How Single Reflection ATR Can Analyze Corrosive Liquids to Hard Solids

The Golden GateTM ATR system is the most adaptable IR accessory available. The system can be used to process any type of sample from hard solids, through to fine powders, and viscous or corrosive liquids.

To make sure accurate measurements are taken, samples are pushed at high pressure into a type IIIa diamond surface, which behaves as a single reflection ATR system. The diamond provides a high level of chemical and physical stability.

The system can be loaded with a wide range of different sample types, from corrosive liquids to single particles or fiber strands. The large stage of the instrument means macro sampling is also possible.

The diamond ATR crystal is bonded using a high temperature method, to a tungsten carbide mount. The strength of this bond allows the system to hold together under the pressures used to provide optical contact between hard samples and the diamond surface.

There is a quick lock and release system so the changing of samples can be carried out rapidly. In addition, an integrated pressure control system guarantees effective sample clamping and reliable results.

The Golden Gate’s high versatility means it can be used in a wide range of situations, including the analysis of ‘difficult’ samples such as hard samples, air sensitive samples and hazardous liquids. The system also provides a high enough level of accuracy to be used for the quality control of pharmaceuticals and for forensic analysis of fibers and paints.

The Internal Structure of the Golden GateTM

The internal structure of the Golden GateTM can be seen in the below diagram. The system’s diamond/tungsten-carbide top plate sits upon an optical unit, which contains beam condensing optics (either KRS-5 or ZnSe) and a series of mirrors, which direct a beam through the system as shown.

The symmetrical design of the system means it can be integrated with most FT-IR systems and, if required, the top plate for the system can be easily changed.

Using a Single Reflection Sample for Improved Results

The use of a diamond surface and a bridge clamping mechanism provides the Golden GateTM with optimum contact.

As the bridge is clamped (and the force on the sample increases) the amount of optical contact also increases. There is a critical amount of force at which the optimal optical contact is reached; following this, the system has reached maximum sensitivity, i.e. there will no further increase in absorbance intensity.

If a researcher were to use an instrument that could only apply a small amount of force the sensitivity would potentially be lower, as the point of maximum contact would be hard to reach. It is essential to reach the point of maximum contact to have a reproducible experiment. Additionally, systems that can only apply small forces show no sensitivity to sample property changes that occur when under pressure.

The high force loading system of the Golden GateTM means results are reproducible and as sensitive as physically possible.

Germanium Top Plates for Strong IR Absorbing Samples

For samples and applications that require more control over how the IR beam penetrates, such as the analysis of carbon black, a germanium top plate can be used. The plate consists of a 4 mm x 4 mm germanium crystal built into a rugged disc of stainless steel to provide structural integrity.

Germanium’s high refractive index provides a shallow penetration and significantly lowers band distortion, allowing materials that strongly absorb IR to be analyzed. The shallow depth also makes this ideal for the analysis of thin films and surface coatings.

As with the diamond surface, the germanium top plate can also be used to analyze corrosive liquids, forensic samples and micro to macro sample sizes.

Applications

  • Very strongly absorbing polymers and rubbers
  • Thin films on semiconductors and other substrates
  • Surface coatings
  • Macro and micro sample volumes
  • Corrosive liquids
  • Forensic science

Features

  • Full compatibility with Golden GateTM ATR series
  • 45o single reflection germanium crystal
  • 4 mm x 4 mm cement bonded stainless steel mount
  • Working range 5000-550 cm-1
  • High throughput
  • Pressures up to 2 kbar
  • Suitable to use with DTGS detectors
  • Good chemical resistance

Anvils for the Golden GateTM

Several different anvils are available for the Golden GateTM system, with each anvil being designed to work optimally for different types of sample.

Sapphire Anvil

An anvil designed to be used with most types of sample.  The anvil is self-leveling, for samples of irregular shape, is easily cleaned to prevent cross-contamination, and is very hard.

Stainless Steel Flat Anvil

Designed for use with fine wires or fibers. The anvil is intentionally not self-leveling, which helps make wire analysis accurate.

Narrow & Wide Grooved Anvils

Designed for research into wire coatings – the platform holds the wire exactly in the middle of the platform so the coating can be analyzed.

Reactive Sample Anvil

This anvil is designed for the analysis of samples that are reactive towards moisture or air. The samples are compressed in a dry box and sealed, allowing the sample to stay in an inert environment whilst measurements are taken.

Volatiles Cover

Used to prevent samples of high volatility from escaping via evaporation.

Concave Pellet Anvil

The pellet anvil’s concave design means pellets can be easily held in place during compression and measurement.

View-Thru Anvil

The View-Thru Anvil has been designed to allow researchers to view the sample using a 4x lens with an integrated reflective illuminator.

Flow-Thru Anvil

The Flow-Thru anvil is designed to function as either a flow cell or reaction chamber with 28 uL of volume. The flow cell seals around the diamond platform and can withstand 1000 psi of pressure.

This information has been sourced, reviewed and adapted from materials provided by Specac.

For more information on this source, please visit Specac.

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