Why Industry Should Use Optical Flow Cells To Eliminate Delayed Sampling

With a real-time ‘virtual window’ into your processes, benefits multiply

Do you take process samples and make offline measurements with optically based instrumentation as part of your production method? If so, you have a lot to gain from installing inline optical flow cells in your process. Moving to online, real-time measurement eliminates the drawbacks of delayed sampling, provides greater transparency, and enables a more immediate response to changing process conditions.

The fact is — in a world of big data through the Internet of Things (IoT) — most industries can benefit from embracing this online approach. In essence, optical flow cells give you a virtual window into your processes.

Online measurements vs. offline sampling

The distinct difference between real-time analytical measurements and time-delayed manual sampling results in distinctly different outcomes. When issues cannot be immediately identified and addressed, it may affect product quality that requires rework to correct or, worse, lead to loss of valuable product.

Online fiber-optic-coupled process flow cells change that potentially damaging dynamic by facilitating the connection of real-time instruments in place of manual sampling and testing. Those offline measurement results can take place in real time using continuous online UV/VIS/NIR absorbance instrumentation instead.

Accumulated benefits of inline UV/VIS/NIR absorbance instrumentation

The benefits of using inline optical flow cells are quite obvious.

  • Cost savings: With real-time insights informing decisions, it creates a domino effect of cost savings in which improvements in one area are felt throughout the entire process. For example, when you eliminate the need to extract samples from the process for analysis (bear in mind some samples can be hazardous), you automatically also reduce the cost for disposal. Removing sample analysis time delays can speed up determination of process endpoints, increasing plant utilization capacity and reducing batch costs.
  • Product improvement: Inline optical cells can collect additional data for product improvement. Initiatives such as PAT (Process Analytical Technology) in the pharmaceutical industry can utilize optical flow cells to gather intelligence and information about the process that might be missed or overlooked when sampling. Samples may, for example, not pick up volatiles present in the line.
  • Robust design: With no electrical components on board, they are ideal in harsh process applications/installations while providing an optimal platform for reliable analytical measurements long-term.

Optical flow cell installation: The variables to consider

Optical flow cells, like any pipeline component, should be installed to suit the process line size and exhibit zero hold-up volume when in line. In systems where sharp peak detection is important (i.e. chromatography systems for fraction separation and collection), hold-up-volume creates internal dilution and blurs peak detection, resulting in lost- and potentially lower quality product.

How the process works in practice

A connected instrument transmits light via an optical fiber cable to one port of the inline flow cell. This light beam passes through a window and across the process stream to a second window where it returns via another optical fiber cable back to the instrument. Different optical path lengths are possible by installing the windows closer or further apart. For low-absorption applications requiring longer optical path lengths, you can utilize a “Z” cell with the process inlet and outlet offset from each other.

Optical flow cells are installed either directly in the process stream or in a “by-pass loop.” With “by-pass loop” installation, the user has the opportunity to isolate the process flow cell from the process cell for routine cleaning, servicing, or calibration.

The role of sapphire

Materials of construction must be compatible with the flowing process. In quality optical flow cells, sapphire windows are standard to ensure the highest level of process cell durability. Sapphire windows have high strength, exceptional abrasion resistance (second only to diamond), and strong resistance to corrosive process fluids. Various sapphire grades are available with high transmission characteristics for wavelengths up to 5 microns. For UV applications, UV grade sapphire should be used. Once sapphire is polished, it has a very low friction coefficient making it less susceptible to fouling from the process stream.

A word on compatibility

Compatibility with most fiber-optic-based photometric and spectroscopic instruments is achieved if industry standard SMA 905 connections are used on flow cells and, of course, when moving to a process environment, ruggedized fiber optic cables are recommended.

How can we help?

In partnership with Kemtrak, a Sweden-based producer of inline measuring instruments and automation solutions, South Fork Instruments offers the highest quality industrial process measurement cells.

The Kemtrak measurement cells are fiber-optic coupled and have no electrical/electronic components, moving parts, or sources of heat on board. In a variety of materials, they can be equally applied to benign and highly corrosive processes. Condensation on optical surfaces is not an issue and they are well suited for hazardous area operation. Disposable cells can be autoclaved/irradiated and are made from biotech-process-friendly materials.

Contact us to learn more how optical flow cells can benefit your operation.

3845 Buffalo Road
Auburn, CA 95602
Tel: (+1) 925-461-5059
Fax: (+1) 925 553 3531

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