Screening for the Presence of Some Heavy Metals, Total Soluble Solids and Caffeine Contents in Some Energy Drinks Sold in Jordanian Market

Overview

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, nickel (Ni), cadmium (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). lead (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 tin (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 chromium (Cr), methylmercury (MeHg) vs total mercury (Hg), inorganic arsenic (iAs) vs total arsenic (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 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.

Related evidence

• Lead
• Copper
• Nickel
• Cadmium
• Iron
• Sports/Energy Drinks
• Codex CXS 193-1995 - Tin maximum levels for canned foods
• Commission Regulation (EC) No 1881/2006 setting maximum levels for certain contaminants in foodstuffs

Update history

The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git.