Overview
ISO 14377:2002 (IDF 168:2002) specifies a validated method for the determination of tin content in sterilized canned evaporated milk using graphite furnace atomic absorption spectrometry (GF-AAS). The method is applicable to samples with tin contents of more than 5 mg/kg and provides a repeatable laboratory procedure for sample preparation, reagents, instrumental settings and calibration.
Key topics and technical requirements
- Scope: Measurement of tin (Sn) in canned evaporated milk (sterilized), applicable > 5 mg/kg; calibration linear up to about 100 mg/kg.
- Analytical principle: 100-fold dilution of a test portion, further diluted 1:1 with 15% ascorbic acid (matrix modifier); measurement by electrothermal (graphite furnace) AAS at 286.3 nm, typically using a tin hollow cathode or EDL lamp.
- Alternative technique: Platform atomization may be used; in that case NH4H2PO4 / Mg(NO3)2 solution is used as matrix modifier instead of ascorbic acid.
- Reagents & standards:
- Water complying with ISO 3696.
- Concentrated HCl (e.g., Suprapur).
- Tin stock (1 000 mg/L) and working standards (100 mg/L), with calibration standards prepared in diluted tin‑free evaporated milk to match sample matrix.
- Matrix modifier solution I: ascorbic acid 150 g/L; Matrix modifier II: specified NH4H2PO4/Mg(NO3)2 composition for platform use.
- Apparatus & settings:
- GF-AAS with autosampler, pyrolytic-coated graphite tubes (or platform), background correction, argon gas and capability to record peak areas.
- Example instrument guide: injection volume 20 µL, lamp energy ~8 W; specific furnace temperature program provided in the standard.
- Sampling & sample prep:
- Sampling is not covered; ISO 707 is recommended.
- Sample homogenization, heating (water bath 40–60 °C for 2 h), careful transfer to avoid contamination, and specified test-portion masses (typically 1.0 g into 100 mL for wall atomization; 0.5 g if platform is used).
- Quality control:
- Measure standards and samples in triplicate.
- Clean graphite tubes regularly (ascorbic acid can cause carbon build-up after 50–100 firings).
- Dilute samples exceeding the highest standard and re-measure (ensure ascorbic acid concentration is maintained).
Applications
- Regulatory and compliance testing of canned evaporated milk for tin contamination resulting from can corrosion or processing.
- Routine quality control in dairy processing laboratories to ensure product safety and labeling compliance.
- Method for research labs evaluating packaging-material interactions and tin leaching.
Who should use this standard
- Food testing laboratories, dairy industry QC teams, regulatory agencies, and analytical chemists involved in metal analysis of dairy products.
Related standards
- ISO 3696 - Water for analytical laboratory use (reagent water quality)
- ISO 707 - Sampling of milk and milk products
Keywords: ISO 14377:2002, canned evaporated milk, tin content, graphite furnace atomic absorption spectrometry, GF-AAS, matrix modifier, ascorbic acid, platform atomization, dairy quality control.