The semivolatile contaminant grouping is composed of compounds with broad chemical properties and structural features. Examples of semivolatiles compounds include hydrocarbons, aldehydes, ethers, esters, phenols, organic acids, ketones, amines, amides, nitroaromatics, PCBs (also known as Aroclors), PAHs, phthalate esters, nitrosamines, haloethers and trihalomethanes.
Sources of these compounds include pesticides and herbicides (containing phosphorus, sulfur, chlorine or nitrogen), flame retardants, ingredients in cleaning agents and personal care products, solvents and chemicals used in textile/electronic manufacturing and material manufacturing process additives.
Method 530 is a gas chromatography/mass spectrometry (GC/MS) method for the determination of selected semivolatile organic compounds in drinking water. A 1-liter water sample is fortified with surrogate analytes and passed through a solid phase extraction (SPE) device to extract the target analytes and surrogates. The compounds are eluted from the solid phase with a small amount of organic solvents. The solvent extract is dried by passing it through a column of anhydrous sodium sulfate, concentrated by evaporation with nitrogen gas, and then adjusted to a 1-mL volume with dichloromethane after adding the internal standards. A splitless injection is made into a GC equipped with a high-resolution fused silica capillary column that is interfaced to an MS. The analytes are separated and identified by comparing the acquired mass spectra and retention times to reference spectra and retention times for calibration standards acquired under identical GC/MS conditions. The concentration of each analyte is calculated by using its integrated peak area and the internal standard technique. Surrogate analytes are added to all Field and Quality Control (QC) Samples to monitor the performance of each extraction and overall method performance.
Method EPA 537 is testing used for the analysis of perfluorinated alkyl acids (PFAS). Six analytes are detected and quantified by this method:
- perfluorooctanesulfonic acid (PFOS)
- perfluorooctanoic acid (PFOA)
- perfluorononanoic acid (PFNA)
- perfluorohexanesulfonic acid (PFHxS)
- perfluoroheptanoic acid (PFHpA)
- perfluorobutanesulfonic acid (PFBS)
The first step in the process is to fortify the sample with surrogates and pass it through a solid phase extraction (SPE) cartridge containing polystyrenedivinylbenzene (SDVB). This allows for extraction of the method analytes and the surrogates. Next, the compounds are eluted from the solid phase with a small amount of methanol. After this, the sample is then concentrated to dryness with nitrogen in a heated water bath. They are then adjusted to a 1-mL volume with 96:4% (vol/vol) methanol:water after adding the internal standards.
The extracts are then injected into liquid chromatograph where the analytes are separated based on polarity. After this, they are passed into two mass spectrometer in tandem for identification based on the molecular masses of the fragmented compounds. This analysis provides a high precise quantitation of these compounds.
Method EPA 541 is a gas chromatography (GC) method for the determination of four analytes:
- 1,4 Dioxane
- 2-Propen-1-ol This method requires detection using mass spectrometry (MS) in selected ion monitoring (SIM) to provide selectivity for the method analytes. RWA Lab Services analysts have the skills necessary in solid phase extractions, the operation of GC/MS instrumentation and in the interpretation of the associated data.
A 250-mL water sample is fortified with surrogates and passed through a solid phase extraction (SPE) cartridge containing polystyrenedivinylbenzene (SDVB) to extract the method analytes and surrogates. The compounds are eluted from the solid phase with a small amount of methanol. The extract is concentrated to dryness with nitrogen in a heated water bath, and then adjusted to a 1-mL volume with 96:4% (vol/vol) methanol:water after adding the IS(s). A 10-μL injection is made into an LC equipped with a C18 column that is interfaced to an MS/MS. The analytes are separated and identified by comparing the acquired mass spectra and retention times to reference spectra and retention times for calibration standards acquired under identical LC/MS/MS conditions. The concentration of each analyte is determined by using the internal standard technique. Surrogate analytes are added to all Field and QC Samples to monitor the extraction efficiency of the method analytes.
Method 544 is used for the analysis six microcystins and nodularin. The six microcystins are microcystin-LA, microcystin-LA, microcystin-LR, microcystin-LY, microcystin-RR, and microcystin-YR.
In this method, the sample is initially filtered, and both the filter and the filtrate are collected. The filter is placed in a solution of methanol containing 20% reagent water and held for at least one hour at -20 ºC. This releases the intracellular toxins from cyanobacteria cells captured on the filter. The methanol solution and the filtrate are processed through a solid phase extraction cartridge. This allows for recovery and concentration of the microcystins and nodularin.
The samples are then injected into a liquid chromatograph, where the analytes are separated based on polarity, and then pass through two mass spectrometers in tandem for identification based on the molecular masses of the fragmented compounds. This analysis provides a highly precise quantitation of these compounds.
Method 545 (Microcystins and Nodularin) is used for the analysis of cylindrospermopsins and anatoxin-a. This method requires a process of freezing the sample at -40oC and thawing, and is performed three times Method 545 testing. The freezing and thawing ensures that all algal cells are ruptured prior to the filtration of the sample.
After the sample is filtered, it is injected into liquid chromatograph. This is where the analytes are separated based on polarity. The sample is then passed through two mass spectrometers in tandem.
Sample identification based on the molecular masses of the fragmented compounds. This analysis provides a high precise quantitation of these compounds.
Microcystins (which includes total microcystin, microcystin-LA, microcystin-LF, microcystin-LR, microcystin-LY, microcystin-RR, microcystin-YR) and nodularin are toxins produced by certain species of cyanobacteria. Cyanobacteria, formerly known as blue-green algae, are sometimes found in surface water when conditions favor growth and formation of algal blooms.
Cyanobacteria are capable of releasing toxins that can persist for weeks to months, and microcystins are the most commonly observed cyanotoxins in the United States. Toxicity to the liver is the greatest concern, but microcystins can also irritate the skin, eyes and throat. After exposure, symptoms may take hours or days to appear.
Nodularin is similar to microcystins in chemical structure. Therefore, while there isn’t as much information on nodularin as there is on microcystins, based on what information is available we assume that nodularin and microcystins have similar properties, including health effects.
Method 546 is a procedure for the determination of “total” microcystins (MC) and nodularins (NOD) in finished drinking water and in ambient water using enzyme-linked immunosorbent assay (ELISA). Total microcystins and nodularins is defined as the sum of the congener-independent, intracellular and extracellular microcystin and nodularin that is measurable in a sample. Method 546 measures the total concentration based on detection of a characteristic feature common to microcystin and nodularin congeners (structural variants), specifically, the Adda amino acid side chain: (4E,6E)-3- amino-9-methoxy-2,6,8-trimethyl-10-phenyldeca-4,6-dienoic acid (Fischer et al., 2001). To ensure comparability between laboratories, the ELISA is calibrated against one congener, MC-LR (CASRN 101043-37-2).
This method is based on the 96-well microtiter plate format. In these wells, microcystins and nodularins in the samples and a microcystin-protein analogue immobilized in the wells compete for the binding sites of a primary detection antibody in solution. After a wash step, an enzyme-conjugate is added to the wells and binds to the primary antibody in an inverse relationship to the original concentration of microcystins and nodularins in the sample. After a second wash step, tetramethylbenzidine substrate is added to develop color via an enzyme-mediated reaction. After a set period, an acidic solution is added to each well to stop color generation. Finally, the absorbance of each well is measured using a plate reader. The concentration of microcystins and nodularins is calculated using a four-parameter logistic calibration curve.
Haloacetic acids (HAA5, HAA6Br, HAA9) are a group of disinfection byproducts that are formed when disinfectants, such as chlorine or chloramine, are used to treat water and react with naturally occurring organic and inorganic matter present in source waters. Which HAA forms depends on several factors, so HAAs are often tracked and described as groups of individual acidic compounds. As more HAAs are included in one of these groupings, the list of compounds that contain bromide increases:
- HAA5 includes: dibromoacetic acid, dichloroacetic acid, monobromoacetic acid, monochloroacetic acid, trichloroacetic acid
- HAA6Br includes: bromochloroacetic acid, bromodichloroacetic acid, dibromoacetic acid, chlorodibromoacetic acid, monobromoacetic acid, tribromoacetic acid
- HAA9 includes: bromochloroacetic acid, bromodichloroacetic acid, chlorodibromoacetic acid, dibromoacetic acid, dichloroacetic acid, monobromoacetic acid, monochloroacetic acid, tribromoacetic acid, trichloroacetic acid
Method 552.3 is a gas chromatography (GC) method for the determination of haloacetic acids and dalapon in drinking waters.
A 40-mL volume of sample is adjusted to a pH of 0.5 or less and extracted with 4 mL of either methyl tert-butyl ether (MTBE) or tert-amyl methyl ether (TAME) containing an internal standard. The haloacetic acids that have been partitioned into the organic phase are then converted to their methyl esters by the addition of acidic methanol followed by heating for 2 hours. The solvent phase containing the methylated haloacetic acids is separated from the acidic methanol by adding 7 mL of a concentrated aqueous solution of sodium sulfate. The aqueous phase is discarded. The extract is then neutralized with a saturated solution of sodium bicarbonate and the solvent layer is removed for analysis. The target analytes are identified and quantified by capillary column gas chromatography using an electron capture detector (GC/ECD). Analytes are quantified using procedural standard calibration.
The main cause of taste and odor in drinking water can be attributed to the microbial production of geosmin and MIB, tertiary alcohols produced by members of certain groups of benthic and pelagic aquatic microorganisms. Geosmim and MIB are found in source waters such as lakes, reservoirs and running water like streams and rivers. Cyanobacteria, also called blue-green algae, are some of the major producers of these compounds. The concentration of these compounds in parts per trillion will cause an earthy musty odor.
Cyanobacteria are a photosynthetic nitrogen-fixing bacteria that survive in a wide variety of habitats, soils and water. The photosynthetic pigments in cyanobateria are cyanophycin, allophycocyanine and erythrophycocyanine. Their thalli vary from unicellular to filamentous and filamentous heterocystous. They fix atmospheric nitrogen in aerobic conditions by heterocyst, specialized cells, and in anaerobic conditions.
Post-treatment production of geosmin due to biological activities can result in odor issues downstream of water treatment and throughout the distribution system. Geosmin and 2-MIB are stable compounds and persist in open water in a dissolved form for extended periods of time. The stability of these compounds makes it difficult for conventional filtration to oxidize and eliminate the problem. Early detection can allow treatment and intake modification to eliminate or reduce the intensity of the problem.
Method 6040E is used to analyze taste and odor compounds inclusive of MIB and geosmin. The method consists of three primary steps: a microextraction procedure, followed by the separation and then mass identification of the compounds.
The compounds are volatilized and collected using solid-phase microextraction (SPME) fiber. The fiber is coated with divinylbenzene-carboxen-polydimethylsiloxane cross-link. It is then placed in the headspace above the sample in a closed vessel. This allows the fibers to equilibrate with the aqueous sample.
Sample Separation and Identification
The fiber is then removed from the headspace and inserted directly into the heated injection port on the gas chromatograph (GC). This allows the analytes to desorb into the GC column. The column provides the separation of the analytes of interest from background interferences. Once this is complete, the compounds will be identified. A mass spectrometer is used to identify the compounds.
This technique allows the RWA Lab to be extremely accurate in the determination of the analytes and highly precise in the concentration of each compound.
Perfluorinated compounds (PFCs), or more accurately perfluoroalkyls, are manmade compounds used in the manufacture of stain, oil and water-resistant consumer products. They are also found in products such as firefighting foams, cleaners, cosmetics, paints, adhesives and insecticides. PFCs are persistent in the environment, because natural processes do not rapidly degrade them.
Environmental risks usually depend on the concentration of the PFC contaminant and on exposure conditions. Individuals exposed to large amounts of PFCs in the air have been found to suffer negative health effects. If ingested above certain levels, various PFCs can cause problems in the liver, kidneys and nervous system and may also create developmental and reproductive issues.
PFCs were included in the EPA’s Third Unregulated Contaminant Monitoring Rule testing in order to determine how prevalent certain perfluorinated compounds are in U.S. drinking water supplies and at what level they appear.
Following that testing, in May 2016, the EPA released health advisories for perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), making a lifetime health advisory for each compound, or a sum total of the two, of 0.07 parts per billion.
EPA Modified Method 537.1 is a solid phase extraction (SPE) liquid chromatography/tandem mass spectrometry (LC/MS/MS) method for the determination of selected per- and polyfluorinated alkyl substances (PFAS) in drinking water.
A 250-mL water sample is fortified with surrogates and passed through an SPE cartridge containing polystyrenedivinylbenzene (SDVB) to extract the method analytes and surrogates. The compounds are eluted from the solid phase sorbent with a small amount of methanol. The extract is concentrated to dryness with nitrogen in a heated water bath, and then adjusted to a 1-mL volume with 96:4% (vol/vol) methanol:water and addition of the internal standards. A 10-μL injection is made into an LC equipped with a C18 column that is interfaced to an MS/MS. The analytes are separated and identified by comparing the acquired mass spectra and retention times to reference spectra and retention times for calibration standards acquired under identical LC/MS/MS conditions. The concentration of each analyte is determined by using the internal standard technique. Surrogate analytes are added to all Field and QC Samples to monitor the extraction efficiency of the method analytes.