Liquid Waveguide Capillary Cell, 500 cm pathlength

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Long pathlengths for small sample volumes

  • 500 cm pathlength, 1250 µL Internal Sample Volume
  • 50–500 fold sensitivity improvement in comparison to 1cm cuvette
  • 0.55 mm ID for low sample volume sampling
  • 2 mm ID for unfiltered liquid samples
  • SMA 905 fiber optic connections
  • Wavelength Range: 280-730nm

Click here to view the current Data Sheet
For more information or help choosing an appropriate flow cell, see the LWCC Details page.


  • Adapts to most fiber optic detection systems
  • 20 years of manufacturing experience
  • Low UV drift


  • Trace detection of nutrients (nitrite, nitrate, phosphate, iron) in seawater
  • Environmental and oceanographic monitoring
  • Drinking water analysis
  • Colored dissolved organic matter (CDOM)
  • Process control

UV/VIS/NIR absorbance spectroscopy is governed by Beer’s Law, where the absorbance signal is proportional to chemical concentration, light path length and the compound’s specific molar absorption coefficient. Typical optical pathlengths of cuvettes and flow cells are between 0.2cm and 10 cm. Longer pathlengths are difficult to achieve due to mechanical constraints. Liquid Waveguide Capillary Cells (LWCCs) fill this gap. LWCCs are fiber optic flow cells that combine an increased optical pathlength (10–500 cm) with small sample volumes ranging from 2.4 µL to about 3mL. Compared with a standard 1cm cell, a 1 mAU signal is enhanced one hundred fold with a 100 cm flowcell to 100 mAU, using WPI’s patented aqueous waveguide technology.* They can be connected via optical fibers to a spectrophotometer with fiber optic capabilities. Ultra-sensitive absorbance measurements can be performed in the ultraviolet (UV), visible (VIS) and near-infrared (NIR) to detect low sample concentrations in a laboratory or process control environment.

Your sample is the core of a light guide

WPI’s Liquid Waveguide Capillary Cells are made of fused silica tubing with an outer coating of a low refractive index polymer. Your liquid sample is guided through the capillary and represents the core of the waveguide. The hydrophilic character of the fused silica capillary inner wall results in high signal stability and easy removal of air bubbles trapped in the flow cell. However, the transmission of the LWCC is mainly dependent on the intrinsic attenuation of the sample liquid. In case of water, a usable wavelength range from 250 nm to 720 nm wavelength can be observed in a 100 cm pathlength LWCC. Using a 500 cm pathlength LWCC will reduce that transmission range from 300 nm to about 700 nm. However, when switching from water to methanol as a solvent, transmission into the NIR are possible with suitable light sources and detectors.


The LWCC-3xxx series of flow cells uses traditional HPLC type 10-32 coned port fittings with 1/32 inch tubing for liquid connection and 500 µm SMA fiber optic adapters for light input and output. The LWCC-4xxx series of flow cells uses 1/4-28 flangless flat bottom fittings with 0.125" tubing 500 µm SMA fiber optic adapters. Liquid can be pumped into the flow cells using (in the simplest case) a sample injector (58006) and a ministar peristaltic pump (MINISTAR). The LWCC may be connected directly to a fluid injection analysis (FIA) system or to a gas segmented fluid injection analysis (GFIA) system via a debubbler. Finally, for routing discrete measurements, WPI’s LWCC Injection system (89372) may be used when the sample is injected into a constant flow via an injection loop of 3–4 times the internal flow cell volume to ensure a stable baseline and avoid the introduction of micro air bubbles into the flow cell.


WPI’s LEDSpec detection system can be used for monochromatic light detection. For example, you may use it for nitrite analysis at 540 nm with up to four (4) LWCCs per instrument. When the entire spectral shape of an absorbance curve is required for analysis, WPI’s TIDAS E Base spectrometer with a D4H or a FO-6000, or the TIDAS S300 spectrophotometer can be used. LWCCs have been used in a variety of applications, such as liquid chromatography, stopped-flow and colormetric detection, drinking water analysis, as well as environmental and oceanographic monitoring systems. Accessory: LWCC Injection System For flow analysis, including simple fluid injection analysis (FIA) setups, add WPI’s LWCC injection system (89372). A selection valve provides baseline or cleaning solutions to the sample stream. The injection valve injects a sample into the stream, avoiding the introduction of air bubbles or changes of flow rate.

Related Patents

Micro Chemical Analysis Employing Flow Through Detectors, 1995, U.S. Patent No. 5,444,807.

Aqueous Fluid Core Waveguide, 1996, U.S. Patent No. 5,507,447.

Long Capillary Waveguide Raman Cell, 1997, U.S. Patent No. 5,604,587.

Chemical Sensing Techniques Employing Liquid-Core Optical Fibers, U.S. Patent No. 6,016,372


These spectra show the optimal detection limits for LWCCs of varying pathlength. 

  LWCC-3050 LWCC-3100 LWCC-3250 LWCC-3500  LWCC-4010 LWCC-4050 LWCC-4100
Optical Pathlength  50 cm  100 cm  250 cm  500 cm 10 cm 50 cm 100 cm
Internal Volume  125 µL  250 µL  625 µL  1250 µL 0.31 mL 1.57 mL 3.1 mL
Fiber Connection  500 µm SMA 600µm SMA
Transmission @254nm*  20  10  5  - 4 3 2
Transmission @540nm*  35  30  25  20 5 4 3
Noise [mAU]**  <0.1  <0.2  <0.1  <1.0 <0.1 <0.2 <0.5
Maximum Pressure  100 PSI
Wetted Material  PEEK, Fused Silica, PTFE
Liquid Input  Standard 10-32 Coned Port Fitting

* Referenced using coupled 500µm fibers        
** Measured using ASTM E685-93            
*** A one-meter waveguide of 550µm internal diameter requires approximately 1.5PSI for water flow of 1.0mL/min.


When comparing light throughput versus wavelength of three fiber optic cables, the greater the diameter of the cable, the better the LWCC performance up to 500µm which is the input diameter of the SMA connector.

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