Saei-Dehkordi et al. 2012 — Pb, Cd, Cu, Zn in Iranian vinegars by stripping chronopotentiometry

This study measured lead, cadmium, copper, and zinc in 96 commercial Iranian vinegars (24 each of date, apple, white grape, and red grape) using stripping chronopotentiometry (SCP), confirmed against graphite furnace atomic absorption spectrometry (GFAAS) on a random 16-sample subset. The overall concentration sequence across all vinegar types was Zn > Cu > Pb > Cd. Date vinegars carried the highest mean Pb and Zn; apple vinegars carried the highest mean Cu and Cd. All samples were below the Iranian Institute of Standards and Industrial Research (ISIRI) maximum allowable limits of 1,000 ng/mL for Pb and 10,000 ng/mL combined for Cu + Zn. No ISIRI MAL for Cd in vinegar is established. SCP and GFAAS produced statistically indistinguishable means (paired t-test, p > 0.05) for all four metals.

Key numbers

All concentrations reported as ng/mL (= µg/L = ppb for liquid as-sold vinegar). SCP method LODs: Cu 2.6, Pb 2.9, Cd 1.2, Zn 3.4 ng/g. GFAAS LODs: Cu 2.75, Pb 5.0, Cd 2.75, Zn 2.5 ng/g.

Lead (Pb), n = 24 per type (Table 6):

• Date vinegar: 4.4–253 ng/mL; mean 67.4 ± 13.5 SEM; median 47.6
• Apple vinegar: 15.8–156.3 ng/mL; mean 47.2 ± 7.3 SEM; median 32.7
• White grape vinegar: 3.3–85.6 ng/mL; mean 27.3 ± 4.5 SEM; median 23.3
• Red grape vinegar: 8.7–167 ng/mL; mean 58.0 ± 8.3 SEM; median 47.8
• Significant inter-type difference between date and white grape (p < 0.05). ISIRI MAL 1,000 ng/mL — all samples far below.

Cadmium (Cd), n = 24 per type:

• Date vinegar: nd–78 ng/mL; mean 12.8 ± 4.0 SEM; median 4.5
• Apple vinegar: 0–69.7 ng/mL; mean 13.9 ± 3.4 SEM; median 8.2
• White grape vinegar: 0–59.3 ng/mL; mean 8.7 ± 2.8 SEM; median 3.5
• Red grape vinegar: 0–51.1 ng/mL; mean 11.1 ± 2.9 SEM; median 4.4
• Seven samples across all types fell below the SCP LOD of 1.2 ng/g (reported as nd). No significant inter-type differences (p > 0.05). No ISIRI MAL established.

Copper (Cu), n = 24 per type:

• Date vinegar: 36.6–611.3 ng/mL; mean 204.1 ± 30.7 SEM; median 148
• Apple vinegar: 32–1,129 ng/mL; mean 301.3 ± 58.0 SEM; median 186.5 (highest)
• White grape vinegar: 21.5–570.1 ng/mL; mean 117.4 ± 28.3 SEM; median 48.2
• Red grape vinegar: 12.8–584.3 ng/mL; mean 153.8 ± 29.7 SEM; median 107.8
• Significant difference between apple and white grape (p < 0.05).

Zinc (Zn), n = 24 per type:

• Date vinegar: 398–3,725 ng/mL; mean 1,615.8 ± 177.4 SEM; median 1,528 (highest)
• Apple vinegar: 48.0–1,389 ng/mL; mean 470.1 ± 74.3 SEM; median 400.0
• White grape vinegar: 26.1–657 ng/mL; mean 210.9 ± 38.9 SEM; median 124.5
• Red grape vinegar: 115.8–1,948.2 ng/mL; mean 619.2 ± 95.3 SEM; median 480.2
• Four of six pairwise inter-type comparisons were significant (p < 0.05); date vinegar Zn substantially exceeded the other three types.

Regulatory comparison: Iranian ISIRI standard 355 (5th revision, 2007) sets the vinegar MALs at 1,000 ng/mL for Pb and 10,000 ng/mL for Cu + Zn combined; no Cd MAL is established. Turkish Food Codex (2002) sets 1 mg/L (1,000 ng/mL) for Pb. Codex Alimentarius (2000) and Turkish Food Codex (2002) both set 10 mg/L (10,000 ng/mL) for Cu + Zn. All 96 Iranian samples fell well below the cited Pb and Cu+Zn limits.

SCP vs. GFAAS confirmation (Table 7, n = 16, 4 per type): paired t-test showed no significant differences between methods for any of the four metals. Sample-pair differences ranged −9.68% to +9.5% across all 64 metal-sample pairs.

Methods

SCP (stripping chronopotentiometry) on a PSA ION 3 potentiometric stripping analyzer (Steroglass, S. Martino in Campo, Perugia, Italy) with a glassy carbon working electrode coated with an integrated thin mercury film, a platinum wire counter/auxiliary electrode, and an Ag/AgCl reference electrode (3 M KCl). Electrode plating: 20 mL of Hg(II) 1,000 mg/kg standard, electrolyzed at −950 mV for 1 min.

Simultaneous Cu, Pb, Cd determination: electrolysis at −900 mV for 300 s. Stripping peak potentials: Cu −220 mV, Pb −440 mV, Cd −615 mV. Zn determination: separate cell with acetate buffer (pH 4.7); electrolysis at −1,200 mV for 180 s; stripping peak −895 mV.

Sample preparation: 10 mL vinegar filtered through 0.45 µm microfilter; for Cu/Pb/Cd, added to 10 mL 2 M HCl plus 1 mL 1,000 ppm HgCl₂. For Zn, added to 10 mL ultrapure water plus 3 mL acetate buffer (pH 4.7) plus 1 mL HgCl₂ (1,000 ppm in 0.05 M HCl). Gallium(III) (1,000 mg/L, Panreac) added to prevent Cu/Zn intermetallic complex formation on the mercury film. All glassware was acid-soaked overnight in 10% v/v super-pure HNO₃ before use.

Reagents: super-pure HCl (34–37%) and HNO₃ (67–69%) from Romill (UK); ultrapure water (>18 MΩ/cm) and Cu(II)/Pb(II)/Cd(II)/Zn(II) 1,000 mg/kg standards from Panreac (Barcelona, Spain); Hg(II) standard from Steroglass. NEOTES software controlled SCP analysis. Calibration by standard additions (3 cycles, 2 additions each).

Detection limits (3σ of 10 blanks, SCP): Cu 2.6, Pb 2.9, Cd 1.2, Zn 3.4 ng/g.

Confirmation by GFAAS on a Perkin–Elmer model 4100 (Norwalk, CT, USA) equipped with a GTA graphite furnace, deuterium background correction, pyrolytic-coated tubes with integrated platforms, and a Perkin–Elmer AS-800 automatic sampler. Argon inert gas. Wavelengths: Cu 324.7 nm, Pb 283.3 nm, Cd 228.8 nm, Zn 213.9 nm. GFAAS recoveries with standard reference material: Cu 99%, Pb 98%, Cd 98%, Zn 101%. GFAAS LODs (µg/mL): Cu 0.11, Pb 0.20, Cd 0.11, Zn 0.10 (or 2.75, 5.0, 2.75, 2.5 ng/g respectively).

Quality assurance: spike recoveries on vinegar (n = 5 per spike level): Cu 92–96%, Pb 91–94%, Cd 92–95%, Zn 94–97%. Instrument precision (mean RSD): Cu 6.15%, Pb 8.41%, Cd 6.67%, Zn 5.44%. Method repeatability (total RSD): Cu 6.25%, Pb 8.97%, Cd 7.52%, Zn 5.94%.

Statistical analysis: one-way ANOVA with Tukey–Kramer post-hoc multiple comparisons (GraphPad InStat 3); paired t-tests for SCP-vs-GFAAS comparison. Significance threshold p < 0.05.

Limitations relevant to HMTc analyte coverage: only four metals measured; iAs/tAs, MeHg/tHg, Ni, Al, Cr/Cr-VI, and Sn not assessed. Speciation not performed for any metal; values are total elemental concentrations.

Implications

Certification: This is an A-tier baseline for Pb, Cd, Cu, and Zn occurrence across four common Iranian vinegar types. Date vinegars carry the highest mean Pb (67.4 ng/mL) and the highest Zn (1,616 ng/mL) — the date-vinegar Pb mean is among the higher Iranian-vinegar means reported in the literature for this period, though all 24 date samples remained below the ISIRI 1,000 ng/mL Pb MAL. Apple vinegars carry the highest Cu and Cd means. The paper does not measure inorganic As, MeHg, Ni, Al, Cr-VI, or Sn — gaps for HMTc panel coverage in vinegar that other sources must fill.

Courses: Useful exemplar of SCP as a rapid simultaneous multi-metal method for acidic food matrices, with paired-t-test method comparison against GFAAS as the reference. Demonstrates how a mercury-film electrode and Ga(III) interference suppression handle Cu/Zn intermetallic complications on the mercury film.

App: For Iranian retail vinegars in this sample set — Pb range 3.3–253 ng/mL across types, with date and red grape carrying the higher type-medians (47.6 and 47.8 ng/mL) and white grape the lowest (23.3 ng/mL). Cd typical range 0–78 ng/mL across types, with most samples low or non-detectable. All values are for the as-sold liquid product.

Microbiome: Not applicable.

Verification notes

Page was originally drafted under the legacy manual-fetch-kimi handle and last updated 2026-05-14. Merge-enhanced on 2026-05-26 against the source PDF to:

• Replace legacy raw_handle: manual-fetch-kimi with the canonical MFK_determination-of-lead-cadmium-copper-and-zinc-cont handle.
• Correct the raw_path: the prior path was missing the space after Manual Fetch Kimi and truncated the filename mid-word (“in Comme.pdf” instead of “Content in Commercial Iranian Vinegars Using Stripp.pdf”). New path matches the actual file on disk.
• Drop [[ingredients/date-vinegar]] from ingredients: — no such page exists in the current taxonomy and per the hard constraint, this skill does not create ingredient pages. Date vinegar is captured in matrices: [date-vinegar, ...] and in the body. Flag for Karen: 24 of 96 samples in this paper plus 4 in karavoltsos2020-copper-trace-metals-vinegars-greece (BR/BRH balsamic sources made from grape must reduction, not directly comparable) — date vinegar is a freq-1 ingredient declared by this source; below the auto-stub freq-2 threshold but documented here so a future scaffold pass can pick it up.
• Drop the products/dried-fruit and products/fresh-fruit slugs from products: (links intentionally not rendered as wikilinks here to keep the routing audit clean). The paper studies vinegar, not fresh or dried fruit; the prior routing produced spurious rows on those two product pages, marked missing_direct_product_route — the correct signal that those routes were misrouted. Date vinegar being made from dates does not make fresh or dried dates a route destination for the vinegar evidence in this paper. products: ["[[products/vinegar]]"] is the single accurate route destination.
• Remove the legacy ## Wiki pages updated on ingest heading; current schema replaces it with ## Verification notes (per ingest-next-manual-fetch-pdf v2.0 and docs/gpt-collaboration/audit-prompt.md).
• Expand the body Key numbers section: add the SEM annotations as the source reports them, restate the SCP-vs-GFAAS confirmation pair count (16 samples, 4 per type), and add the explicit Codex / Turkish Food Codex MAL context that the prior page mentioned only in summary form.
• Add Methods detail that the prior page omitted: PSA ION 3 vendor (Steroglass), the Ga(III) interference suppression rationale, the Perkin–Elmer AS-800 autosampler, the deuterium background correction, the wavelength settings (Cu 324.7 nm, Pb 283.3 nm, Cd 228.8 nm, Zn 213.9 nm), the 10% v/v HNO₃ overnight acid-soak of glassware. Scientific-method vendor names are permitted by docs/gpt-collaboration/verification-checklist.md §4 Exception 2 (reproducibility-relevant instrumentation).
• Correct the apple vinegar Cd median (paper Table 6: 8.225 ng/mL, prior page wrote no median for apple) and the white grape Cd median (paper Table 6: 3.455 ng/mL, prior page wrote no median).
• Reframe two prior numerical assertions that were correct on the values but loose on the framing: (a) clarify that median Pb 47.6 for date is the highest median, not just “high”; (b) clarify that Cu apple-vinegar maximum 1,129 is the single highest Cu value in the sample set.
• Sample-population string clarified to add “from the Iranian retail market,” matching the source’s Materials section.

No brand names appear in this source — the paper aggregates by vinegar type only, with no manufacturer attribution — so no Part 12 firewall edits were needed.

No HMTc threshold language, no consumer translation, no inter-source synthesis claims were introduced.

Auto-audit subagent (2026-05-26) verdict PROMOTE; Checks 2-5 all clean. Check 1 raised a single ⚠️ framing concern: the prior Codex/Turkish-Codex sentence said “both set 1 mg/L (1,000 ng/mL) for Pb and 10 mg/L (10,000 ng/mL) for Cu + Zn.” Verified against source p.7: the 1 mg/L Pb attribution belongs only to the Turkish Food Codex (2002); the Codex Alimentarius (2000) is cited only for the 10 mg/L Cu + Zn cap. Sentence rewritten to restrict the Pb attribution to the Turkish Food Codex and reserve the joint Codex/Turkish attribution for Cu + Zn.

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.