News

50 Years of Purge and Trap

April 30, 2025

When using a concentrator system, it is not essential to understand how it works. However, a good grasp of the fundamentals helps prevent problems and assists you when you are faced with tasks such as method development and troubleshooting.  The purpose of this blog is to help you develop an understanding of how and why compounds are concentrated.

 While gas chromatography is a powerful analytical tool, it does have several limitations. Many different techniques for a wide variety of samples have developed to overcome these limitations. The limitations, which P&T concentration is designed to overcome, include:

1.  

a. Environmental Analysis - Many pollutants must be measured at low levels; sometimes, in the sub-part-per-billion (ppb) range.

b. Flavor and Fragrance Analysis - The human nose is one of the most sensitive detectors in existence.

3. Gas chromatography operates as an interaction between vapor and liquid phases. The sample must start out as a vapor. For this reason, there are many samples, such as pollutants in soil or flavors in solid food that cannot be directly introduced into a GC.

 

The ability to analyze VOCs is a vital part of environmental monitoring, outgassing studies, flavor or fragrance analysis, among others. P&T is a technique that separates the VOCs from a matrix. After separation, the VOCs are then concentrated and injected into the GC for separation.

Brief History

In the 1960s, P&T was used in the study of bodily fluids. In the mid-to-late 1970s, P&T became a technique that was well-known and widely applied due the need to monitor VOCs in drinking water. Using this technique, it was possible to detect sub-ppb level VOCs of a wide variety. Today, P&T is routinely applied in the environmental area for the analysis of VOCs in soil and water. The arrival of microprocessor-driven systems allows the concentrator to be more precise and automated, giving the operator more time for other projects.

Purge and Trap Operation Overview

A measured amount of sample is placed in a sealed vessel. The sample is purged with inert gas, causing VOCs to be swept out of the sample. The VOCs are retained in an analytical trap, which allows the purge gas to pass through to vent. The VOCs are then desorbed by heating the trap, injected into the GC by backflushing the trap with carrier gas, and separated and detected by normal GC operation.

Purging

In the previous section it states, ”The sample is purged with an inert gas, causing VOCs to be swept out of the sample.” This is a very simple-sounding way of describing what is in reality a rather complex process. Purging a sample to extract analytes is a gas extraction. There are many factors that affect the efficiency of this extraction. The amount of each compound purged is proportional to both its vapor pressure and its solubility in the sample. Both of these are in turn, affected by the sample temperature.

Consider the case of a sample sealed in a closed vial. Above the sample is a vapor space, which is usually referred to as the headspace. If you allow the sample sufficient time, VOCs in the sample will migrate into the vapor space. After a certain period of time, equilibrium will be established, and the concentration of the volatile compounds in each phase will be stabilized.

At this point a portion of the headspace can be removed and injected into the GC for analysis. The technique is known as Equilibrium Analysis or Static Headspace Analysis. The amount of material in the vapor phase will be proportional to the partial pressure of the component. The equation below describes the phase distribution of sample.

P_T = P₁ + P₂ + P₃ + ... + P_n = X₁ P₁^o + X₂ P₂^o + X₃ P₃^o + ... + X_nP_n^o

where:

P_T = total vapor pressure of system

P₁, etc. = partial pressure of each compound

P₁^o, etc. = vapor pressures of the pure compounds

x₁, etc. = mole fractions of each compound

In purging a sample, the system is no longer at equilibrium. This is because the VOCs that move into the vapor phase are constantly being removed by the purge gas. Under these circumstances, there is no migration of components from the vapor to liquid phase. This means that the partial pressure of any individual component above the sample at any time is essentially zero. This encourages even greater migration of the VOCs into the vapor phase, purging the sample more efficiently. Purging a sample for 10 minutes with helium (at a flow rate of 50 mL/min.) results in a more efficient extraction of volatiles than equilibrium, using 500 mL headspace. This purging technique is called Dynamic Headspace Analysis. For aqueous matrices, the increase in efficiency can be upwards of 100 fold, using dynamic versus static headspace analysis.

Extraction efficiency improves with an increase in sweep volume. Sweep volume, a function of sweep time and flow rate, is the amount of purge gas used to extract the analytes. Since the analytes are being trapped on a sorbent bed, there are limitations to the sweep times and flow rates that can be used. These limitations are determined by the compounds of interest in the sample and the sorbent material used in the trap.

 

Trapping and Adsorption

An analytical trap is a short gas chromatograph column. Compounds entering the trap will slowly elute with a measurable retention volume. Retention volume is the amount of purge gas that passes through the trap before elution of the analytes begins to occur.

At lower trap temperatures, retention volumes are high. At higher desorption temperatures, retention volumes are much smaller, allowing rapid transfer to the GC. In this context, the use of retention time is not correct. The correct parameter is retention volume.

When elution does occur, it is usually referred to as breakthrough, and the retention volume, at which breakthrough occurs, is often referred to as the breakthrough volume. Sorbent materials are usually chosen so that the breakthrough volume is high for analytes and low for water. Care must be taken that the sorbent chosen does not retain the analytes too strongly or efficient desorption may not be possible. Traps containing combinations of sorbents are often used to enhance performance.

 

The trap is packed with the weaker sorbent on top. The stronger sorbent is placed below the weaker sorbent. Less volatile analytes that are not effectively desorbed by the stronger sorbent are retained by the weaker sorbent.

 

Therefore, the less volatile analytes fail to reach the stronger sorbent. Only the more volatile analytes reach the stronger sorbent; and because of their volatility, these analytes can be efficiently desorbed. The desorption is carried out by backflushing the trap, ensuring that the heavier analytes never come in contact with the stronger sorbent.

 

Teledyne Tekmar developed the first commercial Purge and Trap concentrators in 1975, and today offers a comprehensive line of products, including the Stratum, which uses the Teledyne Hastings Mass Flow Controller to deliver unmatched precision and accuracy. Teledyne’s AQUATek 100 automates the sample preparation steps for analyzing liquid samples, while the Atomx Automated Sample Prep System combines an autosampler and Purge and Trap into a single instrument for analyzing VOCs in soils and water.

 

Streamline your sample preparation

April 23, 2025

Are you looking to streamline your sample preparation to achieve precise fineness in your sample to determine elemental or chemical composition? A major struggle is that it can be an extremely tedious process, often resulting in inconsistent results and repetitive work.

Integrating Retsch grinders, shakers and sievers, offered and supported by ATS Scientific and Hitachi XRF analyzers offered by Folio Instruments into your lab, you get a streamlined solution for your specific requirements. 

Solving the initial problem of size reduction will immediately save you time and money. For larger sample sizes, Retsch's BB 250 jaw crusher is the perfect solution while the BB 50 jaw crusher further reduces your sample size. They can efficiently crush your most difficult samples, significantly cutting down on the time it takes to get them ready for finer grinding.

When it's time for finer grinding, Retsch's mills are the workhorses. They are built for both speed and precision, ensuring you get the particle size you need quickly and consistently. Finish your preparation with a reliable, uniform sample with one of Retsch’s sample dividers or a unit from their full range of sieving equipment.  Discover the finer grinding capabilities of the RS 200 Disc Mill which is perfect for further preparing your sample for Folio Instrument’s offerings of Hitachi XRF analyzers. 

ATS Scientific and Folio Instruments’ offerings will increase productivity, save time and money, and provide accurate and reliable results needed for your application.

To learn more about ATS Scientific’s suite of Retsch grinders, shakers and sievers, click here

Discover Folio Instrument’s Hitachi offerings of XRF analyzers. Click here

 

Smarter Elemental Analysis

April 16, 2025

Are you facing the ongoing challenge of achieving fast, safe, and accurate analysis of Carbon, Nitrogen, and Sulphur (CNS) levels in your samples? Whether you're trying to keep pace with increasing workloads or looking to reduce your lab’s environmental footprint, now is the perfect time to explore smarter solutions that can make a real impact on your workflow.

As spring arrives, bringing warmer days and renewed energy to your operations, it’s also a natural moment to reassess your lab’s efficiency and capabilities. With soil warming and the growing season beginning, especially for those in agricultural and environmental fields, demand for precise and timely analysis is about to spike. Don’t get caught off guard—optimize your lab now with VELP Scientifica’s EMA 502 Elemental Analyzer.

This cutting-edge, all-in-one system is engineered to streamline your CNS analysis without the need for external modules or harmful reagents. The EMA 502 delivers exceptional performance with speed, safety, and simplicity—enabling labs to analyze a wide range of organic matrices including soils, fertilizers, animal feed, polymers, and more. Its fully automated workflow and intuitive software help reduce operator workload, minimize errors, and ensure consistent, high-quality results.

Implementing the EMA 502 not only boosts your lab’s daily efficiency but also future-proofs your operations with a reliable, long-term solution for elemental analysis. With a compact footprint and minimal maintenance requirements, it’s an ideal fit for labs of any size looking to modernize their capabilities.

Whether you’re working in agriculture, environmental science, food and feed analysis, or materials research, the EMA 502 provides the robustness and accuracy needed to meet evolving industry demands. And with VELP’s strong reputation for innovation and support, you gain not just an instrument—but a true partner in your lab’s success.

Optimize your lab with a cost-effective, high-impact testing workflow

April 9, 2025

Are your lab techs analyzing food and feed powders with outdated testing equipment and methods? This can often result in the slowing of your R&D efforts, providing inconsistent batches, and increasing quality assurance frustrations, not just with productivity, but most importantly, accuracy.

As the saying goes “Why work harder when you can work smarter?” The good news is that there is an economical solution without overspending or overcomplicating your workflow! By pairing the Microtrac BEL Belsorp Mini X with the Erweka SVM II 5-in-1 Tapped Density Tester, you create a cost-effective yet high-impact testing workflow.

So, what are these low-profile, benchtop instruments and how exactly can they optimize your lab?

• The Belsorp Mini X is designed using the BET method to determine the amount of gas adsorbed onto the surface of your powders, adsorption behavior along with pore volume and size.
• The Erweka SVM II offers five density tests allowing you to better understand how your powders pack, settle and flow: critical for dosing accuracy, packaging efficiency and downstream manufacturing performance.

Together, this benchtop combo empowers your food and feed lab techs to predict and solve powder flow issues; optimize formulations, reduce batch variability and waste all while meeting food safety regulatory standards with complete confidence.

Whether you are upgrading your current workflow or building out new testing capabilities, the Belsorp Mini X and SVM II offer the flexibility and precision today’s food, and feed labs need.

At ATS Scientific Inc. we have helped labs across Canada bring these tools into their day-to-day operations with expert support, training, and integration guidance.

Proceed to learn more here:

BEL Belsorp Mini X https://ats-scientific.com/products/belsorp-mini-x

ERWEKA SVM II: https://ats-scientific.com/products/svm-ii-5-1-in-tapped-density-tester

 

Enhance Mercury Analysis with the Milestone DMA-80 evo

April 1, 2025

Are you analyzing mercury levels in soils and biota?  The Milestone DMA-80 evo allows these samples to be analyzed without any prior sample preparation in as little as 5 minutes a sample via a sequential sampler.

Our industry standard instrument is now in it’s 7^th generation and assists 1000s of researchers and testing labs across the globe.

Please link to the following for more our detailed application notes.

Industry-report-DMA-80-Environmental-USREV062019.pdf

AppRpt-DMA80evo-Fish_USREV061019.pdf

 

 

 

• 1
• 2
• 3
• 4
• 5
• Next