Pearl | liquid transmission analysis

The Pearl™ is a high specification liquid transmission accessory designed for laboratory spectroscopic sample analysis in the near and mid-infrared. The accessory contains Specac’s innovative Oyster Cell assembly which holds your sample in a horizontal plane. The design of the Pearl™ and Oyster Cell allows for fast and easy application of the sample, and for cleaning between samples with huge benefits to sample throughput.

Quick Enquiry

See all product options

Highly reproducible pathlength Pathlength reproducibility when disassembling and assembling a single Oyster Cell is within 1 μm. Change pathlengths in seconds by changing the bottom window. Spacer-free, defined pathlength liquid transmission cell ZnSe or CaF₂ windows. Wedged or Parallel window options with pathlengths from 25 to 1000 μm. Handles viscous materials with ease For viscous samples there is simply no better choice than the Pearl. Poor pathlength reproducibility, common to demountable cells, have been eliminated thanks to the innovative design. Easy cleaning between samples also makes this a great choice for anyone handling large volumes of samples.

Interchangeable FTIR transmission windows

The Pearl™ is fitted with an Oyster Cell containing either ZnSe or CaF₂ windows which can be interchanged in seconds. These Oyster Cells are available in six pathlengths, 25, 50, 100, 200, 500 and 1,000 μm. Pathlengths can be changed by simply swapping the bottom window for the required pathlength.

Repeatable pathlength

The Pearl™ has been designed to provide a more accurate pathlength than can be achieved when dismantling and reassembling a traditional liquid transmission accessory, with pathlengths repeatable to significantly less than 1 μm thanks to the innovative Oyster Cell.

Wedged or Parallel window options

The Oyster Cells bottom window can be supplied as either parallel or wedged (with respect to the top window). Parallel cells offer the ability to calculate the exact pathlength of the cell using the interference fringing method, although they can cause the appearance of a sinusoidal wave fringing pattern in your spectra when the refractive index of the material between the windows is different between sample and background spectra. Parallel cells work best when analysing an analyte dissolved in a solvent where a background spectrum can be obtained using the neat solvent. Wedged cells greatly reduce the fringing pattern allowing better quality spectra to be obtained when the refractive index of background and sample must be different, such as when analysing neat samples requiring an empty cell background. For wedged cells we offer a heptane pathlength calibration tool to provide an approximation of your cells pathlength (link: https://www.specac.com/en/resources/pathlength-calibration). The intensity of the interference fringing pattern is also dependent upon the refractive index, with higher refractive index materials resulting in a more pronounced pattern in your data. CaF₂ wedged cells offer the greatest spectral quality (in regards to fringing), although its spectral window is lesser than ZnSe. Window specifications and Chemical compatibility

Material	Range (cm^-1)	Refractive index
ZnSe	20,000 to 500	2.41
CaF₂	50,000-1,180	1.31

ZnSe is incompatible with acids and strong bases (recommended range pH 5.0-9.0). CaF₂ is generally resistant to acids, bases and water, although it is slightly soluble in nitric acid, and reacts with sulphuric acid to form hydrofluoric acid. The cell itself is made of corrosion resistant stainless steel, however this can be damaged by exposure to strong acids and bases or prolonged exposure to weak ones. Always confirm the compatibility of your sample and the cell materials before use.

Benefits of the Pearl over other liquid transmission cells

The simplicity of the Oyster Cell allows for quick and easy cleaning greatly increasing sample throughput. With a traditional cell the pathlength changes every time it is dismantled and reassembled which is eliminated by the innovative design of the Oyster Cell. Improper assembly, or over pressurisation caused by injecting a sample into the cell can cause a traditional cell to leak, which is eliminated thanks to the horizontal design of the Pearl and Oyster Cell system. For high throughput analysis of liquid samples there is simply no better choice. For very viscous samples that must be loaded into a disassembled cell, pathlength reproducibility is essentially impossible with a traditional cell. With the Oyster Cell this issue is a thing of the past; pathlengths are reproducible every time the Oyster Cell is assembled! For volatile samples the Oyster also features an injection port to offer maximum versatility.

Compatible with measurement standards

Method	Number
Determination of fatty acid methyl ester (FAME) content in middle distillates. Infrared spectrometry method	EN 14078
In-Service Oil Condition Monitoring standard practice	ASTM D7418
Phosphate Antiwear Additives in In-Service Petroleum and Hydrocarbon Based Lubricants by Trend Analysis	ASTM D7412
Monitoring of Oxidation in In-Service Petroleum and Hydrocarbon Based Lubricants	ASTM D7414
Sulfate By-Products in In-Service Petroleum and Hydrocarbon Based Lubricants	ASTM D7415
Nitration in In-Service Petroleum and Hydrocarbon Based Lubricants	ASTM D7624
Standard Practice for Condition Monitoring of In-Service Lubricants by Trend Analysis Using Fourier Transform Infrared (FT-IR) Spectrometry	ASTM E2412