DMSO dissolve compound caused a huge smearing on tlc

[Thwee]

I am doing some separaion of extracted compound. Both my sample and standard are dissolved in DMSO. After run on the tlc plate, huge smear comes out. I cant even see single spot for my standard control. How shld i solve this problem? Thanks

[danko]

The DMSO is a stronger solvent than your mobile phase, whatever that might be.
The solution must be to dissolve your samples in the mobile phase or something that resembles it with regards to its eluting strength.

Best Regards

[danko]

I forgot: Another possibility is to apply a very smal volume of your sample solutions and preferably dry the spots before runneing the actual TLC.

Best Regards

[lmh]

DMSO is hell to dry

[krickos]

DMSO is hell to dry

Indeed

Here are some data on aprotic solvents (Solvent Chemical Formula Boiling point Dielectric constant Density Dipole moment (D) ), that you may want to try as sample/std solvent instead:

Dichloromethane (DCM) CH2Cl2 40 °C 9.1 1.3266 g/ml 1.60 D
Tetrahydrofuran (THF) /-CH2-CH2-O-CH2-CH2-\ 66 °C 7.5 0.886 g/ml 1.75 D
Ethyl acetate CH3-C(=O)-O-CH2-CH3 77 °C 6.0 0.894 g/ml 1.78 D
Acetone CH3-C(=O)-CH3 56 °C 21 0.786 g/ml 2.88 D
Dimethylformamide (DMF) H-C(=O)N(CH3)2 153 °C 38 0.944 g/ml 3.82 D
Acetonitrile (MeCN) CH3-C≡N 82 °C 37 0.786 g/ml 3.92 D
Dimethyl sulfoxide (DMSO) CH3-S(=O)-CH3 189 °C 47 1.092 g/ml 3.96 D

Apart from DMSO and DMF, the otherones can be fairly fast dried off the plate with a hair fan or a tlc oven.

[Thwee]

Haih..but i already dissolve all my extracts in DMSO.and my standard is juz 1mg in 2 ml of DMSO. i dont think recover it bacl also. even i try a vy small amount of the sample, but it seems to be to little until i see nothing..so sad..i think i need to purchase a new standard again and repeat my whole extraction..but it is time consuming and costly..actually my standard needs to be dissolve in methanol instead,but MeOH is so volatile and i cant confirm the drug concentration will remain the same as it will evaporate out..any idea that can help me to confirm the drug conc in MeOH?

[Gerhard Kratz]

If you have Aircondition in your lab it should be not a problem. Keep the samples in the fridge. Use vials with caps and septum to avoid MeOH will evaporate. What TLC did you use?

[Thwee]

i use silica gel 60F 254..