The U.S. Environmental Protection Agency (EPA) is initiating a peer review of draft scientific modeling approaches to inform EPA’s evaluation of...
The Water Quality Association (WQA) Laboratory in Lisle, Ill., is well known for its testing capabilities for NSF/ANSI standards, including performance testing, structural integrity testing, extraction testing and others. What might not be as well known, however, is that the WQA does have an analytical laboratory. WQA’s lab can test for many contaminants that constitute both aesthetic and health claims right in its own facility. The analytical lab is accredited in both the state of California and the state of Iowa.
What does being accredited mean, and why do labs need to be accredited? In the analytical chemistry world, a lab that is accredited must follow rules set forth by the issuing agency. Sometimes it is a state’s Environmental Protection Agency (EPA), Department of Natural Resources or other federal agency. These labs must follow specific guidelines for quantitative analysis. There are rules about how data is generated and reported in order to ensure high quality and reliable data, and rules about setting data reporting limits and method detection limits. These are two important terms in analytical chemistry. They measure how low we can see and quantitate, and how low we can see and know that the signal is more than just background noise. The lab must also demonstrate analytical performance at the reporting limit and throughout the range of the instrument. Accredited labs must also participate in performance testing studies, in which labs test unknown samples. The labs must pass these exams to keep their accreditations.
Holding an analytical certification requires periodic evaluation of the lab that is performed by auditors. Audits can be conducted either on or offsite. Testing equipment, methods and data are inspected by the auditor. Accreditations expire after a period of time and usually an audit is needed to renew the accreditation. All of this ensures data of very high quality, which is used in WQA’s product certification process.
The lab uses EPA-published analytical methods and Standard Methods, including EPA Method 200.9, EPA Method 300.1, Standard Method 3111B, Standard Method 2340 and Standard Method 2540.
EPA Method 200.9. The EPA’s Method 200.9 is used for graphite furnace analysis of metals. The analytical lab currently holds accreditations for arsenic, lead, selenium, cadmium and chromium. This method employs a technique called stabilized temperature platform graphite furnace atomic absorption spectroscopy, or GFAA for short. In this method, a minute sample is introduced into a small furnace constructed of high-purity graphite. The sample is then turned into an atomic vapor and introduced in front of a lamp, producing light of the wavelength particular to that element. An extremely sensitive detector measures the amount of light absorbed by the sample, which is related to the concentration in the sample. Using this technique, contaminants can be observed at parts per billion (ppb), and sub-ppb levels. One ppb is equal to 1mg/L, which is like being able to see one second per 32 years or one drop of ink in a large swimming pool.
Standard Method 3111B. Standard Method 3111B uses a technique called flame atomic absorption, or FLAA. The sample is introduced into an extremely hot flame fueled by acetylene and compressed air. This produces atoms in a highly energized state that absorb light at a particular wavelength. Again, a light emitted at a frequency specific to the analyte of interest is passed through the flame chamber and a detector measures the amount of light absorbed by the sample, which is related to concentration.
Standard Method 2340 & Standard Method 2540. Two wet chemistry methods used by the lab are SM 2340 for hardness and SM 2540 for total dissolved solids (TDS). The hardness test is done by titration, where a reagent is dispensed into a known sample until a colored endpoint is reached. The hardness value is then calculated using the volume of reagent. In the TDS method, a known amount of sample is filtered and dried. The amount of residue remaining after the sample is completely dry is the TDS.
EPA Method 300.1. The lab is currently working with the state of California to become certified for nitrite and nitrate, phosphate, fluoride, chloride and bromide by ion chromatography (IC) using EPA Method 300.1. In this technique a small sample is introduced through a series of columns containing a special ion exchange resin. Different anions will migrate through the columns at known rates. The outcome is a graph, called a chromatogram, of the peaks of all the different anions. The area of the peak is related to the concentration of the anion. The lab is also working with the state of California’s Environmental Laboratory Accreditation Program (CELAP) to become certified for analysis of sodium by FLAA.
The lab hopes to work with CELAP and similar agencies to get accreditation for the analysis of chloroform by gas chromatography. This method employs a technique similar to ion chromatography. Gases are extracted from the sample through a small syringe and introduced into a capillary column. Just as in IC, different compounds travel through the column at different rates, producing a chromatogram from which concentrations can be calculated. This is also computer controlled. The WQA lab will be developing a method to analyze chloroform, the contaminant used in both volatile organic carbon performance testing and tertiary tri-halomethanes performance testing. The lab is hoping to expand its analytical capabilities even further to better serve WQA’s clients.