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Chemical Shift Referencing Calculator

Below is the protocol I follow for chemical shift referencing (direct for 1H, and indirect for 13C and 15N). 

!!! The referencing should be done on the day of recording experiments !!!

!!! No rounding off of frequency numbers !!!

1. Record a one-D (1H) spectrum (s2pul on Varian and zg on Bruker) of the buffer (or sample) containing DSS.

2. Set the cursor on the rightmost line (DSS line) in the 1H spectrum of the sample. For Varian, type rl(0p) to set the DSS line to 0 ppm. In Bruker, use one of the buttons on the top panel to do the same.

3. Type movetof (Varian) to set the tof at DSS line. In Bruker, use one of the buttons on the top panel to set the O1 at DSS line.

4. Check the 1H frequency (spcfrq command in Varian will display four values; use the first one: RF Channel 1 (Obs) frequency). This frequency will be called as H0

Now,

1. For proton referencing, check for frequency numbers against sfrq (Varian) or SFO1 (Bruker) values in the procpar file (Varian) or the acqu file (Bruker) of any experiment; call them Hval.

2. For nitrogen referencing, check for frequency numbers against dfrq2 (Varian) or SFO3 (Bruker) values in the procpar file (Varian) or the acqu file (Bruker) of any experiment; call them Nval.

3. For carbon-aliphatic referencing, check for frequency numbers against dfrq (Varian) or SFO2 (Bruker) values in the procpar file (Varian) or the acqu file (Bruker) of any of the HNCA, CBCANH type experiment; call them CAval.

4. For carbonyl referencing, check for frequency numbers against dfrq (Varian) or SFO2 (Bruker) values in the procpar file (Varian) or the acqu file (Bruker) of HNCO and HN(CA)CO type experiment; call them COval.