Name: analyzing the photo-oxidation of 2-propanol at indoor air level concentrations using field asymmetric ion mobility spectrometry
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Description: Watch this Scientific Journal Video about Analyzing the Photo-oxidation of 2-propanol at Indoor Air Level Concentrations Using Field Asymmetric Ion Mobility Spectrometry at JoVE.com

作者感谢紧急救济协调员提供的财政支持, 根据赠款259619号照片和授予620298号照片的空气 (概念证明)。

1. VOC 渗透管的组成及扩散速率的测定
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2-丙醇渗透管的组成 注:为了避免污染, 在这个过程中戴上手套。 注意: 2-丙醇是易燃的, 是刺激性的。执行此程序远离任何明火。在处理 2-丙醇时戴上手套。请咨询 2-丙醇的 MSDS 以了解更多信息。<ol>
<li>测量和切割14厘米长的聚四氟乙烯油管。</li>
		<li>将2厘米长的聚四氟乙烯棒插入聚四氟乙烯管的末端, 然后用2厘米的金属卷曲覆盖, 将管子的一端封住并卷曲。</li>
		<li>将聚四氟乙烯油管, 拉杆和卷曲的压接工具, 然后将其放入一个副。转动副, 尽可能拧紧密封聚四氟乙烯管与卷曲。</li>
		<li>吸管进入开端的 PTFE 管的数量为2丙醇, 这样 PTFE 油管大约1/3 满 (大约 3-4 毫升)。</li>
		<li>重复 1.1.2-1.1.3 密封和卷曲渗透管的开口端;渗透源然后完成。</li>
	</ol>
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	<li>
渗透管内 VOC 扩散率的测定
	<ol>
<li>用校准的天平将渗透管称量到至少4个小数位, 同时注意重量和时间。</li>
		<li>从压缩空气供应 (理想的医疗级压缩空气或等效), 连接油管 (聚四氟乙烯管材, 直径1/8 英寸, 内径0.063 英寸) 到一个在线压力调节器。从调节器, 连接, 使用相同直径的聚四氟乙烯管, 到一个港口的 GL45 4 端口连接器, 拧到一个250毫升 GL45 玻璃瓶。封锁两个港口, 并连接一个长度的聚四氟乙烯油管到最后的端口, 并引导这个出口到通风罩。</li>
		<li>将渗透管定位到 GL45 玻璃瓶中, 并确保在流速为2.5 升-1的情况下, 有恒定的压缩空气蒸汽。或者, 将管放在系统的稀释室中, 如图1所示, 并在2.1 节中加以说明。</li>
		<li>在特定的时间间隔(每天) 重复重量测量 (1.2.1) 并重新放置回系统 (1.2.2)。如果使用平衡无法检测到重量减少, 请增加渗透管的称量时间间隔 (每周, 双周)。请注意, 这一校准过程, 取决于扩散率, 可能需要一段时间的几个月。</li>
		<li>在 x 轴和 y 轴上毫微克 (ng) 的质量损失图中, 以分钟为时间的扩散速率。在点之间画一条直线;使用直线方程 (y = mx + c), 确定直线的斜率 (m)。这是-1的渗透率。</li>
	</ol>
</li>
</ol>2. 光氧化反应
<ol><li>
在空白和光氧化反应中使用的设备的设置 (图 1)
	<ol>
<li>连接油管 (聚四氟乙烯管, 直径1/8 英寸, 内径0.063 英寸) 从压缩空气供应到一个在线压力调节器。由此, 连接一个水分陷阱, 以确保一个一致的低湿度进入安装。从这里, 连接聚四氟乙烯管到洗涤器, 进一步清洁压缩空气。</li>
		<li>从潮湿的陷阱或洗涤器, 连接, 使用相同直径的聚四氟乙烯管, 到一个玻璃瓶, 这将是稀释室, 将用于举行渗透管 (GL45, 500 毫升)。为确保气体紧密连接, 使用螺帽高效液相色谱, GL45 4 端口连接器, 完成硅胶密封: 封锁两个端口, 并将油管从洗涤器或潮湿陷阱连接到其他两个端口之一, 确保连接紧密。螺杆高效液相色谱 GL 45 螺钉盖上500毫升玻璃瓶。</li>
		<li>将聚四氟乙烯油管连接到最终端口或 HPCL GL45 螺钉盖, 然后将其连接到第二个 HPLC GL45 4 端口连接器。和2.1.2 一样, 封锁了两个港口。将该液相色谱 FG45 螺钉盖固定在玻璃瓶上 (GL 45, 250 毫升), 将用作反应室。</li>
		<li>将聚四氟乙烯油管连接到最终端口上的 HPLC GL45 螺钉盖上, 并由此将油管连接到 FAIMS 气体分析仪, 使用接头套管1/8 气密管件。确保气体分析仪的外部端口被引导到通风罩, 确保没有污染进入实验室工作区。</li>
		<li>将反应室定位为15厘米, 从紫外线灯 (如紫外线灯, 由 2 x 8 W 管灯组成, 其峰值光子发射波长为 356 nm)。 警告:紫外光对眼睛是危险的;确保灯和反应堆被金属屏蔽包围, 以避免暴露在光线下。</li>
	</ol>
</li>
	<li>
2-丙醇的光氧化
	<ol>
<li>将两个2丙醇渗透管组装前 (1.1) 的稀释室中所述设置。在反应室中放置催化剂 (e., 一种基于二氧化钛的毡, 尺寸55毫米 x 25 毫米 x 1 毫米), 并确保催化剂面对 UV 灯。打开压缩空气的流量, 调整流量为2.5 升最小-1, 压力为1巴。</li>
		<li>打开 FAIMS 仪器, 设置仪器, 使 2-丙醇的离子电流可见。使用为 FAIMS 设备配置的软件, 增加射频波形, 以便在 FAIMS 仪器产生的频谱上能看到不同的离子峰。</li>
		<li>使用为 FAIMS 设备配置的软件, 监视并记录从 FAIMS 产生的光谱上可见的不同离子峰的离子电流, 与在黑暗中的催化剂。峰值将是2丙醇和水。在设定的点 (在离开一夜之后), 打开紫外线灯, 并监测2丙醇和水离子电流的 FAIMS 频谱, 外加来自丙酮等中间挥发物的额外信号。使用系统软件, 增加或减少射频波形, 以确定从中间离子产生的新信号。 警告:确保在灯亮起之前, 紫外线和反应堆都被金属防护罩覆盖, 并且防护罩在整个 uv 光反应中存在。</li>
		<li>在设定的点 (e.4 小时后), 关闭紫外线灯, 并继续监测的 FAIMS 光谱2丙醇和额外的峰值。</li>
	</ol>
</li>
</ol>

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作者劳伦布朗和罗素巴黎是 Owlstone 纳米技术的雇员, 该公司制造 FAIMS 分析仪器, 这是本文所使用的。

该协议描述了一种有效的方法来确定氧化钛基催化剂的有效性, 通过确定其行为在降解的模型 VOC, 2-丙醇, 在紫外线照射下。使用 FAIMS, 2-丙醇的数量可以持续监测整个反应, 除了任何其他 VOC 产品, 可能会产生的反应, 在浓度可比室内空气。这种连续性质与气相色谱法有很大区别, 传统上用于监测光催化室内空气净化, 该方法采用间歇过程。通常需要一个昂贵的、敏感的 GC/MS 系统来确定低浓度的挥发性有机化合物的浓度, 而对光氧化产品的详细分析通常需要进一步处理光氧化产品, 如将产品吸附到活性炭上, 然后将其吸到质谱仪中。虽然质谱能够检测所有的产品, 但 FAIMS 的局限性在于, 只有具有高质子亲和性的产品才能被检测到。FAIMS 在测定低浓度有机化合物方面非常出色, 但能在较高浓度下饱和, 这就限制了系统对室内空气浓度的应用。FAIMS 的优点使系统在这里描述了一个有效的, 简单的工具, 可以提供洞察的光催化反应, 气相色谱是有限的实现。
在这里描述的 FAIMS 系统中, 医疗级空气被用作流动气体。由于 FAIMS 系统是如此敏感, 高质量的空气等级是至关重要的, 使光氧化的分析。这可以确保检测到的任何产品都来自于光氧化过程。同样, 确保没有泄漏到系统中是至关重要的, 因为实验室空气一般含有挥发性有机化合物, FAIMS 能够检测到浓度。为系统设置所列出的消耗品提供了一个可靠的系统, 并且在一段时间内连续监测表明, 当没有催化剂或渗透管时, 不存在可检测到的挥发性有机化合物。
虽然这个系统很简单, 但它也非常灵活--可以用这种方式测试替代的挥发性有机化合物, 简单地制造一个包含替代 VOC 的渗透浴缸, 如乙醇、丙酮或甲苯, 并遵循该协议。光催化反应经常受到湿度的影响。这里开发的系统在低湿气下运作;然而测试可以进行在更高的湿度购买引入加湿器进入系统。根据使用的 VOC, 它可以导致 FAIMS 的灵敏度降低, 但可以进行有效的测试。16
FAIMS 的持续性质突出了气相色谱的优势, 传统上用来确定光催化剂在净化空气中的有效性。16,17气相色谱法采用分批法收集和分析空气样品;FAIMS, 具有连续性的性质, 允许更详细地看光催化反应的动力学, 这可能是挑战解释与间歇气相色谱技术。简单的 FAIMS 是另一个优势。为了进行复杂分析的多挥发性有机化合物 FAIMS 是可以的, 气相色谱仪将需要链接到质谱仪, 这可能是昂贵的, 需要额外的处理。此外, 要用气相色谱仪进行长期反应, 需要昂贵的自动化系统, 或人工密集取样;FAIMS 的情况并非如此。
FAIMS 的持续性质提供了比气相色谱更大的优势, 可以用来获得更多的理解在这些 ppb 浓度的光催化过程。此外, 这里说明的简单设置是灵活的, 允许替代催化剂和挥发性有机化合物在可比条件下进行测试, 进一步提高了对光催化过程的理解。

最近, 室内空气质量已经走到了前列。也许令人惊讶的是, 室内空气中含有更多的挥发性有机碳 (voc), 而且浓度高于室外空气。1人们在室内花费了80% 的时间, 在诸如住宅、工作场所和交通包括汽车、火车和飞机等场所, 空气质量可能是一个真正的问题。许多室内空气中常见的挥发性有机化合物是诱变或致癌物质,2、3等, 因此去除这些物质是一个关键的优先事项, 特别是当 "病态建筑综合症" 现象会导致健康不良, 并通过下班时间失去生产。.1空气净化装置可以包括光催化剂, 半导体, 通常二氧化钛 (2), 用 UV 光激活, 通过光氧化过程降解 VOC。光催化是一个日益增长的研究领域, 其应用在水分裂氢生产和污染物降解4,5,6,7;空气净化是一个特别活跃的区域由于这个应用的商业可行性8。然而, 检测在室内空气中存在的浓度的挥发性有机化合物 (通常是 ppb) 是很有挑战性的。随着艾伦·欣谢尔动力学9的光催化反应动力学, 光催化剂在高浓度降解的挥发性有机化合物上的有效性并不代表其在低浓度下的有效性。在这里, 我们描述了一个通用的系统和协议, 以确定催化剂在低浓度的挥发性有机化合物的有效性, 使用场不对称的离子移动光谱学 (FAIMS), 说明这与2基于光催化剂和模型 VOC 2-丙醇。
电离气体流动, FAIMS 分离和辨认化学离子基于他们的机动性在一个变化的电场之下在大气压10,11,12。具有高质子亲和性的分子, 如挥发性有机化合物, 很适合被 FAIMS 分离和检测, 每亿 (ppb) 的分辨率和 ppb 浓度为13。能同时连续监测多挥发性有机化合物, 是光催化空气净化试验中的理想分析, 除了监测用作污染物的 VOC 外。FAIMS 还可以通过光催化反应检测出具有高质子亲和性的中间体或其他 VOC 产品, 这是证明光催化剂有效的关键要求, 因为如果降解不完全, 一些产生的挥发性有机化合物可能是有毒的或比降解的 VOC 更有毒。
FAIMS 最近才首次在光催化空气净化应用14, 虽然不建议 FAIMS 优于气相色谱, 它显然提供了一个多功能的替代品, 这有可能是一个强有力的研究空气净化的工具。在这里, 我们说明这一技术与一个协议, 涉及光氧化 2-丙醇与二氧化钛基光催化剂。在室内空气水平浓度渗透管中生成 2-丙醇, 使用15。由含有液体 VOC 的聚四氟乙烯管组成, 在两端密封和卷曲, 在恒定流量下, 密封聚四氟乙烯渗透管内的 VOC 以恒定速率扩散, 在与室内空气相媲美的浓度下。然后将此流传递到包含毛毡的反应室, 然后进入 FAIMS 分析仪, 在那里可以确定 VOC 的标识和量化。FAIMS 允许测定 2-丙醇的浓度, 并通过一个已知挥发性有机化合物的光谱库, 在像丙酮这样的光反应中产生的其他挥发性有机化合物的身份与图书馆的光谱进行了比较。这种技术的一个主要优点是它的灵活性: 通过简单地改变渗透管或催化剂, 可以测试替代挥发性有机化合物和催化剂。

<table><tbody><tr><td>PTFE Tubing</td><td>Sigma-Aldrich</td><td>58699 SUPELCO&amp;nbsp;</td><td>L x OD x ID 50 ft x 1/8 in x 0063 in</td></tr><tr><td>In-line pressure regulator</td><td>Sigma-Aldrich</td><td>23882 SUPELCO</td><td>High purity version (outlet pressure 0-100 psi, 1/8 in stainless steel fittings</td></tr><tr><td>Moisture trap</td><td>Sigma-Aldrich</td><td>N9301193</td><td>70 ml 1/8 fittings</td></tr><tr><td>Screw Cap HPLC, GL 45</td><td>VWR</td><td>554-3002</td><td>4 ports complete with silicone seals</td></tr><tr><td>Duran GL 45 Glass Bottle</td><td>Scientific Laboratory Supplies</td><td>BOT5206</td><td>250 ml&amp;nbsp;</td></tr><tr><td>Duran GL 45 Glass Bottle</td><td>Scientific Laboratory Supplies</td><td>BOT5208</td><td>500 ml</td></tr><tr><td>Permeation tube making kit</td><td>Owlstone Nanotechnology</td><td></td><td></td></tr><tr><td>2-propanol</td><td>Fisher Scientific</td><td>10477070</td><td>&amp;nbsp;Isopropanol, extra pure, SLR</td></tr><tr><td>Quartzel PCO Felt</td><td>Saint Gobain</td><td></td><td></td></tr><tr><td>UVIlite&amp;nbsp; Lamp</td><td>UVItec Limited</td><td>LI-208BL</td><td></td></tr><tr><td>Swage Fittings</td><td>Swagelok</td><td>SS-202-1 / SS-200-SET</td><td></td></tr><tr><td>Lonestar Portable Analyzer</td><td>Owlstone Nanotechnology</td><td></td><td></td></tr></tbody></table>

analyzing the photo-oxidation of 2-propanol at indoor air level concentrations using field asymmetric ion mobility spectrometry

我们展示了一个通用的协议, 用于确定催化剂在降解室内空气浓度 (ppb) 挥发性有机碳 (voc) 的有效性, 说明这与二氧化钛催化剂, 和 VOC 2 丙醇。该协议利用了场不对称离子迁移谱 (FAIMS), 该分析工具能够在 ppb 水平上连续识别和监测 2-丙醇和丙酮等挥发性有机化合物的浓度。FAIMS 的持续性质允许详细的动力学分析和长期反应, 提供了一个重要的优势比气相色谱, 一个批次过程传统上用于空气净化表征。FAIMS 在光催化空气净化中的应用最近才首次被使用, 并根据此处所示的协议, 在允许替代挥发性有机化合物和催化剂使用可比协议进行测试方面的灵活性提供了独特的系统阐明光催化空气净化反应在低浓度。

在2.2 中描述的光氧化反应过程中, FAIMS 气体分析仪连续产生离子电流与补偿电压的光谱, 利用稀释室中的两个2丙醇渗透管, 以及一种基于二氧化钛的毡反应室中的光催化剂。通常由 FAIMS 分析仪产生的光谱当毛毡在黑暗中时, 当毛毡被照亮时如图2a 所示。为了获得与 FAIMS 仪器的光谱, 仪器上的射频波形设置为最大值的64%。在这个射频波形值, 离子离子 (水团), 丙酮单体和 2-丙醇单体, 可以形成从 FAIMS 仪器电离过程达到检测器在 FAIMS 在不同的补偿电压 (cv), 所以被分离在光谱。通过 FAIMS 系统完全流动的单个气体可以用来确定每种气体16的光谱和补偿值。在频谱上,-2.15 V 的补偿电压峰值是离子离子, 当空气中的水分被电离时形成水团离子。峰值在-0.14 V 的 cv 是 2-丙醇14。离子电流与 2-丙醇浓度成正比, 利用扩散速率 (1.2) 可以确定 2-丙醇进入 FAIMS 的浓度。同样与丙酮, 发生在-1.44 v 的 cv 图2b 显示离子电流测量在指定的峰值为 2-丙醇和丙酮在光谱与 RF 波形在64% 最大, 作为时间的作用在整个光氧化协议2.2 节所述。由于流动和湿度的细微变化会对离子电流峰值 cv 值进行正面或负的改变, 因此使用 0.2 V 的 cv 值的峰值高度。
2-丙醇进入 FAIMS 分析仪, 随着时间的推移, 在黑暗中的反应室增加。当 2-丙醇进入稀释室时, 2-丙醇吸附在催化剂表面, 这说明最初的低量2丙醇进入 FAIMS。随着时间的推移, 更高的离子电流被记录下来, 表明有较高的2丙醇进入 FAIMS。这表明, 毡表面被2丙醇覆盖, 因此吸附在催化剂上正在减少。
当反应堆室被照亮, 2-丙醇进入 FAIMS 立即增加。这意味着2丙醇 desorbs 从表面的感觉, 并进入 FAIMS 分析仪。同时, 从 cv-1.44 V 的峰值中离子电流的增加, 以前被确定为丙酮, 表明在光照下的感觉有光氧化 2-丙醇到丙酮。随着时间的推移, 2-丙醇的数量下降到一个水平显着低于水平在最初的照明点, 和丙酮继续被检测, 与两个离子电流一致的时间约3小时。这意味着 2-丙醇一直是光氧化, 无论是丙酮, 或二氧化碳和水。2-丙醇吸附到表面, 是光氧化, 和产品脱附和进入 FAIMS, 其中丙酮被记录。当光被关闭后, 2 丙醇离子电流增加, 而丙酮离子电流减少意味着光氧化已经停止。
结果代表了 2-丙醇和丙酮的浓度, 连续监测 ppb 浓度。通过对比光照下的稳态 2-丙醇电流和 2-丙醇电流进入 FAIMS 前的光照, 可以看出催化剂的有效性, 在 2-丙醇的作用下, 进入 FAIMS 指示高级光催化剂。对其他挥发性有机化合物的监测也可以更好地评估光催化剂的有效性。在空气净化应用中, 理想情况下, VOC 应降解为二氧化碳和水。检测到的附加化合物表明催化剂无效或空气净化策略较差 (流速、光强度、湿度)。FAIMS 可以对光反应进行监测, 从而证明了催化剂和空气净化装置的有效性。
<img alt="Figure 1" src="/files/ftp_upload/54209/54209fig1.jpg"> 图1。反应堆安装.图解, 说明了用于 FAIMS 气体分析仪的光催化装置 (见 2.1)。<a href="https://jove.unicartagenaproxy.elogim.com/files/ftp_upload/54209/54209fig1large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<img alt="Figure 2" src="/files/ftp_upload/54209/54209fig2.jpg"> 图2。典型的结果.(a) 当含有毛毡的反应在暗 (灰线) 和被照亮 (绿线) 时, FAIMS 产生的典型光谱是射频波形最大值的64%。(b) 从 2-丙醇光氧化反应中产生的补偿电压 vs 离子电流谱显示峰值的离子电流的图, 当射频波形最大值为64% 时;2-丙醇 (红色线) 和丙酮 (蓝色线) 显示, 与被照亮的反应突出了。<a href="https://jove.unicartagenaproxy.elogim.com/files/ftp_upload/54209/54209fig2large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>

Watch this Scientific Journal Video about Analyzing the Photo-oxidation of 2-propanol at Indoor Air Level Concentrations Using Field Asymmetric Ion Mobility Spectrometry at JoVE.com

Analyzing the Photo-oxidation of 2-propanol at Indoor Air Level Concentrations Using Field Asymmetric Ion Mobility Spectrometry

本文介绍了一种测定催化剂在降解室内空气浓度 (ppb) 模型中挥发性有机碳 (如 2-丙醇) 中的有效性的协议。

用场不对称离子迁移光谱法分析 2-丙醇在室内空气浓度中的光氧化作用

We demonstrate a versatile protocol to be used for determining the effectiveness of photocatalysts in degrading indoor air concentration (ppb) volatile ...

analyzing-photo-oxidation-2-propanol-at-indoor-air-level

Universidad de Cartagena UDEC

Research

JoVE Journal

Chemistry

8.5K 次观看.  University of Cambridge. 本文介绍了一种测定催化剂在降解室内空气浓度 (ppb) 模型中挥发性有机碳 (如 2-丙醇) 中的有效性的协议。

视频: Analyzing the Photo-oxidation of 2-propanol at Indoor Air Level Concentrations Using Field Asymmetric Ion Mobility Spectrometry

Monitoring the Reductive and Oxidative Half-Reactions of a Flavin-Dependent Monooxygenase using Stopped-Flow Spectrophotometry

Aspergillus fumigatus siderophore A (SidA) is an FAD-containing monooxygenase that catalyzes the hydroxylation of ornithine in the biosynthesis of hydroxamate siderophores that are essential for virulence (e.g. ferricrocin or N',N",N'''-triacetylfusarinine C)1. The reaction catalyzed by SidA can be divided into reductive and oxidative half-reactions (Scheme 1). In the reductive half-reaction, the oxidized FAD bound to Af SidA, is reduced by NADPH2,3. In the oxidative half-reaction, the reduced cofactor reacts with molecular oxygen to form a C4a-hydroperoxyflavin intermediate, which transfers an oxygen atom to ornithine. Here, we describe a procedure to measure the rates and detect the different spectral forms of SidA using a stopped-flow instrument installed in an anaerobic glove box. In the stopped-flow instrument, small volumes of reactants are rapidly mixed, and after the flow is stopped by the stop syringe (Figure 1), the spectral changes of the solution placed in the observation cell are recorded over time. In the first part of the experiment, we show how we can use the stopped-flow instrument in single mode, where the anaerobic reduction of the flavin in Af SidA by NADPH is directly measured. We then use double mixing settings where Af SidA is first anaerobically reduced by NADPH for a designated period of time in an aging loop, and then reacted with molecular oxygen in the observation cell (Figure 1). In order to perform this experiment, anaerobic buffers are necessary because when only the reductive half-reaction is monitored, any oxygen in the solutions will react with the reduced flavin cofactor and form a C4a-hydroperoxyflavin intermediate that will ultimately decay back into the oxidized flavin. This would not allow the user to accurately measure rates of reduction since there would be complete turnover of the enzyme. When the oxidative half-reaction is being studied the enzyme must be reduced in the absence of oxygen so that just the steps between reduction and oxidation are observed. One of the buffers used in this experiment is oxygen saturated so that we can study the oxidative half-reaction at higher concentrations of oxygen. These are often the procedures carried out when studying either the reductive or oxidative half-reactions with flavin-containing monooxygenases. The time scale of the pre-steady-state experiments performed with the stopped-flow is milliseconds to seconds, which allow the determination of intrinsic rate constants and the detection and identification of intermediates in the reaction4. The procedures described here can be applied to other flavin-dependent monooxygenases.5,6

We describe the use of a stopped-flow instrument to investigate both the reductive and oxidative half-reactions of Aspergillus fumigatus siderophore A (SidA), a flavin-dependent monooxygenase. We then show the spectra corresponding to the species in the reaction of SidA and we calculate the rate constants for their formation.

监视依赖黄素单加氧酶和氧化还原半反应，用停流分光光度法

Aspergillus fumigatus siderophore A (SidA) is an FAD-containing monooxygenase that catalyzes the hydroxylation of ornithine in the biosynthesis of ...

科研

生物工程

Production and Measurement of Organic Particulate Matter in a Flow Tube Reactor

Organic particulate matter (PM) is increasingly recognized as important to the Earth's climate system as well as public health in urban regions, and the production of synthetic PM for laboratory studies have become a widespread necessity. Herein, experimental protocols demonstrate approaches to produce aerosolized organic PM by &#945;-pinene ozonolysis in a flow tube reactor. Methods are described for measuring the size distributions and morphology of the aerosol particles. The video demonstrates basic operations of the flow tube reactor and related instrumentation. The first part of the video shows the procedure for preparing gas-phase reactants, ozonolysis, and production of organic PM. The second part of the video shows the procedures for determining the properties of the produced particle population. The particle number-diameter distributions show different stages of particle growth, namely condensation, coagulation, or a combination of both, depending on reaction conditions. The particle morphology is characterized by an aerosol particle mass analyzer (APM) and a scanning electron microscope (SEM). The results confirm the existence of non-spherical particles that have grown from coagulation for specific reaction conditions. The experimental results also indicate that the flow tube reactor can be used to study the physical and chemical properties of organic PM for relatively high concentrations and short time frames.

This paper describes the operation procedure for the flow tube reactor and related data collection. It shows the protocols for setting the experiments, recording data and generating the number-diameter distribution as well as the particle mass information, which gives useful information about chemical and physical properties of the organic aerosols.

流管反应器中有机颗粒物的生产与测定

Organic particulate matter (PM) is increasingly recognized as important to the Earth's climate system as well as public health in urban regions, and the ...

环境科学

Production and Measurement of Organic Particulate Matter in the Harvard Environmental Chamber

The production and the evolution of atmospheric organic particulate matter (PM) are insufficiently understood for accurate simulations of atmospheric chemistry and climate. The complex production mechanisms and reaction pathways make this a challenging research topic. To address these issues, an environmental chamber, providing enough residence time and close-to-ambient concentrations of precursors for secondary organic materials, is needed. The Harvard Environmental Chamber (HEC) was built to serve this need, simulating the production of gas and particle phase species from volatile organic compounds (VOCs). The HEC has a volume of 4.7 m3 and a mean residence time of 3.4 h under typical operating conditions. It is operated as a completely mixed flow reactor (CMFR), providing the possibility of indefinite steady-state operation across days for sample collection and data analysis. The operation procedures are described in detail in this article. Several types of instrumentation are used to characterize the produced gas and particles. A High-Resolution Time-of-Fight Aerosol Mass Spectrometer (HR-ToF-AMS) is used to characterize particles. A Proton-Transfer-Reaction Mass Spectrometer (PTR-MS) is used for gaseous analysis. Example results are presented to show the use of the environmental chamber in a wide variety of applications related to the physicochemical properties and reaction mechanisms of organic atmospheric particulate matter.

This paper describes operation procedures for the Harvard Environmental Chamber (HEC) and related instrumentation for measuring gaseous and particle species. The environmental chamber is used to produce and study secondary organic species produced from the organic precursors, especially related to atmospheric organic particulate matter.

哈佛环境室内有机颗粒物的生产与测定

The production and the evolution of atmospheric organic particulate matter (PM) are insufficiently understood for accurate simulations of atmospheric ...

Original Experimental Approach for Assessing Transport Fuel Stability

The study of fuel oxidation stability is an important issue for the development of future fuels. Diesel and kerosene fuel systems have undergone several technological changes to fulfill environmental and economic requirements. These developments have resulted in increasingly severe operating conditions whose suitability for conventional and alternative fuels needs to be addressed. For example, fatty acid methyl esters (FAMEs) introduced as biodiesel are more prone to oxidation and may lead to deposit formation. Although several methods exist to evaluate fuel stability (induction period, peroxides, acids, and insolubles), no technique allows one to monitor the real-time oxidation mechanism and to measure the formation of oxidation intermediates that may lead to deposit formation. In this article, we developed an advanced oxidation procedure (AOP) based on two existing reactors. This procedure allows the simulation of different oxidation conditions and the monitoring of the oxidation progress by the means of macroscopic parameters, such as total acid number (TAN) and advanced analytical methods like gas chromatography coupled to mass spectrometry (GC-MS) and Fourier Transform Infrared - Attenuated Total Reflection (FTIR-ATR). We successfully applied AOP to gain an in-depth understanding of the oxidation kinetics of a model molecule (methyl oleate) and commercial diesel and biodiesel fuels. These developments represent a key strategy for fuel quality monitoring during logistics and on-board utilization.

Oxidation stability of transport fuels has become a concern for future fuel development. This work presents an original methodology developed by IFP Energies Nouvelles for assessing fuel stability using two different reactors. This methodology was successfully applied to gain an in-depth understanding of the oxidation kinetics and pathways of model molecules and commercial fuels.

评定运输燃料的稳定性原始实验方法

The study of fuel oxidation stability is an important issue for the development of future fuels. Diesel and kerosene fuel systems have undergone several ...

化学

Detection of 3-Nitrotyrosine in Atmospheric Environments via a High-performance Liquid Chromatography-electrochemical Detector System

3-nitrotyrosine (3-NT) is generated from the tyrosine residue in atmospheric bio-aerosol proteins via a reaction with ozone (O3) and nitrogen dioxide (NO2). Stable 3-NT is a specific marker for oxidative damage and is reported to have a promotive effect to elicit allergies. In the present study, we report the development of a highly sensitive assay to quantify 3-NT in air sampler filters to collect &#60; 2.5 &#181;m of particulate matter (PM2.5) from urban environmental air, including bio-aerosol. In this method, a 6 mm-diameter round hole was cut from the filters of air samplers and mixed with a nonspecific protease cocktail in order to hydrolyze proteins. Protein samples digested to the amino acid level were tested for 3-NT using a high-performance liquid chromatography-electrochemical detector (HPLC-ECD). The maximum 3-NT content was detected in a prefilter for PM of sizes from 4.5 to 7.3 &#956;m, with a detection limit of 1.13 pg/m3.

Detection of 3-Nitrotyrosine in Atmospheric Environments via a High-performance Liquid Chromatography-electrochemical Detector System

We present a method to detect 3-nitrotyrosine chemical modifications of atmospheric proteins with 6 mm-diameter rounds cut from air sampler prefilters using a high-performance liquid chromatography-electrochemical detector (HPLC-ECD).

利用高效液相色谱-电化学检测仪检测大气环境中的 3-硝基酪氨酸

3-nitrotyrosine (3-NT) is generated from the tyrosine residue in atmospheric bio-aerosol proteins via a reaction with ozone (O3) and nitrogen dioxide ...

Real-time Breath Analysis by Using Secondary Nanoelectrospray Ionization Coupled to High Resolution Mass Spectrometry

Exhaled volatile organic compounds (VOCs) have aroused considerable interest, since they can serve as biomarkers for disease diagnosis and environmental exposure in a non-invasive manner. In this work, we present a protocol to characterize the exhaled VOCs in real time by using secondary nanoelectrospray ionization coupled to high resolution mass spectrometry (Sec-nanoESI-HRMS). The homemade Sec-nanoESI source was readily set up based on a commercial nanoESI source. Hundreds of peaks were observed in the background-subtracted mass spectra of exhaled breath, and the mass accuracy values are -4.0-13.5 ppm and -20.3-1.3 ppm in the positive and negative ion detection modes, respectively. The peaks were assigned with accurate elemental composition according to the accurate mass and isotopic pattern. Less than 30 s is used for one exhalation measurement, and it takes approximately 7 min for six replicated measurements.

A protocol for characterizing chemical composition of exhaled breath in real time by using secondary nanoelectrospray ionization coupled to high resolution mass spectrometry is demonstrated.

利用二次 Nanoelectrospray 电离耦合高分辨质谱的实时呼吸分析

Exhaled volatile organic compounds (VOCs) have aroused considerable interest, since they can serve as biomarkers for disease diagnosis and environmental ...

Combustion Chemistry of Fuels: Quantitative Speciation Data Obtained from an Atmospheric High-temperature Flow Reactor with Coupled Molecular-beam Mass Spectrometer

This manuscript describes a high-temperature flow reactor experiment coupled to the powerful molecular beam mass spectrometry (MBMS) technique. This flexible tool offers a detailed observation of chemical gas-phase kinetics in reacting flows under well-controlled conditions. The vast range of operating conditions available in a laminar flow reactor enables access to extraordinary combustion applications that are typically not achievable by flame experiments. These include rich conditions at high temperatures relevant for gasification processes, the peroxy chemistry governing the low temperature oxidation regime or investigations of complex technical fuels. The presented setup allows measurements of quantitative speciation data for reaction model validation of combustion, gasification and pyrolysis processes, while enabling a systematic general understanding of the reaction chemistry. Validation of kinetic reaction models is generally performed by investigating combustion processes of pure compounds. The flow reactor has been enhanced to be suitable for technical fuels (e.g. multi-component mixtures like Jet A-1) to allow for phenomenological analysis of occurring combustion intermediates like soot precursors or pollutants. The controlled and comparable boundary conditions provided by the experimental design allow for predictions of pollutant formation tendencies. Cold reactants are fed premixed into the reactor that are highly diluted (in around 99 vol% in Ar) in order to suppress self-sustaining combustion reactions. The laminar flowing reactant mixture passes through a known temperature field, while the gas composition is determined at the reactors exhaust as a function of the oven temperature. The flow reactor is operated at atmospheric pressures with temperatures up to 1,800 K. The measurements themselves are performed by decreasing the temperature monotonically at a rate of -200 K/h. With the sensitive MBMS technique, detailed speciation data is acquired and quantified for almost all chemical species in the reactive process, including radical species.

An investigation of the oxidative combustion chemistry of novel biofuels, fuel components, or jet fuels by comparison of quantitative speciation data is presented. The data can be used for kinetic model validation and enables fuel assessment strategies.This manuscript describes the atmospheric high-temperature flow reactor and demonstrates its capabilities.

燃料燃烧化学: 用耦合分子束质谱仪从大气高温流反应器中获得的定量形态数据

This manuscript describes a high-temperature flow reactor experiment coupled to the powerful molecular beam mass spectrometry (MBMS) technique. This ...

Measurement of Ultrafast Vibrational Coherences in Polyatomic Radical Cations with Strong-Field Adiabatic Ionization

We present a pump-probe method for preparing vibrational coherences in polyatomic radical cations and probing their ultrafast dynamics. By shifting the wavelength of the strong-field ionizing pump pulse from the commonly used 800 nm into the near-infrared (1200-1600 nm), the contribution of adiabatic electron tunneling to the ionization process increases relative to multiphoton absorption. Adiabatic ionization results in predominant population of the ground electronic state of the ion upon electron removal, which effectively prepares a coherent vibrational state (&#34;wave packet&#34;) amenable to subsequent excitation. In our experiments, the coherent vibrational dynamics are probed with a weak-field 800 nm pulse and the time-dependent yields of dissociation products measured in a time-of-flight mass spectrometer. We present the measurements on the molecule dimethyl methylphosphonate (DMMP) to illustrate how using 1500 nm pulses for excitation enhances the amplitude of coherent oscillations in ion yields by a factor of 10 as compared to 800 nm pulses. This protocol may be implemented in existing pump-probe setups through the incorporation of an optical parametric amplifier (OPA) for wavelength conversion.

We present a protocol for probing ultrafast vibrational coherences in polyatomic radical cations that result in molecular dissociation.

强场绝热电离多原子自由基阳离子超快振动相干的测量

We present a pump-probe method for preparing vibrational coherences in polyatomic radical cations and probing their ultrafast dynamics. By shifting the ...

Enabling Real-Time Compensation in Fast Photochemical Oxidations of Proteins for the Determination of Protein Topography Changes

Fast photochemical oxidation of proteins (FPOP) is a mass spectrometry-based structural biology technique that probes the solvent-accessible surface area of proteins. This technique relies on the reaction of amino acid side chains with hydroxyl radicals freely diffusing in solution. FPOP generates these radicals in situ by laser photolysis of hydrogen peroxide, creating a burst of hydroxyl radicals that is depleted on the order of a microsecond. When these hydroxyl radicals react with a solvent-accessible amino acid side chain, the reaction products exhibit a mass shift that can be measured and quantified by mass spectrometry. Since the rate of reaction of an amino acid depends in part on the average solvent accessible surface of that amino acid, measured changes in the amount of oxidation of a given region of a protein can be directly correlated to changes in the solvent accessibility of that region between different conformations (e.g., ligand-bound versus ligand-free, monomer vs. aggregate, etc.) FPOP has been applied in a number of problems in biology, including protein-protein interactions, protein conformational changes, and protein-ligand binding. As the available concentration of hydroxyl radicals varies based on many experimental conditions in the FPOP experiment, it is important to monitor the effective radical dose to which the protein analyte is exposed. This monitoring is efficiently achieved by incorporating an inline dosimeter to measure the signal from the FPOP reaction, with laser fluence adjusted in real-time to achieve the desired amount of oxidation. With this compensation, changes in protein topography reflecting conformational changes, ligand-binding surfaces, and/or protein-protein interaction interfaces can be determined in heterogeneous samples using relatively low sample amounts.

Fast photochemical oxidation of proteins is an emerging technique for the structural characterization of proteins. Different solvent additives and ligands have varied hydroxyl radical scavenging properties. To compare the protein structure in different conditions, real-time compensation of hydroxyl radicals generated in the reaction is required to normalize reaction conditions.

实现蛋白质快速光化学氧化的实时补偿，用于确定蛋白质地形变化

Fast photochemical oxidation of proteins (FPOP) is a mass spectrometry-based structural biology technique that probes the solvent-accessible surface area ...

生物化学

Detection of Nitric Oxide and Superoxide Radical Anion by Electron Paramagnetic Resonance Spectroscopy from Cells using Spin Traps

Reactive nitrogen/oxygen species (ROS/RNS) at low concentrations play an important role in regulating cell function, signaling, and immune response but in unregulated concentrations are detrimental to cell viability1, 2. While living systems have evolved with endogenous and dietary antioxidant defense mechanisms to regulate ROS generation, ROS are produced continuously as natural by-products of normal metabolism of oxygen and can cause oxidative damage to biomolecules resulting in loss of protein function, DNA cleavage, or lipid peroxidation3, and ultimately to oxidative stress leading to cell injury or death4. 
Superoxide radical anion (O2&bull;-) is the major precursor of some of the most highly oxidizing species known to exist in biological systems such as peroxynitrite and hydroxyl radical. The generation of O2&bull;- signals the first sign of oxidative burst, and therefore, its detection and/or sequestration in biological systems is important. In this demonstration, O2&bull;- was generated from polymorphonuclear neutrophils (PMNs). Through chemotactic stimulation with phorbol-12-myristate-13-acetate (PMA), PMN generates O2&bull;- via activation of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase5. 
Nitric oxide (NO) synthase which comes in three isoforms, as inducible-, neuronal- and endothelial-NOS, or iNOS, nNOS or eNOS, respectively, catalyzes the conversion of L- arginine to L-citrulline, using NADPH to produce NO6. Here, we generated NO from endothelial cells. Under oxidative stress conditions, eNOS for example can switch from producing NO to O2&bull;- in a process called uncoupling, which is believed to be caused by oxidation of heme7 or the co-factor, tetrahydrobiopterin (BH4)8.
There are only few reliable methods for the detection of free radicals in biological systems but are limited by specificity and sensitivity. Spin trapping is commonly used for the identification of free radicals and involves the addition reaction of a radical to a spin trap forming a persistent spin adduct which can be detected by electron paramagnetic resonance (EPR) spectroscopy. The various radical adducts exhibit distinctive spectrum which can be used to identify the radicals being generated and can provide a wealth of information about the nature and kinetics of radical production9.
The cyclic nitrones, 5,5-dimethyl-pyrroline-N-oxide, DMPO10, the phosphoryl-substituted DEPMPO11, and the ester-substituted, EMPO12 and BMPO13, have been widely employed as spin traps--the latter spin traps exhibiting longer half-lives for O2&bull;- adduct. Iron (II)-N-methyl-D-glucamine dithiocarbamate, Fe(MGD)2 is commonly used to trap NO due to high rate of adduct formation and the high stability of the spin adduct14.

Electron paramagnetic resonance (EPR) spectroscopy was employed to detect nitric oxide from bovine aortic endothelial cells and superoxide radical anion from human neutrophils using iron (II)-N-methyl-D-glucamine dithiocarbamate, Fe(MGD)2 and 5,5-dimethyl-1-pyroroline-N-oxide, DMPO, respectively.

从细胞中一氧化氮和超氧负离子自由基的电子顺磁共振光谱的检测，使用自旋陷阱

Reactive nitrogen/oxygen species (ROS/RNS) at low concentrations play an important role in regulating cell function, signaling, and immune response but in ...