An instrument for quantifying heterogeneous ice nucleation in multiwell plates using infrared emissions to detect freezing
An instrument for quantifying heterogeneous ice nucleation in multiwell plates using infrared emissions to detect freezing
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DOI：
10.5194/amt-11-5629-2018
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发表时间：
2018-10-15
影响因子：
3.8
通讯作者：
Murray, Benjamin J.
中科院分区：
文献类型：
--
作者：
Harrison, Alexander D.;Whale, Thomas F.;Murray, Benjamin J.
低浓度的冰成核粒子（INPs）被认为是重要的混合相云的属性，但他们的检测是具有挑战性的。因此，需要一种仪器，其中小于0.01 L-1的INP浓度可以常规和有效地确定。在液滴测定中使用较大体积的悬浮液增加了实验对更罕见的INPs或更罕见的活性位点的灵敏度，这是由于每个液滴的气溶胶或颗粒表面积增加。在这里，我们描述和描述的浸没粒子仪器（IR-NIPI），一个新的浸没冷冻检测，利用红外发射，以确定每个包含在一个96孔板的一个井中的单个50 μ L液滴的冷冻温度的红色成核。使用红外摄像机可以监测单个等分试样的温度。冻结温度通过检测与冻结引起的热量释放相关的井温急剧上升来确定。在本文中，我们首先提出了红外温度测量的校准，它利用了以下事实，即冰成核等分试样的水加热到冰-液体平衡温度（即0摄氏度时，水活度类似于1），这提供了一个点的校准每个实验中的每个单独的井。然后，我们使用类似于100 μ m的钾长石碎片测试温度校准，通过将这些碎片浸入在建立的冷台（μ L-NIPI）上的1 μ L液滴中以及IR-NIPI上的50 μ L液滴中;结果彼此一致，表明报告的冷冻温度没有偏差。此外，我们目前的测量效率的矿物粉尘NX-伊利石和空气中的气溶胶样品收集在利兹市的过滤器。NX-illite结果与文献数据一致，大气INP浓度与μ L-NIPI仪器的结果吻合良好。这证明了该方法的实用性，其提供了相对高的样品分析通量和获得低INP浓度。
Low concentrations of ice-nucleating particles (INPs) are thought to be important for the properties of mixed-phase clouds, but their detection is challenging. Hence, there is a need for instruments where INP concentrations of less than 0.01 L-1 can be routinely and efficiently determined. The use of larger volumes of suspension in drop assays increases the sensitivity of an experiment to rarer INPs or rarer active sites due to the increase in aerosol or surface area of particulates per droplet. Here we describe and characterise the InfraRed-Nucleation by Immersed Particles Instrument (IR-NIPI), a new immersion freezing assay that makes use of IR emissions to determine the freezing temperature of individual 50 mu L droplets each contained in a well of a 96-well plate. Using an IR camera allows the temperature of individual aliquots to be monitored. Freezing temperatures are determined by detecting the sharp rise in well temperature associated with the release of heat caused by freezing. In this paper we first present the calibration of the IR temperature measurement, which makes use of the fact that following ice nucleation aliquots of water warm to the ice-liquid equilibrium temperature (i.e. 0 degrees C when water activity is similar to 1), which provides a point of calibration for each individual well in each experiment. We then tested the temperature calibration using similar to 100 mu m chips of K-feldspar, by immersing these chips in 1 mu L droplets on an established cold stage ( mu L-NIPI) as well as in 50 mu L droplets on IR-NIPI; the results were consistent with one another, indicating no bias in the reported freezing temperature. In addition we present measurements of the efficiency of the mineral dust NX-illite and a sample of atmospheric aerosol collected on a filter in the city of Leeds. NX-illite results are consistent with literature data, and the atmospheric INP concentrations were in good agreement with the results from the mu L-NIPI instrument. This demonstrates the utility of this approach, which offers a relatively high throughput of sample analysis and access to low INP concentrations.