Rapid identification of stabilisers in polypropylene using time-of-flight mass spectrometry and DART as ion source

Abstract

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.

Direct analysis in real time mass spectrometry combined with single-drop liquid–liquid–liquid microextraction for the rapid analysis of multiple phytohormones in fruit juice

“…Considering the performance achieved for most of the compounds, the heater temperature was finally set to 400°C. The influence of flow rate was investigated, since optimizing the helium flow rate promotes the desolvation of analytes and their transportation towards the transfer tube [11,12]. A flow rate of 0.09 m 3 /h gave the best performance for most of phytohormones, except for GA 3 , which preferred a higher flow rate.…”

“…When DART is coupled to various types of MS, DART-MS provides a rapid and straightforward way to analyze a variety of samples; for example, it has been used for the analysis of pheromones in live Drosophila [9], the quantitation of chemical warfare agents [10], the identification of stabilizers in polypropylene [11], the screening of synthetic drug adulteration [12], and the quantification of small molecules in plasma [13]. During DART-MS analysis, helium (He) or nitrogen (N 2 ) is usually used as the working gas, and excited metastable He or N 2 is generated through a coronato-glow discharge in the DART chamber [14].…”

Quantitative Analysis of Polymer Additives with MALDI-TOF MS Using an Internal Standard Approach

“…di-tert.butylphenol derivatives) but differentiation between individual species is not possible and quantification very complicated. Other methods presented only recently are the analysis of the solid samples by DESI [7], ASAP [8], DART [9], or SIMS [10]. In DESI (Desorption Electrospray Ionization) and DART (Direct Analysis in Realtime), the surface of a polymer is either put into an ESI spray or a helium stream, both resulting in the ionization of the volatile components of the sample.…”

Determination of Dicyandiamide in Powdered Milk Using Direct Analysis in Real Time Quadrupole Time-of-Flight Tandem Mass Spectrometry

“…In recent years, many researches have successfully demonstrated the ability of DART for qualitative and quantitative analysis. Analysis of solids or liquids, including illegal additives [3], Chinese herbal preparations [4], human blood sera [5], peptides [6], oligosaccharides [7], synthetic organic molecules [8], organometallics [9], toxins [10], polymers [11], cosmetics [12], fungicides on wheat [13], counterfeit drugs [14], explosives on clothes or shoes [15,16], biological matrices [17], and environmental samples after stir bar sorptive extraction [18] have shown that the DART is a versatile method for rapid detection of analytes. These chemicals have been detected on surfaces including concrete, asphalt, human skin, currency, paper stock, vegetables, fruit, and even clothing.…”