Electrochemical methods for sample pretreatment for metals determination and related apparatus
Inventors
Schuelke, Thomas • Rusinek, Cory A. • Becker, Michael • Ensch, Mary
Assignees
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Publication Number
US-11592373-B2
Publication Date
2023-02-28
Expiration Date
Abstract
The disclosure relates to a method for pretreating a sample for metals determination. The method includes: providing an aqueous sample mixture comprising a sample containing or suspected of containing one or more metals for detection; contacting the aqueous sample mixture with a first electrode (anode) comprising electrically conducting boron-doped diamond (BDD); electrically contacting the aqueous sample mixture with a second electrode (cathode); applying an electrical potential between the first electrode and the second electrode (i) to provide an electrical current therebetween and through the aqueous sample mixture, (ii) to generate hydroxyl ion (OH−) species at the first electrode, (iii) to oxidize and free the one or more metals for detection in the sample, thereby forming a pretreated aqueous sample comprising free metal ions in aqueous solution and corresponding to the one or more metals in the original sample; and withdrawing the pretreated aqueous sample comprising the free metal ions in aqueous solution. The pretreated aqueous sample can be analyzed for metal content using any desired conventional analysis technique.
Core Innovation
The invention relates to electrochemical advanced oxidation (EAOP) pretreatment for metals determination. An aqueous sample mixture comprising a sample containing or suspected of containing one or more metals for detection is contacted with a first electrode comprising electrically conducting boron-doped diamond (BDD), and an electrical potential is applied between the first electrode and a second electrode to generate hydroxyl ion (OH−) species at the BDD electrode.
The generated hydroxyl ion (OH−) species oxidize and free the one or more metals for detection in the sample, thereby forming a pretreated aqueous sample comprising free metal ions in aqueous solution. The aqueous sample mixture is in direct physical contact with the BDD first electrode, and the aqueous sample mixture is not in direct physical contact with the second electrode during oxidation, and the method includes withdrawing the pretreated aqueous sample comprising the free metal ions.
The electrochemical cell constraints exclude metal reduction or plating prior to withdrawal of the pretreated aqueous sample and during application of the electrical potential, and there is no reduction or plating of metals subsequent to withdrawal of the pretreated aqueous sample. The resulting pretreated aqueous sample is for use in metals detection, including inductively coupled plasma (ICP), mass spectrometry (MS), atomic emission spectroscopy (AES), atomic absorption spectroscopy (AAS), GF-AAS, and stripping voltammetry.
Claims Coverage
The independent claims include three inventive methods, each centered on BDD-electrode electrochemical pretreatment to generate hydroxyl ion (OH−) species, oxidize and free metals into free metal ions, and withdraw a pretreated aqueous sample while excluding metal reduction or plating before, during, and after withdrawal. Dependent claims further narrow the sample type, composition, BDD material parameters, metal selection, free-metal-ion mass fraction, and downstream metal analysis options.
Bdd-electrode hydroxyl ion oxidation to free metal ions
Contacting an aqueous sample mixture comprising one or more metals for detection with a first electrode comprising electrically conducting boron-doped diamond (BDD), electrically contacting the aqueous sample mixture with a second electrode, and applying an electrical potential to generate hydroxyl ion (OH−) species at the first electrode to oxidize and free the one or more metals for detection, thereby forming a pretreated aqueous sample comprising free metal ions in aqueous solution.
Direct physical contact with BDD first electrode, no direct contact with second electrode during oxidation
The aqueous sample mixture is in direct physical contact with the first electrode comprising electrically conducting boron-doped diamond (BDD) and is not in direct physical contact with the second electrode during oxidation.
Withdrawal from an electrochemical cell with no metal reduction or plating before or during withdrawal
The pretreated aqueous sample is formed in an electrochemical cell from which the pretreated aqueous sample is withdrawn, and there is no reduction or plating of metals prior to withdrawal of the pretreated aqueous sample and during application of the electrical potential.
No metal reduction or plating after withdrawal
There is no reduction or plating of metals subsequent to withdrawal of the pretreated aqueous sample.
Substantially solids-free aqueous sample mixture
Providing an aqueous sample mixture comprising a sample containing or suspected of containing one or more metals for detection, wherein the aqueous sample mixture is substantially free from solids.
Biological sample pretreatment
Providing an aqueous sample mixture comprising a biological sample containing or suspected of containing one or more metals for detection.
Biological sample selected from blood, saliva, and urine
The biological sample is selected from blood, saliva, and urine.
Biological sample comprises a blood sample
The biological sample is a blood sample.
Biological sample comprises protein
The biological sample comprises a protein.
Lower pH aqueous sample mixture
The aqueous sample mixture has a pH value of 4 or less.
Matrix chelation and metal-binding protein context
Applied to a sample containing metal-binding protein with bound metal ions and a chelating agent with bound metal ions, where at least 80 wt.% of the total metals from the original sample are present in the pretreated aqueous sample as free metal ions.
Specific metal list selection
Selecting the one or more metals used for detection from a specified list including aluminum (Al), antimony (Sb), arsenic (Ar), barium (Ba), bismuth (Bi), cadmium (Cd), chromium (Cr), cobalt (Co), copper (Cu), iron (Fe), gallium (Ga), germanium (Ge), gold (Au), indium (In), lead (Pb), manganese (Mn), mercury (Hg), nickel (Ni), silver (Ag), thallium (TI), tin (Sn), vanadium (V), zinc (Zn), and combinations thereof.
Bdd material composition via carbon-to-boron atomic ratio
Using a first electrode made of boron-doped diamond whose carbon-to-boron atomic ratio is between 100:1 and 100000:1.
Free metal-ion mass fraction requirement
At least 80 wt.% of the total metals from the original sample are present in the pretreated aqueous sample as free metal ions.
Post-pretreatment metal analysis by ICP, MS, AES, or AAS
Further analyzing a withdrawn pretreated aqueous sample for metal content using one or more selected techniques from inductively coupled plasma (ICP), mass spectrometry (MS), atomic emission spectroscopy (AES), or atomic absorption spectroscopy (AAS).
Overall, the claims focus on BDD-electrode electrochemical generation of hydroxyl ion (OH−) to oxidize and free metals as free metal ions, followed by withdrawing the pretreated aqueous sample. The claims further require no metal reduction or plating before, during, or after withdrawal, and dependent claims narrow by solids content, biological matrix, pH, specific metal selections, BDD carbon-to-boron atomic ratio, free-metal-ion mass fraction, and specified post-pretreatment analytical techniques.
Stated Advantages
Improved digestion efficiency with reduced sample volume, time, and cost versus microwave or heat digestion.
Conversion of metals to free metal ions suitable for conventional metal analysis.
Documented Applications
Metals determination using a withdrawn pretreated aqueous sample analyzed by conventional methods such as ICP-MS, GF-AAS, and stripping voltammetry.
Pretreatment for metals determination in biological samples, including examples such as copper-EDTA and bovine whole blood.
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