1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS ISO 16632:2013Tobacco and tobaccoproducts Determinationof water content Gas-chromatographic methodBS ISO 16632:2013 BRITISH STANDARDNational forewordThis British Standard is t
2、he UK implementation of ISO 16632:2013.The UK participation in its preparation was entrusted to TechnicalCommittee AW/40, Tobacco and tobacco products.A list of organizations represented on this committee can beobtained on request to its secretary.This publication does not purport to include all the
3、 necessaryprovisions of a contract. Users are responsible for its correctapplication. The British Standards Institution 2013. Published by BSI StandardsLimited 2013ISBN 978 0 580 76142 3ICS 65.160Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard wa
4、s published under the authority of theStandards Policy and Strategy Committee on 31 May 2013.Amendments issued since publicationDate Text affectedBS ISO 16632:2013 ISO 2013Tobacco and tobacco products Determination of water content Gas-chromatographic methodTabac et produits du tabac Dtermination de
5、 la teneur en eau Mthode par chromatographie en phase gazeuseINTERNATIONAL STANDARDISO16632Second edition2013-05-15Reference numberISO 16632:2013(E)BS ISO 16632:2013ISO 16632:2013(E)ii ISO 2013 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2013All rights reserved. Unless otherwise specified, n
6、o part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below or ISOs memb
7、er body in the country of the requester.ISO copyright officeCase postale 56 CH-1211 Geneva 20Tel. + 41 22 749 01 11Fax + 41 22 749 09 47E-mail copyrightiso.orgWeb www.iso.orgPublished in SwitzerlandBS ISO 16632:2013ISO 16632:2013(E) ISO 2013 All rights reserved iiiContents PageForeword ivIntroductio
8、n v1 Scope . 12 Normative references 13 Terms and definitions . 14 Principle 15 Reagents 16 Apparatus . 27 Sampling 38 Procedure. 38.1 Sample handling 38.2 Test portion 38.3 Setting up the apparatus. 38.4 Calibration of the gas chromatograph 49 Expression of results 510 Repeatability and reproducibi
9、lity 511 Alternative gas-chromatographic procedures and analysis precautions 711.1 General . 711.2 Alternative columns 712 Test report . 8Bibliography 9BS ISO 16632:2013ISO 16632:2013(E)ForewordISO (the International Organization for Standardization) is a worldwide federation of national standards b
10、odies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizati
11、ons, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.The procedures used to develop this document and those intended for its furthe
12、r maintenance are described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2, www.iso.org/directives.Att
13、ention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent rights identified during the development of the document will be in the Introducti
14、on and/or on the ISO list of patent declarations received, www.iso.org/patents.Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement.The committee responsible for this document is ISO/TC 126, Tobacco and tobacco products.This se
15、cond edition cancels and replaces the first edition (ISO 16632:2003), subclause 5.2 and the bibliography of which have been technically revised and a warning notice has been added.iv ISO 2013 All rights reservedBS ISO 16632:2013ISO 16632:2013(E)IntroductionDuring the development of this Internationa
16、l Standard, interlaboratory tests were carried out using two different principles for the determination of the water content of raw tobacco and tobacco taken from finished products. These were the gas-chromatographic procedure, and the Karl Fischer procedure.These studies show that no differences oc
17、cur between the results obtained by the two different methods. The Karl Fischer method is described in ISO 6488. ISO 2013 All rights reserved vBS ISO 16632:2013BS ISO 16632:2013Tobacco and tobacco products Determination of water content Gas-chromatographic methodWARNING The use of this standard can
18、involve hazardous materials, operations and equipment. This International Standard does not purport to address all the safety problems associated with its use. It is the responsibility of the user of this International Standard to establish appropriate safety and health practices and determine the a
19、pplicability of regulatory limitations prior to use.1 ScopeThis International Standard specifies a gas-chromatographic (GC) method for the determination of water content. It is applicable to raw tobacco as well as tobacco taken from finished products. The method is suitable for water contents rangin
20、g at least from a mass fraction of 2 % to 55 %.2 Normative referencesThe following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition o
21、f the referenced document (including any amendments) applies.ISO 3696, Water for analytical laboratory use Specification and test methodsISO 4874, Tobacco Sampling of batches of raw material General principlesISO 8243, Cigarettes SamplingISO 15592-1, Fine-cut tobacco and smoking articles made from i
22、t Methods of sampling, conditioning and analysis Part 1: Sampling3 Terms and definitionsFor the purposes of this document, the following terms and definitions apply.3.1high-moisture tobaccoany tobacco sample containing volatile matter over 20 % as determined by drying at between 100 C and 105 C4 Pri
23、ncipleThe water content of a sample of tobacco or a tobacco product is determined by methanolic extraction, followed by capillary GC analysis with thermal conductivity detection, using isopropanol as internal standard. The method is applicable to any type of tobacco sample provided that the particle
24、 size reduction is less than 4 mm.NOTE If a size reduction (grinding or cutting) is applied, it can create a decrease in the original water content. Cryogenic techniques may be used to prevent such moisture losses.5 ReagentsUse only reagents of recognized analytical grade.5.1 Carrier gas: helium.INT
25、ERNATIONAL STANDARD ISO 16632:2013(E) ISO 2013 All rights reserved 1BS ISO 16632:2013ISO 16632:2013(E)5.2 Methanol, with a maximum water content of 1,0 mg/ml.This is hygroscopic so it is recommended to cap the bottle with an automatic delivery pipette equipped with a drying tube.5.3 Internal standar
26、d: isopropanol, of at least 99 % purity.5.4 Water, complying with grade 2 of ISO 3696, or better.5.5 Extraction solvent: methanol (5.2) containing 2,0 ml of internal standard (5.3) per litre.5.6 Desiccant: silica gel, freshly activated.5.7 Calibration solutionsPrepare a series of at least four calib
27、ration solutions whose concentrations of added water cover the range expected to be found in the test portion by adding weighed amounts of water (5.4) to the solvent (5.5). One of these calibration solutions shall be the extraction solvent with no added water (solvent blank).To prevent water being a
28、bsorbed, the bulk solvent container shall be fitted with a water trap and all solutions shall be kept sealed. The solvent shall be stirred continuously to ensure the homogeneity of the water concentration in the solvent. The calibration solutions shall be made up using an extraction solvent from the
29、 same batch used in 8.1. Transfer them to injection vials and cap immediately.It is recommended that the calibration solutions be made up at least each week.NOTE For example, calibration solutions may be prepared as follows. Create a stock standard solution by accurately weighing (to the nearest 0,1
30、 mg) 25,000 g of water into a dry 500 ml volumetric flask. Dilute the water with extraction solvent (5.5) to the 500 ml mark. Pipette 0 ml, 5 ml, 10 ml, 20 ml, 30 ml, 40 ml, 50 ml and 60 ml of the stock standard water solution into each of eight dry 100 ml volumetric flasks. Dilute to volume with ex
31、traction solvent (5.5). The standard calibration solutions contain 0,0 mg, 2,5 mg, 5,0 mg, 10,0 mg, 15,0 mg, 20,0 mg, 25,0 mg, and 30,0 mg of water per millilitre of extraction solvent.6 ApparatusUsual laboratory apparatus and, in particular, the following items.All glassware used in the preparation
32、 and in the water determination shall be heated at (105 5) C for at least 1 h after visible water has evaporated. The glassware shall then be cooled and stored in a desiccator over desiccant (5.6) until used.6.1 Extraction vessels, dry serum bottles with crimp caps, or conical flasks with ground gla
33、ss lids, of capacity 125 ml.It is especially important to have excellent seals to prevent water absorption from air exposure.6.2 Shaker, preferably horizontal, but wrist-action acceptable.6.3 Disposable syringes, of capacity 10 ml, equipped with 25 mm diameter membrane filters with 0,45 m pore size,
34、 or equivalent.6.4 Volumetric flasks, of capacities 100 ml, 250 ml and 500 ml.6.5 Gas chromatograph, equipped with a thermal conductivity detector and recorder or integrator.2 ISO 2013 All rights reservedBS ISO 16632:2013ISO 16632:2013(E)6.6 Column, of internal diameter 0,53 mm, and of length 25 m.T
35、he column is preferably made of PLOT fused silica.NOTE PoraPLOT U1), 20 m film thickness, has been found to be satisfactory as the stationary phase (see also Clause 11).7 SamplingSample raw tobacco in accordance with ISO 4874 and cigarettes in accordance with ISO 8243. Sample fine-cut tobacco in acc
36、ordance with ISO 15592-1.Each time a sample is collected and stored, it should be placed in an airtight container having a size just sufficient to contain the sample.If samples are stored at 4 C, allow the closed container to equilibrate at room temperature before opening.8 Procedure8.1 Sample handl
37、ingCombine and mix enough retail units to constitute at least 100 g for each test subsample. If size reduction is employed, the sample should be cut sufficiently small to pass through a 4 mm screen. The sample may be frozen with liquid nitrogen before cutting if the absolute moisture level is of int
38、erest. Cut filler from cigarettes need not be reduced further in size.If high-moisture samples (see 3.1) cannot be analysed immediately, they should be stored below 4 C for no longer than 10 days.8.2 Test portionWeigh, to the nearest 0,1 mg, 5,0 g of the sample (8.1) into the dry extraction vessel (
39、6.1). A minimum of two test portions shall be prepared and analysed for each test sample.Pipette 100,0 ml of extraction solvent (5.5) into the extraction vessel and immediately seal the vessel. Place the extraction vessel in the shaker (6.2) and shake for 3 h. Remove the extraction vessel from the s
40、haker and set it aside overnight. The test portions should be gently swirled or mixed mechanically prior to removal of the analysis aliquot. Assemble a disposable syringe (6.3) with a 0,45 m filter (6.3). Carefully transfer about 5 ml of the supernatant liquid into the disposable filtration assembly
41、. Purge the filter of adsorbed water by disposing of a small volume of the extract. Filter the extract into a 2 ml GC injection vial and cap the vial. Store the filtered extract in a refrigerator below 4 C until GC analysis, making certain of tight seals.If the extract is not analysed on the same da
42、y, store in a refrigerator. After conditioning to room temperature, the extract should be analysed.8.3 Setting up the apparatusSet up the apparatus and operate the gas chromatograph (6.5), recorder or integrator and autosampler (if used) in accordance with the manufacturers instructions. Ensure that
43、 the peaks for water, internal standard and solvent are well resolved. Condition the system just prior to use by injecting two 0,5 l aliquots of the extraction solvent as a primer.Suitable operating conditions are as follows: carrier gas: helium;1) PoraPLOT U is an example of a suitable product comm
44、ercially available. This information is given for the convenience of users of this International Standard, and does not constitute an endorsement by ISO of this product. ISO 2013 All rights reserved 3BS ISO 16632:2013ISO 16632:2013(E) linear velocity: 30 cm/s at 50 C; injection temperature: 250 C; i
45、njection liner: appropriate liner packed with glass wool; injection mode: splitless (split valve closed during injection, to be opened after about 1 min); injection volume: 0,5 l; initial temperature: 60 C; initial hold time: 0 min; temperature ramp A: 5 C/min; final temperature A: 130 C; final hold
46、 time A: 0 min; temperature ramp B: 10 C/min; final temperature B: 170 C; final hold time B: 5 min; total analysis time: 23,00 min; detector: 250 C.Optimize the GC conditions for analyte separation and sensitivity. Once optimized, the same GC conditions shall be used for the analysis of all standard
47、s and samples, including the same injection volume of 0,5 l.8.4 Calibration of the gas chromatograph8.4.1 ProcedureInject an aliquot (0,5 l) of each of the calibration solutions (5.7) into the gas chromatograph. Record the peak areas (or heights) of the water and internal standard (5.3). Carry out t
48、he determination at least twice, with one series preferably interspersed with the test portion injections.Calculate the ratio of the water peak to the internal standard peak (Yi= AH2O/AIS) from the peak area (or height) data for each of the calibration solutions including the solvent blanks. Plot th
49、e graph of the concentrations of added water (X-axis) in accordance with the area ratios (Y-axis). Calculate a linear regression equation (y = a + bx) from these data, and use both the slope and the intercept of the linear regression equation.If the correlation coefficient R2is less than 0,99, the calibration should be repeated. If an individual calibration point differs by 10 % or more from the expected value (estimated by linear regression), it should be omitted. The signal (peak area or
