Spectral Separation of mixtures by solid state NMR

Fig.1 show ¹³C NMR spectra of mixture of L-Histidine and L-Histidine Hydrochloride Monohydrate in solution and solid state. Only a single state is observed in solution state NMR, as a contrast, individual crystal state can be distinguished in solid state NMR. Solid state NMR is a powerful tool to obtain information in the crystalline state which would be lost in the solution state.

Fig.1
upper：¹³C solution NMR spectrum (10mg of each sample solved in D₂O)
lower：¹³C CPMAS spectrum of the mixture

ROSY is a method which provides a separate ¹³C CPMAS spectra from the mixture. Fig.2 shows the spectral separation of each component by utilizing the different ¹H T₁value of L-Histidine and L-Histidine Hydrochloride Monohydrate by ROSY method. Thus, ROSY is clearly useful tool for analysis of mixtures.

Fig.2 ：ROSY spectrum

ROSY method

ROSY(Relaxation Ordered SpectroscopY)¹⁾ is a spectral separation method using the difference of ¹H T₁ value of each components in the mixture. Ordinally, each compound has unique ¹H T₁ value in solid state NMR. Therefore when each compound has significantly different ¹H T₁ value, ROSY method can be applied.

Tips of ROSY

Sometimes, ROSY method fails to separate each component when ¹H T₁ value in a single component becomes not unique by ultra fast MAS.  Therefore MAS speed around 10 kHz is recommended for ROSY, and TOSS is effective to suppress SSB.

Sample：mixture of L-Histidine and L-Histidine Hydrochloride Monohydrate
Spectrometer：JNM-ECZ500R　
Probes：5mmSuperCOOL(solution), 3.2mm HXMAS(solid)

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