PMID- 25225848
OWN - NLM
STAT- PubMed-not-MEDLINE
DCOM- 20150521
LR  - 20141015
IS  - 1364-5528 (Electronic)
IS  - 0003-2654 (Linking)
VI  - 139
IP  - 22
DP  - 2014 Nov 21
TI  - Visualizing mass transport in desorption electrospray ionization using 
      time-of-flight secondary ion mass spectrometry: a look at the geometric 
      configuration of the spray.
PG  - 5868-78
LID - 10.1039/c4an01481b [doi]
AB  - Time-of-flight secondary ion mass spectrometry (ToF-SIMS) was used to visualize 
      the transport of analyte molecules desorbed onto a silicon wafer collection 
      substrate by desorption electrospray ionization (DESI). The effect of spray 
      incidence angle, tip height, and probe distance on the concentration and the 
      spatial distribution of desorbed analyte molecules were investigated with the 
      objective of identifying DESI operational parameters that provide more 
      reproducible results by achieving steady ion transmission and minimized material 
      loss. An incidence angle between 25 degrees  and 35 degrees  with respect to the plane of the 
      surface provided the best compromise between maximizing ambient MS signal and 
      achieving the best reliability. Glancing incidence angles provided higher ambient 
      MS signals through a tighter dispersion of the secondary droplet plume, but 
      run-to-run variability of as much as 40%. On the other hand, steeper incidence 
      angles led to a widening of the lateral dispersion of the secondary droplets and 
      decreased analyte desorption. For all incidence angles, shorter probe distances 
      were preferred since the resulting tighter dispersion of the secondary droplets 
      produced higher ion transmission and therefore higher ambient MS signals. Tip 
      height was found to correlate with the spot size (footprint) of the spray on the 
      surface; changing the tip height from (1 to 2 to 3) mm changed the diameter of 
      the spray impact area from (1.3, 1.8, to 2.1) mm, respectively. For shorter probe 
      to MS inlet distances, larger tip heights increased the ambient MS signal due to 
      increased analyte desorption while maintaining a tighter dispersion of the 
      secondary droplet plume. Equally important to optimizing instrument configuration 
      was the understanding that the deposition of a sample onto the surface resulted 
      in a coffee ring, where the diameter was larger than the spot size of the spray. 
      Higher tip heights may be preferred for a more consistent analyte response since 
      all or a large fraction of the analyte could be sampled to reduce variability in 
      ambient MS response. The study showed that ToF-SIMS can be used as a unique tool 
      for characterizing the transport of desorbed analyte molecules for DESI, and 
      potentially offers insight into new interface designs for improved transmission 
      of analyte into the mass spectrometer.
FAU - Muramoto, Shin
AU  - Muramoto S
AD  - National Institute of Standards and Technology, Gaithersburg, MD 20899, USA. 
      shinichiro.muramoto@nist.gov.
LA  - eng
PT  - Journal Article
PL  - England
TA  - Analyst
JT  - The Analyst
JID - 0372652
EDAT- 2014/09/17 06:00
MHDA- 2014/09/17 06:01
CRDT- 2014/09/17 06:00
PHST- 2014/09/17 06:00 [entrez]
PHST- 2014/09/17 06:00 [pubmed]
PHST- 2014/09/17 06:01 [medline]
AID - 10.1039/c4an01481b [doi]
PST - ppublish
SO  - Analyst. 2014 Nov 21;139(22):5868-78. doi: 10.1039/c4an01481b.