Simultaneous determination of tar (nicotine-free dry particulate matter, NFDPM) and nicotine in cigarette smoke is a core analytical procedure for tobacco product evaluation, quality control, and regulatory compliance worldwide. By combining machine smoking under standardized ISO conditions with gas chromatographic analysis of a single Cambridge filter pad extract, laboratories can quantify total particulate matter (TPM), water, nicotine, and calculated tar in one efficient workflow. This article explains the technical principles, applicable standards, sample requirements, testing procedure, and typical applications of this method.
Technical Overview
Tar, formally defined as nicotine-free dry particulate matter (NFDPM), and nicotine are the two most widely reported smoke constituents for conventional cigarettes. Their simultaneous determination is made possible because both analytes originate from the same trapped particulate phase collected on a Cambridge filter pad during machine smoking. The workflow integrates four internationally standardized steps: conditioning and sampling of cigarettes, smoke generation under a strictly defined puffing regimen, gravimetric determination of total particulate matter (TPM), and chromatographic quantification of nicotine and water from a single pad extract.
The core analytical relationship is expressed as follows: NFDPM (tar) = TPM − Water − Nicotine. Because nicotine and water are both measured from one isopropanol extraction of the same Cambridge filter pad, a dual-detector gas chromatograph configured with a flame ionization detector (FID) for nicotine and a thermal conductivity detector (TCD) for water can deliver both values in a single chromatographic run. This simultaneous approach reduces sample handling, shortens turnaround time, improves data consistency, and minimizes the cigarette quantities required for a complete smoke chemistry characterization.
The method is governed by a coherent family of international and national standards, principally ISO 4387, ISO 10315, ISO 10362-1, ISO 3308, ISO 3402, and ISO 8243, together with their Chinese equivalents GB/T 19609, GB/T 23355, and GB/T 23356. Accredited third-party laboratories and tobacco research institutes routinely apply these methods for regulatory reporting, product development, and quality assurance.
Testing Samples
Simultaneous tar and nicotine determination is applicable to all conventional combusted cigarette formats. Sample types commonly submitted for analysis include:
Flue-Cured (Virginia) Cigarettes
Virginia-type blends produce a particulate phase typically rich in nicotine relative to total particulate matter, and the method reliably quantifies yields across the full tar range of commercial products. Conditioning and puffing parameters remain identical to those used for other blend styles.
Blended and Dark Tobacco Cigarettes
American-style blended and dark tobacco products, including air-cured and oriental components, are fully compatible with the method. Higher total particulate matter loads are accommodated by the high retention efficiency of the Cambridge filter pad, which exceeds 99.9 percent for particles in the mainstream smoke size range.
Menthol and Flavored Cigarettes
Capsule and flavored products can be tested under the same regimen. Because nicotine quantification uses gas chromatography with an internal standard, volatile flavor compounds do not interfere with the nicotine peak, and NFDPM is calculated correctly after subtracting both water and nicotine.
Slim, Super-Slim, and Non-Filter Formats
Reduced-diameter products are smoked with the standard puff volume and duration; only the butt length at which smoking terminates is adjusted according to the product geometry as prescribed by ISO 8243. Non-filter cigarettes are smoked to the marked butt length, and Cambridge filter pads may be protected with a pad holder to prevent physical contact with the burning cone.
Testing Items
A complete simultaneous determination campaign reports the following parameters for each cigarette sample, all expressed in milligrams per cigarette (mg/cig):
- Total particulate matter (TPM): the gravimetric mass gain of the Cambridge filter pad after trapping mainstream smoke particulates.
- Water in TPM: the water content of the pad extract determined gas chromatographically, required for the tar calculation.
- Nicotine in TPM: the nicotine content of the same pad extract determined gas chromatographically.
- Tar (NFDPM): the calculated nicotine-free, water-free dry particulate matter, obtained by subtraction.
- Puff count: the number of puffs taken to reach the specified butt length, a mandatory auxiliary parameter for interpreting yields.
- Optional related measurements: carbon monoxide in vapor phase (ISO 8454) is frequently combined with tar and nicotine to generate the classic "CO–tar–nicotine" yield triplet used on product labels.
Testing Methods
Sample Conditioning and Selection
Cigarettes are conditioned at 22 degrees Celsius and 60 percent relative humidity for at least 48 hours in accordance with ISO 3402. Statistical sampling follows ISO 8243: cigarettes are screened by weight and by ventilation pressure drop so that the smoked subset represents the population median, which markedly improves reproducibility. Insertion marks are applied to define the butt length at which smoking terminates.
Machine Smoking Under Standard Conditions
Smoking is performed on a linear or rotary analytical smoking machine operated to ISO 3308 and ISO 4387 specifications: puff volume of 35 mL, puff duration of 2 seconds, puffing interval of 60 seconds, and a square-wave puff profile. Filter cigarettes are smoked to a butt length of filter overwrap plus 3 mm, while non-filter cigarettes are smoked to the marked butt length. Each determination typically consumes 20 cigarettes per port set, with a minimum of replicates sufficient to satisfy the repeatability limits of the standards.
Particulate Collection and Extraction
Mainstream particulate phase is trapped on a pre-conditioned, pre-weighed 44 mm Cambridge filter pad. After smoking, the pad is re-weighed to obtain TPM, then extracted with a measured volume of isopropanol containing a suitable internal standard such as anethole or quinoline. A single extraction serves both the nicotine and the water determination, which is the essence of the simultaneous approach.
Gas Chromatographic Determination of Nicotine
Nicotine is quantified by gas chromatography with flame ionization detection in line with ISO 10315 and GB/T 23355. The extract is injected onto a polar or moderately polar capillary column; nicotine is resolved from other smoke constituents and quantified against the internal standard using multi-point calibration with certified reference materials.
Water Determination
Water in the pad extract is determined by gas chromatography with thermal conductivity detection in accordance with ISO 10362-1 and GB/T 23356. In modern dual-channel instruments, the FID and TCD signals from one injection provide nicotine and water in parallel, completing the simultaneous measurement and eliminating the need for a separate Karl Fischer titration.
Calculation and Reporting of Tar
Nicotine-free dry particulate matter is calculated for each replicate as TPM minus water minus nicotine, all normalized per cigarette smoked. Results are reported as the arithmetic mean of valid replicates together with puff count, and results outside the repeatability limits specified in ISO 4387 trigger re-testing. The Health Canada Intense regimen, with ventilation blocking, may be applied as a supplementary condition when a more conservative estimate of human exposure is required.
Quality Control and Validation
Method performance is monitored through pad blank controls, calibration verification standards, duplicate smoking runs, and certified reference cigarettes smoked alongside test samples. Typical repeatability limits for tar and nicotine, expressed as the difference between duplicate determinations, are specified within ISO 4387 and ISO 10315, and accredited laboratories demonstrate compliance through inter-laboratory comparisons and proficiency testing schemes.
Applications
- Regulatory compliance and labeling: verifying that declared tar and nicotine yields on cigarette packs meet statutory ceilings in target markets.
- Product design and blend engineering: comparing filter ventilation, paper permeability, and blend modifications against smoke yield targets during development.
- Manufacturing quality control: routine monitoring of production consistency against internal yield specifications batch by batch.
- Harm reduction and tobacco research: characterizing how design changes influence particulate yields in academic and institutional studies.
- Import and export verification: providing internationally recognized ISO-based smoke yield data to support customs, excise, and market surveillance requirements.
- Litigation and consumer protection support: supplying defensible analytical evidence on product chemistry when required by authorities.
FAQ
What is the difference between TPM and tar?
TPM is everything retained on the Cambridge filter pad, including water and nicotine. Tar (NFDPM) is TPM after subtracting water and nicotine, and it is therefore always lower than TPM. The simultaneous method exists precisely because tar cannot be reported without first measuring the other two components of the same pad extract.
Why must water be subtracted in the tar calculation?
Water contributes a large and variable fraction of the particulate mass and is not part of the condensed "tar" fraction as defined internationally. ISO 4387 therefore requires water determination and subtraction, which is why the dual-detector GC configuration that quantifies nicotine and water together is so efficient.
What puffing conditions are used?
The standard ISO regimen specified in ISO 3308 uses a 35 mL puff of 2 seconds duration taken every 60 seconds. Alternative intense regimens with 55 mL puffs or blocked ventilation may be added for supplementary reporting, but ISO yields remain the baseline for labeling in most jurisdictions.
Can menthol or capsule products be analyzed accurately?
Yes. Gas chromatographic separation with an internal standard ensures that menthol and other volatile flavorants do not co-elute with nicotine, and the gravimetric and volumetric steps are unaffected by flavoring. Capsules are activated according to the product instructions before conditioning.
How are the results reported?
All yields are reported in milligrams per cigarette, as the mean of at least duplicate smoking determinations, together with the average puff count. A full report also states the smoking standard applied, the number of cigarettes smoked, and the applicable conditioning parameters.
What precision can be expected?
Under properly validated conditions, duplicate determinations performed in the same laboratory typically agree within a few tenths of a milligram per cigarette, consistent with the repeatability limits published in ISO 4387 and ISO 10315. Participating in recognized inter-laboratory studies is the accepted way to demonstrate ongoing reproducibility.