The Near-infrared region is normally considered to cover the wavelength range from 750 nm to 2500 nm, and Starna have developed reference materials for absorbance and wavelength qualification in this region. A new, NIST traceable polystyrene reference has also been developed for the Mid-infrared that is also suitable for qualifying Attenuated Total Reflectance (ATR) measurements

Absorbance  References

Metal-on-Quartz Neutral Density Filters (250 - 3200 nm) 

absorbance qualification in the ultra-violet, visible and near-infrared regions of the spectrum (250 nm to 3200 nm) 

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NIR Neutral Density Filters (800 nm to 3200 nm) 

absorbance accuracy and linearity over the wavelength range 800 nm - 3200 nm.
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Wavelength References

NIR Wavelength Reference Solution Reference (900 – 2600 nm)

wavelength qualification in the Near Infrared 
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NIR Transflectance Reference (900 – 2600 nm)    

wavelength qualification of near infrared reflectance spectrophotometers.
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Near-and Mid-infrared Polystyrene References 
(1.1µm to 18.5µm, 9000 cm-1 to 540 cm-1)

NIST traceable wavelength references, also accepted by some pharmacopoeias as a wavelength and resolution reference. Versions available for ATR measurements.
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Starna wide-range wavelength reference (335 nm to 1945 nm)

20 peaks for wavelength calibration from UV to NIR
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Some references used in the visible region have useful peaks in the NIR and are included here for information:

Didymium Glass Filter (430 nm to 890 nm)

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Didymium Oxide Solution (290 – 870 nm)  

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These Reference Materials can be used to qualify Mid IR - FTIR spectrophotometers for wavelength accuracy over an operating range of 540 cm-1 to 9000 cm-1  (1.1 µm to 18.5 µm). One version of the product can also be used to qualify the resolution of a Mid IR instrument as required by some pharmacopoeias and for the wavelength qualification of ATR (Attenuated Total Reflectance) measurements in the Mid-IR. Another version has additional certified peaks in the NIR region.

Description and Discussion

Mid IR (540 – 3125 cm-1, 3.2 – 18.5 µm): Starna reference RM-1921/38 consists of a 38µm polystyrene film mounted in a card holder.

14 certified peaks (arrowed in spectrum below) are available for wavelength qualification purposes. The calibration values are traceable to NIST SRM 1921b

539 842 907 1028 1069 1155 1583








The absorption minima and maxima at A and B, C and D can be used to qualify resolution according to pharmacopoeia requirements (EP/JP).

Typical spectra



Note: Pharmacopoeia compliance

Using this reference material, a MIR spectrophotometer may be judged to be pharmacopoeia compliant for the certified parameters if the following criteria are met:

European Pharmacopoeia compliance

The difference between the absorption minima at 2870 cm-1 and the maxima at 2849.5 cm-1 is greater than 0.3 (absorbance) and the difference between the absorption minima at 1589 cm-1 and the maxima at 1583 cm-1 is greater than 0.08 (absorbance). The latest revision of EP 2.2.24 cites the use of 38 µm polystyrene for the wavelength qualification of ATR (Attenuated Total Reflectance) instruments in the Mid-IR region.

Japanese Pharmacopoeia compliance

The depth of the trough from the maximum absorption at about 2850 cm-1 to the minimum at about 2870 cm-1 is not less than 18% transmittance and that from the maximum at about 1583 cm-1 to the minimum at about 1589 cm-1 is not less than 12% transmittance.

US Pharmacopeia compliance

A wavenumber tolerance of +/- 1.0 cm-1 is allowed on the position of the following 3082.21 bands; 3060.0, 2849.5, 1942.9, 1601.2, 1583.0, 1154.5 and 1028.3 cm-1.

TGA Australia compliance

TGA allows the use of either BP/EP or USP as appropriate.


ATR (Attenuated Total Reflectance) references: Two versions of Starna reference RM-1921/38 are designed for use in ATR instrumentation. Available in disc (25mm dia.) or strip (9 x 3 cm) formats

Near IR (1.1 - 3.3 µm, 3000 – 9000 cm-1): An alternative reference material, RM-1921/65, in addition to the 14 peaks in the MIR, has additional peaks on the NIR suitable for wavelength qualification. 

Eight peaks (arrowed in the spectrum below) are available for wavelength qualification purposes. The calibration values are traceable to NIST SRM 2065.

Approximate wavelength values are:

cm-1 3064 3647 4039 4250 4335 4608 5952 8749
nm 3264 2742 2476 2353 2307 2170 1680 1143

Note: The values given in this data sheet are for guidance only. Because the absorption bands are asymmetric, measured values will be spectral bandwidth dependent. The Calibration Certificate accompanying each Starna Mid IR-FTIR Reference gives actual values measured at a bandwidth of 1.00 cm-1, and only these certified values should be used for instrument qualification. Values for the NIR Reference are measured at a resolution of 0.4 nm. On request, Starna can provide certified values at other bandwidths. 


Catalogue Number

  Catalogue  Number
Starna Mid IR-FTIR Polystyrene Reference, 38 µm RM-1921/38       
Starna Mid IR-FTIR/NIR Polystyrene Reference, 65 µm RM-1921/65       
Starna Mid IR-FTIR Polystyrene Reference for ATR, 38 µm  RM-1921/38/ATR       

Starna Mid IR-FTIR Polystyrene Reference for ATR, 38 µm, 3 x 9 cm strip






This exceptionally wide-range filter contains a mixture of rare earth oxides and provides 20 peaks for wavelength calibration between 335 nm in the UV and 1945 nm in the NIR. It is equivalent to NIST SRM 2065.

Nominal peak wavelength values (in nm) are: 335, 345, 361, 375, 386, 402, 418, 485, 538, 583, 642, 748, 804,976, 1076, 1151, 1222, 1366, 1469, 1945





A Certificate of Calibration and Traceability and full instructions for use are provided with each Reference Material. Starna Scientific is accredited to both ISO 17034 (4001) as a Reference Material producer, and ISO/IEC 17025 (0659) as a Calibration Laboratory for optical reference measurements. Starna offers a Lifetime Guarantee on all its Reference Materials.