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Analysis of Drinking Water Contaminants
Protecting our drinking water from contamination
Safe and clean drinking water is critical for health. In 1974, the Safe Drinking Water Act (SDWA) was established to protect the public health from contaminants in drinking water. Federal law requires the US EPA to set the regulatory standards for drinking water. In 1986 and 1996, the EPA made two amendments to the SDWA and made provisions to periodically review current drinking water regulatory standards and monitor other important contaminants through the unregulated contaminants monitoring rule (UCMR) program. The EPA authorizes US states to oversee that their public water systems (about 161,000 systems nationwide) and community water systems (about 54,000 systems nationwide) comply with the drinking water standards.
Drinking water standards
The EPA sets the National Primary Drinking Water Regulatory Standards (NPDWR) and National Secondary Drinking Water Regulatory Standards (NSDPR). The primary standards for more than 90 contaminants are enforceable standards that the public water systems and community water systems must monitor for regulatory compliance. The EPA sets maximum contaminant level goal (MCLG) and maximum contaminant level (MCL) for individual contaminants. If levels of the contaminants in drinking water supply exceed the MCLs, the water has to be treated to remove the contaminants and meet the MCL standards.
The secondary standards are non-enforceable standards. The contaminant levels in the NSDPR do not threaten human health, but change the aesthetic and cosmetic effects of water, such as taste and odor of our drinking water.
Analysis of drinking water
Many different drinking water analysis methods have been approved by the EPA for many different types of contaminants. For example:
- Inorganic ions such as nitrate , nitrite, and fluoride can be analyzed by ion chromatography.
- Regulated metal contaminants can be analyzed using atomic absorption spectroscopy (AAS), inductively coupled plasma optical emission spectrometry (ICP-OES), or inductively coupled plasma mass spectrometry analyzed by GC, GC-MS, GC-MS/MS, HPLC, LC-MS, or LC-MS/MS.
- Because of their unknown characteristics and low concentrations in water, emerging contaminants can be analyzed by high resolution accurate mass (HRAM) Orbitrap-based mass spectrometry coupled with either GC or HPLC.
Regardless of what analytical tools are used, laboratory information management systems (LIMS) provide efficient analytical support from sample management to data mining and reporting. Different combinations of tools allow fast, efficient, and accurate analysis for contaminants in drinking water.
Analysis of inorganic ion contaminants
Inorganic ions consist of anions and cations, and can be analyzed by ion chromatography using anion-exchange and cation-exchange columns, respectively. Primary contaminants include several anions (mentioned above) and inorganic disinfection byproducts (chlorite and bromate) and others. Secondary contaminants include fluoride, sulfate, and chloride. Although cations such as magnesium and calcium are not regulated contaminants, they are often monitored for the drinking water quality.
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Analysis of metal contaminants
Heavy metals are highly toxic, making their presence in drinking water a serious threat to human health. On the primary contaminant list, 11 metals are regulated at different levels that depend on their impact on health.
- Some metals are anionic [i.e., chromium (VI)], or cationic (i.e., calcium and magnesium) and are analyzed by ion chromatography.
- Total metal and metalloid concentration in drinking water for regulatory compliance are analyzed by AA, ICP-OES , or ICP-MS using approved methods such as EPA methods 200.7 (ICP-OES), 200.8 (ICP-MS), and 200.9 (Graphite Furnace AA). Choosing which type of instrument to use depends on the goal and needs of the analysis.
When analyzing many metals in drinking water, testing laboratories often opt to use several types of instruments and meet compliance using regulatory methods.
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Analysis of organic contaminants
Organic contaminants, including volatiles and semi-volatiles, account for a big portion of regulated contaminants in drinking water. Although some of them can be analyzed by HPLC, such as polyaromatic hydrocarbons (PAHs) or IC-MS/MS, and LC-MS/MS such as certain pesticides, a majority of the organic contaminants are analyzed by GC, GC-MS, or GC-MS/MS in EPA methods such as EPA 524 and 525.
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Analysis of emerging contaminants
According to EPA, emerging contaminants are those contaminants with "perceived, potential, or real threat to human health or the environment or by a lack of published health standards". Although these contaminants are not regulated, their presence in drinking water has recently raised great health concerns.
In the most recent UCMR3 and upcoming UCMR4 program, monitoring emerging contaminants—such as perfluorinated compounds, hormones, and microcystins—is required by the public water systems. Regulatory methods such as EPA methods 537, 539, 544, and 545, were developed for measuring the trace concentration of these contaminants by LC-MS/MS.
In addition to chemical compounds, nanoparticles are also a class of emerging contaminants that enter our water systems and can be characterized and quantitated using single particle ICP-MS (spICP-MS).