Alrajhi and Idriss 2020 - Trace metals in Riyadh edible oils
Alrajhi and Idriss measured trace metals in 54 edible vegetable oil samples bought from supermarkets around Riyadh. The study is routeable occurrence evidence for the broad cooking-oils row because Table I reports sample-level and summary concentrations for Cd, Cr, Cu, Fe, Mn, Ni, Zn, Al, Pb, total As, and Se in finished edible oils on an mg/kg basis.
Key numbers
Table I reports all concentrations in mg/kg. The table lists 54 individual samples and then gives source-reported summary statistics:
| Metal | Minimum | Maximum | Average | Standard deviation | Notes |
|---|---|---|---|---|---|
| Cd | 0.001 | 0.011 | 0.0006 | 0.002 | Detected in 14 of 54 samples; non-detects reported as LDL. |
| Cr | 0.002 | 1.898 | 0.072 | 0.307 | Discussion text gives an average of 0.026 mg/kg, conflicting with the summary table. |
| Cu | 0.001 | 0.081 | 0.011 | 0.013 | Source compares the range with a 0.002 mg/kg control sample. |
| Fe | 0.025 | 7.861 | 0.362 | 1.256 | Highest table value was sample 27 at 7.861 mg/kg. |
| Mn | 0.001 | 0.128 | 0.006 | 0.020 | Discussion text says detected in 43 of 54 samples. |
| Ni | 0.002 | 1.215 | 0.065 | 0.196 | Highest table value was sample 27 at 1.215 mg/kg. |
| Zn | 0.001 | 0.511 | 0.047 | 0.077 | Highest table value was sample 46 at 0.511 mg/kg. |
| Al | 0.012 | 0.425 | 0.060 | 0.073 | Source reports limited comparison data for Al in edible oils. |
| Pb | 0.004 | 0.087 | 0.011 | 0.018 | Discussion says Pb was detected in 16 of 37 samples; the study otherwise reports 54 samples. |
| Total As | 0.010 | 0.975 | 0.170 | 0.229 | ICP-OES total arsenic; not arsenic speciation. |
| Se | 0.050 | 0.890 | 0.172 | 0.215 | Strong source-reported correlation with total As. |
The authors conclude that the measured concentrations were below the FAO/WHO limits they cite for edible oils, including Cd 0.5 mg/kg, Pb 0.1 mg/kg, and As 0.5 mg/kg. The study also reports strong correlations for Cr-Fe (0.998), Cr-Mn (0.994), Cr-Ni (0.985), Fe-Mn (0.994), Fe-Ni (0.985), Mn-Ni (0.978), and As-Se (0.997).
Methods (brief)
Samples were collected from supermarkets around Riyadh and described as soybean, palm, and olive oils. For each oil, 2 g sample was digested with 10 mL 65% nitric acid and 2 mL 30% hydrogen peroxide, held in a fume cupboard for two days, heated at 80 degrees C until transparent, filtered, and diluted to 45 mL.
Metals were measured by ICP-AES/ICP-OES using a Genesis ICP optical emission spectrometer with axial plasma observation. The paper reports element-specific detection limits of 0.0001 mg/kg for Cd and Zn, 0.001 mg/kg for Cr, Cu, Ni, and Al, 0.002 mg/kg for Fe, 0.003 mg/kg for Mn, 0.004 mg/kg for Pb, and 0.01 mg/kg for As and Se. Recovery was described as nearly quantitative, around 95%, with relative standard deviations below 10%.
Implications
Certification: This source adds Saudi-market edible vegetable oil occurrence data for the broad cooking-oils row. Because sample rows are not labeled by oil type in the extracted table, the values should not be split into soybean-oil, palm-oil, or olive-oil benchmark pools without additional source support.
App: Useful for showing that edible oil evidence can include both essential trace elements and toxic metals in the same ICP-OES panel. Total arsenic should remain separate from inorganic arsenic.
Courses: Useful for teaching non-detect notation, table-vs-text contradictions, and jurisdiction-aware product evidence routing.
Wiki pages this source may touch
- cooking-oils-other
- vegetable-oils
- cadmium
- chromium
- copper
- iron
- manganese
- nickel
- zinc
- aluminum
- lead
- arsenic-total
- selenium
- icp-oes
Verification notes
This page was built from the full PDF, including Table I sample rows and summary statistics, the digestion and ICP-OES method description, the discussion sections for each metal, Table II correlations, and the conclusion. Two internal inconsistencies were retained rather than silently corrected: Table I reports an average Cr concentration of 0.072 mg/kg while the discussion text gives 0.026 mg/kg, and the Pb discussion says “16 of the 37 samples” although the study and Table I describe 54 samples. This page follows the Table I summary statistics for concentration values and flags both conflicts for audit.
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.
| Commit | Date | Description |
|---|---|---|
| c1aef38 | 2026-06-02 | audit-queue: hamid2021-bacterial-plant-biostimulants-review → audited-promote |