Because many therapeutic agents are contaminated by epimeric impurities or form epimers as a result of metabolism, analytical tools capable of determining epimers are increasingly in demand. This article is a proof-of...Because many therapeutic agents are contaminated by epimeric impurities or form epimers as a result of metabolism, analytical tools capable of determining epimers are increasingly in demand. This article is a proof-of-principle report of a novel DMS–MS/MS method to separate and simultaneously quantify epimers, taking PGF2α and its 8-epimer, 8-iso-PGF2α, as an example. Good accuracy and precision were achieved in the range of 10–500 ng/m L with a run time of only 1.5 min. Isopropanol as organic modifier facilitated a good combination of sensitivity and separation. The method is the first example of the quantitation of epimers without chromatographic separation.展开更多
In this study,hygroscopicity of size-segregated ambient submicron particles in urban Hangzhou was studied from 28th December 2009 to 18th January 2010,using a hygroscopicity-tandem differential mobility analyzer(H-TDM...In this study,hygroscopicity of size-segregated ambient submicron particles in urban Hangzhou was studied from 28th December 2009 to 18th January 2010,using a hygroscopicity-tandem differential mobility analyzer(H-TDMA).The submicron particles in Hangzhou showed a minor hygroscopic growth at 73%relative humidity(RH),and then grew significantly between 77%and 82%RH.Monomodal distribution accounted for 90%for 30 nm particles,17%for 50 nm particles,and less than 7%for particles larger than 50 nm at 82%RH.Deconvolution of the bimodal distribution indicated a less hygroscopic group and a more hygroscopic group,with the fraction of the more hygroscopic group increasing with the initial dry particle size and then remaining almost constant for accumulation mode particles.Our results imply that submicron particles in urban Hangzhou were almost entirely externally mixed,and the hygroscopic properties of ambient particles in urban Hangzhou were mainly a function of their size and chemical composition.展开更多
The inversion of the particle size distribution from electrical mobility measurements is analyzed. Three different methods are adapted for a dot-matrix approach to the problem, especially for non-square or singular ma...The inversion of the particle size distribution from electrical mobility measurements is analyzed. Three different methods are adapted for a dot-matrix approach to the problem, especially for non-square or singular matrices, and applied to electrical mobility measurements from fixed or scanning voltages. Mul- tiply charged particles, diffusion losses, arbitrary voltage steps and noise were considered, which results in non-adjoining and overlapping transfer functions. The individual contribution of the transfer func- tions in each size interval was geometrically estimated, which requires only its characteristic mobilities. The methodology is applied to mobility measurements from particles charged with unipolar and bipolar chargers. However, the method can be extrapolated to any charging method with a defined charge distribution, and retrieval of the singly charged particle distribution and mean charge from a tandem differential mobility analysis configuration was successfully demonstrated.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.81430087 and 81673396)
文摘Because many therapeutic agents are contaminated by epimeric impurities or form epimers as a result of metabolism, analytical tools capable of determining epimers are increasingly in demand. This article is a proof-of-principle report of a novel DMS–MS/MS method to separate and simultaneously quantify epimers, taking PGF2α and its 8-epimer, 8-iso-PGF2α, as an example. Good accuracy and precision were achieved in the range of 10–500 ng/m L with a run time of only 1.5 min. Isopropanol as organic modifier facilitated a good combination of sensitivity and separation. The method is the first example of the quantitation of epimers without chromatographic separation.
基金This work was financially supported by the National Natural Science Foundation of China(Grant Nos.21077025,40875073,40975075,20937001)the Science&Technology Commission of Shanghai Municipality(Nos.09160707700,10231203801,10JC1401600).
文摘In this study,hygroscopicity of size-segregated ambient submicron particles in urban Hangzhou was studied from 28th December 2009 to 18th January 2010,using a hygroscopicity-tandem differential mobility analyzer(H-TDMA).The submicron particles in Hangzhou showed a minor hygroscopic growth at 73%relative humidity(RH),and then grew significantly between 77%and 82%RH.Monomodal distribution accounted for 90%for 30 nm particles,17%for 50 nm particles,and less than 7%for particles larger than 50 nm at 82%RH.Deconvolution of the bimodal distribution indicated a less hygroscopic group and a more hygroscopic group,with the fraction of the more hygroscopic group increasing with the initial dry particle size and then remaining almost constant for accumulation mode particles.Our results imply that submicron particles in urban Hangzhou were almost entirely externally mixed,and the hygroscopic properties of ambient particles in urban Hangzhou were mainly a function of their size and chemical composition.
基金support under the project MEC05CGL2005-05244/CLI and grant BES-2006-12469supported by the Deutsche Forschungsgemeinschaft(DFG) in the framework of the joint research program "Multiparameter Characterization of Particle-based Functional Materials by Innovative Online Measurement Technology" (PAK688)
文摘The inversion of the particle size distribution from electrical mobility measurements is analyzed. Three different methods are adapted for a dot-matrix approach to the problem, especially for non-square or singular matrices, and applied to electrical mobility measurements from fixed or scanning voltages. Mul- tiply charged particles, diffusion losses, arbitrary voltage steps and noise were considered, which results in non-adjoining and overlapping transfer functions. The individual contribution of the transfer func- tions in each size interval was geometrically estimated, which requires only its characteristic mobilities. The methodology is applied to mobility measurements from particles charged with unipolar and bipolar chargers. However, the method can be extrapolated to any charging method with a defined charge distribution, and retrieval of the singly charged particle distribution and mean charge from a tandem differential mobility analysis configuration was successfully demonstrated.
