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Advanced Materials in Mass Spectrometry Instruments

Thu, 06/17/2010 - 9:41am
Morgan Technical Ceramics

The global market for mass spectrometry, already surpassing $3 billion, is expected to grow by eight percent per year through the end of the decade, according to Spectroscopy Magazine and Instrument Business Outlook. The growth is fueled by continual advancements in technology, which have positioned mass spectrometry as a primary detection method in drug discovery and development, in pharmaceutical QA/QC, and in traditional mass spectrometry applications such as isotope dating and tracking in the geosciences, and trace gas analysis for helium-based leak detection. The evolving capability of measuring relative abundance has opened up considerable opportunities in the expanding field of quantitative proteomics.

Advanced Ceramic Components in Mass Spectrometers
Liquid chromatography/mass spectrometry (LC/MS), the largest segment of the hyphenated mass spectrometry market, has experienced especially rapid technological advancement and market growth. For the past two decades, LC/MS has been dramatically transformed by the advent of electrospray ionization (ESI) for which John Bennett Fenn received the 2002 Nobel Prize for Chemistry. The introduction of multimode ionization source devices significantly increased analysis throughput, by offering both positive and negative ionization modes and combining simultaneous ESI and atmospheric-pressure chemical ionization (APCI). Major performance enhancements have also been made inside the mass analyzer, with improvements to triple quadrupole and ion trap technology.

Quest for Higher Accuracy and Resolution

For more precise quantitative measurement, instrument suppliers have continually aimed for higher mass accuracy, increased mass resolution, and cleaner separation of standards and samples from background noise. The market has also sought instruments with higher throughput, reliability, and ease-of-use, as well as more compact equipment and lower purchase costs.

Meeting these goals depends not only on innovations in equipment design and analytical technique, but also on the utilization of high performance components incorporating advanced materials, such as ceramics, braze alloys, and engineered coatings.

These advanced materials serve important functions within all four of the fundamental components of a mass spectrometer, such as the sample introduction chamber, the ion source, the mass analyzer (also called a mass filter or mass separator), and the detector.

High Performance Ceramic Components

Among the most prevalent examples of advanced materials in mass spectrometry  instruments are the ceramic collars, supports, and spacers used to secure the rods and beam focusing lenses that sit within the “heart” of most mass analyzer systems, including quadrupole and time-of-flight designs. Morgan Technical Ceramics, a leading provider of ceramic supports for quadrupole rods and focusing lenses, utilizes high purity alumina ceramic with 99.5% aluminum oxide content.

These high purity alumina components provide a robust support that maintains precise positioning through a range of temperatures, due to the material’s excellent dimensional stability. Durable, stable supports are critical to an instrument’s enduring accuracy and reliability. By minimizing the need for recalibration, high performance supports for quadrupole rods and focusing lenses ensure ease-of-use and protect the instrument’s brand image.

The dense, non-porous, and high purity alumina is suitable for the high vacuum environment of the mass analyzer. This eliminates the risk of out-gassing and contamination that could potentially damage the instrument and distort the results.

Moreover, the electrical properties of the material, including a low dielectric constant and low loss tangent, provide excellent insulation, and prevent possible electrical interference that could cause the instrument to drift. The supports and spacers for these quadrupole rods and beam focusing lenses must be manufactured with a sufficiently smooth surface finish to thwart voltage arcs.

Alumina ceramic is not only employed for the collars, supports, and spacers that secure quadrupole rods, but it is also used for the rods themselves in high-end mass spectrometry equipment. Instruments with gold-plated ceramic rods enable the very high mechanical precision required to achieve high transmission and high resolution. High purity alumina cylindrical rods can be manufactured extremely straight and smooth. They are also able to maintain their shape better than solid metal rods, due to the high dimensional stability of the ceramic material.

Ceramic/Metal Assemblies

Several other critical mass spectrometry components are also composed of alumina ceramic, and these components are often joined to metal parts by brazing. For example, metal heating elements are brazed onto ceramic nebulizers and orifice plates, and a metalizing strip is brazed to the ceramic boats employed in gel electrophoresis mass spectrometry.

Brazing mass spectrometry components involves the use of carefully selected materials and processing techniques. For all mass spectrometry applications, a secure and durable bond is required. Some parts, such as the numerous electrical feedthrus, also require a durable hermetic seal to maintain the high vacuum environment.

The brazing of metal to ceramic is a marriage not only between two very different materials, but it also brings together two very different fields of materials science. Fortunately, within its portfolio of businesses, Morgan Technical Ceramics has Wesgo Metals, a manufacturer of a range of special braze alloys and associated products.

Morgan Technical Ceramics offers various grades of alumina ceramic that are fully compatible with the metalizing process they have developed, ensuring optimum bond strength and reliability. Using this method, they produce ceramic-to-metal assemblies, primarily high voltage feedthrus, with hermetic seals tested to 5x10-9 cc/sec.

In addition to a range of brazing alloys that can be used to bond to a metalized ceramic, Wesgo Metals has developed brazing alloys with an active ingredient that eliminates the need for the ceramic to be metalized. They provide an exceptionally strong bond with ceramic and allow more control over the geometry of the finished piece. This dimensional control is especially important for mass spectrometry components that require precise alignment and hermetic seals.

Engineered Coatings

Another area where materials science is improving the performance of mass spectrometry and related instruments is in the field of engineered coatings. For example, diamond-like carbon coatings (DLC), such as Diamonex DLC coatings from Morgan Technical Ceramics, are applied to the surface of gas and fluid metering valves used in high-performance liquid chromatography (HPLC) and gas chromatography.

The coatings are applied using plasma or ion beam chemical vapor deposition technologies, producing highly-dense, conformal coatings, with excellent adhesion. The DLC coatings provide excellent chemical resistance and dramatically reduce friction and wear. In doing so, they ensure precise and consistent metering, while also extending instrument lifetime and lowering torque requirements.

In Summary

The quality and performance of mass spectrometers and other scientific equipment depends, in part, on the quality of the materials that make up critical components. Morgan Technical Ceramics utilizes high purity alumina ceramic, known for its outstanding dimensional stability, to make supports for quadrupole rods and focusing lenses. Advances in material science will continue to play a key role in the evolution of laboratory instruments, enabling better performance, smaller equipment form factors, and higher reliability.

  

  

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