|Description & NIST Traceability
|Four concentrations of Nicotinic acid in dilute hydrochloric acid together with a blank, permanently sealed by heat fusion in quartz cells. NIST Traceable complete with UKAS ISO/IEC 17025 accredited certificate of calibration
|Testing absorbance scale and linearity in the Far UV region of the spectrum.
|213 nm, 261 nm
|Far UV quartz cells that have been permanently sealed by heat fusion
|Nicotinic Acid, 6mg/l & Blank Cell
|Nicotinic Acid, 12mg/l & Blank Cell
|Nicotinic Acid, 18mg/l & Blank Cell
|Nicotinic Acid, 24mg/l & Blank Cell
|Nicotinic Acid, 4 Concentrations & Blank Cell
Nicotinic acid solvated in dilute hydrochloric acid is a well documented method for validation of the absorbance scale and the linearity of a spectrophotometer in the Far UV region. Prepared in 0.1M hydrochloric acid, nicotinic acid gives a spectral scan containing characteristic peaks at approx. 210 nm and 260 nm. Within the concentration range 5-25 mg/l, if the absorbance scale of a spectrophotometer at 2 nm SBW is linear, the absorbances of a series of concentrations will be a linear function of concentration, at the specified SBW.
The filled cells are tested and certified against the calculated values. A certificate is provided with each set of cells, which shows the certified absorbance values and confidence limit for each cell. The certificate is suitable for use with inspecting agencies when used in the context of a standard operating procedure for the quality control established in your laboratory.
The following is a list of approximate absorbance values for each concentration at 1 nm SBW at the calibration wavelengths:
Suggestions for Use:
Scan the absorbance of the nicotinic acid cells over the certified wavelength range against the blank supplied.
Compare the spectrophotometer absorbance values to the certified absorbance values. Taking the expanded uncertainty budget† of the certified references into consideration, if the absorbance values fall within the expected parameters† of your instrument then your instrument is working correctly.
To evaluate instrument linearity, plot a graph of concentration against absorbance for each of the two wavelengths.
If you determine that your instrument is not giving you the correct values, consult your service technician for advice on how to determine and correct any problem, which this reference may have detected.
† Expected Parameters and Expanded Uncertainty Budget
The expanded uncertainty budget (k=2) is the tolerance that we could expect to measure in the assigned value on any one of our reference spectrophotometers during the 2 year period of certification.
When used to verify the performance of any given spectrophotometer this certificate tolerance must be added in a simple linear manner to the stated appropriate specification accuracy of the instrument on the test, see following example:
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