WHAT'S NEW WITH DART® MS?                                       March 2015   
 The Latest Developments in Direct Analysis in Real Time Mass Spectrometry 

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Lately there has been more interest in the application of DART-MS to problems in polymer characterization so we thought it would be helpful here to show some of the work that has been done in this area. 

We have highlighted a number of papers - from the bulk analysis of polymer molecular weights to the characterization of the additives responsible for polymer properties.  Additionally there are studies looking at some of these additives that get ingested by us.

If you have interest in seeing how DART can be applied to your problems in this area, please contact us.  We are able to run virtual demos where you can watch your sample being analyzed from the comfort of your own desk or iPad.

 Feel free to contact me if you have any questions or comments.  Thanks.


Brian Musselman, Ph.D.
President and CEO

Recent DART Publications on Polymers and Materials

The Complete DART Bibliography is Now Available - CLICK HERE

Capabilities and limitations of direct analysis in real time orbitrap mass spectrometry and tandem mass spectrometry for the analysis of synthetic and natural polymers


Maxime C. Bridoux and Xavier Machuron-Mandard


CEA, DAM, DIF, Arpajon, France


Despite the widespread use of direct analysis in real time mass spectrometry (DART-MS), its capabilities in terms of accessible mass range and the types of polymers that can be analysed are not well known. The goal of this work was to evaluate the capabilities and limitations of this ionization technique combined with orbitrap mass spectrometry and tandem mass spectrometry, for the characterization (structural and polydispersity metrics) of various synthetic and natural polymers.   The capabilities and limitations of DART-MS (and -MS2), using an orbitrap mass spectrometer, for polymer analysis were evaluated using various industrial synthetic polymers and biopolymers.  Protonated oligomers and ammonium adducts were instantaneously detected as the major ionisation products in positive ion mode. Only perfluoropolyethers (PFPEs) were ionised in negative mode and detected as [M]-. ions. Only singly charged molecular species were observed for all oligomers under study, allowing for a rapid determination of the molecular weight and polydispersity metrics of polymers. At elevated DART gas temperatures (400-500°C) the molecular weight and polydispersity metrics compared fairly well with those obtained by GPC, with polymers whose masses ranged from 200 g.mol-1 to 4000 g.mol-1.



Jürgen H. Gross

Institute of Organic Chemistry, Heidelberg University, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany


Direct analysis in real time-mass spectrometry (DART-MS) enables screening of articles of daily use made of polydimethylsiloxanes (PDMS), commonly known as silicone rubber, to assess their tendency to release low molecular weight silicone oligomers. DART-MS analyses were performed on a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. Flexible silicone baking molds, a watch band, and a dough scraper, as baby articles different brands of pacifiers, nipples, and a teething ring have been examined. While somewhat arbitrarily chosen, the set can be regarded as representative of household items, baby articles, and other objects made of silicone rubber. For comparison, two brands of silicone septa and as blanks a glass slide and a latex pacifier were included. Differences between the objects were mainly observed in terms of molecular weight distribution and occasional release of other compounds in addition to PDMS. Other than that, all objects made of silicone rubber released significant amounts of PDMS during DART analysis. To provide a coarse quantification, a calibration based on silicone oil was established, which delivered PDMS losses from 20 μg to >100 μg during the 16-s period per measurement. Also, the extraction of baking molds in rapeseed oil demonstrated a PDMS release at the level of 1 μg mg-1. These findings indicate a potential health hazard from frequent or long-term use of such items. This work does not intend to blame certain brands of such articles. Nonetheless, a higher level of awareness of this source of daily silicone intake is suggested.



Ákos Kuki, Lajos Nagy, Miklós Zsuga,and Sándor Kéki

Department of Applied Chemistry, University of Debrecen, H-4010 Debrecen, Hungary


It was found that the collision energy/voltage necessary to obtain 50% fragmentation (CV50) was linearly dependent on the molecular weight of phthalic acid esters (PAEs). Based on this observation a fast screening technique for the detection of PAEs in poly vinyl chloride (PVC) samples was developed using Direct Analysis in Real Time (DART) ionization tandem mass spectrometry. Based on this observation an automated data acquisition method, including mass-dependent tuning of the collision energy/voltage in DART-MS/MS, was developed thereby reducing the analysis time.    



Direct Monitoring of the Role Played by a Stabilizer in a Solid Sample of Polymer Using Direct Analysis in Real Time Mass Spectrometry: The Case of Irgafos 168 in Polyethylene  


Kevin Fouyer, Olivier Lavastre, and David Rondeau

Institut d'Electronique et de Télécommunication de Rennes (IETR UMR CNRS 6164), Université de Rennes 1, Campus de Beaulieu, 263 Avenue du General Leclerc, 35042 Rennes Cedex, France; Université de Bretagne Occidentale, Département de Chimie, 6 Avenue le Gorgeu, 29238 Brest Cedex 03, France 


Direct analysis in real time (DART) ionization method is used with a time-of-flight (TOF) mass spectrometer to perform the analysis of industrial polyethylene pellets free of additives or containing Irgafos 168 as stabilizing agent without any sampling step. The developed analytical method uses the [M + H]+ ion of the bis(2-ethylhexyl) phthalate (DEHP) for performing the exact mass measurements of the stabilizer and polymer ions using the mass drift compensation procedure available on the AccuTOF mass spectrometer. DEHP is in fact a plastic contaminant always presents on the mass spectra of the analyzed samples. The mass spectra allow one to characterize either the ions of the polyethylene and that of the Irgafos. The analysis of thermally treated samples show that the polymer does not undergo any degradation when the Irgafos is present in the bulk of the material, and the role played by the Irgafos 168 is that of an oxygen trapping agent. Under UV exposure, the DART-TOF MS analyses performed on the exposed polyethylene pellets shows that the Irgafos 168 behavior toward the UV radiations is different since this one reacts by cleavages of its P-O bonds to prevent the degradation of the polymer. These interpretations are supported by all the elemental formula determination of the detected ions.   


Assessing direct analysis in real-time-mass spectrometry (DART-MS) for the rapid identification of additives in food packaging


L.K. Ackermana, G.O. Noonan, and T.H. Begley


US Food and Drug Administration (USFDA), Center for Food Safety and Applied Nutrition , College Park, MD 20740, USA 


The ambient ionization technique direct analysis in real time (DART) was characterized and evaluated for the screening of food packaging for the presence of packaging additives using a benchtop mass spectrometer (MS). Approximate optimum conditions were determined for 13 common food-packaging additives, including plasticizers, anti-oxidants, colorants, grease-proofers, and ultraviolet light stabilizers. Method sensitivity and linearity were evaluated using solutions and characterized polymer samples. Additionally, the response of a model additive (di-ethyl-hexyl-phthalate) was examined across a range of sample positions, DART, and MS conditions (temperature, voltage and helium flow). Under optimal conditions, molecular ion (M+H+) was the major ion for most additives. Additive responses were highly sensitive to sample and DART source orientation, as well as to DART flow rates, temperatures, and MS inlet voltages, respectively. DART-MS response was neither consistently linear nor quantitative in this setting, and sensitivity varied by additive. All additives studied were rapidly identified in multiple food-packaging materials by DART-MS/MS, suggesting this technique can be used to screen food packaging rapidly. However, method sensitivity and quantitation requires further study and improvement.   




Thorsten Rothenbacher and Wolfgang Schwack


Institut für Lebensmittelchemie, Universität Hohenheim, Garbenstrasse 28, 70599 Stuttgart, Germany


Gaskets for lids of glass jars usually consist of poly(vinyl chloride) (PVC) containing plasticisers and additional additives, which may migrate into packed foodstuffs. To conform to legal regulations, any such migration has to be determined analytically, which is a big challenge due to the huge chemical variety of additives in use. Therefore, a rapid screening method by means of direct analysis in real time mass spectrometry (DART-MS), using a single-quadrupole mass spectrometer, was developed. On introducing a plastisol sample into the DART interface, protonated molecules and ammonium adducts were obtained as the typical ionisation products of any additives present, and cleavages of ester bonds as typical fragmentation processes. Generally, additives present in the 1% range could be directly and easily identified if ion suppressive effects deriving from specific molecules did not occur. These effects could be avoided by analysing toluene extracts of plastisol samples, and this also improved the sensivity. Using this method, it was possible to identify phthalates, fatty acid amides, tributyl O-acetylcitrate, dibutyl sebacate, bis(2-ethylhexyl) adipate, 1,2-diisononyl 1,2-cyclohexanedicarboxylate, and even more complex additives like acetylated mono- and diacylglycerides, epoxidised soybean oil, and polyadipates, with a limit of detection of ≤1% in PVC plastisols. Only in the case of epoxidised linseed oil were levels of ≥5% required for identification. The detection of azodicarbonamide, used as a foaming agent within the manufacturing process, was possible in principle, but was not highly reproducible due to the very low concentrations in plastisols.   



Manuela Haunschmidt, Christian W. Klampfl, Wolfgang Buchbergera and Robert Hertsensb  

Institute of Analytical Chemistry, Johannes Kepler University, Altenbergerstr. 69, Linz, Austria; Jeol (Europe) BV, Leuvensesteenweg 542, Zaventem, Belgium 


A method for analysing plastic samples without any sample pretreatment using direct analysis in real time mass spectrometry (DART-MS) was developed. DART-MS allows the direct, simple and rapid identification of polymer additives in plastic products. To demonstrate the suitability of DART-MS for the detection of a wide range of commonly employed stabilising agents, a test set of 21 stabilisers was selected. In a first step standard solutions of these stabilisers in toluene as well as toluene-extracts from polymer samples were analysed. Subsequently, to prove the applicability of the developed DART-MS method also for the direct analysis of plastic products, samples of polypropylene containing a range of stabilisers were prepared using a lab-scale compounder. Polymer samples were cut into 0.5 cm wide pieces and directly placed into the DART ion source. Focusing on the DART ionisation, several parameters like discharge needle potential, potential of the grid electrode and the discharge electrode, the heater temperature and the gas flow had to be varied to guarantee optimum results. Both positive and negative ionisation was tested, whereby the positive ion mode led to higher signal intensities for all analytes. Determination of accurate masses to improve the certainty in signal assignment could be achieved by using PEG 600 as an internal standard for mass calibration. The developed method allowed the detection of all selected additives (including some of their degradation products) in real polymer samples.  






About IonSense
IonSense, Inc. provides OpenSpot Mass Spectrometry™ solutions to the fields of food safety, forensics, drug development, and chemical analysis. We manufacture and develop direct analysis in real time (DART®) technology licensed from JEOL USA, Inc. and atmospheric solids analysis probe (ASAP™) licensed from M&M Consulting.

DART and ASAP Sources are available for most commercial LC/MS systems.  Look here to see if your system is DART-ready.  And  check here to see if your system is ASAP-ready.

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