This Application note demonstrates how MassPREP Neg Ion Mode Calibrant should be prepared for MALDI MS analysis.
MALDI-TOF MS has been widely used as a very practical tool for mass analysis of biopolymers, such as peptides and oligosaccharides. Most analysis is performed in positive ion reflectron mode. Analytes such as acidic peptides, phosphopeptides and sialylated glycans have better ionization efficiency in negative ion mode, therefore, it is ideal to analyze them in the negative ion mode to obtain higher ion counts. Waters has developed a high purity calibration standard under the trade name of MassPREP Neg Ion Mode Calibrant for accurate negative ion mass calibrations. This standard provides polymeric peaks across the mass range of 700 to 4,000 amu. Sample preparation is made simple using the standard. This document demonstrates how MassPREP Neg Ion Mode Calibrant should be prepared for MALDI MS analysis. A general guideline on how to perform negative ion data acquisitions using Waters MALDI micro MX is also included.
Waters MassPREP Neg Ion Mode Calibrant (2AA-Dextran) 100μg lyophilized solids/vial
• Waters MassPREP MALDI Matrix DHB,10 mg/vial
• Ammonium tris-citrate (Sigma-Aldrich)
• Acetonitrile (High purity grade, J.T Baker)
• High purity Milli-Q water
• Waters MALDI Plate
• Glu-fibrino peptide (Glu-Fib, Sigma-Aldrich)
Note: Optimization for specific applications is recommended. Other relative ratios and solvents may be used for reconstitution.
Detector Voltage =2400V
Flight Tube = 15,000V
Negative Anode = 5000V
Mass Range = 700-5000 amu
Laser Firing Rate = 10Hz, 10 shots/spectrum
A MALDI mass spectrum of the calibrant is shown in the following page (Figure 2). The mass accuracy of the instrument after calibration is shown in Figure 3 using glu-fibrino peptide as a test sample.
720002340, September 2007