Demountable Liquid Cell

A Demountable Liquid Cell is a versatile FTIR sampling accessory built for liquid transmission spectroscopy, giving you clean, repeatable spectra while letting you tailor the setup to the sample in front of you. The Firebird Optics IR Demountable Cell Assembly is designed for labs that run a variety of chemistries and concentrations—where a fixed-pathlength cell is either too limiting, too hard to clean, or both. With a demountable design, you can disassemble the cell for thorough cleaning, swap windows as needed, and quickly reset the assembly for the next run.

Unlike sealed or permanent liquid cells, a demountable liquid cell is meant to be opened, serviced, and reconfigured. That makes it ideal for viscous liquids, sticky residues, reactive samples, or frequent sample changeovers. It’s a practical, long-term solution for routine QC and research workflows where uptime matters and contamination control is critical.

Key Features and Advantages

Adjustable lightpath (pathlength control)

The standout advantage of a demountable liquid cell is lightpath flexibility. The Firebird Optics assembly supports precision spacer pathlength options, allowing you to optimize absorbance for both concentrated and dilute samples. Shorter pathlengths help prevent saturated peaks in strongly absorbing samples, while longer pathlengths improve sensitivity for lower concentration liquids—so you can tune the setup instead of compromising the measurement.

Default window materials—and easy swaps

The Firebird Optics IR Demountable Cell Assembly includes default window material options of:

• Sodium Chloride (NaCl Windows)- 250nm-20µm

• Potassium Chloride (KCl Windows)- 210nm-20µm

• Potassium Bromide (KBr Windows)- 250nm-26µm

• Calcium Fluoride (CaF2 Windows)- 130nm-9.5µm

• Zinc Selenide (ZnSe Windows)- 1-14µm

These cover a wide range of common FTIR use cases—from disposable salt windows for general-purpose transmission work to more durable materials for tougher handling. And when your application demands something different, other optical window materials from Firebird Optics can be swapped in, as long as the windows are 32x3 mm and one is drilled and other is undrilled. This means you can match window chemistry and spectral range to your sample without changing the entire cell platform.

Designed for easy maintenance and cleaning

Because the cell is demountable, you can fully open it to clean residues that would otherwise be difficult to remove from sealed cells. This helps reduce carryover, keeps baseline performance stable, and extends the usable life of your windows and seals—especially in high-throughput environments.

FTIR-friendly, lab-ready hardware

This assembly is built for common FTIR sampling workflows, including syringe filling via Luer-Lok style fittings for faster, cleaner loading. The format is designed to integrate smoothly into standard FTIR setups, minimizing the friction of adopting a new sampling accessory.

Applications of a Demountable Liquid Cell

Demountable liquid cells are commonly used anywhere FTIR transmission data is needed with flexibility and repeatability, including:

• Routine QC identification of solvents, oils, and formulated liquids

• Quantitative FTIR measurements where controlling absorbance is essential

• Reaction monitoring and time-series measurements

• R&D and method development, especially when switching between sample types

• Difficult samples (high viscosity, low volatility, or residue-forming liquids) where cleaning access is a must

Choosing the Right Window Material for Your Sample

Window selection is a key part of getting reliable FTIR transmission data. The best choice depends on your spectral range, sample chemistry, and handling needs:

• If you want economical, commonly used FTIR transmission windows, NaCl, KCl, and KBr are popular choices.

• If you need something more durable, Sapphire is a strong option for handling and robustness.

• CaF₂ is widely used when you want broad transmission and good general compatibility.

• ZnSe is often chosen for durability and strong IR transmission performance in many workflows.

If you’re working with unusual chemistries or have a specific spectral requirement, you can swap in other Firebird Optics window materials—just keep the 32 x 3 mm requirement in mind for compatibility with this assembly.

Features at a Glance

• Variable pathlength liquid transmission cell

• Spacers to adjust lightpath from 15 microns to 1 mm

• Mounted on a 2 inch x 3 inch slide to fit standard FTIR slide holders

• (must select minimum of 1 plain and 1 drilled if ordering non-standing windows for this cell)

Assembling a Demountable Liquid Cell