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/uL) 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
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