ISO 6636-3:1983

Overview

ISO 6636-3:1983 is an international standard developed by ISO for the determination of zinc content in fruit and vegetable products using the dithizone spectrometric method. This method is essential for quality control in the food industry, regulatory compliance, and ensuring food safety standards are met. The procedure is based on decomposing organic matter from food samples, neutralizing the solution, complexing zinc with dithizone, extracting with chloroform, and measuring absorbance at 538 nm. The standard is a valuable reference for laboratories conducting zinc analysis in fruit and vegetable products.

Key Topics

• Scope: The standard specifies the use of the dithizone spectrometric method for the quantitative determination of zinc in a wide range of fruit and vegetable products.
• Sample Preparation: Guidelines for homogenizing samples and handling frozen products to ensure representative test portions.
• Reagents and Apparatus: Use of high-purity reagents, with specific attention to zinc-free laboratory water and equipment. Essential apparatus include volumetric flasks, separating funnels, and a spectrometer capable of measurements at 538 nm.
• Analytical Procedure:
  • Decomposition of the sample's organic matter
  • Addition of reagents including 1,5-diphenylthiocarbazone (dithizone)
  • Extraction of the zinc-dithizone complex with chloroform
  • Measurement of absorbance to determine zinc concentration
• Calibration and Quality Assurance: Preparation of standard zinc solutions, calibration curves, and regular validation of spectrometric results. Emphasis on running blank tests and ensuring repeatability.
• Reporting: Standardized reporting of results with calculation methods provided, including guidelines for test reports and identification of samples.

Applications

• Food Safety: Used by food regulatory agencies and quality control laboratories to ensure that zinc levels in fruit and vegetable products meet national and international safety requirements.
• Nutritional Labeling: Supports accurate nutritional analysis for product labeling and consumer information.
• Research and Development: Valuable in the development of new products and in nutritional studies evaluating the zinc content of foods.
• International Trade: Assists exporters and importers of fruit and vegetable products in demonstrating compliance with zinc residue limits as specified in international agreements.

Related Standards

• ISO 5515: Fruits, vegetables, and derived products - Decomposition of organic matter prior to analysis - Wet method. ISO 6636-3 cites this standard for sample preparation.
• ISO 6636-1 / ISO 6636-2: Additional parts of the ISO 6636 series specifying alternative methods for determining zinc content in fruit and vegetable products.
• General Spectrometric Analysis Standards: Other ISO standards that regulate laboratory practices for spectrophotometric determinations.

ISO 6636-3:1983 ensures reliable and reproducible zinc determination in fruit and vegetable products. Adherence to this standard supports robust food quality assurance programs and helps organizations demonstrate due diligence in regulatory compliance, making it a cornerstone reference in food chemistry laboratories worldwide.