Time-of-Flight SIMS / TOF-SIMS
MS/MS Option NEW
Announcing a revolutionary option for the PHI nanoTOF II instrument -
Parallel Imaging MS/MS!
Recent advances in primary ion cluster beam technology have improved TOF-SIMS usefulness by increasing the secondary ion yields of high mass fragments (>200 Da), thus, providing even better chemical speciation. However, with
the increased production of high mass fragments comes the difficulty of identifying the composition or
structure of these fragments. To overcome this obstacle, PHI has developed the first commercial TOF-SIMS tandem mass spectrometry instrument
(MS/MS). The design allows a monoisotopic (i.e., 1 Da) mass window of secondary ions of choice (precursorions) to be selected for fragmentation in a high energy collision induced dissociation (CID) cell and mass analyzed in a separate spectrometer. This provides for unambiguous peak identification and parallel MS/MS imaging capability. At both the MS1 and MS2 detectors, a full mass spectrum is collected for each image pixel.
MS2 CID spectrum of the m/z 201 precursor with the composition of the fragment ions shown. The
inset indicates the fragmentation that produces the specified ions.
Parallel Imaging MS/MS
To exemplify the use of high spatial resolution parallel MS/MS imaging, a heat-treated sample of polyethylene
terephthalate (PET) was analyzed using a Bi3+ primaryion source. During heat-treatment very small thin crystals, believed to be cyclic ethylene terephthalate trimer, are formed on the PET surface. Analysis of these crystals with TOF-SIMS produced a positive ion spectrum containing a strong peak at m/z 577. MS/MS analysis of this peak confirmed its composition as [3M+H]+ (C30H25O12+). The adjacent figure shows the total ion and m/z 149 images from both MS1 and MS2, confirming that identical areas are analyzed simultaneously with the two spectrometers. The MS2 images, originating from the m/z 577 precursor peak, indicate that the PET trimer is indeed localized to the crystals. Line scans across the PET trimer crystals showed lateral beam resolutions of less than 0.2 μm(80/20% measurement).
Unambiguous Peak Identification
Traditional TOF-SIMS analysis of a proprietary material showed the presence of a peak at m/z 201 in the negative polarity, believed to be an unknown additive in the material. To determine the composition of the additive, the m/z 201 peak was selected as the precursor ion and deflected into the CID cell. The composition assignments for the masses observed in
the MS2 spectrum, along with the structure of the precursor ion (diphenylphosphine oxide - DPPO), are shown. A literature search of DPPO indicates that it can be used as a photoinitiator, making perfect sense as an additive in this proprietary material.
Parallel imaging of MS1 and MS2 peaks. Positive secondary ion images, 40 μm field-of-view, 10 μm
scale bar, 256 x 256 pixels, 6nA Bi3+.