NEWS internal capillary. This process often produces a sample capillary with varying inner diameter, an increase in the porosity of the glass, and harmonic vibrations from the flow of argon, all of which degrade performance and lifetime of the nebulizer. A diagram comparing a Glass Expansion nebulizer (A) to other manufacturers (B) is shown in Figure 2. Figure 1. Glass Expansion glass concentric nebulizer design Figure 1A. Constant bore heavy stock glass Figure 1B. Machined aerodynamic exterior Figure 1C. VitriCone machined capillary Figure 2. Comparison of nebulizer designs Figure 2A. Glass Expansion Figure 2B. Other brands The benefits of the VitriCone construction are: • The sample channel is guaranteed a constant internal diameter and resistant to clogging. • The rugged precision-machined capillary resists vibration producing the best possible analytical precision. • The industry’s tightest tolerances ensure that each nebulizer will perform to the same high standards as the previous one. Glass Expansion’s U-Series nebulizer design has an extra advantage for those who are conducting single cell analysis by Mass Cytometry. Combining a U-Series nebulizer with Glass Expansion’s LC Fittings Kit (P/N FT-16-8), allows for the nebulizer to be quickly and easily directly connected to the syringe or pneumatic driven sample introduction system with a zero dead volume connection. Mass Cytometry Instrument Overview The mass cytometer consists of five components including sample introduction, the inductively coupled plasma (ICP) ion source, ion optics, time-of-flight (TOF) analyzer, and detector. The liquid cell suspension sample (1 x 103 cells/mL) is introduced to the nebulizer at a flow rate of 30-45 μL/min and aerosolized into fine single-cell droplets using a nebulizer gas flow of 0.15 to 0.25 L/min argon. A makeup gas of 0.7 to 0.9 L/min argon is used to optimize the ICP conditions independently of the nebulizer gas to ensure appropriate aerosol flow through the plasma and maintain the integrity of individual cells. The single-cell droplets then pass through a singlepass spray chamber which is heated to a temperature of 200°C, resulting in the evaporation of the remaining water within the cells before entering the ICP. Once the single-cells with the specific isotope-tagged antibodies enter the ICP they are atomized, excited and ionized to form an ion cloud. The ion cloud is extracted through a three-aperture plasma– vacuum interface to produce a transient signal with a typical half width of 200μs. After the ions enter the interface, they pass through a high pass optic that transmits ions >80 amu which are then directed toward the time of flight (TOF) analyzer, where they are separated according to their mass-to-charge ratio. The signal from the detector is digitized by an analog-to-digital converter (ADC) and the data is converted to mass and integrated signal intensity (cps). The mass spectra are recorded in 13μs intervals, and the data is exported to a standard flow cytometry data format. Because of the size and complexity of the data collected, several data mining techniques have been applied to mass cytometry datasets. As with traditional ICP-MS instruments, signal drift occurs over time because of several different factors including a buildup of sample material on the interface cones such that daily maintenance is critical. Signal drift compensation in Mass Cytometry uses a single particle-based analog of internal standardization. Samples are spiked with metal-encoded polymer beads that contain a known concentration of cerium, europium, holmium, and lutetium. The beads allow normalization within a run, between different runs on the same instrument, and provides a direct comparison between different instruments and different laboratories. Mass Cytometry Sample Introduction Introducing cells into a Mass cytometer without compromising cell integrity continues to be a major challenge and an active research goal of the ICP atomic spectrometry community(8-11). However, knowledge gained from understanding the fundamentals of aerosol generation and transport into the inductively coupled plasma has led to significant advances in sample introduction which make single-cell analysis a more reliable and routine measurement technique(12-14). These improvements include the combination of high efficiency low flow rate nebulizers with heated single pass spray chambers. Prototype MicroMist Nebulizer Glass Expansion is well known for high quality nebulizer designs and precision manufacturing. Unique to all Glass Expansion glass concentric nebulizers is the trademark VitriCone™ sample channel. The VitriCone sample channel (Figure 1) is created by machining constant bore heavy stock glass tubing (Figure 1A) to create the desired aerodynamic exterior (Figure 2A) while maintaining a consistent internal diameter. Other nebulizer manufacturers heat and draw a thin fragile capillary from glass tubing to create the www.geicp.com Glass Expansion Newsletter | Issue 41 2
GE Newsletter October 2016
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