MALDI/FTMS质量校准新方法

在MAIDL/FTMS质量校准中采用 mz =Af +Bf2 模型 ,通过基质峰的测定频率对模型中的参数A ,B进行调整 ,使模型参数更加接近测定状态 ,调整后模型的计算结果明显改善 ;并对多元回归和单纯形法两种建模方法以及单纯形法的目标函数进行了考察 ,结果表明以最大相对误差绝对值为目标函数的单纯形法建立的模型在预测离子质量方面具有较好的稳健性 ,质量测定相对误差均小于 5× 10 -6.用此法分析了克拉霉素的IRMPD质谱裂解规律 ,得到了合理的裂解规律

Novel Approach of Mass Calibration in MALDI/FTMS

Because all ions in the same experimental conditions undergo the same shift induced by the electric field associated with the charge of the ions in the analyzer cell in MALDI/FFMS, the constants A and B in calibration equation(mz=Af+Bf 2)are amended by the shift of matrix peak observed frequency. The mass obtained by the amended calibration equation is therefore immune to space-charge effects on mass accuracy. Comparison of prediction performance of the calibration models constructed by multivariate regression and simplex method was studied. Simplex method, in which maximum relative error acts as objective function, is superior on solidity of ion mass prediction.And the relative errors of ion mass measured all are less than 5x10 -6. The IRMPD fragment ions of clarithomycin were determined by this method, and the fragmentation patterns were discussed.