User Guide

For an introduction to the application and use of Certified Reference Materials in absorption spectrophotometry


This Reference Material can be used to qualify the accuracy and linearity of the absorbance scale of spectrophotometers with bandwidth less than 2 nm in the far ultraviolet region of the spectrum (210 nm – 260 nm).

Description and Discussion

Nicotinic acid solutions with concentrations from 6 to 60 mg/l in dilute (0.1 M) hydrochloric acid, sealed in high quality far UV quartz cells.  Supplied with a 0.1 M hydrochloric acid blank.

The spectrum of nicotinic acid, when prepared in acid solution, has characteristic peaks at approximately 213 nm and 261 nm. Within the concentration range 6-60 mg/l, if the absorbance scale of a narrow bandwidth (<2 nm) spectrophotometer is linear, the apparent absorbance of a series of concentrations measured at these peaks will be a linear function of concentration. 

 Typical absorbance values at these wavelengths for the different concentrations are as follows:

Concentration Absorbance at Certified Wavelength
  213nm 261nm
6 mg/L 0.24 0.281
12 mg/L 0.477 0.556
18 mg/L 0.73 0.849
24 mg/L 0.988 1.149
36 mg/L 1.452 1.386
48 mg/L 1.936 1.848
60 mg/L 2.421 2.309

Typical spectra


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 the references gives actual values measured at a bandwidth of 1.0 nm, and only these certified values should be used for instrument qualification. On request, Starna can provide certified values at other bandwidth values. 


Catalogue Number

These references are available in a convenient set containing  four concentrations and a hydrochloric acid blank cell:

  Catalogue Number
Nicotinic Acid Linearity Set  6, 12, 18 & 24 mg/l & Blank Cell RM-06A12A18A24A          

References are also available individually. Catalogue numbers and nominal certified values are given below. Any combination of references can be ordered as a set by combining the catalogue numbers as in the example above. A hydrochloric acid blank cell is supplied with each reference or set of references.

Concentration Absorbance at Certified Wavelength Catalogue Number
  213nm 261nm  
6 mg/l 0.244 0.233 RM-06A
12 mg/l 0.489 0.466 RM-12A
18mg/l 0.727 0.694 RM-18A
24mg/l 0.968 0.924 RM-24A
36 mg/l 1.452 1.386 RM-36A
48 mg/l 1.936 1.848 RM-48A
60 mg/l 2.421 2.309 RM-60A