Abundance Stability Study of α-H Cleavage Induced by Free Radical Center Based on Linear Ion Trap Mass Spectrometry / 中国药学杂志

OBJECTIVE: To study the response stability of free radical center-induced α-H cleavage on linear ion trap mass spectrometry (LTQ-MS), and discuss the interaction mechanism in ion trap and the effects of hydrogen and deuterium hybrid loss on quantitation precision. METHODS: The special cleavage mode of D6-ornithine lactam was used to distinguish different α-H cleavage, and the factors that might affect the abundance stability were inferred by mechanism discussion and falsification. RESULTS: The quantitation precision of ion pairs with only hydrogen loss(115.1→97.1;121.1→103.1) and threonine instead of D6-ornithine lactam (115.1→70.1;120.1→74.0)was significantly better than that of ion pairs involving hydrogen-deuterium hybrid loss(115.1→70.1;121.1→75.1). When 115.1→70.1;121.1→75.1 were used, the quantitation precision of tandem quadrupole mass spectrometry was significantly better than that of LTQ-MS. CONCLUSION: The instability of ion abundance, the effect of quality discrimination and the effect of ion concentration saturation are not significant factors affecting the stability of LTQ detection signal. Combined with the fragmentation characteristics of D6-ornithine lactam and Matthew′s equation, it is proposed that the space charge in the trap is the main reason for the instability of the detection signal.

Correlation of molecular state of caffeic acid from Perilla frutescens and its nanofiltration mass transfer process / 中草药

Objective To explore the correlation of molecular state of caffeic acid from Perilla frutescens and its nanofiltration mass transfer process. Methods The pH value of solution was changed and the free-dissociation ratio was adjusted with caffeic acid as an index, the rejection and membrane flux of the corresponding initial concentration and operating pressure in different existence conditions were collected. Based on the solution-diffusion effect and charge effect in nanofiltration separation, the linear equations between the rejection and mass transfer coefficient was constructed, the correlation between mass transfer coefficient and initial concentration was established, the mathematical models which based on the operating pressure and initial concentration to predict the rejection of caffeic acid was developed and used to verify its applicability by aqueous extract of P. frutescens. Results Experiments indicated that there was a linear relationship between operation pressure and membrane flux. Besides, mass transfer coefficient and initial concentration of caffeic acid were positively correlated with each other by solution-diffusion effect and charge effect. The mass transfer coefficient of dissociated caffeic acid was less than those of free state and free-dissociation. Moreover, on the basis of power function relationship between mass transfer coefficient and initial concentration, the results showed that the predicted rejections of caffeic acid from P. frutescens water extract using mathematical model approximate well to real ones. Conclusion The mass transfer coefficient of caffeic acid is associated with existential state and initial concentration. The predicted model of nanofiltration separation has a preferable applicability to caffeic acid and provides references for nanofiltration separation, especially for heat-sensitive traditional Chinese medicine.

Exploring correlation between molecular state and nanofiltration mass transfer process of synephrine from Citrus aurantium / 中国中药杂志

Based on the solution-diffusion effect and the charge effect theory in nanofiltration separation, the correlation between initial concentration and mass transfer coefficient was constructed to establish a mathematic model of synephrine in mass transfer process and verify its applicability. The experimental results showed that there was a linear relationship between operation pressure and membrane flux. Meanwhile, the membrane flux was gradually decayed with the increase of solute concentration. Besides, mass transfer coefficient and initial concentration of synephrine showed power function correlation with each other by solution-diffusion effect and the charge effect, and the regression coefficients were greater than 0.9. The mass transfer coefficient of dissociation synephrine was less than that in the state of free and free-dissociation. Moreover, on the basis of power function relationship between mass transfer coefficient and initial concentration, the results showed that the predicted rejections of synephrine from Citrus aurantium water extract by use of the mathematical model approximated well to real ones, verifying that the model was practical and feasible. The unclear separation mechanism of nanofiltration for alkaloids was clarified preliminary by the predicted model of nanofiltration separation with synephrine as the example, providing theoretical and technical support for nanofiltration separation, especially for traditional Chinese medicine with alkaloids.