Elsevier

Journal of Chromatography A

Volume 1217, Issue 48, 26 November 2010, Pages 7564-7572
Journal of Chromatography A

Optimization of two methods for the analysis of hydrogen peroxide: High performance liquid chromatography with fluorescence detection and high performance liquid chromatography with electrochemical detection in direct current mode,☆☆

https://doi.org/10.1016/j.chroma.2010.10.022Get rights and content

Abstract

Two complementary methods were optimized for the separation and detection of trace levels of hydrogen peroxide. The first method utilized reversed-phase high-performance liquid chromatography with fluorescence detection (HPLC–FD). With this approach, hydrogen peroxide was detected based upon its participation in the hemin-catalyzed oxidation of p-hydroxyphenylacetic acid to yield the fluorescent dimer. The second method utilized high performance liquid chromatography with electrochemical detection (HPLC–ED). With this approach, hydrogen peroxide was detected based upon its oxidation at a gold working electrode at an applied potential of 400 mV vs. hydrogen reference electrode (Pd/H2). Both methods were linear across the range of 15–300 μM, and the electrochemical method was linear across a wider range of 7.4–15,000 μM. The limit of detection for hydrogen peroxide was 6 μM by HPLC/FD, and 0.6 μM by HPLC/ED. A series of organic peroxides and inorganic ions were evaluated for their potential to interfere with the detection of hydrogen peroxide. Studies investigating the recovery of hydrogen peroxide with three different extraction protocols were also performed. Post-blast debris from the detonation of a mixture of concentrated hydrogen peroxide with nitromethane was analyzed on both systems. Hydrogen peroxide residues were successfully detected on this post-blast debris.

Introduction

In recent years there has been increasing concern over the use of hydrogen peroxide in improvised explosive devices. When properly mixed with appropriate fuels, this material can become a powerful explosive. Because hydrogen peroxide is widely used as a strong, environmentally friendly oxidant compared to bleach, it is easy to obtain in a variety of forms. Most municipal and industrial applications utilize 35–50% concentrated solutions of hydrogen peroxide. Household applications involving 3% solutions of hydrogen peroxide include cleaning wounds and bleaching clothing, while the bleaching of hair typically utilizes 15% solutions of hydrogen peroxide. Industrial applications of hydrogen peroxide include pulp and paper bleaching, organic and inorganic chemical processing, the treatment of metal, catalysis of polymerization reactions, and industrial waste treatment [1].

Though stable if uncontaminated, hydrogen peroxide solutions will decompose slowly into oxygen gas and water with the evolution of heat. There is considerable evidence that this process occurs as a chain reaction involving free radicals [2]. Decomposition of hydrogen peroxide into perhydroxy and hydroxyl radicals is accelerated in the presence of near UV light or an iron catalyst. In dilute solutions, the water present can absorb the heat which is evolved through the decomposition of hydrogen peroxide. In more concentrated solutions, the heat evolved from decomposition raises the temperature of the solution, which in turn increases the rate of decomposition. High alkalinity can also increase the decomposition rate of hydrogen peroxide. The catalytic decomposition of hydrogen peroxide at a concentration of 70% or greater proceeds rapidly, and with sufficient heat released that the products are oxygen and steam. The thrust from this reaction can be used to propel torpedoes and small missiles [2].

Hydrogen peroxide based explosives may be prepared as a blend of separate fuel and oxidizer compounds, such as mixtures of concentrated hydrogen peroxide with carbon-based fuels. Alternatively, hydrogen peroxide may be used as a starting component in the production of explosives which contain the fuel and oxidizer within the same molecule. Triacetone triperoxide (TATP) and hexamethylene triperoxide diamine (HMTD) are examples of the latter type.

Research has been published on the development of HPLC-based methods for the analysis of trace levels of hydrogen peroxide and selected organic peroxides which are present in the atmosphere [3], [4], [5], [6]. The combination of an acidic mobile phase with a C-18 analytical column permits the elution of hydrogen peroxide within 6 min [3], [4], [5], [6]. Trace levels of hydrogen peroxide can be detected using the reaction of hydrogen peroxide with p-hydroxyphenylacetic acid in the presence of an iron containing catalyst [3], [4], [5], [6], [7]. The product of this reaction is the dimer 6,6′-dihydroxy-3,3′-biphenyldiacetic acid, the anionic form of which is readily detectable using a standard HPLC fluorescence detector. In addition to the analysis of atmospheric peroxides, this technique has also been applied to the analysis of organic peroxide explosives such as TATP and HMTD [7], [8]. In this procedure, the peroxide explosives are photolytically degraded post-column to form hydrogen peroxide, which then reacts with p-hydroxyphenylacetic acid in the presence of the iron containing catalyst.

While work has been performed on the use of electrochemical detection to analyze hydrogen peroxide in biological samples [9], many biological-based assays require the use of specially modified electrodes [10], which are not commercially available and therefore may be impractical for use in forensic laboratories. There has been a deficiency of peer-reviewed work published on the use of this technology for the analysis of hydrogen peroxide in improvised explosives. However, Schulte-Ladbeck et al. published a study in 2003 detailing a method for the detection of TATP and HMTD by reversed phase HPLC with post-column UV irradiation and electrochemical detection [11]. This method employed a C-18 analytical column in conjunction with a mobile phase which consisted of 65% acetonitrile and 35% aqueous 4 mM sodium phosphate buffer at pH 8.

The goal of this research was to develop and optimize two distinct methods, based on different principles of separation and detection, which could separate and detect trace amounts of hydrogen peroxide. This research could provide a basis for the analysis of hydrogen peroxide residues in post-blast situations. Experiments were also conducted regarding the effects of sampling materials on the collection of hydrogen peroxide. As part of the evaluation, post-blast samples from the detonation of a mixture of concentrated hydrogen peroxide with an organic fuel were collected and analyzed using both methods.

Section snippets

Chemicals

HPLC grade water was used as received from Burdick & Jackson (Honeywell Burdick & Jackson, Morristown, NJ, USA). Deionized water (18.3 MΩ) was obtained using a Nanopure Infinity™ water purification system (Barnstead/Thermolyne, Pittsburgh, PA, USA). Reagent grade hemin powder (Sigma–Aldrich, St. Louis, MO, USA), 4-hydroxyphenylacetic acid (Acros Organics, Geel, Belgium), sodium acetate (Sigma–Aldrich), 10 N sodium hydroxide, sulfuric acid, ethylenediaminetetraacetic acid (EDTA) (Thermo Fisher

Results and discussion

The goal of this study was to test and optimize two methods developed for the analysis of trace levels of hydrogen peroxide. The HPLC/ED and HPLC/FD methods optimized for the analysis of hydrogen peroxide are based upon different principles of separation and detection. Either of the two methods could provide a greater degree of certainty as a confirmation method after an initial screening test. This is particularly important in the event that these techniques are applied to forensic samples.

Conclusions

Two methods were optimized for the analysis of trace levels of hydrogen peroxide: HPLC/FD and HPLC/ED in DC mode. Each method offered the benefits of a low limit of detection (0.6 μM for the HPLC/ED system and 6 μM for the HPLC/FD system), a linear dynamic range from 15 to 300 μM, selectivity to hydrogen peroxide, and insensitivity to a select group of potential interferences. The repeatability of the retention time of hydrogen peroxide for both methods was excellent. Post-blast debris from the

Acknowledgements

This research was supported in part by an appointment to the Research Participation Program at the Federal Bureau of Investigation, Counterterrorism Forensic Science Research Unit administered by the Oak Ridge Institute for Science and Education through an interagency agreement between the U.S. Department of Energy and the FBI.

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Cited by (0)

Portions of this work have been presented in oral form at the 61st Annual Meeting of the American Academy of Forensic Sciences in Denver, CO, February 16–21, 2009.

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Disclaimer: This is publication 10–11 of the Federal Bureau of Investigation's (FBI) Laboratory Division. Names of commercial manufacturers are provided for identification purposes only, and inclusion does not imply endorsement of the manufacturer, or its products or services by the U.S. Government. The views expressed are those of the authors and do not necessarily reflect the official policy or position of the U.S. Government. No outside funding was received for the research reported in this article.

1

Present address: Treasury Obligations Section, United States Secret Service, Washington, DC, USA.

2

Present address: Department of Chemistry, George Washington University, Washington, DC, USA.

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