Overview
ISO 6466:1983 specifies a molecular absorption spectrometric method for determining residues of dithiocarbamate pesticides in tobacco and tobacco products. The procedure measures the carbon disulfide (CS2) released by acid decomposition of dithiocarbamates, using a distillation/absorption step followed by UV spectrometric measurement. The standard describes required reagents, apparatus (including a distillation apparatus shown as an annex), calibration, result expression and reporting.
Key topics and technical requirements
- Scope: Applicable to dithiocarbamate-type pesticides commonly used on tobacco crops; results are reported as mg CS2 per kg of sample and can optionally be converted to specific dithiocarbamate equivalents.
- Reagents (analytical grade): examples given in the standard include concentrated sulfuric acid (96–98%), potassium hydroxide solution (~1 mol/L in 95% methanol), tin(II) chloride (SnCl2), concentrated hydrochloric acid and a sodium diethyldithiocarbamate standard solution (prepared fresh as CS2 equivalent).
- Apparatus: laboratory distillation assembly (shown in annex), nitrogen source (50 mL/min flow), condenser, two absorber flasks (acid and KOH), and a UV spectrometer with 10 mm quartz/silica cuvettes.
- Procedure highlights:
- Acid decomposition with Sn(II) and HCl under nitrogen, distillation of formed CS2 and absorption in KOH/methanol.
- UV absorbance measurements at 272 nm, 302 nm and 332 nm; corrected absorbance A_corr = A302 – (A272 + A332)/2.
- Calibration using aliquots of the sodium diethyldithiocarbamate standard (CS2 equivalents) to build a calibration curve.
- Quality control: repeatability requirement-difference between two determinations by the same analyst should not exceed 7.5% of their mean.
- Reporting: results expressed on an as-is basis or converted to dry-matter basis using moisture content (ISO 6488); test report must document method details, deviations and any operational incidents.
Applications and users
- Tobacco manufacturers and quality control laboratories monitoring pesticide residues in raw leaf and processed tobacco.
- Regulatory and food/smoke-safety testing laboratories verifying compliance with pesticide residue limits.
- Analytical chemistry labs performing method validation, inter-laboratory studies, or routine surveillance for dithiocarbamate residues.
- Research organizations studying pesticide behavior and residue mitigation in tobacco production.
Related standards
- ISO 1750 - common names for pesticides (reference for nomenclature).
- ISO 4874 - sampling of tobacco lots (sample collection procedures).
- ISO 6488 - determination of moisture content in tobacco (for dry-basis reporting).
Keywords: ISO 6466:1983, tobacco testing, dithiocarbamate residues, molecular absorption spectrometry, carbon disulfide, distillation apparatus, pesticide residue analysis.
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