Overview
ISO 9526:1990 specifies a laboratory method for determining iron content in fruits, vegetables and derived products using flame atomic absorption spectrometry (AAS). The standard defines sample preparation, mineralization (dry or wet digestion), required reagents and apparatus, calibration procedures, measurement wavelength (248.3 nm) and quality checks for reliable quantitative analysis.
Key topics and technical requirements
- Scope: Determination of Fe in fruit, vegetable and derived products by flame AAS.
- Sample size & preparation: Typical test portion 5–10 g; samples must be homogenized (mechanical grinding) and frozen samples handled to retain thaw liquids.
- Mineralization:
- Dry ashing (muffle furnace ~525 °C) or wet digestion (concentrated HNO3 + H2SO4) described with procedural steps.
- Blank digestion required under identical conditions.
- Reagents: Analytical-grade acids (concentrated H2SO4, HNO3, diluted HCl preparations), and a Fe standard solution prepared from ferrous ammonium sulfate (solution where 1 mL = 1 mg Fe). Water of at least bidistilled purity.
- Apparatus: AAS instrument with air–acetylene burner, 248.3 nm measurement, platinum/quartz capsules (for dry ashing), borosilicate glassware, acid-washing of glassware, and analytical balance.
- Calibration & measurement:
- Calibration curves prepared from standard dilutions. Typical calibration points for final measurements: 0.4, 0.8, 1.2 and 1.6 mg/L (alternative preparation for higher-range dilutions described).
- Blank absorbance must be ≤ 0.002.
- If sample absorbance exceeds the highest calibration point, dilute and re-measure.
- Quality criteria: Repeatability-difference between two determinations by same analyst should not exceed 10% relative to the mean. Calculation and expression of results are provided (mg Fe/kg), including dilution and moisture corrections.
Practical applications and users
ISO 9526 is intended for:
- Food testing laboratories performing mineral nutrient or contaminant analyses in fruits, vegetables and processed products
- Quality control in food production and ingredient suppliers
- Regulatory and research laboratories assessing dietary iron content or compliance with nutritional labeling and safety requirements
Keywords: ISO 9526, iron content, flame atomic absorption spectrometry, AAS, fruits and vegetables analysis, mineralization, sample preparation, food analysis, analytical method.
Related standards
- ISO 5515:1979 (referenced procedural details for wet decomposition/mineralization)
- Other ISO methods for trace element analysis and sample digestion may be used in conjunction where applicable.