Overview
ISO 15154:2003 - "Tobacco - Determination of the content of reducing carbohydrates - Continuous‑flow analysis method" defines a laboratory procedure to quantify reducing carbohydrates (reducing sugars) in both manufactured and unmanufactured tobacco using a continuous‑flow analyser. The method uses a 5% acetic acid extract reacted with p‑hydroxybenzoic acid hydrazide (PAHBAH) in alkaline medium at 85 °C to form a coloured osazone measured spectrophotometrically at 410 nm. ISO 15154:2003 is intended for quality control, research and regulatory testing where standardized, comparable measurements of reducing carbohydrates are required.
Key topics and requirements
- Scope: Applicable to manufactured and unmanufactured tobacco; focuses on reducing carbohydrates expressed as glucose equivalents.
- Sample preparation: Grind sample to pass a 1 mm sieve, determine moisture, extract ~250 mg tobacco with 25 ml of 5% acetic acid and shake 30 minutes.
- Analytical principle: Reaction with PAHBAH in alkaline medium produces a yellow product with absorbance maximum at 410 nm, measured in a continuous‑flow system.
- Reagents & calibration:
- PAHBAH reagent in dilute HCl with citric acid (purity > 97% recommended).
- 0.5 mol/l NaOH (with surfactant), CaCl2 solution, and 5% acetic acid wash.
- Glucose stock (~10 mg/ml) and working standards (e.g., 0.2–1.8 mg/ml) for calibration.
- Instrumentation: Continuous‑flow analyser components include sampler, proportioning pump, dialyser, heating bath (85 °C), delay coils and colorimeter with 410 nm filter. Annex B provides an example layout.
- Data handling: Use a calibration curve (peak height vs glucose concentration) and account for extract volume, sample mass and moisture to report results on a dry‑weight basis.
- Quality metrics: Repeatability and reproducibility were established from an international study (examples: Burley mean 0.6% dry weight r=0.4, R=0.6; Flue‑cured mean 20.0% r=1.0, R=4.7).
- Interferences: Method is sensitive to non‑sugar reducing substances; water extraction can hydrolyse sucrose in some tobaccos - interpret results accordingly.
Applications and users
- Who uses it: Analytical laboratories, tobacco manufacturers, contract testing labs, QC chemists, and research institutions studying tobacco chemistry.
- Practical uses:
- Routine quality control of leaf and processed tobacco.
- Comparative studies of sugar content across tobacco types (Burley, Oriental, flue‑cured).
- Regulatory submissions and inter‑laboratory comparisons requiring standardized methodology.
- Method development and validation when integrating continuous‑flow analysis in analytical labs.
Related standards (if applicable)
- ISO 15152 - Determination of total alkaloids as nicotine (continuous‑flow).
- ISO 15153 - Determination of reducing substances (continuous‑flow) - alternative method.
- ISO 15517 - Determination of nitrate content (continuous‑flow).
Keywords: ISO 15154:2003, reducing carbohydrates, reducing sugars, continuous‑flow analysis, PAHBAH, tobacco testing, glucose calibration, quality control.
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