《烟草及烟草制品 水分的测定 核磁法》技术报告

烟草及烟草制品水分的测定核磁法技术报告项目组2019年6月目录1项目背景及意义 项目背景及意义烟草和烟草制品中的水分是烟草及烟草制品加工过程中的一项重要质量指标。烟草行业内测定水分的方法主要有烘箱法、卡尔费休滴定法、气相色谱法、红外法、微波法、近红外光谱法等。卡尔费休滴定法作为经典的水分定量方法，能够准确测定样品真实的水分含量，但是大量样品的批量检测效率不高；气相色谱法适合对批量样品进行水分含量的测定（如烟气水分测定），但检测时间特别是前处理时间长，且其对操作人员、仪器设备以及检测试剂的要求比较高，费用比较昂贵。卡尔费休滴定法和气相色谱法两者皆不适用于卷烟工业企业加工过程的烟草及烟草制品水分检测要求。红外法、微波法虽然检测速度快，但检测结果易受物料的颜色、温度以及外界环境的影响，检测数据偏差大。烘箱法已经在行业内得到广泛的应用，相对于气相色谱法、卡尔费休法等而言，其结果中除水分以外还包括烟草及烟草制品的挥发性成分，而非所测样品真实的含水量，准确度较低，且易受其他干扰因素的影响；烘箱法检测时间较长，约需2.5h，检测结果滞后，对于加工生产过程失去了含水率检测原有的作用，不能满足烟草加工生产及时调整的要求。核磁共振作为一种实时、无损、无侵入的定量测量技术，能够从微观的角度反映农产品的含水率、水分赋存状态等多种指标参数，在食品科学研究领域引起国内外学者广泛关注，被应用到农产品的含水率、水分分布等性质的测定，还被应用于农产品成熟度、农产干燥水分扩散等方面的研究。核磁共振技术应用于各种原料的水分含量测定，该技术与其他方法比较，具有迅速、无破坏性和非入侵性等优点。目前，烟草行业尚未建立基于核磁共振技术的烟草及烟草制品水分的测定方法，因此，本项目拟利用核磁检测设备对烟草水分含量的测定，考察样品形态、样品制备方法、检测参数等对检测结果的影响及检测方法可靠性，建立利用核磁检测烟草及烟草制品水分的方法。通过此项研究的开展，建立一种方便、快速、科学的烟草及烟草在制品水分测定方法，为卷烟生产质量控制提供基础数据与理论支撑。2主要研究内容主要利用核磁共振分析检测设备研究烟草及烟草制品的水分含量，考察样品形态、样品制备方法、检测参数等对检测结果的影响及检测方法的可靠性，建立利用核磁检测烟草及烟草制品水分的方法。具体研究内容如下：核磁序列、参数的确定；样品量的确定：试管规格、装样量、样品装样密度的均匀性；扫描频次；检测次数；不同烟草样品（烟丝、叶片或烟梗等）对水分测定影响的分析研究；重复性和再现性；结果表示。3测试原理方法3.1测试原理核磁共振（NMR）是指具有固定磁矩的原子核（如1H）在恒定磁场中，受到相应的射频脉冲激发后，自旋核吸收和释放射频场能量的现象。氢质子所处的化学环境不同，其对应的弛豫时间也不同。低场核磁共振技术的基本原理是在不破坏样品的前提下，通过对处于恒定磁场中的样品施加射频脉冲，使得样品水分子中的质子发生共振，实现从低能态到高能态的跃迁；射频终止后，这些质子就以非辐射的方式返回到低能态，并产生相应的核磁共振信号。此过程即为驰豫过程，产生的核磁共振信号是一个自由震荡衰减的信号，即FID信号。水是最常见的含氢物质，低场核磁共振通过弛豫时间的变化来分析水分的活跃度及含量的确定。3.2测试方法核磁信号强度与水分子中的质子密度存在一定的比例关系，利用核磁共振技术测定已知含水的标样，得出相对应的核磁信号强度，建立核磁信号强度与含水量关系的标线，再测定待测样品的信号强度，可以通过标线得出待测样品的水分含量。4技术路线图1技术路线5仪器及材料试验设备及仪器：核磁共振成像分析仪NMI20-040V-I（苏州纽迈分析仪器股份有限公司，共振频率20.73MHz，磁体强度0.52±0.05T，线圈直径为40mm）；OhausAR2140电子天平（感量：0.0001g，奥豪斯仪器（上海）有限公司）；聚四氟乙烯核磁管（外径40mm，苏州纽迈分析仪器股份有限公司），KBF240恒温恒湿箱（德国Binder公司）。试验材料：钻石（荷花）烤烟型烟片、钻石（荷花）配方叶丝（河北中烟工业有限责任公司提供），烟梗、通用梗丝（河北中烟工业有限责任公司提供），膨胀烟丝（河南中烟工业有限责任公司提供），HBZY-05薄片（河北中烟工业有限责任公司提供）。测试环境温湿度：温度22±2℃；湿度60±5%。6结果分析6.1核磁管规格及装样高度的确定为了充分满足样品量对样品的代表性要求，确定实验所用核磁管外径为40mm（内径约38mm）。基于对仪器磁场均匀性等要求，样品的高度必须小于所设定的视野Fov（40mm）值。为保证样品检测结果的准确性，确定样品装样高度为≤38mm。6.2扫描次数的确定低场核磁共振检测仪的输出信号是数次扫描的累加结果，随着扫描次数（NS）的增加，信噪比随之增加，且信噪比的增加与扫描次数的平方根成正比。但重复扫描次数越多实验耗时越长，影响检测结果的时效性。为确定合适的扫描次数，实验考察了扫描次数对烟片、叶丝、烟梗、梗丝、膨胀烟丝中水分测试核磁信号量的影响。实验分别称取约7.0g的烟片、叶丝、烟梗、梗丝、膨胀烟丝样品，每个样品分别利用FID与CPMG序列测定，并设置不同的扫描次数（扫描次数设置一般为2的幂函数，因此选择了4、8、16、32、64等5组实验参数进行比较），每个条件下平行测试3次求其均值，测试结果如表1所示。表1不同扫描次数下五种烟草物料的核磁信号量测试结果类别扫描次数单次FID信号量单次CPMG信号量FID标偏CPMG标偏FID变异系数CPMG变异系数叶丝2577.72434.688.6610.681.50%2.46%4579.39439.399.9210.691.71%2.43%8581.12442.239.769.911.68%2.24%16584.37445.966.827.351.17%1.65%32584.64449.677.466.851.28%1.52%64585.79453.977.315.601.25%1.23%烟片2518.12398.605.399.561.04%2.40%4520.75399.174.339.780.83%2.45%8521.93400.272.9010.460.56%2.61%16525.96401.932.2011.580.42%2.88%32529.33402.961.0811.370.20%2.82%64532.63412.072.048.410.38%2.04%烟梗2587.44457.2111.0712.811.88%2.80%4591.11458.6010.9013.211.84%2.88%8593.38459.719.8613.351.66%2.90%16595.24461.898.7813.741.48%2.97%32597.17465.608.1913.321.37%2.86%64599.59470.707.7513.351.29%2.84%梗丝2499.14352.0112.605.882.52%1.67%4503.73353.6712.135.442.41%1.54%8507.47355.249.565.391.88%1.52%16509.58358.239.396.151.84%1.72%32512.76361.468.416.791.64%1.88%64516.46365.716.406.911.24%1.89%膨胀烟丝2512.67370.6717.119.213.34%2.48%4513.19372.0316.608.423.23%2.26%8513.66375.4114.689.152.86%2.44%16513.01378.0214.138.692.76%2.30%32512.66381.0612.657.672.47%2.01%64514.91384.2610.326.572.00%1.71%由表1可以看出，不同扫描次数平均单次信号量（累加信号量除以累加次数）差异不大，变异系数随扫描次数增加有所降低。变异系数均满足实验的要求（＜3%），综合考虑测试结果的准确性和测试时间，确定扫描次数为16次。6.3核磁序列及检测次数的确定6.3.1核磁序列的确定据文献调研，目前利用核磁共振分析物料水分含量的序列主要有两种：FID和CPMG序列，试验选取13个不同梯度水分（3%—41%）的叶丝为检测样品进行考察核磁序列对测试结果的影响，每个样品测试五次求其平均值及标准偏差，测试结果及数据处理结果分别见表2和表3。由表3可以看出，在检测范围内，FID和CPMG序列的检测结果均较好，两种序列的检测结果变异系数均小于2%，其中CPMG序列的变异系数均小于1%，优于FID序列的。CPMG脉冲序列以自旋回波脉冲序列为基础，在(90°)x脉冲之后连续施加一系列等间隔偶数个(180°)y脉冲，该序列是由Carr·Purcell·Meiboom·Gill在Hahn回波测量序列的基础上发展起来的，不仅消除了磁场不均匀性对T2的影响，并且可以在信号的回波峰点处采样到不受磁场均匀性影响的数据，通过理论与实际测试结果分析，确定烟草水分核磁共振法的测试序列为CPMG序列。表2核磁序列对样品信号量影响测试数据样品第一次第二次第三次第四次第五次FIDCPMGFIDCPMGFIDCPMGFIDCPMGFIDCPMG14667.444035.014732.714023.944707.904011.804649.654010.674676.284015.11217245.1912842.3917227.3012954.2417328.5112927.6917443.9412993.6717597.3413117.56318579.7914355.7118533.8314337.7118616.2614106.5918742.9414267.1118925.2114417.33416602.5812475.4816625.7512512.0316803.9612534.4216911.9812624.8917044.4712706.89523331.1418907.5823395.2418899.2823480.0118878.5223695.1018895.9923818.4619047.52628670.9424048.1428747.8324321.7628877.9224177.7028909.6424230.6628991.2524419.97732375.0027841.9132359.8527817.0632485.7628043.4032559.2928161.7232630.7828140.96836746.8832464.8936736.7232661.1336706.8832561.9936780.5732749.3436841.7232864.04939794.0136068.7039415.2635826.6939306.0535842.2939265.6735919.3639421.5435902.501042195.7038745.9541952.6438662.5341927.7538630.0941914.6238678.5442045.8638805.831144807.9241546.0544532.2341455.9844433.8141470.7744549.8141469.8544483.7841572.961247197.1844318.9246892.7344210.3046796.0144174.8446747.8044207.8746863.6944300.031349230.3246640.7548944.7546416.3148934.7446483.7248953.0646578.9048948.1946575.64表3测试结果均值、标准偏差及变异系数样品均值标准偏差变异系数FIDCPMGFIDCPMGFIDCPMG14686.794019.3133.2310.200.71%0.25%217368.4612967.11153.95100.770.89%0.78%318679.6114296.89157.77119.090.84%0.83%416797.7512570.74188.1793.951.12%0.75%523543.9918925.78205.9768.880.87%0.36%628839.5224239.64128.68141.290.45%0.58%732482.1328001.01116.72163.070.36%0.58%836762.5532660.2851.49155.960.14%0.48%939440.5035911.91208.9395.960.53%0.27%1042007.3138704.59117.1470.630.28%0.18%1144561.5141503.12144.9752.670.33%0.13%1246899.4844242.39175.8363.180.37%0.14%1349002.2146539.06127.6988.590.26%0.19%6.3.2检测次数的确定对表2中的CPMG序列核磁信号量数据依次进行二次、三次、四次及五次的均值、标准偏差及变异系数计算，处理结果见表4。由表4可以看出，在检测范围内，两次、三次、四次、五次的均值及变异系数没有明显的差异，因此确定核磁共振法检测水分的检测次数为两次。表4检测次数对检测结果信号量的影响样品两次三次四次五次均值标准偏差变异系数均值标准偏差变异系数均值标准偏差变异系数均值标准偏差变异系数14029.477.820.19%4023.5811.610.29%4020.356.010.15%4019.3110.200.25%212898.3179.100.61%12908.1158.440.45%12929.5084.010.65%12967.11100.770.78%314346.7112.720.09%14266.67138.930.97%14266.78132.170.93%14296.89119.090.83%412493.7625.840.21%12507.3129.750.24%12536.7189.380.71%12570.7493.950.75%518903.435.870.03%18895.1314.970.08%18895.3478.660.42%18925.7868.880.36%624184.95193.480.80%24182.53136.870.57%24194.56106.470.44%24239.64141.290.58%727829.4817.570.06%27900.79124.130.44%27966.02157.820.56%28001.01163.070.58%832563.01138.770.43%32562.6798.120.30%32609.34128.540.39%32660.28155.960.48%935947.69171.130.48%35912.56135.440.38%35914.2645.120.13%35911.9195.960.27%1038704.2458.980.15%38679.5259.770.15%38679.2877.070.20%38704.5970.630.18%1141501.0263.690.15%41490.9348.300.12%41485.6654.140.13%41503.1252.670.13%1244264.6176.810.17%44234.6975.070.17%44227.9853.680.12%44242.3963.180.14%1346528.53158.700.34%46513.59115.160.25%46529.9278.470.17%46539.0688.590.19%6.4样品量的确定利用低场核磁共振技术测定烟草内水分含量，需确定合适的样品装样量。装样量大小会影响样品的代表性，为确定合适的装样量，试验选取了平衡后均匀性较好的叶丝样品为考察对象，考察了2g～13g取样范围内叶丝核磁水分检测的信号量。每个质量平行测定两个，每个样品测定3次求其均值，测试结果见表5。由表5可以看出，随着样品量的增大，所测试样品的CPMG核磁信号量变异系数均有所下降，综合考虑样品的代表性及测试结果稳定性分析，确定试验的样品量为7g。表5叶丝样品量对核磁信号量的影响样品重量CPMG信号值归一化均值标偏变异系数2g1.998114256.557135.057042.64130.691.86%1.999413896.296950.233g2.999320988.326997.746929.4796.551.39%3.000620587.726861.204g4.002327809.316948.336939.8212.040.17%4.000927731.456931.305g5.003134913.876978.456941.8551.750.75%5.002734544.926905.256g6.010240568.236749.906796.8366.370.98%6.001641073.506843.767g7.010847282.886744.296778.2047.950.71%7.002147699.026812.108g8.011153885.016726.296728.392.970.04%8.001553854.026730.499g9.007659719.976629.956623.399.280.14%9.001359560.116616.8310g10.005464831.846479.686504.2734.770.53%10.003365310.126528.8611g11.004068237.666201.176226.0735.220.57%11.002168773.826250.9712g12.006470923.205907.125927.0428.170.48%12.003871386.095946.9613g13.009173111.595620.035634.9221.040.37%13.002973463.745649.806.5物料温度对测试结果的影响因烟草水分检测环境温湿度的要求，物料水分一般在室温，而核磁共振分析仪的检测腔体工作温度为（32±0.1）℃，且烟草物料的水分易受温度影响，因此利用间接法考察物料温度对测试结果的影响，即利用带有密封性能的定制聚四氟乙烯管装入烟丝样品，密封并放入核磁中进行检测，分别测量0、5min、10min、15min、20min、25min、30min、40min、50min、60min、70min的CPMG的信号值，通过物料在高于物料温度环境中逐渐升温间接考察被测物料温度变化对测量结果的影响，测试结果见表6。由表6可以看出，烟草物料在（32±0.1）℃检测环境中不断被加温，CPMG信号量没有明显的差异，检测结果变异系数较小，说明物料温度对检测结果没有明显的影响。表6物料温度对检测结果的影响时间/minCPMG信号值09096.2359191.85109228.43159251.89209247.72259213.53309160.99409099.56509071.49609062.96709126.93均值9159.23标准偏差71.25变异系数0.78%6.6装样密度对测试结果的影响核磁法检测烟草水分需要将一定样品的烟草物料装入测试样品管中，为了考察装样密度及其均匀性对检测结果的影响，试验选取了叶丝为测试样品，进行了两种方式的测试：一是同一质量的样品（约7g）不同的装填高度，即将测试样品装填入以聚四氟乙烯材料制作的压实器中，旋扭压实器形成不同的装样高度即装样密度不同，放入核磁分析设备中进行测试；二是不同质量的同一装填高度，分别称取约4.0g、5.0g、6.0g、7.0g的样品，装填高度为38mm，测试结果见表7。由表7可以看出，两种装样密度的测试结果变异系数均＜2%，装样密度对测试结果无明显的影响。表7装样密度对测试结果的影响同一质量不同装填高度同一高度不同装填质量装填高度单位质量信号量装填质量单位质量信号量40mm1948.644.0g2041.6337mm2032.875.0g2048.2134mm1992.416.0g2045.8331mm1969.077.0g2032.8727mm1983.248.0g2010.8124mm2055.669.0g2053.7620mm1994.22均值2004.582038.85标偏32.8115.42变异系数1.64%0.76%6.7标线的建立6.7.1标准工作曲线制作低场核磁共振法是通过傅里叶公式把样品的磁共振信号变换成波普（频率）的一种微观分析方法。T2衰减曲线的信号首点值与样品的总含水量成正比；横向驰豫时间T2的变化可以反映出各种状态水分的流动特性及水分变化，反演后得到的T2弛豫谱的每个波峰对应不同状态的水分，且波峰的信号幅度、峰面积均可以表征所对应状态水分含量及所占比例，如图2所示。即低场核磁共振T2弛豫谱的总峰面积或衰减曲线的首点信号值与样品中氢质子的数量成正比，用总峰面积或者信号首点值可以表示样品的水分含量；通过标样拟合建立的含水量和横向弛豫谱的峰面积或衰减曲线的信号首点值的标准曲线，再通过测量待测样品的核磁信号可以迅速计算待测烟草样品的含水量。图2低场核磁T2衰减曲线及T2弛豫谱（从0至5水含量逐渐增加）称取不同质量的烟草物料（叶丝、烟片、烟梗、梗丝、膨胀烟丝、薄片）样品，形成梯度如3g、4g、5g、6g、7g、8g，利用CPMG序列测量样品的横向弛豫谱，提取信号幅度值，每个样品平行测定5次，以平均值计；用烘箱法测定样品的含水量，以水分含量为纵坐标，核磁信号幅度值为横坐标，绘制关系曲线或计算线性回归方程，拟合信号幅度值和含水量得到一条标准曲线，如图3-图8所示。图3烟片CPMG信号幅度值与含水量的关系图图4叶丝CPMG信号幅度值与含水量的关系图图5烟梗CPMG信号幅度值与含水量的关系图图6梗丝CPMG信号幅度值与含水量的关系图图7膨胀烟丝CPMG信号幅度值与含水量的关系图图8薄片CPMG信号幅度值与含水量的关系图6.7.2结果的计算与表述将待测样品所得两次CPMG信号幅度均值代入标准工作曲线，计算得到样品含水量，进而可求得含水率。试样的水分质量百分含量按照式（1）计算得出：………(1)式中：W——试样的水分质量百分含量，%；m——待测样品测定含水量，g；M——试样质量，g。取两个平行样品的算术平均值为检测结果，结果精确至0.01%。6.7.3标线的适用性以叶丝标线为例，不同牌号（不同模块）的叶丝对所建立的标线进行试验验证，每个牌号（模块）检测五次并与烘箱法进行对比，验证结果见表8。由表8可以看出，所建立的标线对不同牌号不同模块的叶丝均适用。表8标线适用性验证结果牌号序号核磁法烘箱法差值BS-A模块111.02%10.84%0.18%210.63%10.80%-0.17%310.55%10.74%-0.19%410.64%10.71%-0.07%510.64%10.70%-0.07%BS-B模块112.03%11.97%0.06%212.23%11.90%0.33%312.10%11.97%0.13%412.38%12.03%0.35%512.34%12.05%0.29%JS-A模块111.30%11.50%-0.20%211.58%11.86%-0.28%311.60%11.61%-0.01%411.77%11.72%0.05%511.68%11.59%0.10%JS-B模块110.32%10.15%0.17%210.33%10.03%0.31%310.39%10.40%-0.02%410.35%10.11%0.24%510.35%10.05%0.30%YMGZ19.87%10.08%-0.21%210.31%10.20%0.11%310.19%10.17%0.01%410.03%9.99%0.04%59.97%9.96%0.02%6.8检测方法的准确性及测量范围评价6.8.1样品制备6.8.1.1准确性评价样品制备测试样品为烟片、叶丝、烟梗、梗丝、膨胀烟丝、薄片，其中烟梗剪切成2cm左右的，六种待测样品均放入符合GB16447-2004规定调节环境的恒温恒湿箱平衡48小时后待用。6.8.1.2测量范围价样品制备测试样品为叶丝，通过烘、喷洒水的方式形成不同梯度水分的样品，共13个，密封备用。6.8.2试验方法按所建立的核磁法进行待测样品的水分检测，每个形态的样品取15个样进行核磁法水分测定，每个样平行检测2次，以2次的核磁信号量均值计；并对15个样品进行烘箱法测定对比。样品量为（7.0±0.2）g，采用CPMG序列：SW=200KHz，SF=20MHz，O1=731769.68Hz，P1=11.52us，TD=40004，RFD=0.025ms，RG1=10.0db，DRG1=1，Tw=1000ms，P2=22.48us，TE=0.1ms，NECH=2000，PRG=3，NS=16。6.8.3测试结果6.8.3.1准确性评价结果以上述测试方法对六种测试样品进行核磁法和烘箱法检测，得到表9测试数据，并根据各自样品的标线进行水分计算。由表9可以看出，除烟梗个别外，烟片、叶丝、梗丝、膨胀烟丝、薄片几种烟草物料的低场核磁共振法与烘箱法测得的结果差异均小于1个百分点，标准差、变异系数均较小，说明低场核磁共振法的稳定性相对较好。在用烘箱法测得烟草物料水分过程中，由于加热易造成物质挥发而导致测定结果偏大，也可能由于物料内部少量结合水无法彻底烘出而导致结果偏小。而低场核磁共振法克服了这些缺陷，使得测定结果的稳定性相对较好。表9六种测试样品核磁共振法与烘箱法测定水分对比样品序号CPMG均值烘箱法水分核磁法水分差值烟片y=23137x-4909.7113961.6511.41%11.61%0.20%212979.9111.29%10.88%-0.41%315176.7811.92%12.38%0.46%413565.9111.48%11.25%-0.23%514144.3711.68%11.61%-0.07%614169.3211.24%11.70%0.46%713814.5410.75%11.22%0.46%815413.1212.43%12.37%-0.06%915169.1312.86%12.39%-0.47%1014821.3712.24%12.10%-0.14%1113968.8611.13%11.39%0.26%1214461.0811.84%11.65%-0.19%1314633.7712.30%12.09%-0.21%1414741.3911.75%12.15%0.41%1513978.1711.27%11.56%0.29%均值11.71%11.76%0.05%标准偏差0.57%0.47%叶丝y=15388x-353.61113200.4512.21%12.21%0.00%212843.0712.00%11.90%-0.10%312826.5411.97%11.90%-0.07%412470.6211.91%11.84%-0.07%512821.3711.93%11.88%-0.05%612663.1911.98%11.81%-0.17%712951.4311.97%12.05%0.08%812640.7411.98%11.89%-0.09%912686.3011.84%11.79%-0.06%1012611.5011.90%11.97%0.07%1112661.9811.94%11.68%-0.26%1212989.7211.74%11.87%0.13%1312612.2611.82%11.70%-0.11%1412515.4311.87%11.76%-0.11%1512557.5112.07%11.95%-0.12%均值11.94%11.88%-0.06%标准偏差0.11%0.13%烟梗y=14970x+308.6115791.3714.66%14.86%0.20%215574.8514.50%14.61%0.11%315954.4115.31%14.99%-0.32%415544.9613.95%14.53%0.59%515460.9214.24%14.52%0.28%614836.1414.00%13.92%-0.07%715375.9714.27%14.31%0.04%815262.1414.39%14.28%-0.11%915907.7714.21%14.73%0.52%1015715.8814.38%14.57%0.18%1115452.4814.33%14.22%-0.11%1215327.1514.22%14.24%0.02%1315488.5714.30%14.47%0.17%1415129.8314.14%14.03%-0.11%1514837.0414.35%13.92%-0.43%均值14.35%14.41%0.06%标准偏差0.32%0.32%梗丝y=13447x-1296.4110274.9012.35%12.18%-0.17%210284.3112.19%12.07%-0.12%310423.1012.22%12.15%-0.07%410063.4512.46%12.31%-0.15%510574.3312.48%12.15%-0.33%610259.1112.24%12.04%-0.20%710316.0012.28%12.19%-0.09%810319.5712.48%12.32%-0.16%910097.8112.31%12.19%-0.11%109991.7912.34%12.32%-0.02%1110024.9212.29%12.24%-0.05%1210574.5012.40%12.40%0.00%1310152.5312.41%12.22%-0.19%1410531.1412.50%12.43%-0.08%1510391.7112.57%12.53%-0.04%均值12.37%12.25%-0.12%标准偏差0.11%0.14%膨胀烟丝y=16618x-643.15112082.0811.20%11.19%0.00%212748.5911.08%11.35%0.27%312511.5611.20%11.47%0.27%412460.3710.98%11.44%0.46%512895.3311.33%11.59%0.25%612762.3010.74%11.30%0.56%712720.8411.42%11.46%0.03%812440.8711.07%11.17%0.10%912261.8910.94%11.10%0.16%1012439.2011.03%11.24%0.21%1112230.7311.02%11.29%0.27%1212184.3910.83%10.94%0.11%1312985.0811.03%11.53%0.50%1412663.7410.81%11.15%0.34%1512488.4811.05%11.32%0.27%均值11.05%11.30%0.25%标准偏差0.19%0.18%薄片y=11088x-218.1118061.6810.97%10.66%-0.30%27944.1110.92%10.67%-0.24%38293.5810.85%10.69%-0.16%48130.8810.67%10.62%-0.05%58237.1610.82%10.70%-0.12%67981.2710.62%10.61%-0.01%78198.3810.84%10.56%-0.28%88152.4510.50%10.53%0.03%97911.8510.71%10.47%-0.23%108255.7110.97%10.62%-0.35%118041.0510.64%10.55%-0.10%128377.0210.98%10.81%-0.17%138101.3510.95%10.65%-0.30%147931.5710.50%10.52%0.02%158051.4410.45%10.52%0.07%均值10.76%10.61%-0.15%标准偏差0.19%0.09%6.8.3.2测量范围评价结果按所建立的方法对13个待测样品进行核磁法和烘箱法检测，测试结果见表10。由表10可以看出，在3%~41%测量范围内核磁法与烘箱法的差值较小，均在1%以内。表10核磁法测量范围评价结果核磁法烘箱法差值4.25%3.37%-0.88%11.75%11.47%-0.28%12.09%12.22%0.13%13.28%13.55%0.28%17.27%17.25%-0.02%22.08%21.86%-0.22%25.41%25.00%-0.42%29.37%28.60%-0.77%32.39%32.59%0.20%34.83%34.54%-0.29%36.96%36.13%-0.83%39.65%39.42%-0.23%41.23%41.31%0.08%6.9检测方法的重复性和再现性6.9.1检测方法的重复性按照上述建立的方法，选取平衡后的烟丝样品，测试10个样品，在3天内以相同的测试条件进行水分分析，测得的数据求日内、日间标准偏差、平均值、变异系数等来表征，测试结果如表11所示。由于试验在同一试验室进行，精密度可以用标准偏差表示。从表11可知，在试验测试水平范围内，测试结果的精密度在72.00~279.99（换算成水分为0.04%-0.16%）之间，所测烟丝样品的日内重复性和日间重复性结果的变异系数均在2%以内，这表明所建立的测试方法具有较好的重复性,可以较为可靠地用以测定烟草样品的水分含量。表11重复性实验结果样品编号核磁测试信号量均值标准偏差变异系数/%第一天第二天第三天113966.6414288.4214295.5414183.53187.871.32%214251.4414422.314448.3614374.03106.970.74%314379.4614528.714575.4414494.53102.360.71%414507.714584.4814667.7814586.6580.060.55%514584.314687.0614723.0414664.8072.000.49%614677.9814768.314830.9214759.0776.890.52%714700.214812.8814875.7814796.2988.960.60%814755.681485414955.314854.9999.810.67%914810.6214919.2815004.2214911.3797.040.65%1014858.0414942.3215024.1814941.5183.070.56%均值14549.2114680.7714740.06标准偏差279.99219.49244.68变异系数1.92%1.50%1.66%平均值14656.68日间标准偏差97.68变异系数/%0.67%6.9.2检测方法的再现性为了还原生产过程检测，检测样品未经过平衡处理，以切后烟丝、叶丝增温增湿后烟丝、烘后烟丝、干头干尾丝等为测试样品，测试样品水分梯度涵盖了生产过程中的水分范围。由河北中烟、江西中烟、苏州纽迈、上海泰纽、北京农产品加工所五个实验室利用核磁共振分析仪采用所建立的方法分别对23个样品的水分进行测试，由于五家实验室仪器设备型号不一致（设备型号、核磁参数见表12），故采用同一标样样品按照所建立的核磁法进行标线建立及水分测定，每个样品重复测试5次，检测结果见表13。表12共同试验核磁设备参数情况实验室河北中烟江西中烟苏州纽迈上海泰纽北京农产品加工所设备型号NMI20-040V-IMESOMR23-040V-IMESOMR23-040H-IMesoMR23-060H-INM21-060H-I核磁参数SW=200KHz，SF=20MHz，O1=731574.3Hz，P1=12.00us，TD=40004，RFD=0.025ms，RG1=10.0db，DRG1=3，Tw=1000ms，P2=23.52us，TE=0.1ms，NECH=2000，PRG=3，NS=16SW=200KHz，SF=20MHz，O1=468898.23Hz，P1=8.00us，TD=40006，RFD=0.025ms，RG1=20.0db，DRG1=3，Tw=1000ms，P2=16.48us，TE=0.1ms，NECH=2000，PRG=3，NS=16SW=200KHz，SF=20MHz，O1=71898.18Hz，P1=8.00us，TD=40004，RFD=0.025ms，RG1=20.0db，DRG1=3，Tw=1000ms，P2=15.52us，TE=0.1ms，NECH=2000，PRG=3，NS=16SW=200KHz，SF=21MHz，O1=121796.88Hz，P1=11.52us，TD=40004，RFD=0.025ms，RG1=20.0db，DRG1=3，Tw=1000ms，P2=22.48us，TE=0.1ms，NECH=2000，PRG=3，NS=16SW=200KHz，SF=21MHz，O1=386368.51Hz，P1=14.52us，TD=40006，RFD=0.025ms，RG1=20.0db，DRG1=1，Tw=1000ms，P2=30us，TE=0.1ms，NECH=2000，PRG=3，NS=16标线y=25182x-961.7（R2=0.998）y=69144x-32295（R2=0.998）y=29655x-12848（R2=0.998）y=57120x-21013（R2=0.998）y=35996x-14607（R2=0.999）表13不同实验室的检测结果实验室序号核磁信号量均值标偏变异系数12345河北中烟126577.6926446.5826407.3526399.3726465.0926459.2171.590.27%225707.0925747.6225800.4025907.2325983.5225829.17114.350.44%325623.5025707.4825766.4925857.4525932.2325777.43121.520.47%425926.5725965.6926038.6026127.9326192.7926050.32110.600.42%525649.1425678.4125742.6725803.6425864.0425747.5888.320.34%628669.8928701.7528744.6628781.0328845.3628748.5468.590.24%728834.6428825.0228888.0728947.2828997.1128898.4273.640.25%828525.7628542.1128589.9328643.5828686.3128597.5467.610.24%927884.4827913.0627945.8728016.1928053.6127962.6470.690.25%1028056.8928075.0628118.1328183.0128234.2128133.4674.350.26%1112936.5113005.8313074.5313144.9113210.2313074.40108.560.83%1212605.7112651.4412725.4612784.2612828.5412719.0891.790.72%1312715.0612749.5512816.7812826.0612973.4312816.1899.360.78%1412804.8512838.3412905.3212974.5213031.4112910.8993.690.73%1512560.7512605.6712649.9712738.3212797.5012670.4496.690.76%1615609.4115638.4915713.8615788.6615891.0115728.28114.590.73%1715447.4915507.8615570.1515642.1015708.7415575.27103.900.67%1815482.7115501.5715589.1715655.3115737.9615593.35106.580.68%1915619.1015672.7715734.7615805.9115883.6915743.24105.000.67%2015461.8915521.3815569.7815641.5315723.3515583.59102.180.66%216690.006725.316758.126791.616838.186760.6457.480.85%226639.326650.776726.736731.966753.886700.5351.820.77%236349.716359.516419.546413.196444.126397.2140.720.64%江西中烟167134.2867269.6867456.2167649.9667908.1067483.64306.760.45%265021.9965272.5665386.1565458.7665598.9665347.69217.190.33%365229.5765430.7165537.9765616.0265857.8965534.43231.840.35%465980.0466037.1266195.0666377.4466457.9766209.52207.670.31%564128.4764276.6964511.7164679.0264768.1264472.80268.460.42%675060.2375237.3675330.4675478.3975524.5375326.19187.850.25%775435.7975647.5275767.5575858.0575934.2075728.62195.490.26%874412.2174550.0974740.4674799.8374855.2174671.56185.030.25%972849.2372998.5873208.3073363.4173508.0273185.51266.560.36%1072933.9573031.2073156.3773358.8173405.0273177.07203.600.28%1129494.0229621.3729841.1329985.2530227.6429833.88290.980.98%1229009.6529146.4029327.4929549.4129673.0329341.19274.560.94%1329168.5829348.3029501.8129668.0329809.5429499.25253.430.86%1429568.3629693.5929907.5430037.1230211.3729883.60258.390.86%1528985.7329130.7529309.9829406.2929654.2629297.40257.040.88%1636044.9336184.6636357.7536535.3636698.5236364.24262.330.72%1735195.1435296.5135487.7035621.5635812.6835482.72247.770.70%1835208.4335375.2135560.6735758.6135938.4035568.26291.560.82%1935862.4335967.9836168.2436318.7136488.8736161.24254.370.70%2034937.2535134.7335234.5635447.5535607.1335272.24262.410.74%2115720.4815808.9215808.9215968.7316112.9615884.00156.220.98%2215117.7615240.8015336.8415453.2715516.0015332.93160.311.05%2314595.6614664.2914701.2514797.6614872.4214726.25109.530.74%苏州纽迈130543.3630353.9830277.5230132.5330068.4530275.17187.900.62%232115.9331475.5730865.8830351.0429971.9930956.08859.912.78%329422.8029099.9628880.7929356.3729050.6329162.11224.240.77%429442.4629186.2528949.8728851.4328859.4329057.89253.990.87%528584.8628524.1128364.0128244.5728203.2228384.15167.700.59%633054.6832891.0032801.3332728.4632679.8032831.06148.230.45%733427.0333258.6933253.1833370.6533304.1533322.7474.930.22%833194.0933018.5832952.2232840.1232809.5632962.91154.320.47%932227.5732069.5731954.9631918.3031893.0532012.69137.810.43%1032483.6632315.4732329.8532273.4432345.3532349.5579.600.25%1114007.2713901.9113916.8113868.6713990.4513937.0259.380.43%1213445.0313441.3713432.7413406.2513440.7613433.2315.730.12%1313416.1313436.7013545.7813533.2913556.2413497.6365.920.49%1413688.6613601.9813615.8813584.8313666.4913631.5744.120.32%1513490.5513406.7913379.5913419.0413447.8313428.7642.360.32%1616514.7916411.8816380.5816377.9116501.0416437.2466.060.40%1716657.2216698.0416985.6317000.5216900.9016848.46161.160.96%1816633.7016559.4416504.1416498.9916510.4316541.3456.990.34%1916553.3616433.3316419.8916427.1216431.8216453.1056.290.34%2016428.3116774.7016771.8016954.8616866.7316759.28199.831.19%217536.127510.547493.957468.587524.287506.6926.480.35%227326.607291.077299.257262.817328.937301.7327.350.37%236964.066967.936982.617001.797068.026996.8842.440.61%上海泰纽160028.8560108.9360245.6060371.6960396.8060230.38160.670.27%259364.1759321.7859458.1359475.1959576.5559439.1699.920.17%358959.3259044.9859059.4459186.9159126.2859075.3886.140.15%459448.5859485.0759462.4559502.6259606.8959501.1262.650.11%558738.6458772.3358850.5858911.4758961.5158846.9093.000.16%667685.9767744.0667707.0567811.4867911.4467772.0091.380.13%768084.3768075.2868153.8268141.6568256.0268142.2372.310.11%867498.2267567.8267531.0167603.8367726.2867585.4388.110.13%966358.9566368.5666454.9166493.1666538.4166442.8078.050.12%1066559.1966597.6866643.0666734.2866732.5966653.3678.900.12%1131712.5331805.7231895.5831995.7532086.7931899.27148.410.47%1230708.0330828.5730841.7530935.7331006.2030864.06113.400.37%1330917.1430947.1031080.0731127.0131205.1431055.29121.450.39%1431150.2431192.3331218.0031358.3531481.4731280.08137.020.44%1530473.5930567.4630666.4330751.2630843.2930660.41146.010.48%1637602.2437655.4837757.6137884.3037985.6837777.06158.700.42%1736984.3437104.3337172.2437295.1237429.8337197.17171.950.46%1836942.3337001.5437104.5137214.3737318.0737116.16153.220.41%1937470.7337483.8737581.7037732.7337849.6337623.73164.050.44%2036971.6637039.8037120.4537252.6637370.6237151.04161.270.43%2116682.2416752.5716775.4216906.2516908.6416805.0399.610.59%2216374.9116412.4216435.5216494.0216586.2116460.6182.440.50%2315702.8715799.6615810.1115876.9515970.3915831.9999.210.63%北京农产品加工所136918.9036938.3436869.9336907.5536867.0636900.3631.110.08%235884.7935852.4235935.3335952.1135827.4335890.4253.070.15%335480.8035497.8435561.7735613.7435652.7635561.3873.530.21%435814.7635888.3935776.4135859.8735872.6435842.4145.970.13%535241.7935260.9135221.2535235.4335327.2435257.3241.600.12%641363.4641330.0241383.9041315.5341339.6741346.5227.220.07%741630.6141693.8141585.9541649.6441660.3341644.0739.780.10%841057.3341074.3941097.8941157.0341218.8641121.1066.400.16%940077.0340106.6240180.8940191.7340213.2740153.9158.800.15%1040222.5340246.7340275.3940358.3440365.2340293.6465.000.16%1118364.8818503.4418552.7818615.7518696.7818546.73124.760.67%1217892.7517968.4318079.4518037.5618173.7718030.39107.000.59%1317944.6118014.7218079.8718147.3018143.7918066.0686.920.48%1418060.3318048.2918132.9918126.6618214.8018116.6166.800.37%1517653.5017685.1417768.9617756.2317827.9117738.3569.480.39%1621781.0121893.4221919.9121946.7921971.9321902.6174.040.34%1721537.5821460.5221441.5221478.4921554.1321494.4549.060.23%1821538.1221471.7421426.0521535.8421611.7021516.6970.870.33%1921661.0821638.8321687.5621794.4921784.4621713.2871.750.33%2021281.5421327.7921345.3021428.8521500.5021376.7987.290.41%219512.509573.689637.379693.559682.189619.8676.290.79%229388.689394.539388.079450.429508.399426.0152.930.56%239036.089028.708968.639011.389081.269025.2140.820.45%注：其中样品1为序号1-5，样品2为序号6-10，样品3为11-15，样品4为序号16-20，样品5为序号21-23。对表13中的各样品的核磁信号量利用各自的标线进行水分计算，并与烘箱法进行对比，结果见表14。表14核磁法与烘箱法的比对结果序号核磁法烘箱法河北江西苏州上海北京120.77%20.73%20.89%20.43%20.55%20.54%220.38%20.25%21.18%20.20%20.12%20.31%320.16%20.10%20.13%19.92%19.80%20.14%420.28%20.21%20.04%19.99%19.88%19.98%520.21%19.94%19.81%19.92%19.74%19.80%621.98%22.25%22.02%22.22%22.22%22.26%721.87%22.14%22.06%22.12%22.14%21.93%821.97%22.20%22.17%22.26%22.22%22.12%921.62%21.90%21.72%21.98%21.84%21.72%1021.70%21.88%21.86%22.01%21.87%21.49%1113.06%12.83%12.90%13.23%13.15%12.87%1212.81%12.67%12.60%12.91%12.89%12.74%1312.92%12.76%12.69%13.02%12.96%12.77%1412.98%12.85%12.76%13.08%12.99%12.87%1512.84%12.73%12.66%12.93%12.84%12.78%1614.50%14.11%14.04%14.63%14.42%14.30%1714.47%13.98%14.28%14.54%14.31%14.27%1814.50%14.02%14.16%14.54%14.34%14.14%1914.58%14.14%14.11%14.66%14.41%14.34%2014.52%13.99%14.29%14.58%14.31%14.34%219.52%9.99%9.84%9.49%9.65%9.80%229.46%9.85%9.72%9.38%9.55%9.65%239.35%9.79%9.64%9.29%9.45%9.55%由表14可以看出，五家实验室23个样品的核磁法与烘箱法对比差异不超过1%，核磁法与烘箱法的均值差异不超过0.5%，结果接近，结果表明重现性良好。对表14中的数据按GB/T6379.2-2004/ISO5725-2:1994《测量方法与结果的准确度（正确度与精密度）第2部分：确定标准测量方法重复性与再现性的基本方法》评价该测试方法的重复性与再现性分析，分析结果见表15所示：密封度检测方法的重复性标准偏差、再现性标准偏差分别在0.07%～0.36%与0.16%～0.36%范围内，表明该方法稳定性较好，不同实验室间检测结果具有良好的一致性。表15重复性与再现性试验结果样品实验室编号总平均值重复性标准偏差再现性标准偏差河北江西苏州上海北京j120.36%20.25%20.41%20.09%20.02%20.23%0.36%0.36%221.83%22.07%21.97%22.12%22.06%22.01%0.17%0.19%312.92%12.77%12.72%13.03%12.97%12.88%0.11%0.16%414.51%14.05%14.18%14.59%14.36%14.34%0.07%0.23%59.45%9.88%9.73%9.39%9.55%9.60%0.10%0.22%6.10核磁法与其他烟草水分含量测试方法比对选取3种制丝生产线上不同工序的烟草及烟草制品样品，取样后同时进行了核磁法、烘箱法、气相色谱法和卡尔费休法测定烟草水分的对比实验，结果见表16。由表16可以看出核磁法、烘箱法的水分均较卡尔费休法测试数据要高。产生差别的原因是由于核磁法采用的是烘箱法水分定标，烘箱法、卡尔费休法两种测定烟草水分的方法原理不同所致，烘箱法为水和其它挥发性物质之和，卡尔费休法为较为纯粹的水分的含量。表16核磁法与烘箱法、气相色谱法、卡尔费休法的比对结果工序气相色谱卡尔费休烘箱法核磁法烘丝12.22%12.02%12.57%12.26%12.29%11.98%12.67%12.23%切丝19.