Carl A. Groom

Characterization of Metabolites during Biodegradation of Hexahydro-1,3,5-Trinitro-1,3,5-Triazine (RDX) with Municipal Anaerobic Sludge

ABSTRACT The biodegradation of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in liquid cultures with municipal anaerobic sludge showed that at least two degradation routes were involved in the disappearance of the cyclic nitramine. In one route, RDX was reduced to give the familiar nitroso derivatives hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine (MNX) and hexahydro-1,3-dinitroso-5-nitro-1,3,5-triazine (DNX). In the second route, two novel metabolites, methylenedinitramine [(O2NNH)2CH2] and bis(hydroxymethyl)nitramine [(HOCH2)2NNO2], formed and were presumed to be ring cleavage products produced by enzymatic hydrolysis of the inner C—N bonds of RDX. None of the above metabolites accumulated in the system, and they disappeared to produce nitrous oxide (N2O) as a nitrogen-containing end product and formaldehyde (HCHO), methanol (MeOH), and formic acid (HCOOH) that in turn disappeared to produce CH4 and CO2 as carbon-containing end products.

Detection of explosives and their degradation products in soil environments

Polynitro organic explosives [hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) and 2,4,6-trinitrotoluene (TNT)] are typical labile environmental pollutants that can biotransform with soil indigenous microorganisms, photodegrade by sunlight and migrate through subsurface soil to cause groundwater contamination. To be able to determine the type and concentration of explosives and their (bio)transformation products in different soil environments, a comprehensive analytical methodology of sample preparation, separation and detection is thus required. The present paper describes the use of supercritical carbon dioxide (SC-CO2), acetonitrile (MeCN) (US Environmental Protection Agency Method 8330) and solid-phase microextraction (SPME) for the extraction of explosives and their degradation products from various water, soil and plant tissue samples for subsequent analysis by either HPLC-UV, capillary electrophoresis (CE-UV) or GC-MS. Contaminated surface and subsurface soil and groundwater were collected from either a TNT manufacturing facility or an anti-tank firing range. Plant tissue samples were taken fromplants grown in anti-tank firing range soil in a greenhouse experiment. All tested soil and groundwater samples from the former TNT manufacturing plant were found to contain TNT and some of its amino reduced and partially denitrated products. Their concentrations as determined by SPME-GC-MS and LC-UV depended on the location of sampling at the site. In the case of plant tissues, SC-CO2 extraction followed by CE-UV analysis showed only the presence of HMX. The concentrations of HMX (<200 mg/kg) as determined by supercritical fluid extraction (SC-CO2)-CE-UV were comparable to those obtained by MeCN extraction, although the latter technique was found to be more efficient at higher concentrations (>300 mg/kg). Modifiers such as MeCN and water enhanced the SC-CO2 extractability of HMX from plant tissues.

The potential role of biosensors in the food and drink industries.

Despite their apparent potential as analytical tools in the food and drink industries, only a few biosensors are used routinely. This article describes the development of biosensors for these sectors and discusses the technical and economic problems of applying this technology to the monitoring of food and drink products.

Detection of the cyclic nitramine explosives hexahydro-1,3,5-trinitro- 1,3,5-triazine (RDX) and octahydro- 1,3,5,7-tetranitro- 1,3,5,7-tetrazine (HMX) and their degradation products in soil environments.

The cyclic nitramine explosives hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazine (HMX) were examined in field and microcosm soil samples to determine their patterns of degradation and environmental fates. A number of analytical techniques, including solid-phase microextraction with on-fiber derivatization, gas chromatography-mass spectrometry, gas chromatography with electron-capture detection, liquid chromatography-mass spectrometry, and micellar electrokinetic chromatography were required for the analyses. Two different classes of intermediates were detected, both of which lead ultimately to the formation of nitrous oxide (N2O) and carbon dioxide (CO2). The first class was identified as the nitroso derivatives formed by the sequential reduction of -NO2 functional groups. The second class of intermediates, which was favored at higher humidities and in the presence of anaerobic sludge amendments, consisted of ring cleavage products including bis-(hydroxymethyl)-nitramine and methylenedinitramine. Rye-grass (Lolium perenne) present in field samples was found to extract and accumulate HMX from soil without further degradation. In all cases (excepting the plant samples), the indigenous microbes or amended domestic anaerobic sludge consortia degraded the cyclic nitramine explosives eventually to produce N2O and CO2.

Cyclodextrin-assisted capillary electrophoresis for determination of the cyclic nitramine explosives RDX, HMX and CL-20: Comparison with high-performance liquid chromatography

A sulfobutyl ether-beta-cyclodextrin-assisted electrokinetic chromatographic method was developed to rapidly resolve and detect the cyclic nitramine explosives 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaaza-isowurtzitane (CL-20), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and their related degradation intermediates in environmental samples. Development of the electrophoretic method required the measurement of the aqueous solubility of CL-20 which was determined to be 3.59 +/- 0.74 mg/l at 25 degrees C (95% confidence interval, n=3). The performance of the method was then compared to results obtained from existing high-performance liquid chromatography methods including US Environmental Protection Agency method 8330.

Electrical communication between a water-soluble 1,1′-dimethylferrocene-2-hydroxypropyl-β-cyclodextrin complex and glucose oxidase: biosensor applications

Abstract 2-Hydroxypropyl-β-cyclodextrin (HPBC) was used to enclose 1,1′-dimethylferrocene (DMF) into its hydrophobic cavity to form a yellow water-soluble complex with a molar ratio of about 6 to 1. The cyclic voltammogram of the complex solution exhibited one single electron transfer process with a half-wave potential of 170 mV. The oxidation potential of the DMF-HPBC complex was not affected by pH ranging from pH 4·7 to 8·8 and the difference between the anodic and cathodic peak potentials was observed to be 95 mV. The DMF-HPBC complex was used together with immobilized glucose oxidase to construct a mediated biosensor for the determination of β-D-glucose. The enzyme was either convalently immobilized on a preactivated Immunodyne nylon membrane or retained onto the sensing area of the electrode by a dialysis membrane. In the latter preparation, the enzyme electrode exhibited a detection limit of 0·02 mM and a linear range of 0·02 to 0·5 mM. About 2 min was required to attain 90% of full response. The biosensor was effective for the determination of glucose in food and beverage samples.

Novel Approaches to the Development of Mediated Biosensors and Enzyme Assay

2-Hydroxypropyl-β-cyclodextrin (hp-β-CyD), a cyclic and non-reducing Oligosaccharide was used to enclose the hydrophobic guest molecules, ferrocene (FeCp2) and 1,1’-dimethylferrocene (DMFeCp2) to form a water-soluble yellow complex. At 300 mM, hp-β-CyD enclosed up to 100 mM FeCp2 or DMFeCp2. The cyclic voltammogram of the DMFeCp2-hp-β-CyD complex exhibited one single electron transfer process with a half-wave potential of 170 mV. The oxidation potential of the DMFeCp2-β-CyD complex was not affected by pH ranging from pH 4.7 to 8.8 and the difference between the anodic and cathodic peak potentials was observed to be 95 mV.