[LabRat1017]

Im working on the USP Maleic acid monograph testing for Limit of Fumaric Acid. I am having an issue with my TLC plate when i am finished and viewing under UV light. There are diamond shaped spotsa ll over my plate. Has anyone done this test or had this issue with anything else?

[Archer]

Could you elaborate on the test?

Don't copy it verbatim but give the plate type, mobile phase and any visualisation method (i.e. pre-treatment before UV)

[LabRat1017]

Plate: Silica Gel GF 250um
MP : Heptane:Butanol:Chloroform:Anhydrous Formic Acid: (44:36:16:16)
Unsaturated chamber, run about 3/4 length of plate and then dried 100C for 15 min and viewed under UV at 254nm
Plate is predried at 105/30min

Its completed verbatum from USP monograph for Maleic Acid see link :

http://www.pharmacopeia.cn/v29240/usp29nf24s0_m442.html


When viewed under the UV light there are all of these diamond shaped spots all over the plate so you can not see the spots of interest. At first i thought something was sprayed on the plate but we tried 2 more times and same issue. If anyone can help?

[Archer]

Have you checked have you tried with fresh solvents?

[LabRat1017]

I have tried fresh solvents, a new plate.