Home Page Downloads How to Purchase Technical Assistance Starna Banner
Potassium Dichromate Reference
For assessing the absorbance scale of your UV spectrophotometer
Description Potassium dichromate in 0.001N perchloric acid sealed in a
far quartz cell with perchloric acid blank
Primary Usage Validate the absorbance scale of UV spectrophotometers
Useable Range 235nm to 350nm ( 20mg/L to 200mg/L) or 430nm (600mg/L)
Physical Configuration Far UV quartz cells that have been permanently sealed by heat fusion
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

Product Description

View/Download Comprehensive Data Sheet for Potassium Dichromate

Potassium Dichromate solvated in dilute (0.001N) perchlorate acid has been found to be the best method for testing the absorbance scale and linearity of spectrophotometers in the UV. Starna purchases the potassium dichromate crystals directly from NIST (SRM 935a). We then make up the solutions as per the instructions from NIST and permanently heat fuse seal the solutions in UV quartz spectrophotometer cells.

The filled cells are tested and certified against the expected values from NIST and a certificate is provided with each set of cells which has the certified absorbance values for each cell and the confidence limit. The certificate supplied is suitable for use with inspecting agencies when used in the context of a standard operating procedure for the quality control that is established in your laboratory. Each set is supplied with a sealed blank cell that was used for the certified measurement. Below is a table showing approximate absorbances for each concentration:

Concentration 235nm 257nm 313nm 350nm 430nm
20 mg/L 0.2430 0.2810 0.0950 0.2090 n/a
40 mg/L 0.4920 0.5720 0.1920 0.4260 n/a
60 mg/L 0.7410 0.8620 0.2890 0.6340 n/a
80 mg/L 0.9960 1.1590 0.3850 0.8530 n/a
100 mg/L 1.2430 1.4480 0.4800 1.0690 n/a
120 mg/L 1.4820 1.7240 0.5780 1.2680 n/a
140 mg/L 1.7250 2.0050 0.6730 1.4770 n/a
160 mg/L 1.9920 2.3180 0.7700 1.7060 n/a
180 mg/L 2.2350 2.5990 0.8650 1.9150 n/a
200 mg/L 2.4860 2.8960 0.9600 2.1380 n/a
600mg/L n/a n/a n/a n/a 0.950

Suggestions for Use

Measure the absorbance of the potassium dichromate cells at the four wavelengths specified by NIST. These wavelengths for the 20 to 100mg/L solutions are 235, 257, 313 and 350nm and the 600mg/L solution measurement is made at 430nm. The absorbance scale is verified by assuring that the absorbance readings on your instrument are within your instruments tolerance to the readings on the certificate supplied with the reference set. To evaluate linearity, plot a graph of concentration against absorbance for each of the four wavelengths. The 600mg/L solution is used for European Pharmacopoeia compliance with a single wavelength measurment.

Scan of Potassium Dichromate

Linearity Plot of Potassium Dichromate

Interpertation of Results

Consult your spectrophotometer's reference manual for the specification of your instrument's absorbance scale tolerance. This figure will be listed as a plus and minus (+/-) number in absorbance units. Add your instrument's absorbance tolerance to the confidence limit on the certificate supplied with the Potassium Dichromate set for your expected absorbance range. Compare the absorbance values measured on your instrument with the expected values calculated from your instrument manual and the NIST traceable certificate. If the readings are within the expected range for your instrument then your absorbance scale is correct. If not, consult your service techincian and have the instrument evaluated. Quite often if the results of your absorbance measurments are low, it shows that your lamp needs to be replaced.

Quality program

Each time that the analysis is repeated you can compare the new results with the previous results to check for any variance. If your instrument needs service because of a change in absorbance, the historical data will greatly assist the service technician.

How to Order

Catalog Number Description
Linearity Dichromate set
RM-0204060810 Potassium Dichromate Reference set, 5 Concentrations
Linearity Dichromate set with 430nm European Pharmacopoeia Compliance
RM-020406081060 Potassium Dichromate Reference set, 6 Concentrations
Single concentrations:
RM-02 Potassium Dichromate Reference set, 20mg/L
RM-04 Potassium Dichromate Reference set, 40mg/L
RM-06 Potassium Dichromate Reference set, 60mg/L
RM-08 Potassium Dichromate Reference set, 80mg/L
RM-10 Potassium Dichromate Reference set, 100mg/L
Single concentration, European Pharmacopoeia Compliance:
RM-60 Potassium Dichromate Reference set, 600mg/L
Any Combination:
1 concentration & Blank Potassium Dichromate Reference set & Blank
2 concentrations & Blank Potassium Dichromate Reference set & Blank
3 concentrations & Blank Potassium Dichromate Reference set & Blank
4 concentrations & Blank Potassium Dichromate Reference set & Blank
5 concentrations & Blank Potassium Dichromate Reference set & Blank
6 concentrations & Blank Potassium Dichromate Reference set & Blank
7 concentrations & Blank Potassium Dichromate Reference set & Blank

Download MSDS Sheet for RM-PDC