MQ filtering efficiencies represent the ability for a pulse sequence to filter out all spin flip transitions other than the specific MQ transition. We find that the large chemical shift anisotropy (CSA) of 31 P nuclei in nonsymmetric molecular systems such as ATP (Figure ) reduces the DQ filtering efficiency of the SR2 1 8 , R14 2 , and SPC-5 pulse sequences, with SR2 expected to be minimally sensitive to CSA since it is a super cycle version of R2 8 and capable of delivering a theoretical maximum efficiency of around 50 %. Under our experimental conditions, the DQ filtering efficiencies for powdered ATP samples were found to be 3.12, 3.125, and 5.40 % when using the SR2 1 8 , R14 2 , and SPC-5, respectively. In contrast for powdered HAp, the experimentally measured DQ filtering efficiencies were found to be 45, 34.5, and 41.1 % when using the SR2 1 8 , R14 2 , and SPC-5, respectively. Based on these results, we decided to continue our experiments on each sample with SR2 8 to achieve DQ and TQ filtering efficiencies (Supporting Information Listing 1). We independently found an optimal DQ and TQ excitation time of 1.6 ms (3.2 ms mixing time) at a MAS frequency of 10 kHz for each P powdered and vitrified sample. Crystalline HAp exhibits an extended spin lattice network with a DQ/TQ filtering efficiency of 45/6.56 % at room temperature and a DQ efficiency of 38 % at 100 K in DNP juice. Powdered ACP was found to have a slightly lower DQ filtering efficiency of 43 % at room temperature and a DQ/TQ filtering efficiency of 33.4/3.7 % at 100 K in DNP juice. ATP suffered from low DQ and TQ filtering efficiencies of 3.12/0.28 % when powdered at room temperature and 1.3/0.4 % at 100 K (20 and 40 mM ATP in glycerol-d8 DNP juice). The mSBF sample suffered from low overall signal, thus not allowing for TQ filtering signal even after 1024 scans. However DQ filtering efficiency was determined to be 6.25 % at 100 K in DNP juice. Vitrified sodium monophosphate control sample (Figure ) exhibited no DQ filtering signal as expected, even after 512 scans. The refocusing of the CSA will be sensitive to magic angle frequency instabilities since the SR2 is a non-gamma encoded sequence. We carried out the numerical simulations mimicking the MAS fluctuations to find out its effect on DQ efficiency with and without CSA (shown in the Figure ). In both cases of CSA and non-CSA, the DQ signal intensity did not change with a fluctuation rate of ± 5 Hz, however, when the fluctuation was increased to ± 20 Hz, then DQ signal intensity was varied for both cases. During our experiments, the MAS fluctuation was around ± 5 Hz, indicating that the signal intensity variation was minimal as explained by simulation results.