Derivatization assisted LC-p-MRM-MS with high CID voltage for rapid analysis of brassinosteroids.

In this study, a derivatization-assisted pseudo-multiple reaction monitoring with high CID voltage (HV-p-MRM) strategy was proposed for the analysis of brassinosteroids (BRs) by liquid chromatography-triple quadrupole mass spectrometry (LC-QqQ MS). The concept of the HV-p-MRM strategy was proposed on the basis of an assumption that the precursor ion of analyte is stable in collision cell and less prone to fragmentation at high CID voltage, while co-existing ions (impurity) of easy fragmentation can break down into smaller fragment ions. In such case, by increasing the CID voltage, the co-existing ions that are introduced due to the low resolution of the quadrupole 1 (Q1) can be filtered out by quadrupole 3 (Q3), while the stable precursor ion of analyte will pass through Q3, thereby that the signal-to-noise ratio (S/N) of the analysis can be improved. As a proof-of-concept study, BRs were derivatized with rhodamine B-boronic acid (RhB-BA) and then the derivatives were used to investigate their variations in MS signal, background noise, and S/N upon the CID voltage and MS scanning resolution. The results showed that S/N of these derivatives can be improved in HV-p-MRM mode. To further demonstrate the feasibility of HV-p-MRM strategy, a RhB-BA derivatization assisted LC-HV-p-MRM-MS method was developed for the analysis of BRs. Using this method, rapid and sensitive determination of BRs in different organs of rape flower was achieved. It can be expected that HV-p-MRM may be suitable for the analytes that are stable or can be converted into compounds of high stability in collision cell at high CID voltage.

[Mastoid surgery for secretory otitis media with mixed hearing loss].

OBJECTIVE: To analyze the therapeutic effect of mastoid surgery for secretory otitis media with mixed hearing loss. METHODS: A retrospective analysis was conducted of the data from 26 cases (43 ears) of secretory otitis media with bone conduction hearing loss collected from 2001 to 2008. Thirty-two ears were treated with mastoid surgery and myringotomy with insertion of ventilation tubes. All the patients received medications after the operation. RESULTS: All the patients showed obvious improvement after mastoid surgery. The average pure tone of air conduction hearing threshold was about 25 dB after the surgery, with the average pure tone of bone conduction hearing threshold of about 15 dB. The patients were followed up for 1-2 years during which no significant change in hearing was recorded, and no middle ear effusion in the tympanic cavity was found after removal of the ventilation tubes. CONCLUSION: Persistent secretory otitis media can be associated with mixed hearing loss, and mastoid surgery can significantly enhance the hearing level to produce positive therapeutic effects.