Trandafir et al. 2012 — Tin in canned foods by ICP-MS
This Romanian study developed and validated an ICP-MS method using microwave acid digestion for determining inorganic tin (Sn) in 13 canned food types, then applied it to survey total Sn concentrations in commercially available cans. The method targets dissolved inorganic tin from tinplate corrosion, not organotin compounds (TBT/TPT), which are chemically distinct and measured by separate speciation methods. Tin concentrations in all samples just after opening ranged from 0.09 ppm to 73.68 ppm (mg/kg), well below the EU regulatory maximum of 200 mg/kg (EC No. 1881/2006); however, the study also demonstrated that tin concentrations in the liquid fraction can exceed 200 mg/kg within 48 hours of opening an unlacquered can stored at 20°C, creating a practical food safety concern for consumers who store opened cans.
Key numbers
Analytical performance:
- LOD for tin standard solution: 0.01 ppb
- Calibration linearity: R2 >0.9992 (0–1,000 ppb range); R2 >0.9995 (0–15 ppm range)
- Accuracy at 0.5 ppm: 0.505 ppm found (101% recovery); at 5 ppm: 5.12 ppm found (102.4% recovery)
- Repeatability RSD: 2.42% at 0.5 ppm; 1.87% at 5 ppm; 2.2–5.8% for unspiked food samples
- Recovery from spiked foods (25 and 100 ppm spike levels): 91.3–105.2%
Survey results — tin concentrations in cans just after opening (ppm = mg/kg wet weight):
| Product | Syrup/liquid fraction (ppm) | Solid fraction (ppm) | pH | Years since manufacture |
|---|---|---|---|---|
| Pineapple (A) | 0.19±0.010 | 6.75±0.035 | 3.11 | 1.1 |
| Pineapple (B) | 1.28±0.013 | 3.34±0.022 | 4.22 | 1.6 |
| Pineapple (C) | 0.16±0.005 | 30.93±0.088 | 4.22 | 1.8 |
| Pineapple (D) | 3.19±0.026 | 17.91±0.022 | 3.86 | 1.5 |
| Mandarin oranges | 23.45±0.042 | 48.00±0.066 | 3.44 | 1.2 |
| Fruit cocktail | 2.70±0.014 | 8.47±0.089 | 3.57 | 0.4 |
| Small whole carrots | 0.14±0.006 | 0.38±0.014 | 4.93 | 0.5 |
| Mushrooms | 0.70±0.009 | 0.91±0.026 | 4.96 | 0.8 |
| Peeled tomato pieces (A) | 68.18±0.062 | 70.55±0.182 | 4.29 | 0.2 |
| Peeled tomato pieces (B) | 69.59±0.054 | 73.68±0.156 | 4.28 | 2.1 |
| Peas | 0.09±0.005 | 0.09±0.003 | 6.38 | 0.7 |
| Cut green beans | 0.11±0.010 | 0.48±0.012 | 5.45 | 1.4 |
| Whole kernel corn | 0.12±0.018 | 0.18±0.006 | 6.29 | 1.5 |
| Tuna flakes in water | 0.56±0.015 | 0.70±0.014 | 6.24 | 1.1 |
Post-opening corrosion (syrup stored in open cans at 20°C):
- After 48 hours: mandarin, fruit cocktail, and tomato syrup exceeded 200 ppm EU limit
- Acidic products (pH <4.5) showed the greatest tin dissolution kinetics
Regulatory context:
- EU (EC No. 1881/2006): 200 mg/kg for inorganic tin in canned foods; 100 mg/kg for canned beverages; 50 mg/kg for canned liquid foods for young children
- FAO/WHO Codex: 250 mg/kg maximum limit for tin in canned foods
- JECFA PTWI: 14 mg/kg body weight/week (120 mg/day for 60 kg person)
Methods (brief)
ICP-MS (Perkin-Elmer ELAN 9000) following microwave acid digestion (65% HNO3 + 30% H2O2, Milestone Labstation, 200°C max). Measures total dissolved inorganic tin. This method does not speciate between inorganic Sn(II) and Sn(IV), and explicitly does not measure organotin compounds (tributyltin and related species), which require separate speciation analytics by GC-ICP-MS or similar. Sample size: approximately 2.5 g food per vessel; 3 separate cans per product batch; 6 replicate analyses per can.
Implications
Certification: Confirms that canned vegetables (peas, beans, corn) in lacquered or neutral-pH cans have inorganic Sn well below regulatory limits even fresh after opening. The risk product profile is acidic fruits and tomatoes in unlacquered tinplate. For HMT&C purposes: canned food is an important Sn exposure route; the post-opening surge phenomenon (exceeding EU ML within 48 h) is a consumer-behavior issue separate from at-purchase compliance.
Courses: Useful illustration of the pH-dependent corrosion mechanism for Sn in canned foods, and the distinction between inorganic tin (food safety concern from tinplate) versus organotin compounds (environmental/toxicological concern from antifouling agents).
App: Products containing canned tomatoes, canned citrus, or canned acidic fruits carry higher expected Sn than canned neutral-pH vegetables. At-purchase concentrations are below EU ML but the post-opening risk window is a practical consideration.