Gerstel: Intelligent Automation for GC/MS and LC.MS

Detecting Perfluorinated Compounds in Contaminated Community Water Supplies

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We are all aware of the tragedy that has played out in Flint, MI due to the presence of lead in their drinking water supply. Now, another serious water contamination threat is gaining visibility and additional regulatory attention. The source of the problem is perfluorinated compounds (PFCs) introduced in the late 1940’s, which have found their way into everyday products from non-stick cookware to fabrics and from food packaging to firefighting foams.   

Two of these PFCs are of greatest concern. Laboratory animal studies and epidemiological studies of human populations that have been exposed to perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) have shown that exposure to these two PFCs over certain levels may result in adverse health effects. These include, but are not limited to, testicular and kidney cancer, immune system effects, developmental effects to breastfed infants and fetuses during pregnancy, and thyroid effects. Concern over these adverse health effects has led the US Environmental Protection Agency to recently announce updated Health Advisories that lower the advised maximum combined level of PFOS and PFOA to 70 parts per trillion (ppt) in drinking water, from the previous advisory of 400 ppt.

Concern from the EPA is now being echoed in several communities whose water supplies are threatened by these compounds, triggering additional testing and even closing of water wells. These communities are often located near industrial sites that manufacture these compounds or near Air Force bases and Naval Air stations on which fire-fighting foams containing these compounds were used. For example, Hoosick Falls, NY was once a center for production of Teflon-treated products which contained PFOA. Contamination of the drinking water supply has led to an average blood serum level for more than 2,000 residents of Hoosick Falls that is nearly 15 times the national median level, with health problems being reported. The problem has become so severe that concerned residents of Hoosick Falls and nearby Petersburgh are calling for legislative hearings at the state and federal levels.

Contamination of groundwater has also occurred near the closed Wurtsmith Air Force Base near Oscoda, MI where PFC contamination has been found in 70 wells, although not at levels that exceed the EPA health advisory. However, where the fire foam was used on the base, PFOS and PFOA levels are “several orders of magnitude above the advisory”, posing a continuing threat to the local groundwater. PFCs were detected in more than 94 percent of over 1,500 adults and children who drank contaminated water at the former Pease Air Force Base in New Hampshire.

A similar contamination problem has occurred near the Joint Reserve Base in Horsham, PA, the Horsham Air Guard Station, and the former Naval Air Warfare Center in Warminster. PFC contamination has been detected in about 16 public wells and 140 private wells in Horsham, Warrington, and Warminster at levels well above the EPA Health Advisory. Perhaps more alarming is the fact that another Pennsylvania community was forced to shut down a well with PFOA levels three times as high as the new FDA advisory, and the source of the contamination is unknown. Clearly, PFCs present a serious and growing threat to water supplies in the US, and the full extent of the problem may not yet be known.

Accurate, High Throughput Methods are Needed for Detection of PFOS and PFOA

The need for accurate, reliable and sensitive analytical methods for detecting these compounds is obvious and essential given the current threat, and they must also be able to handle the increased work load. A good basis for such a method is the International Organization of Standardization (ISO) method 25101:2009, which utilizes solid phase extraction and liquid chromatography/mass spectrometry (SPE-LC/MS). GERSTEL automation solutions have enabled a modification of this method that provides a simple, high throughput and rugged SPE-LC-MS/MS approach for the determination of not only PFOS and PFOA, but also a wider list of PFCs in both water and sludge samples.

Automating the SPE process eliminates extensive and tedious manual sample preparation steps that are known sources of error in reliability and reproducibility – for example when cartridges run dry or sample matrix restricts the flow of liquids through the cartridge. Automated sample preparation for this method was performed on both the GERSTEL MultiPurpose Autosampler (MPS) and GERSTEL PrepStation (dual rail MPS). The latest GERSTEL MPS RoboticPROAutosampler could also be used with this method to provide versatility and unmatched throughput and reproducibility.

The benefits of automation include higher recovery, improved reproducibility, higher sample throughput, increased flexibility, and reduced exposure of laboratory staff to potentially hazardous solvents. Automated SPE can be performed with the autosampler either coupled directly to the LC-MS/MS instrument or in standalone mode. Coupling enables direct sample introduction of the extracts and fully automated operation from SPE to LC-MS/MS. As a sample preparation platform separate from the analytical instruments, the MPS WorkStation configuration provides the flexibility to choose between different techniques or different instruments for the sample analysis in order to meet individual requirements.

Using either the MPS or PrepStation coupled to the Agilent 1200 Infinity Series LC and Agilent 6400 Series Triple Quadrupole LC/MS, this automated ISO 25101 method provided excellent linearity of calibration from 5-500 ng/mL, with correlation coefficients (R2) above 0.996 for all seven PFCs that were analyzed. Reproducibility was also very good, with relative standard deviations (%RSDs) for spiked standards between 1 and 3%. The limits of quantitation (LOQs) were 0.5 ng/mL (500 ppt), after a 2.5 fold enrichment of the SPE eluate. This automated system can enrich (or concentrate) SPE eluate up to a factor of 100, putting the operating LOQ well below the allowed 70 ppt limit provided by the EPA Health Advisory. 

Thanks to the PrepAhead function in the MAESTRO software, LC/MS analysis of the current sample and SPE of the next sample are performed simultaneously, ensuring maximum productivity. Sample preparation took 25 minutes to complete, and apart from the time required to prepare the first sample for introduction, the LC/MS system was never slowed down by sample preparation. Setup of each run required only a few mouse clicks in MAESTRO.

GERSTEL multifunctional autosamplers and sample preparation robots can improve the reliability and productivity of not only this sensitive and automated SPE analysis method for PFCs, but also practically all standard sample preparation techniques used for LC/MS and GC/MS. This capability provides you with significant added value, as method development tasks can be performed in a highly flexible manner, and routine analysis chores can be handled efficiently and productively with minimal intervention.