Pehlivan et al. 2008 — Inorganic metals in Turkish edible vegetable oils by ICP-AES

This study determined nine metals (Cu, Fe, Mn, Co, Cr, Pb, Cd, Ni, Zn) in 17 edible vegetable oil samples from Turkish markets using ICP-AES after direct acid extraction with dilute nitric acid. The study demonstrates a simple sample preparation approach — 2–3 g oil + 1 mL 10% HNO3, shaken and incubated 2 h at 50°C, then centrifuged — that avoided the losses associated with wet digestion or dry ashing. Lead concentrations were below the 2001 vegetable-oil Pb limit cited by the authors; the paper does not provide vegetable-oil regulatory limits for most other measured metals. Virgin olive oil had the highest lead among oil types (0.0074 mg/kg), and almond oil showed the highest values for Cu, Cr, Ni, and Zn.

Note on evidence tier: downgraded from A to B. The study is older (2008), uses ICP-AES without speciation, and the variety of oil subtypes within a single category (e.g., 5 sunflower oil brands) means per-variety n=1. Total chromium is reported; this cannot be treated as Cr-VI.

Key numbers

All values in mg/kg wet weight. n=17 total; analysis in triplicate.

Selected maximum concentrations by oil type:

• Cu: almond oil 0.0850 mg/kg (highest); corn oil-c 0.0082 mg/kg (lowest)
• Fe: corn oil-c 0.0352 mg/kg (highest); corn oil-a 0.0039 mg/kg (lowest)
• Mn: soybean oil 0.0220 mg/kg (highest); riviera olive-a 0.0007 mg/kg (lowest)
• Co: sunflower oil-b and almond oil 0.0040 mg/kg (highest)
• Cr (total): almond oil 0.0010 mg/kg (highest); sunflower oil-d 0.0005 mg/kg (lowest) — note: total Cr, not Cr-VI
• Pb: virgin olive oil 0.0074 mg/kg (highest); many oils at or near 0 mg/kg
• Cd: sunflower oil-e 0.0045 mg/kg (highest); Table 4 reports corn oil-a 0.0002 mg/kg as lowest, despite discussion prose naming almond oil 0.0003 mg/kg
• Ni: almond oil 0.0254 mg/kg (highest); natural olive oil 0.0013 mg/kg (lowest)
• Zn: almond oil 0.2870 mg/kg (highest); sunflower oil-e 0.0184 mg/kg (lowest)

Key per-oil-type summary (mg/kg, mean ± SD from Tables 2–4): Olive oils (natural, riviera a/b/c, virgin, frying):

• Pb: 0.0000–0.0074 (virgin highest); Cd: 0.0009–0.0033; Ni: 0.0013–0.0041; Cu: 0.0097–0.0194; Fe: 0.0125–0.0295 Sunflower oils (a–e):
• Pb: 0.0000–0.0026; Cd: 0.0007–0.0045; Ni: 0.0015–0.0060 Corn oils (a–c):
• Pb: 0.0000; Cd: 0.0002–0.0013; Fe: 0.0039–0.0352 Soybean oil:
• Pb: 0.0000; Cd: 0.0013; Mn: 0.0220; Cu: 0.0273

EU regulatory limit (2001, as noted by authors): Pb 0.10 mg/kg for vegetable oils. All Pb values were below this limit. The authors state that no legislation existed for Cd, Cu, and Zn in vegetable oils at the time of publication; the paper does not identify vegetable-oil limits for the other measured metals.

Recovery: the authors state that average standard-addition recoveries were higher than 95% for all metal ions, although Table 1’s added/found central values are lower for some low-level spikes. Precision: RSD below 10% for Cu, 5% for Fe, 15% for Mn, 8% for Co, 10% for Cr, 20% for Pb, 5% for Cd, 16% for Ni, and 11% for Zn.

Methods (brief)

ICP-AES (Varian Vista). Acid extraction: 2–3 g oil + 1 mL 10% HNO3; shaken at 50 Hz for 60 s; incubated in shaking water bath at 50°C for 2 h; centrifuged at 2800 rpm for 10 min; aqueous layer diluted to 25 mL. No microwave digestion — direct extraction method. Wavelengths: Al 396.152, Cd 228.802, Cu 324.754, Fe 259.940, Mn 257.610, Co 238.892, Cr 257.716, Pb 220.353, Ni 231.604, Zn 213.857 nm. Working range 0.001–0.1 ppm for all metals. No speciation performed: total Pb, total Cd, total Cr. Data collected from Turkish food markets, specific city/date not stated. Study published in Grasas y Aceites (Spain), received 2/2/06, accepted 7/2/08.

Limitation: This is a 2008 study with no speciation. The method is dilute-acid extraction rather than total microwave digestion or dry ashing, so comparisons with digestion-based studies should preserve the sample-preparation difference. Per-oil n=1–5 across 17 total samples, with several oil subtypes represented by one sample.

Implications

• Certification (HMTc): Provides historical Turkish market baseline values for Pb and Cd in edible vegetable oils. Values are low in this 17-sample set (Pb maximum 0.0074 mg/kg in virgin olive oil, Cd maximum 0.0045 mg/kg in sunflower oil-e) and sit well below the 2001 Pb limit cited by the authors.

• Courses: Useful as an older reference illustrating the acid-extraction methodology for ICP-AES and the range of metals determinable in a single run. Also illustrates that total Cr data (not Cr-VI) does not enable toxicological assessment for the hexavalent form.

• App: Values are low and relatively dated (2008, Turkish market). Use only for broad order-of-magnitude framing; prefer more recent and larger-n studies for ingredient profiling.

Wiki pages this source may touch

• olive-oil
• sunflower-oil
• corn-oil
• soybean-oil
• vegetable-oils
• olive-oil
• cooking-oils-other
• lead
• cadmium
• nickel
• copper
• iron
• manganese
• cobalt
• chromium
• zinc
• eu-466-2001-contaminants-superseded

Verification notes

• 2026-05-17 Codex merge-enhance: identity checked against the manual-fetch PDF; corrected legacy raw_handle/truncated path, replaced the erroneous products/nuts-seeds-other route with products/olive-oil and products/cooking-oils-other, changed legacy headings to current source-page headings, and removed the non-taxonomy testing/icp-oes wikilink.
• Source reports total Cr by ICP-AES, not Cr-VI; the page therefore uses Cr and links [[metals/chromium]].
• olive-oil, sunflower-oil, corn-oil, soybean-oil, hazelnut-oil, almond-oil, and edible-oil are source-specific matrix descriptors used for routing/context; ingredient and product declarations use existing wiki slugs.
• 2026-05-18 Codex DOI cleanup: DOI, access URL, license, and raw SHA-256 verified against article metadata and the local manual-fetch PDF. The local PDF does not print the DOI, so DOI provenance is from the article metadata rather than the PDF body.
• 2026-05-18 Codex regulation cleanup: created eu-466-2001-contaminants-superseded as the historical regulation node for the EC 466/2001 citation; the paper’s Pb 0.10 mg/kg vegetable-oil benchmark is preserved as an author-cited comparison.
• 2026-05-18 Cross-vendor audit (Codex) tightened regulatory framing: the paper supports the EC 466/2001 Pb comparison and explicitly says no legislation existed for Cd, Cu, and Zn, but it does not support a broad all-metals “within regulatory limits” statement or a Ni no-limit claim.
• Source-internal note: the Discussion prose says the lowest Pb value was 0.012 mg/kg for sunflower oil (c), but Table 3 reports 0.0012 mg/kg for sunflower oil (c) and several 0.0000 entries; this page follows Table 3. The prose also says the lowest Cd value was 0.0003 mg/kg in almond oil, while Table 4 reports 0.0002 mg/kg in corn oil (a); this page follows Table 4.

Page history

The five most recent substantive edits to this page. The full version history lives in git; when DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.