Electrochemical probe for detection of chlorate explosives
Inventors
Dressick, Walter J. • Trammell, Scott A. • Shriver-Lake, Lisa C.
Assignees
Publication Number
US-9945811-B2
Publication Date
2018-04-17
Expiration Date
2036-08-11
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Abstract
A method of detecting chlorate in soil includes contacting soil wetted with a solvent containing an electrically conductive salt with an electrode comprising layers of vanadium-substituted phosphomolybdate alternating with layers of para-rosaniline, and performing voltammetry with the electrode, wherein a catalytic reduction current indicates a likelihood of the presence or absence of chlorate in the soil. A system includes a potentiostat operably connected to the electrode and in communication with hardware and software sufficient to produce an output indicating a chlorate level in soil.
Core Innovation
The invention provides a method and system for detecting chlorate in soil samples by contacting the soil wetted with a solvent containing an electrically conductive salt with an electrode comprising alternating layers of vanadium-substituted phosphomolybdate and para-rosaniline and performing voltammetry. The detection relies on the observation of a catalytic reduction current indicative of the presence or absence of chlorate. This approach operates under ambient conditions without exclusion or removal of oxygen and without the need for strong acid, representing a solution compatible with field use.
The problem addressed relates to the dangers posed by improvised explosive devices (IEDs) that employ chlorate-based explosives, for which reliable field detection methodologies remain scarce. Existing detection methods struggle due to chlorate's complex pH-dependent redox chemistry and interference from other chlorine-containing species. Moreover, oxygen presence adversely affects electrochemical detection by generating interfering signals close in potential to chlorate reduction. Laboratory techniques like ion chromatography and spectrophotometric methods suffer limitations related to equipment complexity, specificity, and field applicability.
The innovation overcomes these challenges by employing a porous composite electrode fabricated via layer-by-layer electrostatic deposition of vanadium-substituted phosphomolybdate (specifically Na4H[(VMo11)O40]) and para-rosaniline, which enables catalytic electroreduction of chlorate with minimal interference from oxygen and other common contaminants such as TNT. The electrode demonstrates stability over several months, facile preparation, and applicability for rapid on-site detection. Experiments further optimized key operational parameters, establishing that the system functions effectively without acidification or oxygen removal and can be integrated with portable potentiostats and computer systems for timely soil analysis.
Claims Coverage
The patent discloses two independent claims covering methods for detecting chlorate in soil using an electrode comprising layers of vanadium-substituted phosphomolybdate alternating with layers of para-rosaniline and performing voltammetry, emphasizing detection without oxygen exclusion and strong acid use.
Detection of chlorate in soil using composite electrodes
A method of detecting chlorate by contacting soil wetted with a solvent containing an electrically conductive salt with an electrode comprising layers of vanadium-substituted phosphomolybdate alternating with layers of para-rosaniline and performing voltammetry wherein a catalytic reduction current indicates chlorate presence or absence.
Operation under ambient oxygen and without strong acid
Detecting chlorate in soil using the same electrode and method without excluding or removing oxygen from the environment and without employing strong acid in the testing environment.
The patent claims primarily cover the use of layered vanadium-substituted phosphomolybdate and para-rosaniline electrodes for electrochemical detection of chlorate directly in wetted soil samples through voltammetry, including embodiments that operate effectively under ambient oxygen conditions and without acidification.
Stated Advantages
The electrode system is portable, small, and lightweight along with the potentiostat and electronics.
It operates without interference from oxygen, permitting field use without degassed solutions.
It exhibits no response to common nitrogen-based explosives such as TNT and RDX, enhancing selectivity.
The composite film is rugged and adheres well to substrates like indium tin oxide and glassy carbon.
The electrode is easy to prepare via a simple dipcoating process producing uniform, reproducible active films.
The composite film is stable and retains catalytic activity for chlorate electroreduction after dry storage at room temperature for at least eight weeks.
Documented Applications
Detection of chlorate explosives extracted from soil and other solid samples relevant to identifying improvised explosive device (IED) manufacturing or storage sites.
Field surveillance to determine if an area or structure contains chlorate-based explosive residues, supporting military and civilian safety operations.
Integration with unmanned aerial vehicles (UAVs) equipped with the electrode and potentiostat for remote soil analysis and real-time transmission of chlorate detection results.
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