SPME结合GC×GC-TOFMS测定白酒中的氨基甲酸乙酯

基于顶空固相微萃取(head space solid phase microextraction,HS-SPME)结合全二维气相色谱-飞行时间质谱(comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry,GC×GC-TOFMS)建立了一种准确定量白酒中氨基甲酸乙酯(ethyl carbamate,EC)的方法。实验对HS-SPME方法进行了优化,在酒精度12%vol、加NaCl 3 g、萃取温度70℃,萃取时间40 min的条件下,能够显著提高目标物的响应值。实验以D_(5)-氨基甲酸乙酯(D_(5)-EC)为内标,对不同浓度的样品溶液进行GC×GC-TOFMS定量分析。结果表明,EC在10~500μg/L范围内线性关系良好,回归系数(R^(2))>0.998,检出限为0.19μg/L,定量限为0.64μg/L,平均回收率为97.57%,精密度为8.66%。测定结果与国标方法相比无显著性差异(P>0.05)。该方法前处理简单,检测灵敏度更高,为白酒中EC自动化定量测定提供了新思路。

顶空固相微萃取-全二维气相色谱-飞行时间质谱解析泉香型白酒的风味物质

泉香型白酒是一种创新香型,属于其他香型。为了定性泉香型白酒挥发性组分的种类数和解析泉香型白酒的风味物质,该研究采用顶空固相微萃取-全二维气相色谱-飞行时间质谱(headspace solid phase microextraction-comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry,HS-SPME-GC×GC-TOF-MS)对泉香型白酒挥发性风味物质进行组分鉴定,根据正向和反向匹配度均>800、可能性≥75%,再结合C7~C40正构烷烃保留指数(retention index,RI)进行定性,采用归一化法与内标法进行半定量,计算气味活度值(odor activity values,OAV)。共检测出1258种成分,利用匹配度和可能性定性,鉴定出可信度较高的566种香气成分,其中酯类峰面积最大,其次是醇类、酸类、醛类和酮类,说明这五类是泉香型白酒重要香气组分。再利用正构烷烃RI值定性出泉香型白酒重要成分251种。根据OAV值,共鉴定出21种关键酯类香气化合物,通过对泉香型白酒与浓香型白酒和芝麻香型白酒样品中酯类、醇类、酸类、醛类、酮类、吡嗪和硫化物等不同种类香气组分比较分析,鉴定出泉香型白酒与浓香型白酒和芝麻香型白酒的共性与差异性。基于HS-SPME-GC×GC-TOF-MS检测方法对泉香型白酒风味物质进行全面解析,将有助于对泉香型白酒风格独特的认识,进而科学有效地进行质量控制和品质提升。

VOCs走航系统在响水环境应急监测中的探索应用

文章介绍了以移动监测车为载体的集成了VOCs在线质谱仪、GPS信息记录仪、气象参数仪等设备的VOCs走航观测系统,该系统对VOCs的测定限优于10-9(V/V)。在连续走航模式下,可在5 s、27 m内产生一组监测数据,实现了VOCs的高时空分辨监测。在江苏响水"3·21"特别重大爆炸事故中,将该系统探索性地应用于对事故核心区域附近VOCs的高时空分辨率的连续走航观测(2019年3月22日-26日)及核心区域外围点位的定点观测(2019年3月27日-30日)。监测过程发现:苯为主要污染物,最高瞬时浓度为43.4 mg/m^(3),其次为甲苯、二甲苯等有机污染物;2019年3月22日开始,污染物浓度有逐渐降低的趋势;爆炸点600 m范围内VOCs浓度较高;主要受影响区域为爆炸点2 km范围内,另外VOCs的分布有着巨大的时空差异;定点观测发现,事故处置期间在距离爆炸点1.4 km处偶有检出较高浓度的苯。

车内空气质量检测的在线质谱技术研究

文章介绍了在线质谱技术的原理和在线质谱仪的特点,初步研究了在线质谱技术在车内空气质量检测方面的应用,分析对比了在线技术和离线技术应用在空气质量检测优势和缺点,展望了快速线检测技术的发展前景。

嘉兴市臭氧污染特征及其与气象条件的关系

利用2014-2018年嘉兴市14个监测站的臭氧(O_(3))观测资料,分析了嘉兴市O_(3)污染的时间变化趋势和空间分布特征,并讨论了温湿度和O_(3)污染的关系。结果表明:嘉兴市近五年来环境空气质量超标天数有所下降,但O_(3)超标天数占比却在逐渐升高,从2014年的43%上升到2018年的64%;嘉兴市O_(3)浓度夏季>春季>秋季>冬季,O_(3)污染主要集中在春末至早秋,4-9月O_(3)-8h月度超标天数平均可达到8天以上;嘉兴市O_(3)污染主要集中在以市本级为中心的城市中、北部地区,清河小学站的O_(3)小时浓度高值(>200μg/m^(3))占比率最高,7-9月高值持续时间最长;温度、相对湿度和O_(3)污染的相关性显著,气温高于33℃或相对湿度低于50%时,O_(3)浓度及超标率均会显著上升。

基于单颗粒气溶胶质谱仪的气溶胶化学组分的半定量研究

单颗粒气溶胶质谱仪(SPAMS,single particle aerosol mass spectrometer)可以实时、连续和高时间分辨率的提供单个气溶胶颗粒的粒径和化学组分信息,具有良好的定性能力。但,SPAMS对气溶胶化学组分的定量分析能力尚待评估。采用SPAMS结合滤膜采样的分析方法,于2017-12-01至2018-02-28日在郑州市高新区、航空港区和中原区展开观测,通过对比单颗粒中的元素碳(EC)、有机碳(OC)、硫酸盐、硝酸盐和铵盐的峰面积、数浓度与滤膜采集的质量浓度,以回归分析系数(R)评估了SPAMS对5种组分的定量能力。结果表明:EC单颗粒的数浓度和峰面积与其质量浓度的相关性始终很低(R<0.3),说明尚无法通过相关性分析建立EC单颗粒与质量浓度的定量关系;OC单颗粒与质量浓度的相关性从低度到中度相关分布(0.3<R<0.5),因此可通过优化OC单颗粒的特征离子选取标准,实现OC的半定量化分析;硫酸盐、硝酸盐和铵盐单颗粒与质量浓度都有中度以上的相关性(R>0.5),可以通过相关性建立硫酸盐、硝酸盐和铵盐的半定量系数。三个站点各组分相关性对比结果表明:中原区各组分数浓度与质量浓度的相关性高于高新区和航空港区,且中原区测径颗粒数浓度与PM_(2.5)质量浓度的相关性也显著高于其他两个采样点,因此测径颗粒数浓度与PM_(2.5)质量浓度的相关性可能是评估SPAMS定量化结果好坏的前提条件。

Analysis of Sources of Atmospheric Fine Particulates in Nan'ao County

Based on on-line single particle aerosol mass spectrometry （SPAMS） with high time resolution, the sources of atmospheric fine particu- late matter in Nan＇ao County were analyzed. The results showed that during the monitoring period from March 24 to 27 in 2015, the primary source of fine particulate matter in Nao＇ao County was motor vehicle exhaust, that is, 24.7% of fine particulates were from motor vehicle exhaust, followed by biomass burning （17.2%）, fire coal （17.2%）, and sea salt （13.3%）. The proportions of fire coal and sea salt revealed the peculiarity of sources of atmospheric fine particulate matter in Nan＇ao County. Therefore, it is suggested that some measures should be adopted to limit tourist traffic to reduce the adverse impact of motor vehicle exhaust on ambient air quality in Nan＇ao County.

区域大气细颗粒物化学组分及来源年变化趋势

利用单颗粒气溶胶质谱仪(SPAMS)于2018年1月1日—2019年12月31日对上海市浦东新区环境空气PM2.5开展高时间分辨化学成分监测。结果表明,2019年监测点空气质量总体优于2018年,AQI达标率由74.8%升高至86.6%。通过对PM2.5成分分类,最终确定了8类颗粒物,相较于2018年,2019年富钾颗粒物升幅较为明显,左旋葡聚糖、重金属和元素碳有小幅增加,其余各组分相对减少。对PM2.5排放源分类分析显示,机动车尾气源占比>25%,其中2018年3月、2018年7月、2019年2和3月贡献超过40%;二次无机源和燃煤源呈现一定的季节变化特点,整体秋冬季高于春夏季,2019年燃煤源占比较2018年下降了41%;工业排放源2018年5和10月、2019年1和5月占比相对较高,其余各月份占比相对较为稳定。

New insights into the formation of ammonium nitrate from a physical and chemical level perspective

High levels of fine particulate matter(PM_(2.5))is linked to poor air quality and premature deaths,so haze pollution deserves the attention of the world.As abundant inorganic components in PM_(2.5),ammonium nitrate(NH_(4)NO_(3))formation includes two processes,the diffusion process(molecule of ammonia and nitric acid move from gas phase to liquid phase)and the ionization process(subsequent dissociation to form ions).In this study,we discuss the impact of meteorological factors,emission sources,and gaseous precursors on NH4NO3 formation based on thermodynamic theory,and identify the dominant factors during clean periods and haze periods.Results show that aerosol liquid water content has a more significant effect on ammonium nitrate formation regardless of the severity of pollution.The dust source is dominant emission source in clean periods;while a combination of coal combustion and vehicle exhaust sources is more important in haze periods.And the control of ammonia emission is more effective in reducing the formation of ammonium nitrate.The findings of this work inform the design of effective strategies to control particulate matter pollution.

Detection of polycyclic aromatic hydrocarbons using a high performance-single particle aerosol mass spectrometer

The real-time detection of the mixing states of polycyclic aromatic hydrocarbons(PAHs)and nitro-PAHs in ambient particles is of great significance for analyzing the source,aging process,and health effects of PAHs and nitro-PAHs;yet there is still few effective technology to achieve this type of detection.In this study,11 types of PAH and nitro-PAH standard sampleswere analyzed using a high performance-single particle aerosolmass spectrometer(HP-SPAMS)in lab studies.The identification principles‘parent ions’and‘mass-to-charge(m/z)=77’of each compound were obtained in this study.It was found that different laser energies did not affect the identification of the parent ions.The comparative experiments of ambient atmospheric particles,cooking and biomass burning emitted particles with and without the addition of PAHs were conducted and ruled out the interferences from primary and secondary organics on the identification of PAHs.Besides,the reliability of the characteristic ions extraction method was evaluated through the comparative study of similarity algorithm and deep learning algorithm.In addition,the real PAH-containing particles from vehicle exhaust emissions and ambient particles were also analyzed.This study improves the ability of single particle mass spectrometry technology to detect PAHs and nitro-PAHs,and HP-SPAMS was superior to SPAMS for detecting single particles containing PAHs and nitro-PAHs.This study provides support for subsequent ambient observations to identify the characteristic spectrum of single particles containing PAHs and nitro-PAHs.

Insights into Free and Conjugated Forms of Neonicotinoid Insecticides in Human Serum and Their Association with Oxidative Stress

Following exposure,neonicotinoid insecticides(NEOs)can be metabolized by both Phase Ⅰ and Phase Ⅱ reactions catalyzed by human cytochrome P450 enzymes.However,toxicities of parent NEOs and their metabolites are still unclear,and little is known about biotransformation rates and pathways of NEOs in humans.In this study,98 serum samples collected in China were analyzed for free,conjugated and total forms of six parent NEOs(i.e.,acetamiprid(ACE),imidacloprid(IMI),clothianidin(CLO),thiacloprid(THD),thiamethoxam(THM),and dinotefuran(DIN))and four metabolites(i.e.,N-desmethyl-acetamiprid(N-dm-ACE),1-methyl-3-(tetrahydro-3-furylmethyl)(DIN-U),5-hydroxy-imidacloprid(5-OH-IMI),olefin-imidacloprid(Of-IMI)).NEOs and their metabolites were detected in all serum samples,and the total median concentrations of free,conjugated,and total forms of 10 NEOs were 2.04,2.01,and 5.12 ng/mL,respectively.Conjugated forms of NEOs accounted for only half(53%)of the total forms of NEOs.Based on the profiles of Phase Ⅰ and Phase Ⅱ metabolites of NEOs in serum,it was found that age is a determinant in Phase Ⅰmetabolism of DIN and Phase Ⅱ metabolism of IMI.The Phase Ⅱmetabolites of NEOs are associated with oxidative DNA damage,and the conjugated forms of IMI,DIN,and 5-OH-IMI in serum were significantly positively correlated with oxidative stress.Overall,the amount of NEOs present in conjugated forms in human serum was determined to document the existence of a considerable proportion of free forms of these insecticides.

远距离多通道的无组织排放VOCs连续在线监测系统

研制了一套远距离多通道VOCs连续采样在线监测系统。监测系统主要由远距离多通道VOCs连续采样装置与真空紫外灯单光子电离源飞行时间质谱仪组成。通过PAMS与有机硫标准气体对该系统进行了性能表征测试。结果表明:各物质连续7次实验RSD≤7%;最优检测限为0.004μmol·mol^(−1);在0.01~1.00μmol·mol^(−1)浓度范围内各物质判定系数大于0.99;定量误差在−13%~25%之间,可以满足环境中VOCs监测要求。该监测系统采样距离为500 m,可在1 h内完成10个不同点位的采样,并可对C4~C10烃类、有机硫化物和苯系物VOCs进行在线分析。该系统可应用于化工园区无组织排放VOCs的在线监测中。