《煙草及煙草制品 水分的測定 核磁法》技術(shù)報(bào)告

煙草及煙草制品水分的測定核磁法技術(shù)報(bào)告項(xiàng)目組2019年6月目錄1項(xiàng)目背景及意義 項(xiàng)目背景及意義煙草和煙草制品中的水分是煙草及煙草制品加工過程中的一項(xiàng)重要質(zhì)量指標(biāo)。煙草行業(yè)內(nèi)測定水分的方法主要有烘箱法、卡爾費(fèi)休滴定法、氣相色譜法、紅外法、微波法、近紅外光譜法等?？栙M(fèi)休滴定法作為經(jīng)典的水分定量方法，能夠準(zhǔn)確測定樣品真實(shí)的水分含量，但是大量樣品的批量檢測效率不高；氣相色譜法適合對批量樣品進(jìn)行水分含量的測定（如煙氣水分測定），但檢測時(shí)間特別是前處理時(shí)間長，且其對操作人員、儀器設(shè)備以及檢測試劑的要求比較高，費(fèi)用比較昂貴?？栙M(fèi)休滴定法和氣相色譜法兩者皆不適用于卷煙工業(yè)企業(yè)加工過程的煙草及煙草制品水分檢測要求。紅外法、微波法雖然檢測速度快，但檢測結(jié)果易受物料的顏色、溫度以及外界環(huán)境的影響，檢測數(shù)據(jù)偏差大。烘箱法已經(jīng)在行業(yè)內(nèi)得到廣泛的應(yīng)用，相對于氣相色譜法、卡爾費(fèi)休法等而言，其結(jié)果中除水分以外還包括煙草及煙草制品的揮發(fā)性成分，而非所測樣品真實(shí)的含水量，準(zhǔn)確度較低，且易受其他干擾因素的影響；烘箱法檢測時(shí)間較長，約需2.5h，檢測結(jié)果滯后，對于加工生產(chǎn)過程失去了含水率檢測原有的作用，不能滿足煙草加工生產(chǎn)及時(shí)調(diào)整的要求。核磁共振作為一種實(shí)時(shí)、無損、無侵入的定量測量技術(shù)，能夠從微觀的角度反映農(nóng)產(chǎn)品的含水率、水分賦存狀態(tài)等多種指標(biāo)參數(shù)，在食品科學(xué)研究領(lǐng)域引起國內(nèi)外學(xué)者廣泛關(guān)注，被應(yīng)用到農(nóng)產(chǎn)品的含水率、水分分布等性質(zhì)的測定，還被應(yīng)用于農(nóng)產(chǎn)品成熟度、農(nóng)產(chǎn)干燥水分?jǐn)U散等方面的研究。核磁共振技術(shù)應(yīng)用于各種原料的水分含量測定，該技術(shù)與其他方法比較，具有迅速、無破壞性和非入侵性等優(yōu)點(diǎn)。目前，煙草行業(yè)尚未建立基于核磁共振技術(shù)的煙草及煙草制品水分的測定方法，因此，本項(xiàng)目擬利用核磁檢測設(shè)備對煙草水分含量的測定，考察樣品形態(tài)、樣品制備方法、檢測參數(shù)等對檢測結(jié)果的影響及檢測方法可靠性，建立利用核磁檢測煙草及煙草制品水分的方法。通過此項(xiàng)研究的開展，建立一種方便、快速、科學(xué)的煙草及煙草在制品水分測定方法，為卷煙生產(chǎn)質(zhì)量控制提供基礎(chǔ)數(shù)據(jù)與理論支撐。2主要研究內(nèi)容主要利用核磁共振分析檢測設(shè)備研究煙草及煙草制品的水分含量，考察樣品形態(tài)、樣品制備方法、檢測參數(shù)等對檢測結(jié)果的影響及檢測方法的可靠性，建立利用核磁檢測煙草及煙草制品水分的方法。具體研究內(nèi)容如下：核磁序列、參數(shù)的確定；樣品量的確定：試管規(guī)格、裝樣量、樣品裝樣密度的均勻性；掃描頻次；檢測次數(shù)；不同煙草樣品（煙絲、葉片或煙梗等）對水分測定影響的分析研究；重復(fù)性和再現(xiàn)性；結(jié)果表示。3測試原理方法3.1測試原理核磁共振（NMR）是指具有固定磁矩的原子核（如1H）在恒定磁場中，受到相應(yīng)的射頻脈沖激發(fā)后，自旋核吸收和釋放射頻場能量的現(xiàn)象。氫質(zhì)子所處的化學(xué)環(huán)境不同，其對應(yīng)的弛豫時(shí)間也不同。低場核磁共振技術(shù)的基本原理是在不破壞樣品的前提下，通過對處于恒定磁場中的樣品施加射頻脈沖，使得樣品水分子中的質(zhì)子發(fā)生共振，實(shí)現(xiàn)從低能態(tài)到高能態(tài)的躍遷；射頻終止后，這些質(zhì)子就以非輻射的方式返回到低能態(tài)，并產(chǎn)生相應(yīng)的核磁共振信號。此過程即為馳豫過程，產(chǎn)生的核磁共振信號是一個(gè)自由震蕩衰減的信號，即FID信號。水是最常見的含氫物質(zhì)，低場核磁共振通過弛豫時(shí)間的變化來分析水分的活躍度及含量的確定。3.2測試方法核磁信號強(qiáng)度與水分子中的質(zhì)子密度存在一定的比例關(guān)系，利用核磁共振技術(shù)測定已知含水的標(biāo)樣，得出相對應(yīng)的核磁信號強(qiáng)度，建立核磁信號強(qiáng)度與含水量關(guān)系的標(biāo)線，再測定待測樣品的信號強(qiáng)度，可以通過標(biāo)線得出待測樣品的水分含量。4技術(shù)路線圖1技術(shù)路線5儀器及材料試驗(yàn)設(shè)備及儀器：核磁共振成像分析儀NMI20-040V-I（蘇州紐邁分析儀器股份有限公司，共振頻率20.73MHz，磁體強(qiáng)度0.52±0.05T，線圈直徑為40mm）；OhausAR2140電子天平（感量：0.0001g，奧豪斯儀器（上海）有限公司）；聚四氟乙烯核磁管（外徑40mm，蘇州紐邁分析儀器股份有限公司），KBF240恒溫恒濕箱（德國Binder公司）。試驗(yàn)材料：鉆石（荷花）烤煙型煙片、鉆石（荷花）配方葉絲（河北中煙工業(yè)有限責(zé)任公司提供），煙梗、通用梗絲（河北中煙工業(yè)有限責(zé)任公司提供），膨脹煙絲（河南中煙工業(yè)有限責(zé)任公司提供），HBZY-05薄片（河北中煙工業(yè)有限責(zé)任公司提供）。測試環(huán)境溫濕度：溫度22±2℃；濕度60±5%。6結(jié)果分析6.1核磁管規(guī)格及裝樣高度的確定為了充分滿足樣品量對樣品的代表性要求，確定實(shí)驗(yàn)所用核磁管外徑為40mm（內(nèi)徑約38mm）?；趯x器磁場均勻性等要求，樣品的高度必須小于所設(shè)定的視野Fov（40mm）值。為保證樣品檢測結(jié)果的準(zhǔn)確性，確定樣品裝樣高度為≤38mm。6.2掃描次數(shù)的確定低場核磁共振檢測儀的輸出信號是數(shù)次掃描的累加結(jié)果，隨著掃描次數(shù)（NS）的增加，信噪比隨之增加，且信噪比的增加與掃描次數(shù)的平方根成正比。但重復(fù)掃描次數(shù)越多實(shí)驗(yàn)耗時(shí)越長，影響檢測結(jié)果的時(shí)效性。為確定合適的掃描次數(shù)，實(shí)驗(yàn)考察了掃描次數(shù)對煙片、葉絲、煙梗、梗絲、膨脹煙絲中水分測試核磁信號量的影響。實(shí)驗(yàn)分別稱取約7.0g的煙片、葉絲、煙梗、梗絲、膨脹煙絲樣品，每個(gè)樣品分別利用FID與CPMG序列測定，并設(shè)置不同的掃描次數(shù)（掃描次數(shù)設(shè)置一般為2的冪函數(shù)，因此選擇了4、8、16、32、64等5組實(shí)驗(yàn)參數(shù)進(jìn)行比較），每個(gè)條件下平行測試3次求其均值，測試結(jié)果如表1所示。表1不同掃描次數(shù)下五種煙草物料的核磁信號量測試結(jié)果類別掃描次數(shù)單次FID信號量單次CPMG信號量FID標(biāo)偏CPMG標(biāo)偏FID變異系數(shù)CPMG變異系數(shù)葉絲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%煙片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%煙梗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%梗絲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%膨脹煙絲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，不同掃描次數(shù)平均單次信號量（累加信號量除以累加次數(shù)）差異不大，變異系數(shù)隨掃描次數(shù)增加有所降低。變異系數(shù)均滿足實(shí)驗(yàn)的要求（＜3%），綜合考慮測試結(jié)果的準(zhǔn)確性和測試時(shí)間，確定掃描次數(shù)為16次。6.3核磁序列及檢測次數(shù)的確定6.3.1核磁序列的確定據(jù)文獻(xiàn)調(diào)研，目前利用核磁共振分析物料水分含量的序列主要有兩種：FID和CPMG序列，試驗(yàn)選取13個(gè)不同梯度水分（3%—41%）的葉絲為檢測樣品進(jìn)行考察核磁序列對測試結(jié)果的影響，每個(gè)樣品測試五次求其平均值及標(biāo)準(zhǔn)偏差，測試結(jié)果及數(shù)據(jù)處理結(jié)果分別見表2和表3。由表3可以看出，在檢測范圍內(nèi)，F(xiàn)ID和CPMG序列的檢測結(jié)果均較好，兩種序列的檢測結(jié)果變異系數(shù)均小于2%，其中CPMG序列的變異系數(shù)均小于1%，優(yōu)于FID序列的。CPMG脈沖序列以自旋回波脈沖序列為基礎(chǔ)，在(90°)x脈沖之后連續(xù)施加一系列等間隔偶數(shù)個(gè)(180°)y脈沖，該序列是由Carr·Purcell·Meiboom·Gill在Hahn回波測量序列的基礎(chǔ)上發(fā)展起來的，不僅消除了磁場不均勻性對T2的影響，并且可以在信號的回波峰點(diǎn)處采樣到不受磁場均勻性影響的數(shù)據(jù)，通過理論與實(shí)際測試結(jié)果分析，確定煙草水分核磁共振法的測試序列為CPMG序列。表2核磁序列對樣品信號量影響測試數(shù)據(jù)樣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測試結(jié)果均值、標(biāo)準(zhǔn)偏差及變異系數(shù)樣品均值標(biāo)準(zhǔn)偏差變異系數(shù)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檢測次數(shù)的確定對表2中的CPMG序列核磁信號量數(shù)據(jù)依次進(jìn)行二次、三次、四次及五次的均值、標(biāo)準(zhǔn)偏差及變異系數(shù)計(jì)算，處理結(jié)果見表4。由表4可以看出，在檢測范圍內(nèi)，兩次、三次、四次、五次的均值及變異系數(shù)沒有明顯的差異，因此確定核磁共振法檢測水分的檢測次數(shù)為兩次。表4檢測次數(shù)對檢測結(jié)果信號量的影響樣品兩次三次四次五次均值標(biāo)準(zhǔn)偏差變異系數(shù)均值標(biāo)準(zhǔn)偏差變異系數(shù)均值標(biāo)準(zhǔn)偏差變異系數(shù)均值標(biāo)準(zhǔn)偏差變異系數(shù)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樣品量的確定利用低場核磁共振技術(shù)測定煙草內(nèi)水分含量，需確定合適的樣品裝樣量。裝樣量大小會影響樣品的代表性，為確定合適的裝樣量，試驗(yàn)選取了平衡后均勻性較好的葉絲樣品為考察對象，考察了2g～13g取樣范圍內(nèi)葉絲核磁水分檢測的信號量。每個(gè)質(zhì)量平行測定兩個(gè)，每個(gè)樣品測定3次求其均值，測試結(jié)果見表5。由表5可以看出，隨著樣品量的增大，所測試樣品的CPMG核磁信號量變異系數(shù)均有所下降，綜合考慮樣品的代表性及測試結(jié)果穩(wěn)定性分析，確定試驗(yàn)的樣品量為7g。表5葉絲樣品量對核磁信號量的影響樣品重量CPMG信號值歸一化均值標(biāo)偏變異系數(shù)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物料溫度對測試結(jié)果的影響因煙草水分檢測環(huán)境溫濕度的要求，物料水分一般在室溫，而核磁共振分析儀的檢測腔體工作溫度為（32±0.1）℃，且煙草物料的水分易受溫度影響，因此利用間接法考察物料溫度對測試結(jié)果的影響，即利用帶有密封性能的定制聚四氟乙烯管裝入煙絲樣品，密封并放入核磁中進(jìn)行檢測，分別測量0、5min、10min、15min、20min、25min、30min、40min、50min、60min、70min的CPMG的信號值，通過物料在高于物料溫度環(huán)境中逐漸升溫間接考察被測物料溫度變化對測量結(jié)果的影響，測試結(jié)果見表6。由表6可以看出，煙草物料在（32±0.1）℃檢測環(huán)境中不斷被加溫，CPMG信號量沒有明顯的差異，檢測結(jié)果變異系數(shù)較小，說明物料溫度對檢測結(jié)果沒有明顯的影響。表6物料溫度對檢測結(jié)果的影響時(shí)間/minCPMG信號值09096.2359191.85109228.43159251.89209247.72259213.53309160.99409099.56509071.49609062.96709126.93均值9159.23標(biāo)準(zhǔn)偏差71.25變異系數(shù)0.78%6.6裝樣密度對測試結(jié)果的影響核磁法檢測煙草水分需要將一定樣品的煙草物料裝入測試樣品管中，為了考察裝樣密度及其均勻性對檢測結(jié)果的影響，試驗(yàn)選取了葉絲為測試樣品，進(jìn)行了兩種方式的測試：一是同一質(zhì)量的樣品（約7g）不同的裝填高度，即將測試樣品裝填入以聚四氟乙烯材料制作的壓實(shí)器中，旋扭壓實(shí)器形成不同的裝樣高度即裝樣密度不同，放入核磁分析設(shè)備中進(jìn)行測試；二是不同質(zhì)量的同一裝填高度，分別稱取約4.0g、5.0g、6.0g、7.0g的樣品，裝填高度為38mm，測試結(jié)果見表7。由表7可以看出，兩種裝樣密度的測試結(jié)果變異系數(shù)均＜2%，裝樣密度對測試結(jié)果無明顯的影響。表7裝樣密度對測試結(jié)果的影響同一質(zhì)量不同裝填高度同一高度不同裝填質(zhì)量裝填高度單位質(zhì)量信號量裝填質(zhì)量單位質(zhì)量信號量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標(biāo)偏32.8115.42變異系數(shù)1.64%0.76%6.7標(biāo)線的建立6.7.1標(biāo)準(zhǔn)工作曲線制作低場核磁共振法是通過傅里葉公式把樣品的磁共振信號變換成波普（頻率）的一種微觀分析方法。T2衰減曲線的信號首點(diǎn)值與樣品的總含水量成正比；橫向馳豫時(shí)間T2的變化可以反映出各種狀態(tài)水分的流動特性及水分變化，反演后得到的T2弛豫譜的每個(gè)波峰對應(yīng)不同狀態(tài)的水分，且波峰的信號幅度、峰面積均可以表征所對應(yīng)狀態(tài)水分含量及所占比例，如圖2所示。即低場核磁共振T2弛豫譜的總峰面積或衰減曲線的首點(diǎn)信號值與樣品中氫質(zhì)子的數(shù)量成正比，用總峰面積或者信號首點(diǎn)值可以表示樣品的水分含量；通過標(biāo)樣擬合建立的含水量和橫向弛豫譜的峰面積或衰減曲線的信號首點(diǎn)值的標(biāo)準(zhǔn)曲線，再通過測量待測樣品的核磁信號可以迅速計(jì)算待測煙草樣品的含水量。圖2低場核磁T2衰減曲線及T2弛豫譜（從0至5水含量逐漸增加）稱取不同質(zhì)量的煙草物料（葉絲、煙片、煙梗、梗絲、膨脹煙絲、薄片）樣品，形成梯度如3g、4g、5g、6g、7g、8g，利用CPMG序列測量樣品的橫向弛豫譜，提取信號幅度值，每個(gè)樣品平行測定5次，以平均值計(jì)；用烘箱法測定樣品的含水量，以水分含量為縱坐標(biāo)，核磁信號幅度值為橫坐標(biāo)，繪制關(guān)系曲線或計(jì)算線性回歸方程，擬合信號幅度值和含水量得到一條標(biāo)準(zhǔn)曲線，如圖3-圖8所示。圖3煙片CPMG信號幅度值與含水量的關(guān)系圖圖4葉絲CPMG信號幅度值與含水量的關(guān)系圖圖5煙梗CPMG信號幅度值與含水量的關(guān)系圖圖6梗絲CPMG信號幅度值與含水量的關(guān)系圖圖7膨脹煙絲CPMG信號幅度值與含水量的關(guān)系圖圖8薄片CPMG信號幅度值與含水量的關(guān)系圖6.7.2結(jié)果的計(jì)算與表述將待測樣品所得兩次CPMG信號幅度均值代入標(biāo)準(zhǔn)工作曲線，計(jì)算得到樣品含水量，進(jìn)而可求得含水率。試樣的水分質(zhì)量百分含量按照式（1）計(jì)算得出：………(1)式中：W——試樣的水分質(zhì)量百分含量，%；m——待測樣品測定含水量，g；M——試樣質(zhì)量，g。取兩個(gè)平行樣品的算術(shù)平均值為檢測結(jié)果，結(jié)果精確至0.01%。6.7.3標(biāo)線的適用性以葉絲標(biāo)線為例，不同牌號（不同模塊）的葉絲對所建立的標(biāo)線進(jìn)行試驗(yàn)驗(yàn)證，每個(gè)牌號（模塊）檢測五次并與烘箱法進(jìn)行對比，驗(yàn)證結(jié)果見表8。由表8可以看出，所建立的標(biāo)線對不同牌號不同模塊的葉絲均適用。表8標(biāo)線適用性驗(yàn)證結(jié)果牌號序號核磁法烘箱法差值BS-A模塊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模塊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模塊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模塊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檢測方法的準(zhǔn)確性及測量范圍評價(jià)6.8.1樣品制備6.8.1.1準(zhǔn)確性評價(jià)樣品制備測試樣品為煙片、葉絲、煙梗、梗絲、膨脹煙絲、薄片，其中煙梗剪切成2cm左右的，六種待測樣品均放入符合GB16447-2004規(guī)定調(diào)節(jié)環(huán)境的恒溫恒濕箱平衡48小時(shí)后待用。6.8.1.2測量范圍價(jià)樣品制備測試樣品為葉絲，通過烘、噴灑水的方式形成不同梯度水分的樣品，共13個(gè)，密封備用。6.8.2試驗(yàn)方法按所建立的核磁法進(jìn)行待測樣品的水分檢測，每個(gè)形態(tài)的樣品取15個(gè)樣進(jìn)行核磁法水分測定，每個(gè)樣平行檢測2次，以2次的核磁信號量均值計(jì)；并對15個(gè)樣品進(jìn)行烘箱法測定對比。樣品量為（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測試結(jié)果6.8.3.1準(zhǔn)確性評價(jià)結(jié)果以上述測試方法對六種測試樣品進(jìn)行核磁法和烘箱法檢測，得到表9測試數(shù)據(jù)，并根據(jù)各自樣品的標(biāo)線進(jìn)行水分計(jì)算。由表9可以看出，除煙梗個(gè)別外，煙片、葉絲、梗絲、膨脹煙絲、薄片幾種煙草物料的低場核磁共振法與烘箱法測得的結(jié)果差異均小于1個(gè)百分點(diǎn)，標(biāo)準(zhǔn)差、變異系數(shù)均較小，說明低場核磁共振法的穩(wěn)定性相對較好。在用烘箱法測得煙草物料水分過程中，由于加熱易造成物質(zhì)揮發(fā)而導(dǎo)致測定結(jié)果偏大，也可能由于物料內(nèi)部少量結(jié)合水無法徹底烘出而導(dǎo)致結(jié)果偏小。而低場核磁共振法克服了這些缺陷，使得測定結(jié)果的穩(wěn)定性相對較好。表9六種測試樣品核磁共振法與烘箱法測定水分對比樣品序號CPMG均值烘箱法水分核磁法水分差值煙片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%標(biāo)準(zhǔn)偏差0.57%0.47%葉絲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%標(biāo)準(zhǔn)偏差0.11%0.13%煙梗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%標(biāo)準(zhǔn)偏差0.32%0.32%梗絲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%標(biāo)準(zhǔn)偏差0.11%0.14%膨脹煙絲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%標(biāo)準(zhǔn)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%標(biāo)準(zhǔn)偏差0.19%0.09%6.8.3.2測量范圍評價(jià)結(jié)果按所建立的方法對13個(gè)待測樣品進(jìn)行核磁法和烘箱法檢測，測試結(jié)果見表10。由表10可以看出，在3%~41%測量范圍內(nèi)核磁法與烘箱法的差值較小，均在1%以內(nèi)。表10核磁法測量范圍評價(jià)結(jié)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檢測方法的重復(fù)性和再現(xiàn)性6.9.1檢測方法的重復(fù)性按照上述建立的方法，選取平衡后的煙絲樣品，測試10個(gè)樣品，在3天內(nèi)以相同的測試條件進(jìn)行水分分析，測得的數(shù)據(jù)求日內(nèi)、日間標(biāo)準(zhǔn)偏差、平均值、變異系數(shù)等來表征，測試結(jié)果如表11所示。由于試驗(yàn)在同一試驗(yàn)室進(jìn)行，精密度可以用標(biāo)準(zhǔn)偏差表示。從表11可知，在試驗(yàn)測試水平范圍內(nèi)，測試結(jié)果的精密度在72.00~279.99（換算成水分為0.04%-0.16%）之間，所測煙絲樣品的日內(nèi)重復(fù)性和日間重復(fù)性結(jié)果的變異系數(shù)均在2%以內(nèi)，這表明所建立的測試方法具有較好的重復(fù)性,可以較為可靠地用以測定煙草樣品的水分含量。表11重復(fù)性實(shí)驗(yàn)結(jié)果樣品編號核磁測試信號量均值標(biāo)準(zhǔn)偏差變異系數(shù)/%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標(biāo)準(zhǔn)偏差279.99219.49244.68變異系數(shù)1.92%1.50%1.66%平均值14656.68日間標(biāo)準(zhǔn)偏差97.68變異系數(shù)/%0.67%6.9.2檢測方法的再現(xiàn)性為了還原生產(chǎn)過程檢測，檢測樣品未經(jīng)過平衡處理，以切后煙絲、葉絲增溫增濕后煙絲、烘后煙絲、干頭干尾絲等為測試樣品，測試樣品水分梯度涵蓋了生產(chǎn)過程中的水分范圍。由河北中煙、江西中煙、蘇州紐邁、上海泰紐、北京農(nóng)產(chǎn)品加工所五個(gè)實(shí)驗(yàn)室利用核磁共振分析儀采用所建立的方法分別對23個(gè)樣品的水分進(jìn)行測試，由于五家實(shí)驗(yàn)室儀器設(shè)備型號不一致（設(shè)備型號、核磁參數(shù)見表12），故采用同一標(biāo)樣樣品按照所建立的核磁法進(jìn)行標(biāo)線建立及水分測定，每個(gè)樣品重復(fù)測試5次，檢測結(jié)果見表13。表12共同試驗(yàn)核磁設(shè)備參數(shù)情況實(shí)驗(yàn)室河北中煙江西中煙蘇州紐邁上海泰紐北京農(nóng)產(chǎn)品加工所設(shè)備型號NMI20-040V-IMESOMR23-040V-IMESOMR23-040H-IMesoMR23-060H-INM21-060H-I核磁參數(shù)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標(biāo)線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不同實(shí)驗(yàn)室的檢測結(jié)果實(shí)驗(yàn)室序號核磁信號量均值標(biāo)偏變異系數(shù)12345河北中煙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%江西中煙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%蘇州紐邁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%上海泰紐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%北京農(nóng)產(chǎn)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：其中樣品1為序號1-5，樣品2為序號6-10，樣品3為11-15，樣品4為序號16-20，樣品5為序號21-23。對表13中的各樣品的核磁信號量利用各自的標(biāo)線進(jìn)行水分計(jì)算，并與烘箱法進(jìn)行對比，結(jié)果見表14。表14核磁法與烘箱法的比對結(jié)果序號核磁法烘箱法河北江西蘇州上海北京120.77%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，五家實(shí)驗(yàn)室23個(gè)樣品的核磁法與烘箱法對比差異不超過1%，核磁法與烘箱法的均值差異不超過0.5%，結(jié)果接近，結(jié)果表明重現(xiàn)性良好。對表14中的數(shù)據(jù)按GB/T6379.2-2004/ISO5725-2:1994《測量方法與結(jié)果的準(zhǔn)確度（正確度與精密度）第2部分：確定標(biāo)準(zhǔn)測量方法重復(fù)性與再現(xiàn)性的基本方法》評價(jià)該測試方法的重復(fù)性與再現(xiàn)性分析，分析結(jié)果見表15所示：密封度檢測方法的重復(fù)性標(biāo)準(zhǔn)偏差、再現(xiàn)性標(biāo)準(zhǔn)偏差分別在0.07%～0.36%與0.16%～0.36%范圍內(nèi)，表明該方法穩(wěn)定性較好，不同實(shí)驗(yàn)室間檢測結(jié)果具有良好的一致性。表15重復(fù)性與再現(xiàn)性試驗(yàn)結(jié)果樣品實(shí)驗(yàn)室編號總平均值重復(fù)性標(biāo)準(zhǔn)偏差再現(xiàn)性標(biāo)準(zhǔn)偏差河北江西蘇州上海北京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核磁法與其他煙草水分含量測試方法比對選取3種制絲生產(chǎn)線上不同工序的煙草及煙草制品樣品，取樣后同時(shí)進(jìn)行了核磁法、烘箱法、氣相色譜法和卡爾費(fèi)休法測定煙草水分的對比實(shí)驗(yàn)，結(jié)果見表16。由表16可以看出核磁法、烘箱法的水分均較卡爾費(fèi)休法測試數(shù)據(jù)要高。產(chǎn)生差別的原因是由于核磁法采用的是烘箱法水分定標(biāo)，烘箱法、卡爾費(fèi)休法兩種測定煙草水分的方法原理不同所致，烘箱法為水和其它揮發(fā)性物質(zhì)之和，卡爾費(fèi)休法為較為純粹的水分的含量。表16核磁法與烘箱法、氣相色譜法、卡爾費(fèi)休法的比對結(jié)果工序氣相色譜卡爾費(fèi)休烘箱法核磁法烘絲12.22%12.02%12.57%12.26%12.29%11.98%12.67%12.23%切絲19.