IR5 Detector

IR5 Detector

IR5 Detector Overview


The IR5 is a high-performance Infrared (IR) detector designed to determine on-line concentration and composition, through the continuous monitoring of absorbance at several selected wavelengths simultaneously.

It incorporates a high-temperature flow-through cell and interference filters at five different wavelengths.

Integrated into Polymer Char’s GPC-IR, CEF/TGIC, CFC or SGIC 2D instruments for the analysis of Polyolefins, it is an ideal combination since it provides excellent sensitivity and outstanding long term baseline stability in all absorbance channels, including total CH (concentration) as well as methyl and methylene used for chemical composition determination (comonomer content or short chain branching).

The high-sensitivity and extremely low noise of the IR5 detector results in the ability to discriminate differences of even 1 short-chain branch per 1,000 atoms of carbon. Therefore, this detector is especially suitable for the most demanding applications such as the determination of short-chain branching distribution along MMD of HPDE pipe grade resins.

2-dimensional separation techniques (CFC cross-fractionation TREFxGPC and SGIC 2D) also benefit from the high sensitivity of IR5, which allows detection of even minute polymer fractions, and also their identification by chemical composition.


Other Infrared detectors available are IR4 and IR6. Their capabilities vary from one another, so the choice of IR detector will depend on the types of samples to analyze: comparison of Infrared detectors (IR4, IR5, and IR6)


The technology used in Polymer Char’s infrared detection is patented. 


IR5 Detector Features

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High-performance detection in high-temperature solution techniques for polyolefin characterization: GPC-IR, GPC QC, CEF/TGIC, CFC, SGIC 2D

Outstanding baseline stability

Short stabilization time after flow rate change or oven temperature variation and outstanding baseline stability ideal for GPC application.

Spurious injection peaks usually seen in DRI do not appear in IR. The baseline is very clean before and after the sample peak which helps in a more precise definition of baseline and integration range. Therefore, consistent values of Mw and Mn are obtained.

Short Chain Branching along the MMD

Independent absorbance channels for methyl and methylene groups allow the detection of short-chain branching and variation along the MMD in LLDPE, HDPE, and others. Sensitivity as low as 1 methyl group per thousand carbons allows detection and quantification of small amounts of short-chain branching added to the high molar mass fraction of pipe grade bimodal high-density polyethylene (biHDPE).

Very high sensitivity

The superb IR5 detector sensitivity allows reducing the injected mass, by a factor of 10 or more. Required for analysis of highly viscous samples and UHMWPE

Uniform response to concentration of polyolefin homopolymers and copolymers

The "total CH" absorbance channel in the IR5 detector provides a universal concentration signal for all kinds of polyolefins. The same response is observed for homopolymer polypropylene, homopolymer polyethylene as seen in the graph, as well as for copolymers. Figure from: A. Ortín, J. Montesinos, E. López, P. del Hierro, B. Monrabal, J.R. Torres Lapasió, M.C. García Álvarez-Coque Macromolecular Symposia, 330 (2013) 63–80

Potential applications to other types of polymers such as polycarbonate, styrene-butadiene copolymers, epoxy resins, PET or PBT. Standard and custom filters in the range 2.5 to 5 microns allow the detection of absorbance for different chemical groups. A solvent transparent in that spectral region must be used.

Simple calibration and processing

IR band ratio (methyl over methylene absorbance) is calibrated to SCB or methyl groups frequency, using a reduced number of standards (4-5 calibration points are typically used). Therefore, if a change in response is detected, recalibration is easily performed.

A high-performance semiconductive alloy detector, optimized for the highest sensitivity in the CH stretching band of the MID-IR is at the core of the IR5. The operation of this sensitive element below zero degrees is achieved by thermoelectric cooling and an efficient heat evacuation design, which removes the need for using liquid nitrogen as a coolant. Stable optimum operation conditions are maintained on the detector with convenience without interruptions or drifts due to cooling fluid refills.

Frequently Asked Questions about the IR5 Detector

IR5 is an infrared detector with a heated flow-through cell, which uses the principle of infrared absorption spectroscopy at fixed wavelengths, through the use of interference filters, to measure the concentration and composition in polymer solutions.

The continuous signals at different bands in the MID-IR from the multiple filter system included in the detector are provided in real-time, allowing very simple processing and fast analysis applications as high-throughput GPC, and 2-dimensional chromatography.

No, it doesn’t. All the components of the detector were intended for a very robust and simple equipment; that is why thermoelectric cooled detectors were included, avoiding the use of liquid nitrogen.

Any solvent which is transparent in the band of interest and compatible with the detector cell materials: stainless steel, sapphire, and Teflon, etc.
1,2,4-Trichlorobenzene (TCB), or ortho-dichlorobenzene are typically used.

IR5 is a very sensitive and stable detector for polyolefin concentration so it is used advantageously as main detector in separation techniques when high sensitivity is required.
As chemical composition detector it is used to quantify the methyl frequency (CH3/1000TC) with very good resolution, after proper calibration.
Main application is found in high temperature GPC providing molar mass distribution and short chain branching or comonomer content simultaneously, for all types of polyethylene and propylene, including HDPE with low levels of short chain branching as well as high to ultrahigh polyethylene.
2-dimensional chromatography (SGIC 2D) and analytical cross-fractionation (CFC) also benefit from the high sensitivity of IR5 for detection of even the smallest fractions.
Other applications of IR5 are CEF/TREF and TGIC, and in general any solution analytical technique in polyolefin.

IR4 is the optoelectronic standard detector for most applications. It is provided with two measuring elements. The IR4 is a very robust detector for concentration measurement in GPC, TREF, CRYSTAF, etc. It also provides the possibility to measure composition (methyls per 1000 carbons or level of carbonyls, acetate, acrylate…) in copolymers.

The IR5 is the most sensitive detector by using a specially designed thermoelectrically cooled sensing element. It can incorporate up to 5 wavelengths measurement and it provides a superior stability and sensitivity in the GPC analysis of Polyolefins. It is being used in most demanding applications such as the analysis of very low levels of branching (methyls) in HDPE pipe resins, as well as main detector in 2-dimensional separation techniques (CFC, SGIC 2D).

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