Sequential Colorimetric Measurement of Zinc and Copper in Aqueous Samples

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Solution Overview

Problem

Conventional methods for measuring zinc and copper in aqueous samples are limited by the use of hazardous reagents, interference from various substances, and bleaching chemistry, leading to inaccurate and cumbersome measurements.

Innovation Solution

A colorimetric method using sodium ascorbate reduction, bicinchoninic acid for copper chelation, and 2-Carboxy-2'-hydroxy-5'-sulfoformazyl-benzene monosodium salt for zinc chelation, with absorbance measurement to determine copper and zinc concentrations, eliminating hazardous reagents and bleaching chemistry.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional spectrophotometric methods using Zincon are used for zinc determination, then zinc measurement is achieved, but copper interference occurs and hazardous reagents are required

Engineering Contradiction:

Improvezinc measurement accuracyVSAvoidcopper interference and hazardous reagents

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The measurement process is divided into two separate sequential measurements: first measuring copper using BCA reagent, then measuring zinc using Zincon reagent. This segmentation allows each metal to be measured with its own optimized reagent system, eliminating cross-interference while maintaining accuracy for both metals

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Bicinchoninic acid (BCA) serves as an intermediary reagent that selectively binds to copper ions to form a purple complex measurable at 562 nm. This intermediary step allows copper to be measured and accounted for separately before zinc measurement, eliminating copper's interfering effect on zinc determination

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If conventional copper testing methods are used, then copper measurement is achieved, but zinc interference occurs and bleaching chemistry is required

Engineering Contradiction:

Improvecopper measurement accuracyVSAvoidzinc interference and bleaching chemistry

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The measurement wavelength is changed to 562 nm for copper determination using BCA, which is the absorption maximum for the copper-BCA complex. This parameter change optimizes copper measurement sensitivity and eliminates interference from zinc, which does not absorb significantly at this wavelength

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If sequential measurement procedures are used to eliminate interference, then measurement accuracy improves, but measurement time and complexity increase

Engineering Contradiction:

Improvemetal concentration accuracyVSAvoidmeasurement time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The measurement process continues without interruption between copper and zinc determinations. The same sample and cuvette are used throughout, with reagents added sequentially and measurements taken back-to-back. This continuous approach eliminates time-consuming intermediate steps such as sample transfer, cleaning, or re-preparation between measurements

Inventive Principle:

Principle #20Continuity of useful action

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

Provides accurate and efficient measurement of copper and zinc at low concentrations with reduced interference, using safer reagents and minimizing human error, enabling real-time data acquisition and automated alerts for threshold violations.

Implementation Method 1

The aqueous sample is reduced with sodium ascorbate

Methodology Applied

Scientific EffectReduction: Reduction

Implementation Method 2

A copper chelating agent, such as bicinchoninic acid, is added to the reduced and buffered aqueous sample

Methodology Applied

Scientific EffectChelation: Chemical Bonding

Implementation Method 3

A zinc chelating agent, such as 2-Carboxy-2'-hydroxy-5'-sulfoformazyl-benzene monosodium salt (zincon), is added to the reduced and buffered aqueous sample

Methodology Applied

Scientific EffectChelation: Chemical Bonding

Implementation Method 4

A measurement device measures an amount of copper in the reduced and buffered aqueous sample by measuring a change in an intensity of an absorbance of the reduced and buffered aqueous sample

Methodology Applied

Scientific EffectAbsorbance measurement: Absorption Spectroscopy

Data Source

PatentEP4211456B1Zinc and copper measurement

Publication Date: 2025.10.15 HACH

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Figure 3A~3B

AI summary

An embodiment provides a method for measuring zinc and copper in an aqueous sample, including: reducing an aqueous sample containing an amount of zinc and an amount of copper with a reducing agent; buffering the reduced aqueous sample; chelating the amount of copper in the buffered aqueous sample with a copper(I) chelating agent; measuring the amount of copper in the aqueous sample by measuring a first change in intensity of the absorbance of the copper chelated aqueous sample; chelating the amount of zinc in the buffered aqueous sample with a zinc(II) chelating agent; and measuring the amount of zinc in the aqueous sample by measuring a second change in intensity of the absorbance of the zinc chelated aqueous sample. Other aspects are described and claimed.