Analysis of heterogeneous fluorescence decays. Distribution of pyrene derivatives in an octadecylsilane layer in capillary electrochromatography.
Analysis of heterogeneous fluorescence decays. Distribution of pyrene derivatives in an octadecylsilane layer in capillary electrochromatography.
复制标题
异质荧光衰变分析。
DOI：
10.1021/ac010293u
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发表时间：
2001
影响因子：
7.4
通讯作者：
Lei Geng
中科院分区：
文献类型：
--
作者：
Yan He;Lei Geng
用时间分辨荧光频域技术研究了毛细管电色谱（CEC）固定相中溶质分子的分布。荧光衰减的分析提出了一个具有挑战性的问题，复杂的衰减动力学的非均相系统，如C18固定相。非线性最小二乘（NLLS）方法通过最小化卡方值来选择衰减模型。卡方2准则，结合残差应该随机分布在零附近的要求，经常会导致一组可行的多个衰变模型，这些模型都可以令人满意地拟合数据。最大熵方法（MEM）通过最大化香农-杰恩斯熵，进一步从可行模型组中选择唯一的模型。然而，唯一的模型不一定是最可能的模型。本文利用卡方统计量、拟合的稳定性和重复实验的一致性，用非线性最小二乘法选择溶质分子荧光衰减的最佳模型。此外，当实验条件改变时，真实模型的恢复寿命参数应显示与荧光衰减曲线相同的趋势。使用这些标准，荧光寿命的高斯分布令人满意地拟合在所有实验条件下的数据。具有离散寿命的附加次要部件归因于测量中的系统误差。这种分布是CEC稳定期异质微环境集合的表现。MEM是不适合CEC数据的建模，因为它在恢复广泛的荧光寿命分布的不准确性和它的重复测量在高电压效应的研究缺乏一致性。
The distribution of solute molecules in the stationary phase in capillary electrochromatography (CEC) has been investigated with time-resolved fluorescence in the frequency domain. The analysis of fluorescence decay poses a challenging problem for the complex decay kinetics of heterogeneous systems such as the C18 stationary phase. The nonlinear least-squares (NLLS) method selects the decay model by minimizing the chi2 value. The chi2 criterion, in conjunction with the requirement that the residues should be randomly distributed around zero, frequently leads to a feasible set of multiple decay models that can all fit the data satisfactorily. The maximum entropy method (MEM) further chooses a unique model from the group of feasible ones by maximizing the Shannon-Jaynes entropy. The unique model, however, is not necessarily the most probable one. In this paper, the best model for the fluorescence decays of solute molecules is selected with NLLS using the chi2 statistics, the stability of the fit, and the consistency within replicate experiments. In addition, the recovered lifetime parameters of the true model should display the same trend as the fluorescence decay profiles when an experimental condition is varied. Using these criteria, a Gaussian distribution of fluorescence lifetimes satisfactorily fits the data under all experimental conditions. An additional minor component with a discrete lifetime is attributed to the systematic errors in the measurements. The distribution is a manifestation of an ensemble of heterogeneous microenvironments in the stationary phase of CEC. MEM is not suitable for the modeling of CEC data because of its inaccuracy in recovering broad fluorescence lifetime distributions and its lack of consistency in the replicate measurements in the studies of high-voltage effects.