ISO 16632:2021

Overview

ISO 16632:2021 specifies a gas‑chromatographic (GC) method for the determination of water content in tobacco and tobacco products. Applicable to raw tobacco and tobacco taken from finished products (including cigars and smokeless reference products), the method reliably measures water mass fractions from about 2 % to 55 %. The procedure uses methanolic extraction with isopropanol as an internal standard and analysis by capillary GC with a thermal conductivity detector (TCD).

Key topics and technical requirements

• Principle: Methanolic extraction of water from a defined sample portion, followed by GC‑TCD analysis with an internal standard (isopropanol).
• Scope and range: Suitable for a wide variety of tobaccos and finished products; validated for ~2–55 % water content.
• Reagents:
  • Methanol (max. 1.0 mg/ml water) - hygroscopic and toxic (safety MSDS required).
  • Isopropanol (≥99 %) as internal standard (typical addition ~2.0 ml/L).
  • Water conforming to ISO 3696 (grade 2 or better).
• Apparatus:
  • GC with thermal conductivity detector, autosampler and data system.
  • Example column: PLOT fused silica with PoraPLOT U phase (25 m × 0.53 mm).
  • Standard lab glassware, shaker and filtration (0.45 µm) supplies.
• Sample preparation:
  • Typical test portion: (5.0 ± 0.25) g sample with 100.0 ml extraction solution.
  • Shake 3 h, set aside overnight, filter supernatant (0.45 µm) and refrigerate (< 4 °C) until analysis.
  • Cryogenic size reduction may be used to prevent moisture loss.
• GC conditions (recommended examples):
  • Injection 0.5 µl, splitless; injection temp ~250 °C.
  • Carrier gas helium (or nitrogen); TCD used for detection.
  • Method includes conditioning, calibration and blank tests.
• Quality/validation:
  • Calibration series of at least four standards covering expected water range.
  • Repeatability and reproducibility data from interlaboratory studies (2018) are included.
• Safety: Methanol handling warnings and recommended use of drying tubes for hygroscopic solvents.

Applications and users

ISO 16632:2021 is intended for:

• Quality control laboratories in the tobacco industry (manufacturers of cigarettes, cigars, smokeless products).
• Regulatory and compliance testing laboratories measuring moisture content.
• Research labs studying tobacco chemistry, product stability and storage effects.
• Third‑party testing and certification organizations that require standardized GC water determination.

Practical benefits include reproducible moisture data for process control, product specification, shelf‑life assessment and comparability across labs.

Related standards

• ISO 3696 - Water for analytical laboratory use (referenced for reagent water quality).
• Prepared by ISO/TC 126 (Tobacco and tobacco products); includes guidance on sampling, calibration, alternative columns and test reporting.

Keywords: ISO 16632:2021, water content determination, tobacco testing, gas chromatography (GC), methanolic extraction, thermal conductivity detector, isopropanol internal standard, tobacco laboratory method.