NIST SRM Equivalent Neutral Density Filter Sets with Blank Holder (SRM 930e, SRM 1930, SRM 2930, or Combined)

StarnaSKU: RM-1N2N3N

Sale price$1,299.48


Part Number, NIST Traceable
SRM 930e Set: 10, 20 & 30 %T Neutral Density Filters and blank holder RM-1N2N3N
SRM 1930 Set: 1, 3 & 50 %T Neutral Density Filters and blank holder RM-N1N35N
SRM 2930 Set: 0.1, 0.3 &92 %T Neutral Density Filters and blank holder RM-D1D39N
Combined SRM Set: All 9 Neutral Density Filters listed above and blank holder RM-SRM9ND


Description All of the references in one set for qualification of UV/VIS spectrophotometer for USP
Primary Usage Validate the performance of UV spectrophotometers for USP qualification
Useable Range See lising of references in each set below
Physical Configuration Far UV quartz cells that have been permanently sealed by heat fusion and glass filters in aluminum holders
NIST Traceability Each set is supplied with a Certificate of Analysis and NIST Traceability
ISO Accredited Accredited by UKAS ISO 17025, ISO Guide34 and ISO 9001


These SRMs are specifically cited in USP <857> as evidence of NIST traceability

Absorbance Accuracy, 440-635 nm

These references can be used to qualify the absorbance accuracy and linearity of visible spectrophotometers with a spectral bandwidth of 6.5 nm or less, over the wavelength range 440 - 635 nm. They are accepted for this purpose by most pharmacopoeias and other regulatory bodies.

Schott NG type glass filters, from which a wide range of transmission and absorbance can be produced, have been available for over forty years. All Starna neutral density filters are manufactured and certified in accordance with the ‘Technical Specification for Certification of Spectrophotometric NIST Traceable Reference Materials’ (NIST Special Publication 260-140). This recommends calibration at 440 nm, 465 nm 546.1 nm, 590 nm and 635 nm, and Starna filters are certified at these wavelengths. Starna absorbance references are calibrated at a bandwidth of 1 nm, however other bandwidths are available on request They can also be certified at other wavelengths to suit customer requirements with the provision that the 440 nm, 546.1 nm and 635 nm wavelengths are included for traceability.

A range of 18 filters is available from Starna, covering absorbance values from approximately 0.04 A to 3.5 A. Originally, these filters were manufactured with selected transmission values. Available transmission values and equivalent absorbances are:

% Transmission





73  0.14
60  0.22
56.5 0.25
50  0.30
40 0.40
30 0.52
25 0.60
20 0.70
10 1.00
6 1.22
3 1.52
1.5 1.82
1 2.00
0.3 2.52
0.1 3.00
0.06 3.22
0.03 3.52


This recommends calibration at 440 nm, 465 nm 546.1 nm 590 nm and 635 nm, and Starna filters are certified at these wavelengths.

NIST also lists three specifications for neutral density filter Standard Reference Materials (SRMs): SRM 930e, SRM 1930 and SRM 2930. These specifications also stipulate the maximum spectral bandwidth to be used at these wavelengths for certification measurements:














For those users wishing to work to these specifications, sets of filters equivalent to these SRMs are available (see How to Order). For convenience, but to comply with the SRM specifications, all certification measurements are made at a SBW of 1.0 nm. These sets consist of three filters together with an empty aluminium holder, to be used as a blank.


SRM 930e

SRM 1930

SRM 2930


%T, A %T, A %T, A

Filter 1

10, 1.0 1, 2.0 0.1, 3.0

Filter 2

20, 0.7 3, 1.5 0.3, 2.5

Filter 3

30, 0.5 05, 0.3 92, 0.04


These SRMs were originally specified in transmittance, the specified nominal transmittance and approximate absorbance values are given below: Certificate values are given in both %T and Absorbance.


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