Using the Spinsolve 90 MHz Benchtop NMR Spectrometer

The Spinsolve benchtop NMR spectrometer offers an array of rapid, powerful and advanced multi-nuclear methods for structure confirmation.

This article presents results from a number of typical use cases and example studies, highlighting the instrument’s accuracy and adaptability to a wide range of sectors and applications.

Use Case: Artemisinin

Artemisinin is a drug commonly used to treat malaria. The drug can be produced in a semi-synthetic manner, or it can be extracted from the plant Artemisia annua (sweet wormwood).

Figure 1 displays the ¹H NMR spectrum of a 250 mM Artemisinin sample in CDCl₃. This spectrum took 10 seconds to acquire and was measured in a single scan.

1D Proton Spectrum

Figure 1. ¹H NMR spectrum of a 250 mM Artemisinin sample in CDCl₃ measured on a Spinsolve 90 MHz system in a single scan. Image Credit: Magritek

1D Carbon Spectrum

Figure 2 displays the ¹³C NMR spectrum of 250 mM Artemisinin in CDCl₃. This spectrum was acquired via a combination of NOE polarization transfer from ¹H to ¹³C and ¹H decoupling.

The 1D Carbon experiment using NOE was found to be sensitive to all ¹³C nuclei present in the sample, confidently resolving all anticipated resonances.

Figure 2. ¹³C NMR spectrum of a 250 mM Artemisinin sample in CDCl₃ measured on a Spinsolve 90 MHz system in 120 minutes. Image Credit: Magritek

2D COSY Spectrum

The 2D COSY spectrum facilitates the identification of coupled ¹H nuclei. These nuclei generate cross peaks out of the diagonal of the 2D data set.

Figure 3 displays a notable amount of clearly observable cross peaks; for example, protons at positions 4 and 17 (dark blue) are coupled, while proton 18 couples with protons 17 (cyan) and 19 (pink).

Figure 3. ¹H 2D COSY experiment of a 250 mM Artemisinin sample in CDCl₃ acquired in 13 minutes on a Spinsolve 90 MHz system. Image Credit: Magritek

2D HSQC-ME

HSQC is a robust, useful method widely employed in the correlation of ¹H with one-bond coupled ¹³C nuclei. The Spinsolve features an innovative multiplicity-edited version (HSQC-ME) of this sequence.

HSQC-ME features the editing power of the DEPT-135 sequence – ideal for differentiating signals of CH₂ groups (blue) from CH and CH₃ groups (red).

Figure 4 displays the HSQC-ME spectrum of a 250 mM Artemisinin sample in CDCl₃. This spectrum was acquired in 8 minutes, with measurement time optimized via NUS (non-uniform sampling).

Figure 4. HSQC-ME spectrum of a 250 mM Artemisinin sample in CDCl₃ showing the correlation between the ¹H (horizontal) and ¹³C (vertical) signals. Image Credit: Magritek

2D HMBC

The Heteronuclear Multiple Bond Correlation (HMBC) experiment can be utilized to acquire long-range ¹H-¹³C correlations through two or three bond couplings.

Figure 5 displays the HMBC spectrum of a 250 mM Artemisinin sample. This spectrum was acquired in 34 minutes using the Spinsolve 90 MHz.

The experiment highlights the long-range correlation of protons 19 with carbons 2, 17 and 18, as well as the correlation with quaternary carbons.

Figure 5. HMBC spectrum of a 250 mM Artemisinin sample in CDCl₃ showing the long-range couplings between ¹H and ¹³C nuclei. Image Credit: Magritek

Use Case: Brucine (2,3-Dimethoxystrychnidin-10-one)

Brucine (2,3-Dimethoxystrychnidin-10-one) is an alkaloid that is structurally related to strychnine but exhibits reduced toxicity.

Figure 1 displays the ¹H NMR spectrum of a 250 mM Brucine sample in CDCl₃. This spectrum was acquired in 10 seconds and was measured in a single scan.

1D Proton Spectrum

Figure 1. ¹H NMR spectrum of a 250 mM Brucine sample in CDCl₃ measured on a Spinsolve 90 MHz system in a single scan. Image Credit: Magritek

1D Carbon Spectrum

Figure 2 displays the ¹³C NMR spectrum of 250 mM Brucine in CDCl₃. This was acquired via a combination of NOE polarization transfer from ¹H to ¹³C and ¹H decoupling.

The 1D Carbon experiment via NOE confidently resolves all anticipated resonances and is sensitive to all ¹³C nuclei present in the sample.

Figure 2. ¹³C NMR spectrum of a 250 mM Brucine sample in CDCl₃ measured on a Spinsolve 90 MHz system in 120 minutes. Image Credit: Magritek

2D COSY Spectrum

The 2D COSY experiment enables coupled ¹H nuclei to be identified, as these generate cross peaks out of the diagonal of the 2D data set. A significant number of cross peaks can be clearly observed in Figure 2.

In the example presented, protons at positions 6 and 11 (light green) are coupled, while proton 19 couples with proton 10 (light blue), 12 (orange) and 20 (pink).

Couplings between protons 8 and 9 (dark blue) can be clearly seen, as well as couplings between protons 8 and 9 and protons 14 and 15 (dark green).

Figure 3. ¹H 2D COSY experiment of a 250 mM Brucine sample in CDCl₃ acquired in 13 minutes on a Spinsolve 90 MHz system (top); zoom into the aliphatic region (0.5-5.0 ppm) of the ¹H 2D COSY spectrum which underlines the superb resolution. Image Credit: Magritek

2D JRES Spectrum

The JRES experiment is a useful tool in identifying chemical groups. This experiment generates a single line for each group by collapsing J-coupling along the direct direction. This experiment results in multiplets being generated along the vertical direction.

Figure 4. Homonuclear J-resolved (JRES) spectrum of 250 mM Brucine in CDCl₃ on a Spinsolve 90 MHz. Image Credit: Magritek

2D HSQC-ME

HSQC is a powerful method typically employed in the correlation of 1H with one-bond coupled ¹³C nuclei. A multiplicity-edited version (HSQC-ME) of this sequence is included with the Spinsolve.

HSQC-ME offers the editing power of the DEPT-135 sequence – an ideal tool for users looking to differentiate between signals of CH₂ groups (blue) and signals of CH and CH₃ groups (red).

Figure 5 displays the HSQC-ME spectrum of a 250 mM Brucine sample in CDCl₃. This sample was acquired in 2 minutes, with measurement time optimized via NUS (non-uniform sampling).

Figure 5. HSQC-ME spectrum of a 250 mM Brucine sample in CDCl₃ showing the correlation between the ¹H (horizontal) and ¹³C (vertical) signals. Image Credit: Magritek

2D HMBC

The Heteronuclear Multiple Bond Correlation (HMBC) experiment can be employed in the acquisition of long-range ¹H-¹³C correlations via two or three bond couplings.

Figure 6 illustrates the long-range correlation of proton 8 with carbons 2, 3, 5, 7, 9 and 17. This sequence also highlights the correlation with quaternary carbons.

Figure 6. HMBC spectrum of a 250 mM Brucine sample in CDCl₃ showing the long-range couplings between ¹H and ¹³C nuclei. Image Credit: Magritek

Use Case: Gibberellic Acid

The plant hormone Gibberellic acid is the most widely used substance from the group of Gibberellins. Gibberellic acid sees routine use in industry to stimulate rapid root and stem growth and improve germination speeds.

Figure 1 displays the ¹H NMR spectrum of a 250 mM Gibberellic acid sample in MeOH-d₄. This spectrum was measured in a single 10-second scan.

1D Proton Spectrum

Figure 1. ¹H NMR spectrum of a 250 mM Gibberellic acid sample in MeOH-d₄ measured on a Spinsolve 90 MHz system in a single scan. Image Credit: Magritek

1D Carbon Spectrum

Figure 2 displays the ¹³C NMR spectrum of 250 mM Gibberellic acid in MeOH-d₄. This spectrum was acquired via a combination of NOE polarization transfer from ¹H to ¹³C and ¹H decoupling.

The 1D Carbon experiment via NOE was confirmed to be sensitive to all ¹³C nuclei present in the sample. It also confidently resolves all expected resonances.

Figure 2. ¹³C NMR spectrum of a 250 mM Gibberellic acid sample in MeOH-d₄ measured on a Spinsolve 90 MHz system in 60 minutes. Image Credit: Magritek

2D COSY Spectrum

The 2D COSY experiment facilitates the identification of coupled ¹H nuclei as these generate cross peaks out of the diagonal of the 2D data set.

Figure 3 confirms that a large number of cross peaks can be easily observed, including the proton at position 11, which couples to proton 16 (orange), proton 12 (light green) and proton 10 (dark blue).

It is possible to note proton 16 coupling with proton 14 (dark green) and proton 12 (light blue). The coupling between protons 1 and 14 (pink) can also be seen.

Figure 3. ¹H 2D COSY experiment of a 250 mM Gibberellic acid sample in MeOH-d₄ acquired in 13 minutes on a Spinsolve 90 MHz system. Image Credit: Magritek

2D HSQC-ME

The Spinsolve is equipped with a multiplicity edited version (HSQC-ME) of the HSQC method – a powerful sequence able to confidently correlate ¹H with one-bond coupled ¹³C nuclei.

HSQC-ME leverages the robust editing power of the DEPT-135 sequence to differentiate signals of CH₂ groups (blue) from those of CH and CH₃ groups (red).

Figure 4 displays the HSQC-ME spectrum of a 250 mM Gibberellic acid sample in MeOH-d₄. This spectrum was acquired in 2 minutes – a short measurement time that was optimized via NUS (non-uniform sampling).

Figure 4. HSQC-ME spectrum of a 250 mM Gibberellic acid sample in MeOH-d₄ showing the correlation between the ¹H (horizontal) and ¹³C (vertical) signals. Image Credit: Magritek

2D HMBC

The Heteronuclear Multiple Bond Correlation (HMBC) experiment is ideal for acquiring via long-range ¹H-¹³C correlations via two or three bond couplings.

Figure 5 illustrates the HMBC spectrum of a 250 mM Gibberellic acid sample. This spectrum was acquired in a total of 34 minutes using the Spinsolve 90 MHz.

The spectrum highlights long-range correlations between proton 11 and carbons 13 (orange), 12 (blue) and 9 (green). These correlations are marked with circles. The experiment also highlights the correlation with quaternary carbons.

Figure 5. HMBC spectrum of a 250 mM Gibberellic acid sample in MeOH-d₄ showing the long-range couplings between ¹H and ¹³C nuclei. Image Credit: Magritek

Use Case: Quinine

Quinine is regarded as one of the WHO’s (World Health Organization’s) “Essential Medicines” due to its importance in the treatment of a range of conditions, including malaria.

Figure 1 displays the ¹H NMR spectrum of a 250 mM Quinine in CDCl₃. This spectrum was acquired in 10 seconds and measured in a single scan.

1D Proton Spectrum

Figure 1. ¹H NMR spectrum of a 250 mM Quinine in CDCl₃ measured on a Spinsolve 90 MHz system in a single scan. Image Credit: Magritek

1D Carbon Spectrum

Figure 2 displays the ¹³C NMR spectrum of 250 mM Quinine in CDCl₃. The spectrum was acquired via NOE polarization transfer from ¹H to ¹³C and ¹H decoupling.

The 1D Carbon experiment using NOE was found to be sensitive to all ¹³C nuclei present in the sample while clearly resolving all anticipated resonances.

Figure 2. ¹³C NMR spectrum of a 250 mM Quinine in CDCl₃ measured on a Spinsolve 90 MHz system in 120 minutes. Image Credit: Magritek

2D COSY Spectrum

The 2D COSY spectrum can be used to identify coupled ¹H nuclei as these generate cross peaks out of the diagonal of the 2D data set. Figure 3 highlights a large number of clear cross peaks.

Figure 3 shows that the proton at position 13 couples to proton 12 (dark blue), and that protons 16 and 18 couple to proton 20 (orange). It should also be noted that proton 18 couples to proton 19 (light green), while proton 2 couples with protons 1 (pink) and proton 3 (light blue).

Further coupling can be observed between protons 3 and 9 (dark green) and protons 6 and 10 (red).

Figure 3. ¹H 2D COSY experiment of a 250 mM Quinine in CDCl₃ acquired in 6.5 minutes on a Spinsolve 90 MHz system. Image Credit: Magritek

2D HSQC-ME

HSQC is a sequence commonly employed in the correlation of ¹H with one-bond coupled ¹³C nuclei. The Spinsolve features a multiplicity edited version (HSQC-ME) of this highly useful method.

HSQC uses the editing power of the DEPT-135 sequence to differentiate signals of CH₂ groups (blue) from CH and CH₃ groups (red).

Figure 4 displays the HSQC-ME spectrum of a 250 mM Quinine in CDCl₃. The 4-minute measurement time for this spectrum was optimized by applying NUS (non-uniform sampling).

Figure 4. HSQC-ME spectrum of a 250 mM Quinine sample in CDCl₃ showing the correlation between the ¹H (horizontal) and ¹³C (vertical) signals. Image Credit: Magritek

2D HMBC

The Heteronuclear Multiple Bond Correlation (HMBC) experiment is typically employed in the acquisition of long-range ¹H-¹³C correlations through two or three bond couplings.

Figure 5 displays the HMBC spectrum of a 250 mM Quinine sample which has been measured in 34 minutes via the Spinsolve 90 MHz.

The spectrum highlights the long-range correlations of proton 13 with carbons 12 (dark blue), 14 (light green) and 11 (red).

It illustrates couplings of proton 19 with carbons 15 (light blue) and 17 (pink), while the coupling of proton 12 with carbon 10 (orange) and the couplings of protons 20 with carbon 17 (dark green) are marked with circles.

The experiment also highlights the correlation with quaternary carbons.

Figure 5. HMBC spectrum of a 250 mM Quinine sample in CDCl₃ showing the long-range couplings between ¹H and ¹³C nuclei. Image Credit: Magritek

This information has been sourced, reviewed and adapted from materials provided by Magritek.

For more information on this source, please visit Magritek.