Agilent Technologies 4000, 5000, 6000i DATA SHEET
Photometric accuracy of internal
DRAs in the UV-Vis region using
certified potassium dichromate
solution
Data Sheet
Introduction
Photometric accuracy is important for many applications of UV-Vis
instruments. It is defined as how accurately an instrument measures
absorbance, and is critical in every analytical measurement. When
comparing the results for a sample measured on different instruments, it is
essential to know the accuracy of each instrument before useful analysis
and comparisons can be made.
Photometric accuracy is part of the standard test required by many
regulatory bodies including the Pharmacopoeias, and is typically performed
on the spectrophotometer. When using accessories such as diffuse
reflectance accessories (DRAs) which have in-built detectors, it is important
to determine the photometric accuracy of the whole system. This test uses a
standard potassium dichromate solution to demonstrate the photometric
accuracy of the New Generation Cary 4000/5000/6000i spectrophotometers
with the Agilent DRA.
Cary 4000, 5000 and 6000i instruments provide excellent photometric accuracy
Wavelength
(nm)
Certificate
Value (Abs)
Agilent DRA
(Abs)
Difference
(Abs)
350
0.638
0.642
0.004
313
0.289
0.291
0.002
257
0.859
0.860
0.001
235
0.738
0.736
0.002
Materials
Cary 4000, 5000 or 6000i spectrophotometer with a
DRA
DRA cuvette holder, part number 0210187900
Standard potassium dichromate solution, Starna
standard kit part number 9910085200
A Cary 5000 with an Internal DRA 2500 Internal was
used for this experiment.
Method
1. Warm up the Cary spectrophotometer for at least
1 h prior to use.
2. Calibrate the DRA by running the Auto-calibrate
feature in the Validate application.
3. Mount the cuvette holder over the transmittance
port of the DRA and ensure that the DRA is aligned.
4. Set up the instrument as follows:
absorbance of the standard on the instrument. It also
corresponds well to the certified values at the selected
wavelengths. The values below are well within the
acceptable error of 0.01 absorbance.
Wavelength range: 200–800 nm
Scan rate: 60.0 nm/min with a data interval of
1.0 nm, signal averaging time 0.1 s
SBW: 1.5 nm
Zero/Baseline correction: ON
All other parameters: default
5. Perform a Zero/Baseline correction on the blank
solution.
6. Remove the blank solution and then measure the
standard potassium dichromate solution.
7. The expected values and tolerances of the standard
potassium dichromate solution can be obtained
from the Certificate of calibration and traceability.
Results
The spectrum of the standard potassium dichromate
solution measured with the DRA can be seen below. It
is overlaid with a spectrum of standard potassium
dichromate solution collected on the instrument. The
measured absorbance of the potassium dichromate
solution on the DRA compares well with the measured
The Internal Diffuse Reflectance Accessory
Conclusion
This method demonstrates the excellent photometric
accuracy of Agilent DRA and the New Generation Cary
spectrophotometers.
Reference
Solution Validation Test kit, part number 9910085200
2
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