High-Chloride COD Measurement Using Chloride Correction
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Solution Overview
Problem
Existing methods for determining chemical oxygen demand (COD) in high chloride samples are inaccurate and often require the use of mercury (II) sulfate, posing health and environmental risks, and are limited by chloride concentration thresholds, necessitating sample dilution.
Innovation Solution
A method involving pre-dosing a container with acid, oxidizing agent, and mercury (II) sulfate, followed by photometric determination of preliminary COD, and applying a chloride correction using individually determined calibration curves to accurately measure COD in high chloride samples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional COD determination methods are used for high chloride samples, then the measurement process is simple, but the measurement precision deteriorates due to chloride interference
Solution Approach 1:
The method applies preliminary action by determining the chloride concentration in the sample before performing the COD measurement. This preliminary knowledge of chloride content allows for subsequent correction of the COD value to compensate for chloride interference, thereby improving measurement precision without requiring complex real-time interference management during the measurement process
Solution Approach 2:
The method implements feedback by using the measured chloride concentration to correct the COD measurement result. The chloride correction factor, determined from calibration curves that relate chloride concentration to measurement interference, is applied to adjust the raw COD value, creating a closed-loop correction system that improves accuracy based on actual sample conditions
2Measurement precision
If sample dilution is applied to reduce chloride concentration, then chloride interference is reduced, but the COD value loses accuracy due to dilution effects
Solution Approach 1:
The method applies parameter changes by measuring and utilizing the chloride concentration parameter to correct the COD measurement. Instead of physically altering the sample composition through dilution or removal, the approach changes the measurement parameter (COD value) based on the measured chloride parameter, thereby maintaining sample integrity while achieving accurate results
3Reliability
If mercury (II) sulfate is added to complex chloride ions, then chloride interference is eliminated, but health and environmental safety deteriorates
Solution Approach 1:
The method extracts or removes the harmful substance (mercury sulfate) from the measurement process entirely. Instead of using mercury sulfate to complex chloride ions, the invention replaces this toxic approach with a mathematical correction method based on chloride concentration measurement, thereby eliminating health and environmental risks while maintaining measurement reliability through the chloride correction factor
Solution Approach 2:
The method substitutes a mechanical/chemical system (mercury sulfate complexation) with an analytical/mathematical system (chloride measurement and correction calculation). This replacement eliminates the need for toxic chemicals while achieving the same goal of eliminating chloride interference through a safer, intelligence-based approach
4Productivity
If existing photometric methods are used for high chloride samples, then the method is simple and fast, but measurement precision deteriorates above 1,000 mg/L chloride
Solution Approach 1:
The method applies preliminary action by determining the chloride concentration in the sample before performing the COD measurement. This preliminary knowledge of chloride content allows for subsequent correction of the COD value to compensate for chloride interference, thereby improving measurement precision without requiring complex real-time interference management during the measurement process
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate COD determination in samples with chloride concentrations up to 20,000 mg/L without mercury (II) sulfate, ensuring precision and safety while allowing use with existing analytical devices.
Implementation Method 1
nearly all organic compounds can be fully oxidized to carbon dioxide with a strong oxidizing agent under acidic conditions
Implementation Method 2
photometrically determining a preliminary chemical oxygen demand (COD) of the analyte in an analytic device
Data Source
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AI summary
The present invention provides a method of determining chemical oxygen demand (COD) for a sample with a high concentration of chloride. The method includes obtaining the sample, determining a concentration of chloride in the sample to obtain a known concentration of chloride in the sample, dosing an amount of the sample, an acid and an oxidizing agent into a container to obtain an analyte, heating the container containing the analyte, photometrically determining a preliminary chemical oxygen demand (COD) of the analyte in an analytic device, and correcting for the high concentration of chloride using a chloride correction to obtain the chemical oxygen demand (COD).