Using Mass Spectrometry for Reaction Monitoring and Real-Time Gas Analysis

In laboratories across the world, gas chromatographs are indispensable instruments that are used for the identification and purification of unknown chemical compounds. However, in spite of its many abilities, gas chromatography (GC) by itself cannot always be used for the specific identification of chemical compounds.1

Therefore, such instruments are usually coupled to mass spectrometers, where the ability to mass-resolve the peaks in a gas chromatogram enables sample identification with greater confidence. For identification of forensic substances, gas chromatography mass spectrometry (GC-MS) is usually considered the ‘gold standard’ and is now extensively employed in areas such as pharmacology, chemical synthesis and petrochemical industries.2

Continuous and Accurate Reaction Monitoring

GC-MS instruments with adequately short run times can now be designed for ‘real-time’ analysis. Constant quantitative and qualitative information on the evolution of chemical concentrations or the formation of new species in an active reaction mixture is provided by this type of on-line analysis. Such an analysis is vital in many fermentation and biotech processes that require carefully balanced oxygen uptake and carbon production rates for optimum yields. On-Line GC-MS also makes it possible for scientists to create automated feedback loops for control of the reaction parameters, enabling fine tuning of the reactions behavior.3

Real-time gas analysis has several other applications such as exploring the efficiency of catalysts for capture and reduction and carbon dioxide, and for atmospheric monitoring.4 However, regardless of the power of continuous monitoring, there are quite a few challenges in designing instruments that can provide real time analysis.

A typical GC-MS experiment may have a total run time of about 20 minutes from the initial injection to the final data. Hence, analyzers should be designed with considerably shorter run times, to make an instrument versatile for a wide range of uses and to make sample inlets that can be used with materials in many different phases. Through this, even the sample preparation time can be reduced.

New Tools for On-Line Analysis

Hiden’s HPR series is a range of systems that are particularly targeted to resolve these problems. Building upon Hiden’s three decades of expertise in the design and development of quadrupole mass spectrometers, the HPR series is developed for continuous real-time analysis of vapors and gases at near-atmospheric pressures.5 These also come with a host of sampling inlets suited for use in catalysis, electrochemistry, fermentation and sedimentology.6

Apart from the remarkable technical specifications, the HPR series is designed to be compact, bolt-on units, keeping the user experience in mind. This means even non-expert users can operate the analyzer. Also, multiple reaction chambers can be monitored at the same time. For applications such as optimizing fermentation processes, fully automated process integrated solutions and network multiple analysis heads can be used together for more complex process chemistry.3

Sensitivity and Speed

Not only is the HPR series easy to use but it also has a very fast response with high speed measurements. They can make up to 650 measurements per second, with the high speed crucial for transient reaction analysis. Data acquisition can be optimized by the user. This is necessary for accurate and real time on-line analysis.

The dynamic range, a measure of the sensitivity of detection, of the HPR series is in the parts per billion (PPB). Therefore, the HPR series is suitable for applications where there are only low concentrations of analytes. The triple filter quadrupole mass detector makes it possible to achieve high performance and sensitivity across the mass range. This detector is also designed with filtering technologies in order to safeguard it from the aggressive and corrosive nature of many of the gases in industrial processes, such as chemical vapors deposition.5

Versatility and Applications

An ideal real-time gas analyzer should be able to carry out fast measurements and should also be able to separate complex mixtures of products and reactants. The HPR series enables the detection of multiple chemical species including light gases, such as helium/hydrogen and others such as carbon dioxide and methane. Sample inlets are also available for monitoring dissolved gases in real-time, which is important in solution phase reactions or aquatic environments.

The HPR series has been effectively utilized in a study of the photocatalytic hydroxylation of phenol as a means for selective synthesis of dihydroxybenzenes. The HPR analyzer was used to track concentration of phenol and two reaction products in real-time in a complex mixture, thus making it possible to optimize the reaction conditions on-the-fly.

Species such as volatile organic compounds can be studied with the HPR series, or the HPR series can be used in tandem with other techniques such as monitoring the output of thermogravimetric analysis, a method in which samples are characterized by monitoring their reaction to rising temperatures.

To summarize, the compact HPR series is readily configured for multi-stream, real-time analysis on a variety of sample types and is also suitable for non-expert users.

References

1. P.J. Baugh, Gas Chromatography: A Practical Approach, Oxford University Press, USA, 1994

2. J. Petruzzi, Anal. Chem., 1973, 45(14), 1213A

3. Fermentation/Bio Reaction Monitoring, http://www.hidenanalytical.com/applications/gas-analysis/fermentation/ , (accessed December 2017)

4. CO2 Adsorption, http://www.hidenanalytical.com/wp-content/uploads/2016/06/AP0025_Newsletter.pdf , (accessed December 2017)

5. Quadrupole Mass Spectrometers for Advanced Science, http://www.hidenanalytical.com/wp-content/uploads/2016/06/HPR-20_QIC_RD_Plus_Widescreen.pdf , (accessed December 2017)

6. Hiden Gas Catalogue, http://hideninc.com/wp-content/uploads/2016/12/Hiden-Gas-Analysis-Catalog.pdf, (accessed December 2017)

7. Photocatalytic Hydroxylation of Phenol, http://www.hidenanalytical.com/wp-content/uploads/2016/06/AP0172_newsletter.pdf, (accessed December 2017)

Hiden Analytical

This information has been sourced, reviewed and adapted from materials provided by Hiden Analytical.

For more information on this source, please visit Hiden Analytical.

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