Hi, If you want to measure spin-spin coupling constants (J value) you have a few ways to do it:

• simple COSY will not work in case of this problem. If you want to measure (by raw manner) J coupling constants you need to do at least DQF-COSY (Double Quantum Filtered) for Bruker Topspin3.2 it's cosydfetgp.2 pulse program name.

• next step it's a ECOSY (Exclusive Correlation Spectroscopy) - Gradient E.COSY (ecosygpph)

• here you have some articles concerning this topic:

http://link.springer.com/article/10.1023%2FA%3A1008372630606

http://spin.niddk.nih.gov/bax/lit/508/292.pdf

https://www.researchgate.net/publication/7795413Spin-edited2DHSQC-TOCSYexperimentsforthemeasurementofhomonuclearandheteronuclearcouplingconstantsapplicationtocarbohydratesandpeptides

Best regards, A. Leniak

Hi. I'll try a different interpretation of your question: there is NO J-value parameter to set in a COSY experiment. Compare for example selective 1D COSY in which you have to set a J-value parameter. If I understand correctly, in basic 2D COSY the J couplings just determine the structure of your diagonal and cross peaks. But probably the best thing to do, if you want to understand more on this, is to take a book (Keeler's?) and look at the equations for the COSY.