Fast scan high resolution mass spectrometer system for use with gas chromatography instrumentatio

Lipsky, S. R.

English

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SC-N~G-l92/07-004-008 
S.R. Lipsky 
Yale Ulqiversity School of Medicine 
333 Cedar S t r e e t  
Xew Haven, Connecticut 06510 
February 25, 1966 
Progress Report 
During t h e  period extending from J u l y  1, 1965 through December 
31, 1965, t h i s  labora tory  completed i t s  development of a fas t  scan 
high r e so lu t ion  mass spectrometer system f o r  use i n  conj ui-ictloi-1 
w i t h  gas chronatography instrumentation. From t h e  r e s u l t s  obtained 
t o  da te ,  w e  are of t h e  opinion t h a t  t h i s  system represents  the  
most advanced state of the art  and appears t o  have gene-ratea w l c e  
spread i n t e r e s t  i n  the s c i e n t i f i c  community. 
l a b o r a t o r i e s  are now i n  t h e  process of ai;?ting this  technique. 
Because of c h i s ,  ; n a y  
I n  essence w e  now have t h e  capabi l lcy of 
- .  a)  Rapid High Resolution Scanning 
A chromatographic peak can be scanned i n  6 t o  1 0  secon&s, 
w i t h  a reso lv ing  power of a t  l e a s t  1 i n  10 ,000 ,  cover5ns a decaaz 
i n  mass. T h i s  can be ca r r i ed  out  or: a peak containing cpproximately 
0.6 micrograin. 
b) Rapid Re t r i eva l  of Data 
The da ta  i s  recorded on a magnetic t ape  system a t  60 inches 
per  second. 
at- 17/8 i p s .  a t  any time t o  check the spectrum. 
One can then  play it back i n t o  an  osc i l lographic  recorder  
The analog cape 
I s  then d i g i t i z e d .  The d i g i t i z e d  data  i s  then  analyzed by means 
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of comp-cer programs and a l l  t h e  fragments of t h e  spectrum are 
converted i n t o  accurate  masses (accuracy better then  1 0  ppm) and 
t h e  elemental  composition of each mass i s  determined. The stare 
of the technology i s  such t h a t  t h i s  information can be obtained 
i n  rea l  t i m e  i f  a fast d i g i t i z e r  i s  a v a i l a b l e  f o r  on l i n e  operation. 
Approximately 60 mass spec t ra  can be conveniently obtained fror. 6 
Chroiii&tographiz run if nezessai.y. 
c )  Automatic switching from 'nigh t o  low r e s o l u t i c n  m o d e  dur ing 
t h e  course of a chromatographic analysis. This enables one co 
procure low re so lu t ion  spec t ra  (1 i n  1500)  on trace cornpone,.- kzds 
containing less t h m  0.3 microgram of material. 
d) Rapid High Resolution Scans on r e l a t i v e l y  non-volat i le  samples 
introduced i n t o  the ion  source by means of a d i r e c t  i n s e r t i o n  probe. 
By scanning over a 72 second t o  1 0 0  second period, eepending upon 
sample s i z e  arid r e so lu t ion  des i red  (one i n  1 0  t o  20,000 plus) and 
recording on m g n e t i c  tape ,  'elemem maps' can be procured very 
r e a d i l y  here.  
Molecular Separators 
One of t h e  most important f ace t s  of t h e  mass s?ectror .c- t r -  
gas chromatograph taridem operat ion i s  t h e  i n t e r f a c i n g  with a molecular 
separa tor .  
of t h e  c a r r i e r  gas p r i o r  t o  t h e  entrance of t h e  chromatographic 
e f f l u e n t s  i n c s  the ion  source cont r ibu tes  much t o  th  o v e r a l l  
Tke e f i i c i ency  of t h e  separator  i n  removing t h e  bulk 
, 
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s e n s i t i v i t y  of che system. Tnus E 6 r  t'hree systems have been invescigated. 
a )  The f r i t t e d  tube system (Watson-Biemann). Uncer oj?tin&l con- 
d i t i o n s ,  t h i s  sys-cem was found t o  provide e f f i c i e n c i e s  of 8 co 20% 
depending upon flow rate,  temperature, p u q i n g  speed, and t h e  molecular 
weight of compounds being analyzed. 
b) The molecular separator syscern (Ryhage) Ihder optimal  condi t ions  
e a r l y  vers ions  of th is  device provided e f f i c i e n c i e s  in t h e  1-3% 
range. 
speed on t h e  secocd s tage  of t h e  sys2em p o v l d e d  a s l p i f i c a n t  
iiprovement. 
Clanging t h e  diameters of tke j e t s  and increas ing  t h e  p-mpin5 
Ef f i c i enc ie s  are now 5-n t h e  40-50% range. 
c) High temperature membrar'es . Zarly resulcs here a r e  i n t r i p i n s  
and w i l l  be pursiled. Using t e f i o n  o r  s i l i c o n e  f i l m  one not ices  
absorpt ion,  s o l u b i l i z a t i o n  and/or d i f fus ion  of organic rr,olecules 
across  t h e s e  membranes, depending upon temperature, menbrane * .  
th ickness ,  pdmping speed, t i m e  cocstants ,  e t c .  
t h a t  one can procure organic molecules cox@eizely f r e e  of c a r r i e r  
gas under t k e  ?ro$er circumstances. 
sample loss under optimal conditions w i l l  be undertaken shor t ly .  
Ind ic&t ions  &re  
Experinenzs determinicg 
Support Coated Porous Layer Columns 
Tais type of column developed severa l  years  ago by Horvath 
(who now i s  a member of our laboratory group) was ca-lefully 
appraised for use i n  conjunction w i t h  t h e  tandem combination of 
instruments.  It appears i d e a l l y  su i t ed  f o r  t h i s  app l i ca t ion  for 
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t h e  fol lowin5 reasons : 
a )  a 50 ft .  0.020 i . d .  column y ie lds  25,000 t h e o r e t i c a l  p l a t e s  
3) it w i l l  accept  loads varying from f r a c t i o n s  of a microgram 
t o  hundreds of micrograms without a p p e c i a b l e  l o s s  of resoluzior, 
c) carrier gas flow rates are small - 4 t o  10 m l .  helium per  
minute 
d )  the bleed race of l i q u i d  phase i s  exceedingly low - thus 
providing one w i t h  an exce l l en t  s i p a l t o  noise  r a t i o  
e )  sample s 2 l l c t i n g  i s  nc t  require6 
f) colurins can be made reproducibly 
Computer Programs 
Programs were devised t o  f i n d  t h e  masses and elemental con2ositior. 
of a l l  of t h e  fragments of a spectrum obtained during t h e  f a s t  scan 
mode. -. 
Biochem5cal h a l y s  i s  
Followizg t h e  completion of the  e f f o r t  t o  optimize molecular 
separa tor  design and funct ions,  w e  w i l l  be i n  a pos i t i on  t o  s t a r t  
our inves t igac ions  cha rac t e r i z ing  organic comsoilnds found i n  
d i f f e r e n t  types of rocks,  s o i l s  etc. 
planned t o  perform pyro lys is  s tud ie s  on known Siochemical compounds, 
bacteria, fungus, v i ruses  etc. Pyrolysis condi t ions w i l l  be optimized 
and products i d e n t i f i e d  i n  an ateempt t o  recons t ruc t  t h e  na ture  of 
the o r i g i n a l  s tGr t ing  mater ia l .  
I n  th i s  regard it i s  a l s o  
I 


Conduct Research on Gas Chromatographic Systems to Analyze Certain Chemical Constituents of the Surface of the Moon Progress Report, 1 Jul. - 31 Dec. 1965

Conduct Research on Gas Chromatographic Systems to Analyze Certain Chemical Constituents of the Surface of the Moon Progress Report, 1 Jul. - 31 Dec. 1965

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