利用近红外光谱快速测定制浆材化学成分含量

为实现实际生产中制浆材综纤维素和木质素含量的快速测定和在线分析,按国家标准测定了5种制浆材共计87个样品的综纤维素和木质素含量,并利用国产便携式光谱仪采集了样品的近红外光谱。原始光谱经过MSC预处理之后,采用偏最小二乘法和留一法交叉验证方法分别建立相应的混合样品预测模型。预测结果表明:综纤维素和木质素模型的预测决定系数(RP2)分别为0.9658和0.9471,预测均方根误差(RMSEP)分别为1.1438%和1.1805%,相对分析误差(RPD)分别为5.41和4.35,这说明2个模型均具有较高的预测精度。因此利用便携式光谱仪对多种制浆材混合样品的综纤维素和木质素含量进行快速测定是可行的。     

食品包装瓶用PET树脂乙醛含量测定结果的影响因素研究

目的探究氮气、水分、粉碎时间、粒径对食品包装瓶用聚对苯二甲酸乙二醇酯(PET)树脂粒子中残留乙醛含量测定结果的影响。方法根据SH/T 1817-2017《瓶用聚对苯二甲酸乙二醇酯(PET)树脂中残留乙醛含量的测定顶空气相色谱法》,采用控制变量法,考察氮气吹扫顶空瓶、样品含水量、粉碎时间、粒径对瓶用PET树脂粒子乙醛含量测试结果的影响。结果经过氮气保护的测试结果高于未经氮气保护的测试结果;含5、10、15μL蒸馏水试样的测试结果高于干燥样品的测试结果,且含水量越大测试结果越大;粉碎时间对测试结果的影响不明显(P=95%);粒径越小测试结果越大。结论测试食品包装瓶用PET树脂粒子乙醛含量时,样品须用氮气保护且保持干燥状态,以获得准确的测试结果。建议SH/T 1817-2017中对于试样粒径的要求进一步细化,以提高测试方法的统一性。     

顶空-气相色谱/质谱法测定互叶白千层茶树精油中的挥发性成分

目的 建立顶空-气相色谱/质谱法测定茶树精油中的挥发性成分的分析方法。方法 茶树精油样品用正己烷溶解,放入顶空迚样瓶中,用顶空-气相色谱/质谱迚行测定。结果 用该方法共分离了15个组分,用NIST Chemical Structures库和Wiley Library质谱库迚行检索,以质谱相似度和利用标准品对部分主要成分迚行迚一步确认,最终确认13种主要成分;采用峰面积归一化法确定各组分峰的相对含量,有效成分含量占总流出物的98.46%。结论 该方法快速、准确、灵敏,适合茶树精油等精油类物质中挥发性成分的测定。     

浸出油厂废水中溶剂含量的测定

开发了一种测定废水中溶剂含量的方法.将样品放入密封的平衡瓶中,在一定温度下,使溶剂汽化达到平衡,取液上气体注入气相色谱中测定,与标准曲线比较定量,取得了理想的分析结果.     

热转换元素分析-同位素比质谱法测定低氘包装饮用水中氘含量

建立热转换元素分析-同位素比质谱联用(thermal conversion/elemental analysis-isotope ratio mass spectrometry,TC/EA-IRMS)检测低氘水中氘含量分析方法,用于低氘包装饮用水中氘含量的监督检测。水样采用0.22μm微孔滤膜过滤样品适量,移取2 mL水样装满进样瓶,进样量0.1μL,反应炉温度1 380℃,柱温箱温度85℃,载气He流速100 mL/min,每个水样进行4⁶次分析。测试样品瓶不留顶空和剔除第1个数据点可以避免样品瓶顶空体积和记忆效应对δ2H测定值的影响,从而提高计算得到的氘含量值的精度。该方法适用于12.624¹55.760μg/g范围内水中氘含量的测定,测量值与理论值的相对标准偏差低于0.6%。对同一低氘水样连续8次测定值除第1个点后氘含量标准偏差(standard deviation,SD)为0.08μg/g,30 d内分3次测定同一低氘水样氘含量SD为0.086μg/g,重复性和再现性好。不同仪器方法测定的低氘水样SD低于1μg/g。检测8个市售低氘包...     

一次性可降解餐饮具中氟含量的测定

建立了灰化蒸馏和氧瓶燃烧两种样品前处理方法,利用离子色谱法定量测定氟元素含量。验证发现,灰化蒸馏-离子色谱法和氧瓶燃烧-离子色谱法用于一次性可降解餐饮具及其原料中氟元素含量的测定,重复性好、准确度高,两种方法均具有操作简单、灵敏度高、准确度高等特点。     

连续流动法快速测定基因编辑素材中淀粉含量

为实现烟草中淀粉的高通量准确测定,设计了无需样品转移即可实现去除干扰成分、萃取和过滤的样品萃取瓶,并将其作为前处理装置,建立了一种连续流动法快速测定基因编辑素材中淀粉含量(质量分数)的方法。结果表明:①设计的样品萃取瓶可以集萃取、过滤和废液转移为一体,使样品前处理效率得到了有效提高。②淀粉含量具有较好的线性关系(相关系数r=0.999 6);不同添加水平下的平均回收率为96.40%～101.30%,日内和日间RSD均小于3.3%。③8个基因编辑素材样品中淀粉含量与行业标准方法检测结果基本一致。该方法前处理简单快捷,灵敏度高,重复性较好,可以满足烟草样品中淀粉的高通量检测要求。     

近红外光谱法快速测定木材纤维素、戊聚糖和木质素含量的研究

探讨了近红外光谱法快速测定木材纤维素、戊聚糖和Klason木质素含量的可行性。用常规实验室方法测定106种木材样品的纤维素、戊聚糖和Klason木质素含量,用近红外光谱仪采集相应样品的光谱。利用偏最小二乘法（PLS）和完全交叉验证方式,对原始光谱进行一阶导数＋矢量归一化（SNV）和一阶导数＋多元散射校正（MSC）预处理后,选择7502-5446 cm^-1、4601-4247cm^-1和6102-4597 cm^-1区间建立样品纤维素、戊聚糖、Klason木质素含量和光谱数据之间的相关性模型。模型的决定系数（R2）高,分别为0.9705、0.9927和0.9827;交叉验证均方根偏差（RMSECV）低,分别为0.40%、0.38%和0.49%;残留预测偏差（RPD）分别为5.83、11.7和7.61。采用3个模型分别对样品进行预测,预测偏差分别为-0.36%-0.34%、-0.40%-0.32%和-0.36%-0.39%。结果表明,可以利用近红外光谱法快速测定木材纤维素、戊聚糖和Klason木质素含量。     

稻壳中纤维素、半纤维素和木质素的测定

阐述了几种不同的测定稻壳中纤维素、半纤维素和木质素含量的方法。最终选定测定稻壳中纤维素、半纤维素和木质素含量的方法分别为72％浓硫酸水解法、2mol／L盐酸水解法和浓硫酸法。结果测得纤维素、半纤维素、木质素含量分别为21．9％、19．0％、17．8％。     

碱水解法测定乳及乳制品中脂肪的含量

目的建立简单、快速的碱水解法测定乳及乳制品中脂肪的含量。方法取0.5 g样品于离心管中,用10 mL纯水复溶后加入2 mL氨水(25%)水解并65℃水浴20 min。加入乙醇沉淀蛋白质并使用乙醚、石油醚提取样品中脂肪。将上清液提取至收集瓶中,蒸干提取液,称量收集瓶前后质量,计算样品中脂肪含量。结果此法测得样品脂肪含量为26.53 g/100 g,结果相对偏差为0.37%。测定值在质控样品值满意区间内,且符合国标规定的两次独立测定结果之差≤0.3 g/100 g的要求。结论本法测定乳及乳制品中脂肪的含量具有简便、快速、重现性好的优点,适合实验室日常样品测定及考核使用。     

Test method of methanol content in detergent

A test method of methanol content in detergent using a headspace-GC method was established. A 1 g aliquot of test sample was mixed with 0.4 mg of 2-propanol and made up to 20 mL with water. Then, 5 mL of test solution was placed in a headspace vial. The vial was sealed and incubated for 30 min at 60°C, then the headspace gas was analyzed by GC-FID. The recovery from spiked 1 mg/g of methanol was 95.6-100.6%. The determination limit was 0.1 mg/g. Using this method, the methanol content in 14 kinds of detergents was quantified. Methanol was detected from two detergents at the levels of 0.13 and 0.27 mg/g.     

Headspace GC/MS analysis of residual vinyl chloride and vinylidene chloride in polyvinyl chloride and polyvinylidene chloride products

A headspace GC/MS analysis method for the simultaneous determination of residual vinyl chloride (VC) and vinylidene chloride (VDC) in polyvinyl chloride (PVC) and polyvinylidene chloride (PVDC) products was developed. A test sample was swelled overnight with N,N-dimethylacetamide in a sealed vial. The vial was incubated for 1 hour at 90 degrees C, then the headspace gas was analyzed by GC/MS using a PLOT capillary column. The recoveries from spiked PVC and PVDC samples were 90.0-112.3% for VC and 85.2-108.3% for VDC. The determination limits were 0.01 microg/g for VC and 0.06/microg/g for VDC, respectively. By this method, VC was detected in two PVC water supply pipes at the levels of 0.61 and 0.01 microg/g. On the other hand, VC and VDC were not detected in any of the food container-packages or toys tested.     

顶空固相微萃取分析白酒香气物质的条件优化

利用顶空固相微萃取与气质联用相结合的方法分析白酒香气物质组成,对影响顶空固相微萃取的操作条件装液量、盐离子浓度、平衡温度、平衡时间、萃取时间和解析时间进行系统地优化.结果表明:项空固相微萃取白酒香气的最佳条件为装液率40%、NaC1质量浓度0.2g/mL,在磁力搅拌加热器上50℃甲衡30min后,萃取头插入样品瓶顶空吸...     

A rapid headspace gas chromatographic method for the determination of the butyric acid content in edible fats

 A rapid headspace gas chromatographic method for the precise and accurate quantitation of butyric acid in edible fats was developed and validated by means of a reference material with a certified content of butyric acid. Sample preparation consisted only of weighing a fat sample into a suitable container, and adding the transesterification reagent before crimp-sealing the vial. By using an automatic sampler the sample throughput was eight samples per hour. The calibration function relating peak area to butyric acid concentration was linear over the range 0.2 g to 4.5 g per 100 g fat. The relative standard deviation of repeated measurements, as an indicator of the repeatability of the method, was between 0.90 and 1.32%. Received: 15 October 1997 / Revised version: 5 December 1997     

A rapid headspace gas chromatographic method for the determination of the butyric acid content in edible fats

 A rapid headspace gas chromatographic method for the precise and accurate quantitation of butyric acid in edible fats was developed and validated by means of a reference material with a certified content of butyric acid. Sample preparation consisted only of weighing a fat sample into a suitable container, and adding the transesterification reagent before crimp-sealing the vial. By using an automatic sampler the sample throughput was eight samples per hour. The calibration function relating peak area to butyric acid concentration was linear over the range 0.2 g to 4.5 g per 100 g fat. The relative standard deviation of repeated measurements, as an indicator of the repeatability of the method, was between 0.90 and 1.32%. Received: 15 October 1997 / Revised version: 5 December 1997     

全挥发顶空气相色谱法测定乙氧基含量

本文建立了一种全挥发顶空气相色谱法测定乙基纤维素乙氧基含量的方法。按照改进的蔡氏法(Zeisel),在顶空瓶中通过氢碘酸与乙基纤维素反应,使乙氧基转化为碘乙烷,反应结束后加碱液中和过量氢碘酸防止腐蚀进样器和色谱柱,随后抽取μL级样品全挥发顶空进样,进行气相色谱分析。以甲苯为内标物,采用内标法测定碘乙烷含量,从而计算得出乙基纤维素乙氧基含量。考察了平衡温度,平衡时间和样品量等影响因素,结果表明μL级样品(<40μL)在90℃的平衡温度下4min内可达到近乎完全挥发,碘乙烷和甲苯的质量比与它们的峰面积比呈良好的线性关系(r=0.9998,n=7),碘乙烷回收率98.9%(RSD=2.2%,n=6)。该方法操作简便,快速准确,可用于乙基纤维素的质量控制。     

Development and validation of a headspace method for determination of furan in food.

In the past furan had been found to form in foods during thermal processing. These findings and a recent classification of furan as a possible human carcinogen prompted us to develop a simple isotope dilution method for its determination in foods. We also investigated effects of furan volatility, sample matrix and partitioning of furan between water and fat constituents of sample on the analytical determination of furan. The method is based on headspace sampling of a 2 ml vial containing 1 g of sample. For analysis, samples were spiked with d(4)-furan, homogenized in a blender at 0 degree C, with water if required, and sub-sampled to vials containing sodium sulphate. After equilibration at 30 degrees C, 50 microl of headspace was injected into the split/splitless injection port of a GC/MS (EI, SIM). The method is linear in the 0.4-1000 ng/g range with a limit of detection of 0.1 ng/g.     

Determination of Total Acid Content in Vinegars by Reaction-Based Headspace Gas Chromatography

This work reports on a simple and efficient method for the determination of total acid content in vinegars by reaction-based headspace gas chromatography. The method is based on the neutralization reaction between the acids in vinegar and carbonate solution in a closed headspace sample vial, from which the carbon dioxide generated from the reaction is analyzed by gas chromatograph equipped with a thermal conductivity detector. The results showed that the headspace equilibration of CO₂ generated from the reaction was achieved in 15 min at 60 °C. The method has a good precision and accuracy, in which the relative standard deviation in the repeatability measurement was 1.73 %, and the relative differences between the data obtained by the headspace gas chromatographic method and the reference titration method were within 4.81 %. The present method is particularly suitable to be used for determining the total acid content of vinegar not only in the process control but also the quality check of point-of-sale samples from commercial markets.     

应用顶空气相色谱测定纸浆纤维的羧基含量

报道了一种应用顶空气相色谱测定纸浆纤维羧基含量的方法.用稀盐酸对纸浆进行预处理可以使其羧酸盐转化成羧酸的形式.在封闭的测试瓶内,碳酸氢钠溶液作为反应剂与测试瓶内纤维的羧酸反应生成二氧化碳.通过气相色谱的热导检测器对二氧化碳进行检测,推算出纸浆纤维的羧基含量.     

顶空-气相色谱法测定木耳中的磷化铝残留量

目的建立木耳中磷化铝残留量的顶空-气相色谱检测方法。方法将样品称量于顶空进样瓶中,加入硫酸溶液,使磷化铝与酸反应生成磷化氢,用气相色谱-氮磷检测器检测磷化氢的含量,得到样品中磷化铝的含量。结果磷化铝在0.05~5.00 mg线性关系良好,相关系数0.995,加标回收率在83.4%~112.6%,相对标准偏差为9.4%~10.2%之间,方法检出限为0.02 mg/kg。结论该方法快速简便、灵敏度高、准确性好,满足相关法规的限量要求,可用于木耳中磷化铝含量的实际检测工作。