Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, USA.
Rapid Commun Mass Spectrom. 2009 Dec;23(24):3963-8. doi: 10.1002/rcm.4331.
An online nano-aerosol sample deposition method for matrix-assisted laser desorption/ionization (MALDI) mass spectrometry is described in which matrix and analyte particles between 50 and 500 nm are aerodynamically focused onto a tight spot, ca. 200 microm in diameter, on the target plate under vacuum. MALDI analysis of the target is performed without additional sample preparation. The method is evaluated with insulin as the analyte and alpha-cyano-4-hydroxycinnamic acid (CHCA) as the matrix. Two preparation modes are compared with conventional dried-droplet deposition: mixture deposition where a single layer is deposited consisting of particles that contain both matrix and analyte, and layered deposition where an underlayer of matrix particles and an overlayer of analyte particles are deposited separately. Desalting is performed by adding ammonium sulfate to the solution used to generate the matrix aerosol. With mixture deposition, the optimum matrix-to-analyte mole ratio is about 500:1 compared with 5000:1 for the conventional dried-droplet method. With layered deposition, the thicknesses of the matrix and analyte layers are more important determinants of the analyte signal intensity than the matrix-to-analyte mole ratio. Analyte signal intensities are independent of matrix layer thickness above 200 nm, and the optimum analyte signal is obtained with an analyte layer thickness of about 100 nm.
一种用于基质辅助激光解吸/电离（MALDI）质谱的在线纳米气溶胶样品沉积方法，其中 50nm 至 500nm 之间的基质和分析物颗粒在真空中被气动聚焦到靶板上约 200μm 直径的紧密点上。无需额外的样品制备即可对目标进行 MALDI 分析。该方法使用胰岛素作为分析物和α-氰基-4-羟基肉桂酸（CHCA）作为基质进行评估。将两种制备模式与传统的干液滴沉积进行比较：混合物沉积，其中沉积单层，其中包含既含有基质又含有分析物的颗粒，以及分层沉积，其中沉积基质颗粒的底层和分析物颗粒的顶层分别沉积。通过向用于生成基质气溶胶的溶液中添加硫酸铵来进行脱盐。对于混合物沉积，最佳的基质与分析物摩尔比约为 500:1，而传统的干液滴方法为 5000:1。对于分层沉积，基质和分析物层的厚度比基质与分析物摩尔比更能决定分析物信号强度。分析物信号强度不依赖于基质层厚度超过 200nm，并且在分析物层厚度约为 100nm 时获得最佳的分析物信号。
