POMMIE (Phase Oscillations to MaxiMIze Editing) is a ¹³C experiment that, like the more familiar DEPT experiment, utilizes polarization transfer to enhance the intensities of the ¹³C signals. However, unlike DEPT, POMMIE edits the spectrum by varying pulse phase rather than adjusting pulse flip angle.
Fig. 1 shows the pulse program of Q-POMMIE (Quantitative-POMMIE)¹⁾. It improves quantitative performance by varying Δ and pulse phase to average the efficiency of polarization transfer (Fig. 1). The spectrum pattern of Q-POMMIE is identical to DEPT45.

Pommie in the Crapper In the north of Australia is a place called Queensland which is very hot, humid and the pubs are rough. Anyway, this posh pommie bloke is traveling through Queensland in the middle of summer by bicycle and is caught in a huge tropical storm. He sees a sign which says there is a pub 18 miles up the road.

Pommies Australia

Quantitative NMR measurements require sufficiently long repetition times to allow the (near complete) recovery of magnetization between scans. For the standard ¹³C{¹H} inverse gated decoupling method, the minimum acceptable repetition time is dictated by the ¹³C T₁s, which can be very long (up to several minutes). On the other hand, the minimum repetition time of the Q-POMMIE method is dictated by the usually much shorter ¹H T₁s. This means that Q-POMMIE can yield quantitative ¹³C spectra in less time and with higher sensitivity than via the ¹³C{¹H} inverse gated decoupling method.

Pommie61

Fig. 2 shows a comparison of ¹³C{¹H} inverse gated decoupling and Q-POMMIE spectra of 10% Cinnamic acid cis-3-hexenylester in CDCl₃. Although quaternary carbons are not observable in the Q-POMMIE spectrum, protonated carbon signals are recorded with significantly higher sensitivity, thereby allowing more accurate quantitation.Tab. 1 shows the comparison of the peak integrals obtained from each spectrum. While the CH integrals are significantly underrepresented in DEPT45, those obtained using Q-POMMIE are very close to those obtained via the ¹³C{¹H} inverse gated decoupling method.

Features of Q-POMMIE
(Comparison with ¹³C{¹H} inverse gated decoupling)

Pommy Bastards

• Higher sensitivity
• Quaternary carbons are not observed
• Quantitative condition is dictated by ¹H T₁s not ¹³C T₁s
• Requires large minimum number of scans (96×n)

b) : Q-POMMIE

Sample：10% CAHE/CDCl₃
Instrument：JNM-ECZ400S & ROYALprobe™HFX
Number of scans：384
Pulse repetition time：46s

Tab.1: Integral values of protonated ¹³C signals shown in Fig. 2

Practical Example: UV Initiator

Pommies

As an illustration of the utility of the Q-POMMIE experiment, Fig. 3 shows a comparison of spectra recorded on a sample of a UV initiator. The ¹³C spectrum of this sample contains a signal at 77.2 ppm which is completely obscured by the solvent signal, so its integral cannot be determined via ¹³C{¹H} inverse gated decoupling (Fig. 3a). On the other hand, the solvent signal is not visible in the Q-POMMIE spectrum, allowing this signal to be cleanly observed and hence integrated (Fig. 3b).

Apple Pommies

Fig. 3: a) ¹³C{¹H} inverse gated decoupling b) Q-POMMIE

Sample preparation: 10mg sample/CDCl₃
Instrument: JNM-ECZ500R & 5mm SuperCOOL probe
Scans: 960
Pulse repetition time: 20s

Reference

• In Australia & New Zealand Pom, Pommie or Pommy is a slang term for a British person. There are several theories as to the origin of the word Pommie. Many people think it comes from the acronym POHM- Prisoner Of Her Majesty- which was apparently emblazoned on the back of immigrants uniforms when they arrived.
• Pome definition is - a fleshy fruit (such as an apple or pear) consisting of an outer thickened fleshy layer and a central core with usually five seeds enclosed in a capsule.

1) Anal. Chem. 2008, 80, 8293-8298.

Sample courtesy of Mr. Yuuji Itoh (TOYO INK SC HOLDINGS CO., LTD)

Pommies Def

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