2011_ST20_Taylor.pdf. SSPT Document not peer-reviewed by CORESTA

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1 An Ion Chromatographic Method for the Quantitative Determination of Hydrogen Cyanide in Cigarette Smoke using Pulsed Amperometric Detection Dr W Guthery and Dr M J Taylor Filtrona Technology Centre CORESTA Joint Study Group Meeting, Graz 9 13 October 2011

2 Introduction Hydrogen Cyanide has long been considered an important smoke compound due to its toxicity It is considered to be extremely toxic and short-term exposure can lead to headaches, dizziness, nausea and vomiting. Hydrogen Cyanide is thought to be a respiratory irritant and a contributor to smoking related chronic obstructive lung disease and cardiovascular disease The levels of hydrogen cyanide in smoke have been studied for many years and it has been on the list of compounds measured and reported in Canada and Brazil for over ten years More recently it has been included on the emissions list in Taiwan and Thailand and is also on the FDA draft list of toxicants and the second WHO list of nine compounds Hydrogen cyanide is one of seven compounds on the STMA harm reduction index used in China Typical yields of Hydrogen Cyanide in smoke can be up to 500 ppm but the short term WEL in the UK for continuous exposure is 10 ppm The accurate measurement of Hydrogen Cyanide levels in smoke are essential to monitor any reduction in Hydrogen Cyanide levels

3 Background Hydrogen Cyanide in whole smoke has in the past been measured by a range of techniques including, ion selective electrodes, potentiometric titrations, colourmetric titrations, gas chromatography and automated colourmetric systems using continuous flow analysers More recently continuous flow analysers seem to be the method of choice Whole smoke Hydrogen cyanide is trapped in impingers containing sodium hydroxide solution Cyanides are converted to cyanogen chloride by reaction with chloramine-t and then react with a pyridine/pyrazolone solution to form a coloured compound measured at 540 nm The continuous flow analysers can measure 50 samples per hour and has a reasonable linear range 0.08 to 4 µg /ml However, the method has some disadvantages mainly the use of toxic and very odourous pyridine as one of the required reagents and the lower limit of detection can cause problems for cigarettes with yields below 5 µg/cig

4 Continuous Flow Analyser AA3 2.0 ml/min Wash Solution 0.80 ml/min Sample 5 x Turn Coil 0.8 ml/min NaOH Solution 0.32 ml/min Air 0.23 ml/min Air 5 x Turn Coil 0.80 ml/min Phosphate buffer 10 x Turn Coil 20 x Turn Coil Waste Colourimeter 540 nm 0.10 ml/min Resample 0.23 ml/min Chloramine - T 0.80 ml/min Pyridine/Pyrazolone Solution Computer Waste

5 Ion Chromatography Method - Summary Ten cigarettes smoked on rotary smoking machine Whole smoke trapped in two impingers Aliquot of trap solution syringe filtered Analysed using IC with electrochemical detection

6 Dionex Ion Chromatograph

7 Electrochemical Cell

8 Principle of Operation The ED40 amperometry cell is a miniature flow-through cell with a titanium cell body (counter electrode) and a Ag/AgCl reference electrode. Installed directly after the ion chromatography column (suppressor not required) Mobile phase flows in a thin channel (0.2 ml) parallel to the surface of a flat disc electrode. A potentiostat diverts the cell current through the counter electrode Two modes of operation - DC Amperometry, a constant voltage is applied to the working electrode and the resulting current is the detector output - Integrated or Pulsed Amperometry, a repetitive series of potentials is applied to the cell. The integrated current (charge) from the oxidation is measured during a portion of a repeating potential vs. time waveform

9 Silver Working Electrodes Two types of working electrode solid and disposable Disposable electrodes have been reported to have shown comparable or better reproducibility and linearity compared with solid electrodes 1. Advantage of ease of use compared with solid electrodes which require regular cleaning. Disadvantage is the cost 1 Liang, L et al., J.Chromatogr. A, 2005, 1085, 37-41

10 Analytical Conditions Instrument: Columns: Injection: Column Temp: 30 C Eluent: Flow rate: Pressure: Detection: Working electrode: Collection rate: Run time: Dionex ion chromatography system with gradient pump and ED40 electrochemical cell IonPac AS7 (4 x 250mm) anion-exchange column with AG7 (4 x 50mm) guard column and Metal-Free Trap column (MFC-1) 25 ml full loop 0.1M NaOH/ 0.2M NaOAc 1 ml/min ~1800 psi Pulsed Amperometric Detection (PAD) Disposable Ag with Ag/AgCl reference electrode 1.00 Hz 20 mins

11 The Cyanide Optimised Waveform Silver is oxidised in the presence of the cyanide ions and its electrons are released A series of potentials is defined as a waveform A three-potential PAD waveform using E 1, E 2 and E 3 is applied over 1-sec. E 1 is the detection potential. The remaining potentials clean and restore the electrode for subsequent detection Cyanide Waveform Time (sec) Potential vs Ag/AgCl (V) Gain region Integration Ramp Off Off On On On (Start) On On Off (End) On On Off On Off Off On Off Off On

12 Whole Smoke Trapping Method Summary 10 cigs smoked on a Rotary smoking machine 8 mm Teflon insert positioned at the MS head All of the smoke phases trapped into two impingers containing 100 and 20 ml 0.1M NaOH/0.2M NaOAc 55 mm CF pad placed at the syringe head Extracts combined then shaken and filtered through 0.45 mm nylon filter

13 1 2: cyanide Example Chromatogram Silver electrodes are selective to other ions including sulphides, bromides, and thiosulphates. AS7 column demonstrated clear separation from matrix interferences AS7 contains a strong anion exchange (SAX) stationary phase (alkyl quaternary ammonium). It was necessary to use a high ionic strength mobile phase to enable elution with a reasonable turnaround time MAY 2011_ #17 MS 1R5F 1 ED_1 nc min

14 Calibration Data Quantitative analysis was performed using standards made up from certified reference material, CN - standard (1000ppm in OH - ), supplied by SPEX CertiPrep. Seven calibration standards ( mg/ml) prepared in 0.1M NaOH Linear response; Corr. Coeff. (%) cyanide External ED_1 Area [nc*min] Concentration mg/ml

15 Sample Stability Storage Time (at 22C) K3R4F Mean µg/cig SD < 12 hours > 24 hours

16 Reference Cigarette Values Sample Mean Yield µg/cig AA 3 IC K3R4F K1R5F CM SATF 2006 Collaborative Study Mean Yield for all Laboratories for K1R5F = 20.2 µg/cig

17 Comparison of Trapping Techniques K3R4F Cigarettes Sample Mean Yield µg/cig AA 3 IC Impingers Granular Traps Granular Trap Extended 44 mm CF Holder Silica Gel Beads 0.5 to 1.5 mm Diameter Approximately 8 g of beads per trap 3 Cigarettes per trap smoked using linear smoking machine

18 Comparison of Methods Parameter AA 3 IC Range mg/ml 0.08 to to 10.0 Samples/Hour 50 3 Reagents Pyridine Aqueous Overnight Operation No Yes Coefficient of Linearity

19 Conclusions A method for the determination of Hydrogen cyanide in whole smoke using IC/PAD is under development Yield values are comparable with current methods The IC method has lower limits of detection and does not use any organic reagents but is slower More work will be carried out on the long term stability of the method and its applicability to sidestream smoke

20 2011_ST20_Taylor.pdf