since the first practical implementation of electrospray ionization ( esi ) with mass spectrometry reported by yamashita and fenn in 1984 , a number of different atmospheric pressure ionization ( api ) techniques have been developed .
many api techniques require extensive sample preparation as well as costly consumables to obtain mass spectra .
one of the most cost effective and widely available media for chemical separation and analysis is paper .
it has been shown that an electro - osmotic flow similar to that of static electrospray can be utilized to interface a triangle of wetted paper to a mass spectrometer ( ms ) ; this form of analysis is called paper spray ( ps ) [ 49 ] .
the use of a chromatographic medium such as paper allows for the analysis of complex mixtures since separations will occur as the analyte is being driven along the paper medium .
separating analytes on a paper medium provides the benefits of reduced probability of ion suppression and rapid analysis .
the paper medium allows for analysis of complex samples such as biological tissue and dried blood spots which are not suitable for traditional infusion techniques due to their complex matrices [ 4 , 7 ] .
one limitation to ps , like many ms techniques that utilize incomplete chromatographic separations is the detector being utilized to perform the analysis .
when dealing with complex samples or unknown samples , there is a need for high - quality data in order to determine what is being analyzed .
fourier transform ion cyclotron resonance ( ft - icr ) mass spectrometers are powerful tools for analysis of complex mixtures due to their unsurpassed capability to obtain broadband high - resolution mass spectra with high mass accuracy . utilizing ps with a fourier transform ion cyclotron resonance ( ft - icr ) mass spectrometer as a detector allows for rapid analysis of both unknowns and/or complex mixtures . in this present work ,
we show the suitability of a 12  tesla ft - icr ms to obtain high - resolution broadband mass spectra utilizing a coffee filter paper spray medium .
high - resolution mass spectra were first obtained for polypropylene glycol ( ppg ) and polyethylene glycol ( peg ) standards to test the source .
second , urine and calf lung surfactant extract ( clse ) were analyzed to test the ps source for analysis of complex mixtures not suitable for direct infusion .
all solvents used were hplc grade obtained from sigma aldrich ( st . louis , mo , usa ) .
ppg was obtained in the form of a tuning standard from applied biosystems ( bedford , ma , usa ) .
peg standard was made by dissolving 1  mg of peg 2000 obtained from sigma aldrich ( st . louis , mo , usa ) in 1  ml of hplc grade water .
coffee filter , wegmans brand ( rochester , ny , usa ) , was cut by hand into an isosceles triangle with dimensions of approximately 5  mm ( base ) by 10  mm ( height ) . 

samples for ppg and peg ps analysis were prepared by wetting the coffee filter triangle with 10  l of the standard solutions .
the wet filter paper samples were allowed to dry under ambient conditions before ps analysis was performed .
mass spectra were then obtained by wetting the dried paper triangle with 10  l of 50  :  50 methanol  :  water and using the method described in section 2.5 .
( amherst , ny , usa ) . prior to analysis , the sample was stored in chloroform in the refrigerator .
samples for clse analysis were produced by wetting a coffee paper triangle with 2  l of clse and allowing the sample to dry under ambient conditions before ps analysis was performed .
mass spectra were then obtained by wetting the paper with 10  l of 50  :  50 methanol  :  water using the instrument method described in section 2.5 .
urine samples were collected from two healthy adult males into sterile polypropylene centrifuge tubes ( vwr scientific ) and immediately placed in the freezer .
the samples were collected in accordance with the health sciences institutional review board at the university at buffalo ( hsirb no .
prior to analysis , the samples were thawed to room temperature and 1  ml was pipetted into 2  ml sample vials ( agilent , santa clara , ca , usa ) for use .
ten l was injected directly onto a triangular coffee filter and allowed to dry under ambient conditions .
once dry , the filter paper was attached to the mass spectrometer via a copper clip and rewetted using 50  :  50 methanol  :  water for ps analysis using the instrument method described in section 2.5 .
high - resolution spectra were obtained on a 12 t bruker solarix ft - icr ms ( bruker daltonics inc . ,
the positive potential was obtained by grounding the paper triangle using a copper clip and applying a negative voltage at the inlet to the mass spectrometer ( figure 1 shows an image of the source ) .
mass spectra were obtained at various mass to charge ranges with a pre - ft - icr - trap hexapole accumulation time of 0.400 seconds and an ft - icr trap accumulation time of 0.025 seconds .
all mass spectra were obtained in the positive mode at a spray voltage of 2  kv .
  polymeric standards were utilized to determine the suitability of ps with high - resolution ft - icr ms . in ft - icr ms the resolution of the mass spectra is relative to m / z as well as the number of data points that can be obtained during the detection process .
high - resolution spectra require a time domain signal stable for longer than several hundred milliseconds .
polyethylene glycol and polypropylene glycol produce a broad m / z range of ions ideal for testing the suitability of ps with high - resolution mass spectrometry .
high - resolution mass spectra of peg and ppg are displayed in figures 2 and 3 , respectively .
identifies of the oligomer ion detected and their associated errors is given in tables 1 and 2 , respectively .
signal - to - noise obtained for peg and ppg after tuning spectra was in excess of 100/1 with absolute intensities that varied shot - to - shot by less than 20% .
this allowed ample time for adjustment of the filter paper towards the inlet of the mass spectrometer so as to optimize instrument setup and analysis .
utilizing polymers of known m 
 n values ( provided by the manufacturers ; polydispersity not given ) such as peg 2000 and ppg 2000 provides a detection window several hundred m / z wide for broad mass accuracy calibrations for ft - icr ms .   
calf lung surfactant extract ( clse ) , which is commercially available in drug form as infasurf , is used to treat respiratory distress syndrome .
clse is obtained by doing a total lipid extraction on the lavage fluid from a slaughtered calf lung [ 11 , 12 ] .
phosphatidylcholine ( pc ) makes 79% of the molar distribution of lipids and consists of a choline head group attached to the phospholipid with varying degrees of unsaturation in the fatty acid chains .
based on the optimized setup determined from previously analyzing the standards , clse was then analyzed .
ps mass spectra of clse are given in figures 4 and 5 , and the identities with associated error provided in table 3 .  
due to the complex nature of urine , many small molecules and metabolites were detected at varying intensities using ps with ft - icr .
ps mass spectra , showing numerous lipids and other metabolites obtained from the analyzed urine specimens of two healthy adult male subjects , are shown in figure 6 ; an inset of one of these ps mass spectra is shown in figure 7 while the other is shown in figure 8 .
a few of the metabolites identified in the 27-year - old volunteer using the exact mass capability of ft - icr are provided in table 4 .
metabolites identified in the 44-year - old volunteer using the exact mass capability of ft - icr are given in table 5 .
of note , the 44-year - old volunteer , who was taking prescribed vitamin d supplements , showed indications of the vitamin d metabolite 25-hydroxyvitamin d2 - 25-glucuronide in the urine .
interestingly , both adult male subjects had indications of one or more glucuronides in urine .
this may signal a particularly strong propensity for glucuronides to ionize via the ps ionization mechanism ; this capability of ps should be further explored .
we developed a ps source for bruker ft - icr instrumentation that can be utilized for a broad range of chemical species .
the ps source was tested on a range of samples and determined the source was suitable for both polymer and biological samples .
the ps source provided an api medium for the analysis of complex mixtures while mitigating the possibility of cross contamination due to the disposable nature of coffee filter paper .
 paper spray ionization is an atmospheric pressure ionization technique that utilizes an offline electro - osmotic flow to generate ions off a paper medium . 
 this technique can be performed on a bruker solarix fourier transform ion cyclotron resonance mass spectrometer by modifying the existing nanospray source . 
 high - resolution paper spray spectra were obtained for both organic and biological samples to demonstrate the benefit of linking the technique with a high - resolution mass analyzer . 
 error values in the range 0.23 to 2.14  ppm were obtained for calf lung surfactant extract with broadband mass resolving power ( m/m50% ) above 60,000 utilizing an external calibration standard . 