A nebulizer design for inductively coupled plasma spectrometry

电感耦合等离子体发射光谱（ICP-OES）和质谱（ICP-MS）是无机分析化学中最重要的工具。在这些系统中，液体样品被雾化成小液滴并引入等离子体。为了正确操作，液滴尺寸应该小，最好小于5微米。大多数商用系统使用气动雾化器，它产生的液滴尺寸分布范围很广，主要在1-100微米的范围内。因此，在雾化器的下游增加了一个喷雾室以去除大液滴。然而，这导致只有一小部分（小于5%）的雾化样品实际上有助于测量信号。对于非常小的样本量，使用微型雾化器，它具有非常小的孔，可以产生小液滴，用于小样品的吸收。然而，这些系统很容易堵塞，特别是对于高粘度溶液和含有总溶解固体的溶液，这使得它们基本上不实用。****尽管有大量的研究和大量的出版物致力于液体样品的引入，但这个问题仍然是限制原子光谱法效率的原因。**我们提出了一种雾化液体样品的新方法，我们认为这将显著提高ICP系统的效率。所提出的方法是基于使用超声波雾化器与受控气体混合系统相结合来限制液滴碰撞和聚并。超声波雾化器可以设计成产生非常小的液滴（~ 5微米）。然而，在某些频率下液滴的大小也取决于液体的性质。本研究的一个目标是确定这种依赖于广泛的实际流体特性，并确定在相对较高的粘度（高达100 cP）下保持液滴尺寸较小所需的超声频率和振幅。本研究的另一个目标是研制一种混合室，将超声雾化器产生的高密度气溶胶快速分散，防止二次碰撞和聚结，从而导致液滴尺寸增大。＊＊＊＊

Inductively coupled plasma optical emission spectroscopy (ICP-OES) and mass spectrometry (ICP-MS) can be considered as the most important tools in inorganic analytical chemistry. In these system, a liquid sample is atomized into small droplets and introduced into a plasma. For a proper operation, the droplet sizes should be small, preferably less than 5 microns. Most commercially available systems use pneumatic nebulizers, which generate a broad range of droplet size distributions, mainly in the range of 1-100 microns. Therefore, a spray chambers is added downstream of the nebulizer to remove large droplets. This, however, results that only a small fraction (less than 5%) of the nebulized sample actually contributes to the measured signal. For very small sample sizes, micro-nebulizers are used, which have very small size orifices to generate small droplets for small sample uptakes. However, these systems are prone to blockage and clogging, in particular for high viscosity solutions and solutions containing total dissolved solid, making them basically impractical. ****Despite a significant amount of research and the high number of publications devoted to liquid sample introduction, this problem still persists to be what limits the efficiency of atomic spectrometry.**We are proposing a novel method for the nebulization of liquid samples, which we believe would significantly improve the efficiency of ICP systems. The proposed method is based on using an ultrasound nebulizer in combination with a controlled gas mixing system to limit the droplet collision and coalescence. Ultrasound nebulizers can be designed to generate very small droplets (~ 5micorns). However, the droplet sizes at certain frequencies also depends on the liquid properties. One objective of the present research is to determine this dependency for a wide range of practical fluid properties, and determine the ultrasound frequency and amplitude needed to keep the droplet sizes small for a relatively higher viscosities (up to 100 cP). Another objective of the present research is to develop a mixing chamber to rapidly disperse the high density aerosol that is generated by the ultrasound nebulizer in order to prevent secondary collision and coalescence, which may result in an increase in droplet sizes. ****