Page 32 - Solutions for Plastic Evaluation

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Product Evaluation
Hazardous Substances Hazardous Metals
UV

Evaluation of Plastic Materials Analysis of Hexavalent Chromium in Plastic Using a UV-VIS Spectrophotometer
The content of hexavalent chromium is regulated by the ELV, WEEE, and RoHS directives, which regulate hazardous substances in Europe
(EU). Hexavalent chromium in plastic is analyzed by pretreating the sample to extract the hexavalent chromium into solution and then
analyzing the solution by colorimetry using a UV-VIS spectrophotometer. A process flowchart for extracting the hexavalent chromium from
plastic is shown to the right.

[IEC 62321 Ed.1]
Evaluation of Raw Materials (2) Pulverize by freeze shattering
(1) Prepare sample

Alkali extraction Filter (3) Extract by alkali extraction, then filter
(to separate sample from extract)
Product Evaluation Adjust the sample volume (4) Add diphenylcarbazide colorizing

reagent to extract
Add coloring reagent

Purify Perform UV measurement (5) Measure color level after specified time
Process Flow of Actual Analysis Process Flowchart of Extracting Hexavalent Chromium from Plastic
Product Information Colorimetric Analysis Using a UV-VIS Spectrophotometer

UV-VIS spectrophotometers disperse light from a light source with a grating to irradiate samples with the light, and then measure how
much light the sample absorbed based on the difference in light energy level before and after irradiating the sample. Hexavalent chromium
is analyzed by extraction into a solution and then colorization using diphenylcarbazide reagent. After colorization of the hexavalent
chromium, the spectrophotometer measures the level of color.

UVmini-1240 Hexavalent Chrome Analysis

I 0 I
Diphenylcarbazide

I

Beer-Lambert Law
Transmittance T = I/I 0 = 10 -εcl
ε: Absorption coefficient
c: Solution concentration Measurement
l: Optical path length
AbsorbanceA = log (1/T)
= εcl Coloring
The solution concentration is
proportional to the absorbance. Absorption Curve of Cr(VI) Diphenylcarbazide
Complex

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