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How Modern GC-MS Is Raising the Bar in Semivolatile Organic Compound Analysis

Team TFS
Team TFS
Semivolatile organic coshutterstock_443763160mpounds (SVOCs) are generated as byproducts from a wide range of industrial processes and have been linked to a number of health issues, including cancer. These substances remain in the environment for extended periods of time and are regularly detected in our waterways and drinking water. Worryingly, many of these compounds persist in the water supply even after treatment attempts and, if ingested, can accumulate in our bodies.

Given the risks to human health, the United States Environmental Protection Agency (EPA) has established maximum contaminant levels (MCLs) for SVOCs in ground and drinking water, with environmental monitoring laboratories performing routine analysis for these compounds. To support consistent measurement practices, the EPA has recently updated the guidance for SVOC analysis by gas chromatography-mass spectrometry (GC-MS). The latest version of these recommendations, known as Method 8270E, is followed by most environmental testing laboratories that analyze SVOCs in extracts prepared from solid waste matrices, soils, air sampling media and water samples by methods such as liquid-liquid extraction, solid-phase extraction (SPE), Soxhlet extraction, ultrasonic extraction and accelerated solvent extraction (ASE). This last sample preparation technique uses a pressurized fluid extraction device according to the Method EPA 3545, recently included in the latest 8270E revision as a suitable preparation technique.

Since the original EPA guidelines were introduced, improvements in GC-MS technology have continually pushed the limits of what’s possible in environmental analysis. Single and triple quadrupole mass spectrometers have become considerably more sensitive and source fragmentation methods have advanced substantially. These technological improvements and a more in-depth understanding of SVOCs mean that even stricter water safety standards can now be enforced. To bring Method 8270 testing protocols in line with modern GC-MS instrument capabilities, the EPA has recently updated the ion abundance criteria for the determination of ion ratios of decafluorotriphenylphosphine (DFTPP), an important standard that’s used to demonstrate the validity of analytical measurements in environmental monitoring. Moreover, the use of the GC-MS/MS technology and selected ion monitoring/chemical-ionization (SIM/CI) acquisition mode have been added, permitting higher selectivity and even more sensitivity for multi-components analysis.

Driving Improvements in SVOC Testing by GC-MS

Driving the updates to the guidance is a number of improvements in GC-MS technology, which enable the detection of SVOCs across a much wider range of concentrations. The broad dynamic range achieved by modern quadrupole systems allows laboratories to easily detect trace levels of compounds in multi-analyte samples. By applying both split and splitless methods, the extended dynamic range detection system of the Thermo Scientific ISQ 7000 GC-MS system, allows users to cover the 0.2–200 ppm working range with the same column, in compliance with EPA 8270 requirements in terms of minimum response factors and linearity.

Moreover, modern chromatography data systems, used to control testing runs and manage data, can incorporate automated tune check reports and system suitability test reports to quickly determine compliance with EPA requirements. Thermo Scientific Chromeleon Chromatography Data System (CDS) Software, version 7.2, features a dedicated Environmental Package including report templates and e-Workflows designed to help environmental laboratories to accelerate data collection and achieve the highest quality assurance standards.

Reducing Downtime and Accelerating SVOC Analysis

It’s not just the enhanced sensitivity of the latest GC-MS systems that are setting new standards in SVOC testing – improvements in instrument design mean modern quadrupole systems are driving more robust, reliable and cost-effective performance too.

The determination of SVOCs in environmental samples like solid and liquid waste, soils and sludge, implies the analysis of dirty extracts, so instrument maintenance procedures requiring venting and re-establishment of the vacuum must be regularly performed. These can be labor-intensive, taking valuable laboratory time away from data collection.

A focus on simplifying routine maintenance operations has resulted in innovative solutions designed to maximize instrument uptime. The new ISQ 7000 single quadrupole and TSQ 9000 triple quadrupole GC-MS systems allow the ion source to be cleaned or the column to be replaced without breaking the MS vacuum. The advanced NeverVent design permits complete removal of the ion source, lenses and repeller through the front vacuum interlock, without the need for system venting. Additionally, maintenance tasks on the GC side such as septum or column replacement, can be accomplished as well with minimal downtime, without venting the MS detector.

Enabling More Cost-effective  Carrier Gas Usage

Traditional GC-MS methods use helium as a carrier gas to move analytes quickly enough through the column. However, with the cost of helium increasing due to diminishing global supplies, many laboratories are looking towards using cheaper substitutes. Hydrogen is often used instead of helium, but this can limit safety concerns and can possibly have negative impacts on detector performance. Nitrogen is an inert gas that can also be used as an alternative to helium; however, it has a relatively low optimum linear velocity, which can extend analysis times. Fortunately, modern GC-MS instruments make more efficient use of helium as a carrier gas, reducing significantly its consumption without affecting the separation process.

The Thermo Scientific TRACE 1300 series of gas chromatographs can be configured with the proprietary split/splitless (SSL) Instant Connect Helium Saver injector, which can accommodate nitrogen alongside helium: nitrogen is used for the highest gas consumption processes like split and purge flows, while helium is used only in the analytical column for separation at the optimum flow rate. As a result, helium saving injectors can help extend the lifetime of a single cylinder of helium to as much as 14 years, depending on the experimental conditions. This smart solution offers significant cost savings by cutting the amount of helium used without compromising on performance and without the need to re-validate methods.

Innovations such as these are raising the bar for sensitive, robust and reliable SVOC testing, and setting new expectations when it comes to safeguarding human health.

Want to learn more?

Find out more about SVOC analysis with the following resources: