC Field Screening
This Screening analysis is exempt from the QC hurdles that are commonly faced and makes use of the large volume extract by providing many subset samples.
Avoid the QC Hurdles – Provide Quality Data
Ensuring the safety of the world’s drinking water supply is critically important. The health of the world’s lakes, rivers, streams and oceans can be impacted by human and natural activities, and monitoring of these resources is of increasing concern worldwide. It is not possible to monitor for everything as a strategy of adopting a full suite of analysis is cost prohibitive.
A novel screening tool called the CLAM (Continuous Low-level Aquatic Monitoring) has been developed which uses in-situ time integrative SPE (solid phase extraction) field extraction. This provides a deployed SPE disk which represents a 36 time integrative extractive event representing up to 100 liters of water.
The small dry disk is sent back to the laboratory leaving the water behind, and the pre-extracted disk is simply solvent eluted, concentrated to a known extract volume. This enhanced extract represents a huge sample volume which will allow a novel analysis strategy that incorporates a magnified chemical, biological, and genotoxic-active compound initial screening step. This Screening step representing up to 100 liters of water can provide magnification and a wide overview of the environmental landscape employing new MS technologies and retention time locking libraries. After screening, the remaining extract volume allows for many subsets for trace organic methods to be run, providing required QC samples, and re-analysis volume for failed QA/QC, and re-analysis of outliers each still representing many liters of water.
- The CLAM disk is field deployed and then sent to the laboratory after extracting up to 100 liters of water in situ, leaving the water behind.
- The CLAM disk is elusted with solvents into a collection flask.
- The solvents are evaporated and reduced in volume using KD reduction flasks or blowing the volume down with nitrogen.
- The final elution volume after reduction is usually 1 ml.
- The initial 1 ml volume represents up to 100 liters of water field extracted rather than the standard 1 liter bottle of water.
- Because of the sheer volume of water extracted, many subsets of the initial 1-10 ml extract can be used for many analytical methods, and still represent a much greater volume than the standard 1 liter grab.
- The original extract is used for screening, providing a time integrative, magnified view of the environment.
When the laboratory uses a wide array of methods to determine whats out there rather than enhanced screening they are forced to comply with each methods QA/QC requirnments inherient in the method which are some of the following:
- Initial Calibration 5 point high to low calibration of all the analytes to repeated each time ICV fails the recovery criteria, which happens very often per batch
- ICV=Initial calibration verification, shows that the calibration is holding
- MB=Method Blank must be clean no hits over MDL, If so the sample has to be re-extracted or resampled.
- LCS/LCSD= Lab Control spike/duplicate, results must meet recovery criteria, if any analyte fails the recovery, retention time, and relative percent difference from its duplicate the whole batch must be repeated until it passes.
- MS/MSD=Matric spike/duplicate results must meet recovery criteria, if any analyte fails the recovery, retention time, and relative percent difference from its duplicate the whole batch must be repeated until it passes.
- CCV= continuing calibration verification, half way through batch, shows that calibration and sample set are accurate. If it fails acceptance criteria all analytes run after it have to be reanalyzed
- End of run calibration a check to see if calibration was holding if not the whole run criteria failure may require reanalysis.
- Surrogates Added to all QC and samples, recovery failures may require reanalysis, re-extraction or resampling of failed samples
- Internal standards Added to all QC, samples, calibration standards. If any of these fail in recovery criteria the reanalysis of everything is possible.
- Finally Samples
- Once internal standards surrogates are added to the extract it cannot be used for other analysis. Example if method 8081 pesticides are run one could not run methods 8141 or 8270 as the surrogates internal standards and solvent would interfere.
Enhanced cost savings from one field extraction
The enhance screening only requires a initial calibration or the retention time lock MS library in newer MS systems to provide qualitative and tentative numbers while also providing genotoxic-active compound screen. The screen provides pre-knowledge of the environmental terrain and guidance as to which methods are necessary to run. The extract remaining provides enough extract volume to run many compliance methods with associated QC and reanalysis volumes for failures. The advantages of this strategy is listed below:
- Large Volume extraction: provides for ultra-low analysis or a large extracted sample supply for many analysis methods. This lowers the costs as each method otherwise would require its own sample bottle to be extracted, eluted and concentrated for instrumental analysis. The CLAM strategy requires only one extraction and elution and can provide many subset samples ready for instrumental analysis.
- Time integrative Sample : Provides a better representation of what is in the field
- Huge extraction, material and cost savings as only one field extraction is needed to rum many many methods each would have to be samples, extracted eluted separately
- The screening analysis is exempt from the QC gauntlet, the only requirement would be the initial calibration and CCV to start.
- The CLAM extract would provide a magnified overview of the samples pollutants up to 100x what the one liter sample would supply, and allow the analyst to provide approximate quantitation’s as well as qualifying other positive hits using GC/MS.
- High volume TIC’s tentatively identified compounds could be obtained.
- The eluent extract representing up to 100 liters of water could be made into dozens of specific method extracts still representing many liters each and would all be virgin without internal standards or surrogates. These could be used for specific methods once the analyst knows who the pollution players are from the Initial High volume screening.
- The initial field disk extract or subset could be used to run toxicological studies augmenting the value of the screening tool.
- Holding time pressures are reduced and the disk extract is good for 45 days, and the disk unextracted is good frozen for months.
- Do not need to resample if QC fails, just grab another subset and reanalyze