Overview
ISO 7952:1994 is an international standard published by the International Organization for Standardization (ISO) that defines a flame atomic absorption spectrometric method for determining the copper content in fruits, vegetables, and derived products. This method ensures precise quantification of copper levels, which is essential for food safety, quality control, and compliance with regulatory limits.
The standard outlines the procedure for sample preparation, mineralization, measurement, and calculation of copper concentration. It emphasizes the use of analytical grade reagents, appropriate sample homogenization, and precise instrumental settings to guarantee reliable and reproducible results.
Key Topics
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Scope and Application
Applicable to a wide range of fresh, processed, and derived fruit and vegetable products, ISO 7952:1994 enables food laboratories to assess copper content accurately to meet health and safety standards.
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Principle of the Method
The method is based on mineralizing organic matter in samples by either dry ashing or wet digestion to extract copper ions. These ions are then quantified using flame atomic absorption spectrometry (FAAS) at a wavelength of 324.7 nm.
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Sample Preparation
Samples must be homogenized thoroughly, with removal of inedible parts if necessary. Mechanical grinding with polytetrafluoroethylene-coated equipment is recommended for uniformity.
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Mineralization Procedures
Two main methods are specified:
- Dry ashing at controlled temperatures up to 525°C in a muffle furnace.
- Wet digestion using mixtures of concentrated acids such as sulfuric and nitric acids under controlled heating.
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Reagents and Standards
Uses analytical-grade sulfuric acid, nitric acid, hydrochloric acid (diluted), and copper standard solutions prepared from copper sulfate or metallic copper for calibration.
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Instrumentation and Measurement
Requires a flame atomic absorption spectrometer equipped with an air-acetylene burner and finely controlled gas flows to ensure stable absorbance readings for copper quantification.
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Calibration and Calculation
Calibration curves are prepared using standard copper solutions at known concentrations. Sample absorbance values are measured, compared against standards, and copper concentration calculated considering sample dilution and moisture content.
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Repeatability
The method specifies that repeatability between two independent determinations within the same laboratory should not exceed 10% relative difference, ensuring reliability.
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Reporting
Test reports must detail the sampling, method applied, results with units, repeatability verification, and any unusual observations affecting the results.
Applications
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Food Safety Monitoring
Accurate copper determination helps assess potentially harmful copper contamination in fruits and vegetables, protecting consumer health.
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Agricultural Quality Control
Enables farmers and producers to monitor copper uptake in crops, aiding in optimizing fertilization and minimizing heavy metal accumulation.
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Regulatory Compliance
Supports compliance with national and international food safety regulations regarding maximum residue limits for copper in agricultural products.
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Research and Development
Used by food scientists and laboratories conducting nutritional analysis or studying metal ion behavior in plant-derived foodstuffs.
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Processed Food Testing
Applicable to a variety of derived products, including juices, purees, and dried vegetables, ensuring quality throughout processing stages.
Related Standards
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ISO 5515:1979 – Fruits, vegetables, and derived products - Decomposition of organic matter for analysis by wet digestion methods, which complements ISO 7952 by specifying mineralization techniques.
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Other ISO standards covering heavy metal determination in food matrices, analytical quality control, and sampling methods for agricultural products.
Keywords: ISO 7952, copper content determination, flame atomic absorption spectrometry, fruits and vegetables analysis, food safety testing, analytical chemistry, sample mineralization, heavy metals in food, copper spectroscopy, atomic absorption method.
Open preview (PDF)Fruits, vegetables and derived products — Determination of copper content — Method using flame atomic absorption spectrometry
