Overview
This paper develops a bismuth-rich metal-organic framework (MOF(Bi)) electrochemical sensor for cadmium (Cd2+) detection, applied across the full tea supply chain from contaminated garden soil through raw tea leaves to brewed infusions. The sensor uses cysteine as a chelating agent and Nafion for membrane stability, achieving a LOD of 0.18 µg/L with a linear range of 0.2–25 µg/L. Beyond the sensor development itself, the paper provides useful literature-synthesized concentration context for Cd in tea matrices, drawing on multiple prior studies.
Key numbers
- Sensor LOD: 0.18 µg/L (S/N = 3); linear range: 0.2–25 µg/L
- Literature-derived Cd context (Introduction, cited literature):
- Soil background: 0.01–0.5 mg/kg (uncontaminated agricultural soil); global average ~0.1–0.3 mg/kg
- Tea leaves: “rarely exceed 1–8 mg/kg dry weight even when grown in moderately contaminated soils”
- Brewed tea infusions: “generally much lower, typically below 5 µg/L” with <10% transfer efficiency from dried leaves under typical brewing conditions
- Regulatory limits cited: EU 0.1 mg/kg (EC No 1881/2006); China 0.2 mg/kg (GB 2762-2017); Brazil 20 µg/L (ANVISA)
- Methods: MOF(Bi)/GCE electrochemical sensor; validated against ICP-MS results; applied to real contaminated garden soil, tea leaf, and infusion samples
Methods (brief)
MOF(Bi) synthesized via solvothermal method and deposited on glassy carbon electrode (GCE) with cysteine and Nafion modifiers. Square-wave anodic stripping voltammetry (SWASV). ICP-MS used as the reference method for cross-validation. Contaminated garden soil and commercial tea leaves spiked with Cd2+ and also measured at ambient concentrations; paper shows correlation between sensor readings and ICP-MS for the real matrix samples.
Implications
Certification: Provides regulatory context (EU, CN, Brazil) and usable background ranges for Cd in tea leaves and brewed infusions. The <5 µg/L infusion range and <10% transfer efficiency are relevant to exposure assessment for tea consumers. Courses: Tea supply chain case study from soil to cup. App: The literature-synthesized ranges (tea leaves 1–8 mg/kg DW under contamination; infusions typically <5 µg/L) are useful background for tea ingredient contamination profiles, though these are secondary literature summaries rather than primary occurrence data from a systematic survey. Microbiome: Not applicable.
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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. When DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.
| Commit | Date | Change | Description |
|---|---|---|---|
| a8052bb | 2026-08-09 | major | 6 sections added; narrative text revised |