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^-1to 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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Purpose

These traceable reference materials can be used to qualify Mid IR - FTIR spectrophotometers for wavelength accuracy over an operating range of 540 cm^-1 to 3125 cm^-1 (3.2 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

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.

NOMINAL WAVENUMBER VALUES (cm^-1)
539	842	907	1028	1069	1155	1583	1601	1943	2849	3001	3026	3060	3082

The absorption minima and maxima at A and B, C and D can be used to qualify resolution according to pharmacopoeia requirements (EP/JP). This material can also be used for the Wavelength Qualification of ATR (Attenuated Total Reflectance) instrumentation.

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.

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. It is not, however, suitable for Pharmacopoeia resolution compliance measurements, Eight peaks (arrowed in spectrum below) are available for wavelength qualification purposes. The calibration values are traceable to NIST SRM 2065.

NOMINAL WAVENUMBER/WAVELENGTH VALUES
cm^-1	3064	3647	4039	4250	4335	4608	5952	8749
nm	3264	2742	2476	2353	2307	2170	1680	1143

Note: The values given here 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	RM-1921/38/ATR/3x9

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Data sheet

Purpose

This material is equivalent to NIST SRM 2065 and similar to other NIST references SRM 2035a and b. It is suitable for qualifying the wavelength scale of UV, Visible and NIR spectrophotometers over the range 335 nm to 1945 nm.

Description and Discussion

Glass filter containing a combination of oxides of rare earths holmium, samarium, ytterbium, neodymium, lanthanum and other elements. Variations from melt to melt of the glass can cause small uncertainties in peak position, so each Starna filter is individually certified. Sliding window covers protect the surface from damage when not in use. This material is equivalent to NIST SRM 2065 and similar to other NIST references NIST 2035a and b. The spectrum provides 20 peaks for wavelength calibration, evenly-spaced between 335 nm in the UV and 1945 nm in the NIR, so that instruments can now be qualified over this wide range using a single reference.

Typical spectra

Approximate 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 Note: The above values are for guidance only. Because the absorption bands are asymmetric, measured values will be spectral bandwidth dependent. The Calibration Certificate accompanying each Reference gives actual values measured at bandwidths of 0.50, 1.00, 1.50, 2.00, 3.00 and 5.00nm, and only these certified values should be used for instrument qualification. On request, Starna can provide certified values at other wavelengths and bandwidth values.

Catalogue Number

	Catalogue Number
Starna wide range wavelength reference	RM-2065

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Data sheet

Technique

Visible References

Near-infrared and Mid-infrared References

Absorbance References

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

NIR Neutral Density Filters (800 nm to 3200 nm)

Wavelength References

NIR Wavelength Reference Solution Reference (900 – 2600 nm)

NIR Transflectance Reference (900 – 2600 nm)

Near-and Mid-infrared Polystyrene References
(1.1µm to 18.5µm, 9000 cm^-1to 540 cm^-1)

Starna wide-range wavelength reference (335 nm to 1945 nm)

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)

Didymium Oxide Solution (290 – 870 nm)

Starna Polystyrene References

Purpose

Description and Discussion

Typical spectra

Note: Pharmacopoeia compliance

Catalogue Number

Product enquiry

Data sheet

Wide Range Wavelength Reference

Purpose

Description and Discussion

Typical spectra

Catalogue Number

Product enquiry

Data sheet

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Technique

Visible References

Near-infrared and Mid-infrared References

Absorbance References

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

NIR Neutral Density Filters (800 nm to 3200 nm)

Wavelength References

NIR Wavelength Reference Solution Reference (900 – 2600 nm)

NIR Transflectance Reference (900 – 2600 nm)

Near-and Mid-infrared Polystyrene References (1.1µm to 18.5µm, 9000 cm-1 to 540 cm-1)

Starna wide-range wavelength reference (335 nm to 1945 nm)

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)

Didymium Oxide Solution (290 – 870 nm)

Starna Polystyrene References

Purpose

Wide Range Wavelength Reference

Purpose

Near-and Mid-infrared Polystyrene References
(1.1µm to 18.5µm, 9000 cm^-1to 540 cm^-1)