Nuclear Magnetic Resonance (NMR) Spectroscopy

chemiSPEC is equipped with two high field NMR spectrometers - Bruker AVANCE 300MHz and 500MHz - as well as automated sample changers, remote processing stations and a liquid chromatography-nuclear magnetic resonance (LC-NMR) platform. This equipment allows the complete range of solution-state NMR experiments to be run, from the acquisition of 1H NMR spectra to the more advanced correlation spectroscopy (2D NMR).

We offer a rapid response routine NMR service using our AVANCE DPX 300MHz Bruker NMR instrument. This service allows customers to receive data files quickly via e-mail for processing, storage and interpretation at their own facility. NMR processing software is readily available and offers the scientist much more control over data interpretation.

If data handling software is unavailable and time is of the essence, then chemiSPEC offer image file delivery. Image files of processed spectra are sent either as word.doc or Adobe. PDF files via e-mail, for interpretation by the customer. These files are easily printed and simple to include in lab-books and report documents.

For those customers who require it, we can supply hardcopies of spectra via fax and post.
Our NMR instruments are capable of a wide range of 1D and 2D experiments. Below is a list of some common experiments. Click on individual items for further details or explanations.

- 1H, 13C, 31P, 19F experiments
- DEPT
- 1D NOESY
- 2D experiments COSY, HMQC, HMBC, NOESY.
- Variable temperature
- LCNMR

2D NMR Experiments

COSY (Correlation Spectroscopy)
This experiment correlates 1H-1H spin systems, showing homonuclear through-bond interactions by analysis of the 2D spectum generated. There are many variations on the COSY experiment which yield slightly different information.

HMQC (Heteronuclear Multiple-Quantum Correlation and
HSQC (Heteronuclear Single-Quantum Correlation)
These experiments generate chemical shift correlation maps between directly-bonded 1H and 13C. They are both based on proton-detection so offer high sensitivity when compared to carbon direct detection methods. The HSQC experiment is more sensitive and yields better resolved spectra than the HMQC experiment.

chemiSPEC routinely run HMQC for 1H and 13C correlation but can run HSQC if requested.

HMBC (Heteronuclear Multiple Bond Correlation)
This experiment compliments the HMQC and HSQC, showing a chemical shift correlation for 1H to distant coupled 13C or 15N (2 or more bonds). This yields useful information for structure characterisation and identification.

NOESY (Nuclear Overhauser Effect Spectroscopy)
NOE experiments give useful structural information as they show close range through space interactions. By selecting and irradiating one resonance and observing the enhancement of other signals in the spectrum, information on the spatial proximity and/or orientation of groups can be obtained.

Mass Spectrometry

We employ an Esquire 3000+ Ion Trap mass spectrometer with electrospray source.

Esquire Ion Trap mass spectrometer 3000+ Features:

- Low resolution mass spectrometry
- MS-MS, MSn (up to MS6), giving structural information
- SIM (Single Ion Monitoring) and MRM (Multiple Reaction Monitoring)

Carbon, Hydrogen and Nitrogen Analysis

chemiSPEC offers a fast response C, H&N service to customers using our Exeter Analytical CE 440 Elemental Analyzer instrument

This precise and accurate technique can be used over a wide range of sample types. The data obtained can be used to confirm sample purity and in conjunction with NMR and/or MS can be most useful for structure confirmation.

Samples are normally analysed in duplicate in order to ensure that good quality data is obtained. Typical response times are of the order of 3 days from receipt of sample. Results can be provided by electronic mail or as paper copy as meets the client's needs.

Data quality is assured by the routine use of standards and check samples throughout the analysis.

It has been demonstrated that this model of analyzer is a leader in terms of measurement precision in independent studies by the Royal Society of Chemistry (Micro Analytical group).

HPLC

chemiSPEC is equipped with Agilent 1100 series HPLC. This equipment can be used to separate and quantify individual components from mixture using a UV detector. It is however more routinely used in conjunction with Mass Spectrometry.

HPLC-MS

The Agilent 1100 series HPLC is connected to a Bruker Esquire 3000+ ion trap mass spectrometer. This instrumentation can be used as a tool to routinely confirm the mass of a synthesized compound. However, the "TRAP" configuration of this instrument allows the fragmentation of molecules to be performed up to 6 stages (MS6), thus enabling more specific structural information on unknown compounds to be obtained.

This versatile TRAP analyzer can also be run in the "Single Ion Monitoring" or "Multiple Reaction Monitoring" modes to detect and quantify specific components at very low levels.

HPLC-NMR

chemiSPEC is equipped with an AVANCE DRX 500MHz NMR spectrometer fitted with a 4mm selective inverse probe. This allows the acquisition of proton and carbon NMR data in the stop-flow mode.

When used in conjunction with liquid chromatography, the LC-NMR platform is a powerful tool for the analysis of samples in small quantities and allows structure elucidation of components in complex mixtures, at low concentrations and/or where difficult to purify.

For even more confidence in data interpretation, LC-NMR data can be correlated to LC-MS data converting these instruments into unique tools for the structure elucidation of Chemicals side products, metabolites, biomolecules modifications etc.

Other Techniques

Access to a range of other techniques can be arranged by agreement, either in the University or through our partners.

Techniques such as Gas Chromatography, Atomic Absorption Spectroscopy and Fourier Transform Infra-Red can be easily arranged through other University departments. A wider range of techniques can be accessed through our partners and contacts in the region.

Please ask for information.