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


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From the recent Sanibel meeting, we have some new results to share on the use of SPME with DART to expand the range and robustness of DART for detection of drugs of abuse. 

Additionally there are some interesting publications on clinical, environmental, and food safety applications.

Finally we would like to thank Prof. Kenyon Evans-Nguyen and the University of Tampa for hosting and sponsoring our recent Forensics Symposium

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


Regards,

Brian Musselman, Ph.D.
President and CEO

Optimizing DART: Solid Phase Microextraction (SPME) with Thermal Separation

The direct analysis of a range of drugs in urine is challenging since they tend to have very different chemical properties and conditions for efficient detection.  

In this poster recently presented at the Sanibel Conference on Forensics and Security, we showed how the use of SPME and varying DART gas temperatures can increase coverage and provide more robust measurements. 
  • Through the use of SPME fibers, in combination with DART, it is possible to analyze samples by reducing ion suppression caused by matrix effects.
  • Extracting a sample with different SPME fiber coatings allows for different components to be selectively collected from the sample.
  • Desorption ionization of the sample from the SPME fibers surface by using the DART gas at different temperatures allows for different components of a sample to be ionized independently of each other.
  • By varying the sorbent coating type and desorption temperature a unique chemical signature can be determined for most samples.
You can click here to read the full poster.


In addition, scientists at the Alabama Department of Forensics Sciences and the University of Alabama at Birmingham presented their results showing the use of SPME and DART for the detection of the ever-growing problem of opioids.  Novel Screening Technique for Opioids in Toxicological Specimens via SPME DART™ TOF MS.   If you would like information on this, please let us know and we will put you in contact with them.


 

Recent DART Publications

The Complete DART Bibliography is Now Available - CLICK HERE



A novel approach to determine the tyrosine concentration in human plasma by DART-MS/MS

 

Yu-qiao Song, Jie Liao, Cheng Zha, Bin Wanga and  Charles C. Liu

 

Medical Experiment and Analysis Center of PLA General Hospital, Fuxing Road, Haidian District, Beijing 100853, China; Aspec Technologies Limited Beijing, Beijing, China

 

A novel method for determining the tyrosine (Tyr) concentration in human plasma using direct analysis in real time mass spectrometry (DART-MS/MS) was developed. DART-MS/MS was performed in the positive ionization mode with multiple reaction monitoring (MRM) while using the ion transitions at m/z of 182.2/136.2 (Tyr). The experimental conditions and the sample preparation method were optimized to maximize the signal intensity. The linear range was determined to be 2-50 μg mL−1 from the calibration curve. The limit of quantification (LOQ) was 2 μg mL−1. The intra- and inter-day precisions did not exceed 15%, and the accuracies were less than ±15% for the 4, 18 and 38 μg mL−1 quality control (QC) samples. In addition, the extents of the matrix effects for the QC samples were also evaluated. Using the proposed method, samples could be analyzed simultaneously. The proposed DART-MS/MS-based method is not only rapid and simple with a high throughput but is also economical, as a mobile phase is not used. Furthermore, the method was used successfully to determine the Tyr levels in the plasmas of healthy volunteers and liver cancer patients. The proposed method should also be theoretically suitable for screening newborn babies for the hereditary tyrosinemia.

 


Maxime C. Bridoux, Hélène Malandain, Françoise Leprince, Frédéric Progent, Xavier Machuron-Mandard

CEA, DAM, DIF, F-91297 Arpajon, France; SANTEN SAS, 1 rue Pierre Fontaine, Bâtiment Genavenir IV, F-91058 Evry, France

 

A novel hyphenated technique, namely the combination of stir bar sorptive extraction (SBSE) with isotope dilution direct analysis in real time (DART) Orbitrap™ mass spectrometry (OT-MS) is presented for the extraction of phosphoric acid alkyl esters (tri- (TnBP), di- (HDBP), and mono-butyl phosphate (H2MBP)) from aqueous samples. First, SBSE of phosphate esters was performed using a Twister™ coated with 24 μL of polydimethylsiloxane (PDMS) as the extracting phase. SBSE was optimized for extraction pH, phase ratio (PDMS volume/aqueous phase volume), stirring speed, extraction time and temperature. Then, coupling of SBSE to DART/Orbitrap-MS was achieved by placing the Twister™ in the middle of an open-ended glass tube between the DART and the Orbitrap™. The DART mass spectrometric response of phosphate esters was probed using commercially available and synthesized alkyl phosphate ester standards. The positive ion full scan spectra of alkyl phosphate triesters (TnBP) was characterized by the product of self-protonation [M + H]+ and, during collision-induced dissociation (CID), the major fragmentation ions corresponded to consecutive loss of alkyl chains. Negative ionization gave abundant [M − H]− ions for both HDnBP and H2MnBP. Twisters™ coated with PDMS successfully extracted phosphate acid esters (tri-, di- and mono-esters) granted that the analytes are present in the aqueous solution in the neutral form. SBSE/DART/Orbitrap-MS results show a good linearity between the concentrations and relative peak areas for the analytes in the concentration range studied (0.1-750 ng mL−1). Reproducibility of this SBSE/DART/Orbitrap-MS method was evaluated in terms of %RSD by extracting a sample of water fortified with the analytes. The %RSDs for TnBP, HDnBP and H2MnBP were 4, 3 and 3% (n = 5) using the respective perdeuterated internal standards. Matrix effects were investigated by matrix matched calibration standards using underground water samples (UWS) and river water samples (RWS). Matrix effects were effectively compensated by the addition of the perdeuterated internal standards. The application of this new SBSE/DART/Orbitrap-MS method should be very valuable for on-site sampling/monitoring, limiting the transport of large volumes of water samples from the sampling site to the laboratory.

 

 

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.

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.

For your local representative, please see our distributor network.

Phone - 781.484.1043  | info@ionsense.com | http://www.ionsense.com