Advancements in analytical technologies enable laboratories that support public water supplies to analyze for more contaminants in drinking water and do so with greater specificity and sensitivity than ever before. Current research has uncovered the presence of a variety of classes of unregulated compounds in drinking water sources. These chemicals, collectively referred to as contaminants of emerging concern, include newly identified disinfection by-products, pesticide degradates, household cleaners, industrial chemicals, cosmetics and medications. While these compounds remain unregulated, public water suppliers are interested in understanding the presence of these compounds, the impact of seasonal fluctuations on their concentrations and efficacy of their treatment systems for these compounds.
In order to help stay ahead of regulations, laboratories are challenged to develop new testing methods for detecting contaminants of emerging concern as well as improving the sensitivity for well documented contaminants. Underwriters Laboratories’ (UL) water laboratory in South Bend, IN is one of the few in the country with the capabilities to test for a wide range of contaminants, including the expanding Pharmaceutically Active Compound (PhAC) segment, which includes estrogens and other hormones. While the casual observer may think of a laboratory as a ‘black box’ that generates numbers, the analytical process is very complex and some of the steps to ensure quality data actually begin before the sample is even taken. To help illustrate this, the UL team recently took a group of reporters on a tour of UL’s South Bend facility, enabling attendees to travel the path a water sample takes when it’s tested and analyzed at the site.
Shipping and receiving
At the point of entry to and departure from the facility, guests observed how water-sampling kits are packed. Team leaders emphasized the importance of using meticulously cleaned sample containers made of appropriate materials, which contain the precise amount and type of preservative as specified by the analytical methods. Incorrect amounts or types of preservatives, which include sulfuric acid, hydrochloric acid and sodium sulfite, can lead to analyte degradation, interferences from the sample matrix (such as residual chlorine), or add unwanted interference to the analytical process.
Sample collection is accomplished by the client upon receipt of the kits. Sampling for several analytes goes beyond simply filling a bottle with water. In particular, to sample for volatile contaminants, it is imperative to maintain proper sample flow and ensure that no air bubbles are present in the sample. Bacteriological samples are highly prone to contamination and as such, special care must be taken when capturing a sample. The team discussed how special labels are used for microbiology and short hold-time samples in order to ensure that samples are tested within the time limits set by US EPA. Additionally, they reviewed receiving department procedures including sample login, the importance of the sample temperature upon receipt and the management of chain-of-custody discrepancies.
Water sample preparation for testing
UL staff demonstrated the preparation process for UL Method L221, Pharmaceutically Active Compounds, a proprietary method developed for analysis of various prescription drugs, as well as compounds used in personal-care products. The staff also demonstrated the cleaning and conditioning of the extraction cartridges followed by extraction, elution and the concentration of sample extracts. The demonstration concluded with the addition of internal standards to the concentrated sample extracts for quality control and the transfer of auto-sampler vials.
Sample preparation begins with a pre-extraction procedure that includes measurement of pH, residual chlorine and sample weight, as well as the addition of method-specified surrogate compounds and other quality-control standards. It is critical to establish the proper flowrates through the solid-phase extraction disk when preparing the sample. Too much flow will lead to breakthrough of the sample, in which analytes of concern will pass through the media and lead to low recoveries. Too little flow not only slows down the production process, it also potentially could lead to the degradation of select analytes.
At this stop on the tour, guests received an overview of the company’s analysis of PhACs using liquid chromatography–tandem mass spectrometry. Discussion and demonstration focused on:
- The type and number of compounds analyzed in a typical field sample, as well as the concentration levels at which these compounds can be detected.
- Demonstration of a shortened analysis batch, including quality-control samples (LMB, LFB, CCC), including peak elution of well-known compounds, including caffeine and nicotine.
- Process for submission of results to the laboratory information management system and typical data entry sheets.
The data interpretation of this analysis is particularly challenging, and only chemists with a high level of experience with LC/MS/MS are allowed to perform data interpretation and review. Because of the extremely sensitive nature of the test, there may be multiple interferences; the experience of the analyst is critical in resolving these interferences and properly integrating the peak. Positive identification of a compound requires that two critical conditions are met: the compound must elute from the column in the expected retention time window (determined largely by the physical size of the compound and its polarity); and the spectrum generated by the detector (essentially a fingerprint) must match the spectrum of the same compound in the calibration standard.
UL’s overview of metals analysis included the instrumentation and parameters tested. Discussion centered on inductively coupled plasma (ICP)—mass spectroscopy technology, including the generation of metal ions using argon plasma—and how the ions are used for calibration and quality control. Guests observed real-time analysis with on-screen mass spectra displays.
Plasma, which is the inert gas argon energized by high-frequency radio waves, is at an extremely high temperature. The high temperature excites the metallic ions, instilling an electrical charge. The charge enables a quadrupole mass spectrometer to selectively separate the ions according to their mass. As mass is a very selective property of an element, this technique greatly increases the sensitivity over traditional ICP, which measures the light emitted by the elements as they return from their excited state.
Cryptosporidium and Giardia are protozoa found in surface water sources contaminated with human and/or animal fecal waste and are capable of causing gastrointestinal illness in humans. US EPA regulates Cryptosporidium under its Long Term 2 Enhanced Surface Water Treatment Rule that requires public water systems using surface water sources to test for this contaminant. Samples submitted to UL are concentrated through a series of steps, and multiple stains are used to allow for microscopic analysis. The concentration step includes adding an antibody that is magnetized, and the organisms are actually pulled away from the debris of the sample using magnets. Once parasites are isolated, the analyst applies two stains prior to viewing under a microscope. One stain adheres to the outer wall of the cyst and enables observation of the size and shape of the organism. The second stain intercalates into the DNA to highlight the organism’s internal structures. Observation under differential interference contract (DIC) microscopy also provides structural information. These observations can be used to confirm the presence of Cryptosporidium and Giardia.
The tour provided a first-hand understanding of the level of complexity, technological sophistication and attention to detail required for the analysis of drinking water. From the procedures for packing sample kits to the development of new methods to test for emerging contaminants, UL offered the guests a comprehensive look into the company’s commitment to public safety.
About the author
As Business Manager of Global Water Business at UL, Dennis Leeke is responsible for the daily operation of the company’s water product certification services and Site Manager for the 70,000-square-foot water analytical laboratory in South Bend. Prior to joining UL in 2005, Leeke held several senior management and executive positions in the environmental laboratory industry. He received his Bachelor’s Degree in biology from Franklin College and an MBA from the University of Notre Dame, Mendoza College of Business.
About the company
Underwriters Laboratories, Inc., which has provided testing and certification programs for drinking water and water delivery systems for more than 20 years, performs virtually all analyses required by the federal Safe Drinking Water Act, including organic and inorganic constituents; metals; disinfection byproducts; microbial contaminants; radiological parameters and dioxin. UL is certified in 48 states and Puerto Rico, making it the most certified laboratory for drinking water analysis in the US. In addition to testing to SDWA standards, UL has a dedicated research and development staff that is committed to providing cutting-edge analytical services for emerging contaminants.