Al-Sayyed et al. 2024 — Heavy metal, caffeine, and total soluble solids screening in energy drinks sold in the Jordanian market

Al-Sayyed and colleagues (University of Petra, Amman; American University of Madaba) screened the ten most commonly consumed energy-drink brands sold in the Jordanian market for five heavy metals (Pb, Cu, Ni, Cd, Fe), total soluble solids (TSS), and caffeine content. The metal panel was measured by flame atomic absorption spectrophotometry after concentrated-nitric-acid digestion; caffeine by HPLC-UV; TSS by Abbé refractometry. The authors frame the study as a precursor to setting a Jordanian standard for energy drinks, since no national specification existed in Jordan at the time of writing and imports were referred by default to Codex Alimentarius and European Commission contaminants frameworks. Lead was not detected in any sample (LOD reported as 0.5 mg kg⁻¹), but Ni was reported across all ten samples at concentrations the authors describe as exceeding the European Commission reference of 0.003 mg kg⁻¹ and overlapping with WHO drinking-water carcinogenic-threshold concern; Cu in one Polish-origin sample (sample 6, 2.8 mg kg⁻¹) exceeded the Gulf and WHO 2 mg kg⁻¹ reference; Fe in seven of ten samples exceeded WHO (0.3 mg kg⁻¹) and Bangladesh (0.3 mg kg⁻¹) soft-drink references.

Key numbers

All concentrations are reported in the source as mg kg⁻¹ (equivalent to ppm) on an as-sold beverage basis. Each value in Table 1 is the average of triplicate measurements ± standard deviation; the reported standard deviation is uniformly ±0.05 mg kg⁻¹ across every detected value in the table. The instrument was a RayLEiGH (China) atomic absorption spectrophotometer; the reported instrument limit of detection is 0.5 mg kg⁻¹ (Table 1 footnote 2, p. 22).

Heavy metal content of the ten energy drinks (Table 1, p. 22, mg kg⁻¹, n=3 per sample)

ND = not detected (< 0.5 mg kg⁻¹ per the Table 1 footnote). Per-analyte detected ranges across the panel: Cu 0.1–2.8 mg kg⁻¹ (n=10 detected), Ni 1.8–6.5 mg kg⁻¹ (n=10 detected), Cd 0.1 mg kg⁻¹ in four samples (n=4 detected, n=6 ND), Fe 0.2–4.1 mg kg⁻¹ (n=9 detected, n=1 ND). Pb was not detected in any of the ten samples.

Total soluble solids (Table 2, p. 23, g/100 mL, n=3 per sample)

Reported (label) sugar content (Table 3, p. 23, g/100 mL)

Caffeine content (Table 4, p. 23, mg/100 mL)

Analyzed caffeine across the ten samples ranged 24.0–32.0 mg/100 mL; reported (label) caffeine across the ten samples ranged 29–36.3 mg/100 mL. The authors note that the analyzed value is consistently a little lower than the label-reported value across most of the panel.

Regulatory comparators cited by the authors (p. 21–23)

• Codex Alimentarius (CXS 193-1995): permitted ranges for Cd and Pb in food of 0.05–2 ppm and 0.01–3 ppm respectively; maximum caffeine in EDs cited as 320 ppm; permitted Sn in canned beverages of 150 mg kg⁻¹.
• Gulf standard (GSO): 0.2 mg kg⁻¹ Pb and 2 mg kg⁻¹ Cu in EDs; caffeine ceiling 32 mg/100 mL.
• WHO: 0.05 mg kg⁻¹ Pb and 2.00 mg kg⁻¹ Cu in EDs; 70 ppb Ni potentially-carcinogenic threshold in drinking water; 3 ppb Cd ceiling in drinking water; 0.3 mg kg⁻¹ Fe in soft drinks.
• European Commission (Regulation 1881/2006): Ni > 0.003 mg kg⁻¹ flagged as exceedance basis; 200 mg kg⁻¹ Pb-and-Fe ceiling referenced for energy drinks (as cited in source text, p. 22).
• US EPA: 1 mg kg⁻¹ Fe in soft drinks.
• Tanzanian standard (TBS 838:2018): 0.1 mg kg⁻¹ Pb and 3 mg kg⁻¹ Cu; 20–32 mg caffeine/100 mL; 2–4.3 mg kg⁻¹ TSS.
• Bangladesh standard (per Ahmed 2019 in the source): 0.3 mg kg⁻¹ Fe in soft drinks; 1000 mg kg⁻¹ TSS in EDs.

The authors report that all ten samples exceed the WHO and Bangladesh TSS reference values of 500 and 1000 mg kg⁻¹ respectively (only sample 1 falls within the Tanzanian 2–4.3 mg kg⁻¹ band) and that seven of ten samples exceed the WHO/USEPA/Bangladesh Fe references. Pb is below detection across the panel and therefore in compliance with all cited Pb caps. Cu compliance: nine of ten samples are below the Gulf/WHO 2 mg kg⁻¹ Cu cap; sample 6 (Polish origin) at 2.8 mg kg⁻¹ exceeds.

Methods (brief)

Ten energy-drink samples, representing the ten most commonly consumed brands in the Jordanian market, were purchased from local retail; the prior consumption-survey reference is Elsahoury et al. 2021 (the source’s reference [4]). Each sample was analyzed in triplicate. Reported accuracy floor: ≥97%.

For heavy metal analysis, 25 mL of beverage was wet-digested with 25.0 mL concentrated HNO₃ (Fluka, Germany), evaporated under heat until brown fumes converted to white, reconstituted with 50.0 mL distilled water, concentrated under heat back to 25.0 mL, brought to 50.0 mL final volume, and vacuum-filtered. Absorbance was measured on a RayLEiGH (China) atomic absorption spectrophotometer; the source does not specify whether flame or graphite-furnace AAS was used, but the 0.5 mg kg⁻¹ instrument LOD reported in the Table 1 footnote (p. 22) is consistent with flame AAS rather than graphite-furnace operation. Standard curves were prepared for each of Pb, Cd, Fe, Cu, and Ni with R² = 0.99–1.00 (calibration references the source’s [10,11]). The source does not specify wavelengths used for each metal, certified-reference-material recovery, or analytical blank-correction details.

For caffeine, samples were measured by HPLC with AZURA UV detector on a Fortis C18 (100 Å, 5 µm, 4.6 × 250 mm) column; mobile phase water:methanol 60:40, detection at 273 nm, run time 10 min. Caffeine standards prepared from 10 mg caffeine in 100 mL mobile phase, diluted to 2, 5, 10, 25, 50, and 100 mg kg⁻¹. Standards and samples were sonicated (Branson/ultrasonic, Japan) for 10–15 min, filtered through 0.45 µm membrane, degassed, diluted with mobile phase, and re-sonicated before injection.

For TSS, an Abbé refractometer (Germany) calibrated with deionized water (refractive index 1.3330, 0° Brix at 20 °C) was used at the calibration temperature.

Sugar content was not measured analytically; it was extracted from the can label as a manufacturer-declared value.

The source does not report instrument-method limits of quantification, reference-material recoveries, or blank-correction details beyond the calibration-curve R² value. Metal speciation is not addressed: the analytes Pb, Cu, Ni, Cd, and Fe are reported as total elemental concentrations.

Evidence Fitness

This source contributes direct primary occurrence values for the finished-energy-drinks matrix sold in Jordan, with named country of origin per sample. The principal limitations bearing on pooling eligibility and synthesis weight are:

(i) Small sample size. Ten brands × three replicates yields n=30 measurements per analyte; the per-brand value is the triplicate mean. This is adequate for screening but limits inference to broader market populations.

(ii) Single-laboratory single-instrument-class screening method. Flame AAS with a 0.5 mg kg⁻¹ instrument LOD is appropriate for major-element screening (Cu, Fe, Ni at typical concentrations) but is operating near its detection floor for Pb (where all samples returned ND) and for Cd (where four samples returned 0.1 ± 0.05 mg kg⁻¹, a value formally below the LOD declared in the same table — see paper-internal contradictions in Verification notes). For analytes where measured values cluster near or below the LOD, the reported numerics should be treated as qualitative-positive signals rather than as defensible quantitative pool inputs. ICP-MS or graphite-furnace AAS would be required for defensible per-brand Cd or Pb quantification at the µg kg⁻¹ scale typical for these analytes in beverages.

(iii) No certified reference material or recovery data reported. Analytical quality control cannot be independently verified from the published article.

(iv) No metal speciation. Inorganic vs total Cr, MeHg vs total Hg, iAs vs tAs distinctions are not applicable to this analyte panel (Pb, Cu, Ni, Cd, Fe are routinely reported as total elemental). The chromium and mercury panels were not measured at all.

(v) No EDI / HQ / ILCR risk computation. Unlike the comparator Polish-market study (Czarnek et al. 2024, this wiki) and the Nigerian comparator (Babayo et al. 2026, this wiki), this source does not compute exposure or risk metrics. The contribution is restricted to raw occurrence values.

(vi) Paper-internal data-reporting inconsistencies. The abstract states Cd at “0.01” mg kg⁻¹ (single value, not a range) while Table 1 reports four samples at “0.1 ± 0.05” mg kg⁻¹ and six samples as ND; the in-body discussion of Cd (p. 22) repeats “0.01 ± 0.0.5” with a clear typo for the standard deviation. The Table 1 footnote declares the AAS instrument LOD as 0.5 mg kg⁻¹, but four Cd values are reported as 0.1 ± 0.05 mg kg⁻¹ (below the declared LOD) without explanation. The abstract states the analyzed caffeine range as 24.7–32 mg/100 mL while Table 4 actually shows 24.0–32.0 mg/100 mL (sample 8 reads 24.0, not 24.7). The TSS range in the abstract is given as “4.8 to 15.4 g/100 g” while Table 2 is headed “g/100 ml”. These are recorded faithfully against Table 1 / Table 2 / Table 4 (the most-internally-consistent representation) in this wiki page; the inconsistencies are noted in Verification notes for downstream synthesis.

Evidence tier set to C. The source is primary research, peer-reviewed (Methods and Objects of Chemical Analysis, Taras Shevchenko National University of Kyiv, indexed but small specialty journal), with the methodological caveats above. Tier-B would require larger n, ICP-MS or graphite-furnace AAS for trace analytes, CRM-anchored QC, and reconciled internal numerics. Tier-A would additionally require multi-laboratory or multi-region sampling. The source is well above tier-C-narrative-review threshold because it generates new measurements, but it does not clear the tier-B bar on QC and internal-consistency grounds.

Implications

• Certification: contributes direct primary occurrence values for the sports-energy-drinks HMTc category (Category 5 row 9). The Pb column is uniformly ND, which under the standards-methodology in Part 19 contributes left-censored data to the per-analyte pool for the energy-drinks row. The Ni column ranges 1.8–6.5 mg kg⁻¹ — these are mg kg⁻¹ values in finished beverage and are roughly two-to-three orders of magnitude higher than the µg L⁻¹-scale Ni values reported by Czarnek et al. 2024 for Polish-market energy drinks (range 2.04–6.57 µg L⁻¹), which is an order-of-magnitude inconsistency that requires investigation at synthesis time (see Verification notes on units/basis). The Cu range 0.1–2.8 mg kg⁻¹ likewise sits well above the Czarnek µg L⁻¹-scale Cu values (range 2.94–16.76 µg L⁻¹). The Fe range 0.2–4.1 mg kg⁻¹ sits above the Czarnek µg L⁻¹-scale Fe (121.86–308.31). The most likely explanation is a unit-reporting basis mismatch in this source rather than a true two-to-three-orders-of-magnitude population difference; flagged for synthesis review and unit verification.
• Courses: useful as a teaching reference for (1) the limitations of AAS screening at trace-element concentrations relative to ICP-MS; (2) the importance of analytical-quality-control reporting (CRM recoveries, LOQs distinct from LODs) for defensible occurrence data; (3) the regulatory landscape for beverages in a jurisdiction without a domestic contaminant standard, where the de facto framework is Codex + EU + WHO + Gulf + neighbor-country specifications applied piecewise.
• App: contributes per-product country-of-origin annotated values for the sports/energy-drinks product class in the Jordanian retail context. Per-brand identities are not disclosed in the source (samples are labelled by number, with only country of origin attached); no brand-firewall handling per CLAUDE.md Part 12 was required.
• Discovery: useful regulatory-comparator citations referenced for downstream ingestion include the Gulf GSO specification on energy drinks (referenced as the source’s [14]), the Tanzanian TBS 838:2018 energy-drink specification (referenced as the source’s [14] — note: this citation conflates GSO and TBS in the source’s reference list), Ahmed 2019 Bangladesh energy-drinks heavy-metal report (the source’s [23]), Kilic et al. 2018 (Turkish ICP-MS energy-drinks survey, the source’s [21]), Szymczycha-Madeja et al. 2013 (Polish ICP-OES energy drinks, the source’s [19]), and Gimba et al. 2014 (Nigerian energy-drinks physicochemical, the source’s [18]). The Czarnek et al. 2024 Polish-market study is the most directly comparable already in the wiki corpus; Babayo et al. 2026 Nigerian-market is the second.

Provenance notes

Open-access article distributed under CC BY 4.0 (license declaration on p. 20 of the PDF: “Copyright © 2024 Hiba Al-Sayyed. Open access article distributed under the Creative Commons Attribution License CC BY 4.0”). Received 7 December 2023; accepted 10 January 2024; published in Methods and Objects of Chemical Analysis 2024, Vol. 19, No. 1, pp. 20–24. DOI 10.17721/moca.2024.20-24. Corresponding author: Abdelmnim M. Altwaiq (aaltweiq@uop.edu.jo). Affiliations: Nutrition Department, Faculty of Pharmacy and Medical Sciences, University of Petra, Amman, Jordan (Al-Sayyed); Chemistry Department, University of Petra, P.O. Box 961343, 11196 Amman, Jordan (Altwaiq, Ali); Department of Basic Sciences, American University of Madaba (AUM), Madaba, Jordan (Khouri). Funding: Deanship of Scientific Research, University of Petra, project number 2/1/2022 (Acknowledgment and Funding Sources, p. 23). Conflict of Interest: “The authors declare no conflict of interest” (p. 24). Accessed via the Manual Fetch Discovery autopilot.

Wiki pages this source may touch

• lead
• copper
• nickel
• cadmium
• iron
• sports-energy-drinks
• codex-cxs-193-1995-tin-canned-foods
• eu-1881-2006-contaminants-superseded

Verification notes

Sample population. The source samples are the ten most commonly consumed energy-drink brands sold in the Jordanian retail market. Country of origin is named in Table 1 for each sample, but commercial brand identities are not disclosed; samples are labelled by number 1–10 only. No CLAUDE.md Part 12 brand-firewall handling was required because the source itself does not name commercial brands. The sample-population breakdown by country of origin is: Jordan (n=2, samples 1 and 4), Poland (n=2, samples 2 and 6), Austria (n=2, samples 3 and 7), Saudi Arabia (n=2, samples 5 and 10), USA (n=1, sample 8), Jamaica (n=1, sample 9).

Speciation handling per CLAUDE.md Part 14. This source measures total elemental Pb, Cu, Ni, Cd, and Fe by AAS without speciation. Pb, Cu, Ni, Cd, Fe are recorded as such in the metals: frontmatter field (no iAs/tAs, MeHg/tHg, or Cr-VI/Cr distinctions applicable to this panel). Mercury, arsenic, chromium, aluminum, tin, antimony, and uranium were not in the source’s analyte panel and are not recorded. Among the ten HMTc/HMI analytes, this source covers Pb and Cd only (two of ten); the remaining three metals it measures (Cu, Ni, Fe) sit outside the HMTc certification panel but are tracked in the HMI wiki vocabulary as copper, nickel, and iron.

Products frontmatter. The products: frontmatter lists sports-energy-drinks only. The source’s matrix is energy drinks, which the wiki taxonomy locates as HMTc Category 5 row 9 (“Sports/energy drinks”) per wiki/products/sports-energy-drinks.md. The energy drinks measured are commercially defined energy drinks (caffeine + taurine + vitamin matrix) and not as carbonated soft drinks; routing to soft-drinks-carbonated-beverages as a second product would over-route on a category basis. The conservative routing is to sports-energy-drinks only.

Ingredients frontmatter. The ingredients: field is empty. The energy drinks measured are finished beverages, not single-ingredient measurements. The source does not measure heavy-metal content at the ingredient level.

Matrices frontmatter. The matrices: field uses energy-drinks (established vocabulary, used in czarnek2024-heavy-metals-energy-drinks, babayo2026-heavy-metals-energy-drinks-nigeria, salaheldin2025-multimatrix-foods-egypt).

Jurisdictions frontmatter. JO (Jordan). The sample population is restricted to the Jordanian retail market. The samples themselves originate from six countries (Jordan, Poland, Austria, Saudi Arabia, USA, Jamaica) but the relevant jurisdiction for occurrence-evidence purposes is the country of sale (Jordan), per the convention used elsewhere in the wiki for market-survey sources.

Paper-internal inconsistencies flagged for synthesis-pass attention. The source has several internal data-reporting inconsistencies that the wiki records faithfully but cannot reconcile:

1. Cd value mismatch between abstract and Table 1. The abstract states the analyzed samples “contained … 0.01 … mg kg⁻¹ … Cd” (a single value, not a range, p. 20). Table 1 (p. 22) actually reports four samples (4, 5, 6, 10) at “0.1 ± 0.05 mg kg⁻¹” and six samples (1, 2, 3, 7, 8, 9) as ND. The Cd discussion paragraph on p. 22 repeats “0.01 ± 0.0.5” (the “0.0.5” is a clear typesetting typo). The wiki records the Table 1 values (0.1 ± 0.05 for the four samples) as the authoritative dataset.

2. Cd values below the declared LOD. The Table 1 footnote (p. 22) declares the AAS instrument LOD as “<0.5 ppm” (i.e., 0.5 mg kg⁻¹), but four Cd values are reported as 0.1 ± 0.05 mg kg⁻¹ — formally five-fold below the declared LOD. Either the actual analyte-specific LOD for Cd was lower than 0.5 mg kg⁻¹ on this instrument, or the Cd column values include below-LOD measurements that should not have been quantified. The source does not address the discrepancy. The wiki records the Cd values as reported in Table 1 but flags them in Evidence Fitness item (ii) and (vi) as not pool-eligible without external corroboration.

3. Caffeine range mismatch between abstract and Table 4. The abstract states the analyzed caffeine content “ranged between 24.7 to 32 mg/100 mL” (p. 20). Table 4 (p. 23) actually shows the minimum at 24.0 mg/100 mL (sample 8), not 24.7 (which is the value for sample 4). The wiki records the Table 4 values as authoritative.

4. TSS unit-basis label inconsistency. The abstract gives the TSS range as “4.8 to 15.4 g/100 g” (p. 20) while Table 2 (p. 23) is headed “g/100 ml”. The values themselves match between abstract and Table 2; only the unit label differs. The wiki records Table 2’s “g/100 mL” headings (the analytical instrument is a refractometer reading dissolved-solids per volume).

5. Reference-list conflation of GSO and TBS. The source’s reference [14] in the bibliography is listed as “Tanzania Bearue of Standards. TBS / AFDC 12 ( 6771 ) P3 / REV . TZS 838 : 2018 DRAFT TANZANIA STANDARD Energy Drink – Specification TANZANIA BUREAU OF STANDARDS. 2018, 12.” but the in-body text repeatedly cites [14] as both the Gulf GSO standard and the Tanzanian TBS standard. The source’s reference [15] is “GSO GSO. Recommendation of Handling Energy Drinks, 2009.” The Gulf and Tanzanian standards are conflated as a single reference in the source’s text. This wiki page records the two regulatory frameworks separately under the Regulatory comparators block but flags the source’s reference-list conflation for downstream regulation-page ingestion.

6. EC Regulation 1881/2006 Pb/Fe ceiling claim. The source (p. 22) states that “the EC allow the presence of 200 Pb and Fe in energy drinks” — the units appear to be missing and the regulation does not, in its standard published form, set a 200-unit ceiling on both Pb and Fe in energy drinks specifically. The wiki records the claim as the source’s text, with the unit ambiguity flagged for verification against eu-1881-2006-contaminants-superseded when that page is next maintained.

7. Order-of-magnitude inconsistency with Polish ICP-MS comparator. As noted in Implications, the Ni/Cu/Fe ranges reported here (mg kg⁻¹) are two to three orders of magnitude higher than the Ni/Cu/Fe ranges Czarnek et al. 2024 report by ICP-MS (µg L⁻¹) for Polish-market energy drinks. The two sources should report values on the same order of magnitude for the same product class. The most likely explanation is a unit-reporting basis confusion in the present source rather than a true population difference; this requires synthesis-time investigation before either source’s values are pooled into per-analyte percentile arithmetic for the energy-drinks row.

Wiki/HMTc firewall per CLAUDE.md Part 2. No HMTc threshold proposals, no consumer-audience translations, no risk advisories, and no synthesis claims of the form “this confirms the literature consensus that…” appear in this wiki page body. The compliance/exceedance observations against Codex, WHO, EU, Gulf, Tanzanian, and Bangladesh references are reported as the source itself reports them — as unit-comparison observations against the regulatory comparator values the source itself cited — and are not framed as HMTc threshold recommendations or as consumer-safety claims.

Brand firewall per CLAUDE.md Part 12. The source does not name commercial brands; samples are labelled 1–10 by number with only country of origin attached. No brand-firewall handling was required. The Methods (brief) section names scientific-method vendor identities (RayLEiGH atomic absorption spectrophotometer; Fluka HNO₃; Branson/ultrasonic; AZURA UV detector; Fortis C18 column; Abbé refractometer) per the scientific-method-vendor exception locked 2026-05-17.

Page history

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