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Semivolatile Organic Compounds (SVOC) Analysis
What are semivolatiles?
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.
*H range defined as volatility from liquid to air.
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.
Semivolatile Environmental Sampling
Environmental analysts sample air, water, soil and biota to monitor for the presence and concentrations of contaminants present. Due to the tendency of contaminants to accumulate, concentrate and persist in these natural matrices analysts can gain valuable information to help limit the spread and impact of contamination on environmental health by analyzing these matrices. Generally environmental analysis for SVOCs focuses on the extraction, identification and quantitation of contaminants.
水性
- 飲料水
- 廃水
- 源水
- 地下水
- 地上水
Solids & semisolids
- 土壌
- 堆積物
- 汚泥
- 植物組織
- 動物組織
- バイオソリッド
空気
- 環境大気フィルター/トラップ
- 外気フィルター/トラップ
- 煙突排気フィルター
- 汚染場所からの空気フィルター
- 粉塵
Semivolatile extraction methods
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The sample type or matrix dictates the technique needed to successfully extract target contaminants or contaminant groups. Sample preparation technology is constantly evolving with improvements in technology extraction efficiency and cost. Several extraction techniques can be used to remove semivolatile contaminants from aqueous or solid/semisolid matrices.
Solid/semisolid samples
Extraction techniques for solid samples like soil or sediment are designed to remove the native substances from these complex multi component mixtures and transfer the semivolatiles present into an organic solvent. In nonaqueous matrices acid- base partitioning is typically not required. However, due to the complex component nature of solid samples additional sample cleanup steps such as gel permeation chromatography (GPC) may be necessary.
Chromatographic techniques
Environmental analysts rely on traditional chromatographic techniques for separation and detection of many semivolatile compounds.
Gas chromatography for SVOCs
For semivolatile analysis specifically, most environmental laboratories rely on gas chromatography for detection and quantitation. It is important to note that gas chromatography has been at the center of U.S. EPA’s strategy for monitoring organic contaminants since the early to mid 1970s. The ability to quickly separate large compound groups with high resolution and the availability of detectors with various affinities provide a definite advantage when analyzing complex samples.
High performance liquid chromatography for SVOCs
In environmental analysis, HPLC is often used to analyze compounds that are not amenable to GC. The high temperatures that compounds are exposed to for the required vaporization step of GC sample introduction can cause difficulty when analyzing thermally labile or chemically active compounds. Strategies for managing this influence of temperature induced instability such as derivatization or analyte protectants are often not required when using HPLC. Examples of semivolatiles typically analyzed using HPLC include PAHs, nitro-aromatics, explosives and many other compounds.
Mass spectrometry for SVOCs
GC and HPLC provide the initial separation of sample components prior to introduction into mass spectrometry instrumentation. The complexity of environmental samples like soil extracts requires separation mechanisms that can isolate target compounds and remove unwanted interferences. Furthermore the presence of many chemical groups, the influence of conflicting chemical properties, matrix interferences and chromatographic resolution limitations on columns create challenges for accurate identification and quantitation.
Through mass spectrometry a mass spectrum is created with mass assignments corresponding to the atomic weight of a target compound and/or its ionized fragments. This data can assist in the identification and confirmation of semivolatile compounds. In addition, mass spectrometry provides the ability to analyze broader compound classes, remove additional matrix interferences as well as gain sensitivity/selectivity.
GC-MS resources
LC-MS resources
SVOCs of recent concern
PAH
Polycyclic aromatic hydrocarbons (PAHs) are some of the most widespread organic pollutants. In addition to occurring naturally in oil, coal, and tar deposits, PAHs are produced by incomplete combustion of fossil fuels and other organic matter. The compounds are of concern because many have been identified as carcinogenic, mutagenic, or teratogenic. Due to these health risks, regulatory agencies, such as the Environmental Protection Agency (EPA), have defined maximum allowable levels of PAHs in the environment. Sensitive analytical methods are essential in the determination of the presence and levels of PAHs.
PCB
Polychlorinated biphenyls were traditionally used as coolants and insulating fluids (transformer oil) for transformers and capacitors. Production was banned in 1979 due to their toxic and persistent characteristics that are potential threats to the environmental health. Due to their significant presence as an additive in a vast array of other manufactured goods from 1930-1970 continuous monitoring efforts are necessary.
Nitrosamines
Nitrosamines are a type of disinfection byproduct that stems from drinking water disinfection treatment through the chloramination process. Due to the carcinogenic nature of nitrosamines at very low levels, new regulations setting detection limits at PPT (ng/L) levels have been set for nitrosamines in drinking water and food products. EPA Method 521 recommends carbon SPE cartridges and this method can be easily adapted for the analysis of nitrosamines.
Methods for SVOC analysis
Regulatory agencies publish guidance for monitoring semivolatile contaminants in the environment. Despite the common goal of limiting environmental exposure to these compounds due to their potentially detrimental impact, regulations can vary based on location. Regulations often group SVOC based on several criteria including detection methods, end use, common compound structural attributes and other justifications. Frequently used SVOC methods are listed below.
EPA methods for SVOC
- US EPA 543 - Determination of Selected Organic Chemicals in Drinking Water by On-line Solid Phase Extraction - Liquid Chromatography/Tandem Mass Spectrometry (On-line SPE - LC/MS/MS).
- US EPA 525 - Determination of Semivolatile Organic Chemicals in Drinking Water by Solid Phase Extraction and Capillary Column Gas Chromatography/Mass Spectrometry (GC/MS)
- US EPA 625 - Methods for Organic Chemical Analysis of Municipal and Industrial Waters. 625 - Base/Neutrals and Acids
- US EPA 8270 - Semivolatile Organic Compounds by Gas Chromatography /Mass spec (GC-MS)
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