Requirements for service NMR spectra in solution

The routine service analyses in liquid phase are performed on the Bruker AVNEO 400 spectrometer equipped with a 5 mm iTBO triple resonance broadband probehead (BBF/H/F/D) in automation mode using automatic sample changer.

The service analyses in liquid state are requested ONLY via the electronic submission platform of the Bulgarian NMR Centre. Please, submit a separate request form for each sample and provide all the requested information!

Requests for NMR spectra submitted until 16:30 h and for samples provided in the NMR laboratory by 17:00 h (at the latest) are performed on the same day during the night.

Special experiments which cannot be recorded in automation mode are measured on Fridays, and the requests should be submitted by the end of the working day on Thursday at the latest.

The samples are prepared by the customer! The sample must be fully dissolved in an appropriate deuterated solvent and provided in 5 mm NMR tubes containing 0.6 ml of solution (the height of the solution should be minimum 4 cm from the bottom of the 5 mm tube). Sample tubes (5 mm o.d.) with an engraved quality mark provide better resolution and better overall quality of the spectra. The length of the sample tube should be at least 17.5 cm, with a clear label of the sample code name corresponding exactly to the code name indicated in the request form. Please use permanent marker for labeling the sample name on the NMR tube! DO NOT USE TAPE TO FIX THE LABEL! The label should be positioned at a height of at least 14 cm from the bottom of the tube.

Samples that do not correspond to the above requirements will not be measured!

Preparation of samples by the NMR staff is offered only to external users and at additional costs. If the sample is provided in a solid state, the provided quantity should be fully soluble in 0.6 ml of solvent. Spectra of samples that do not fully dissolve in 0.6 ml of the solvent specified in the request form will not be measured. If necessary, the solubility can be determined by the NMR staff at additional cost.

The concentration of the sample should be indicated in the request form. This information is particularly important for measurement of NMR spectra of heteronuclei for determination of the appropriate number of scans.  If the concentration is not known (unknown substance or mixture of several substances) this should be indicated in the request form.

Recommended concentration for 1H spectra is 0.005M while for 13C spectra the optimal concentration is 0.05M.

The approximate time for recording different NMR experiments depending on the sample concentration is given in the following table.

We offer the following routine experimental techniques:

Experiments recorded using sample changer Experiments recorded without sample changerb
1D 2D sel. NOEa
1H spectrum COSY Solvent suppression
1H + D2O HSQC Spectra in mixed sovents
13C {H} HMBC Spectra in non-deuterated solvents
DEPT 135 NOESYa Diffusion experiments
DEPT 90 HMQC Special experiments
31P {H} ROESYa
31P
19F
19F {H}
a For a better result, the sample should be degassed before the measurement (e.g. by purging with nitrogen or argon or by placing in an ultrasonic bath for 10-15 minutes).

b Mesured on Friday every week

A brief description of the proposed experimental techniques can be found here (hyperlink experiments_en.pdf).

If necessary, other types of experiments can be performed after prior arrangement.

Some general rules regarding NMR spectra recording can be found here.

We can provide a broad range of deuterated solvents. Prices for the preparation of one sample for the most commonly used solvents can be found in Appendix 3 of the service price list.