Investigation on the suitability of ablated carbon as an internal standard in laser ablation ICP-MS of polymers

Abstract

The conventional quantitative method for the analysis of inorganic elements in polymer matrices is a complex and time consuming process that presents a significant risk for error. Typically, polymers are digested in a microwave oven or other devices under high temperature and pressure for several hours while employing different mixtures of high purity acids. In many cases, particularly when high concentrations of doped elements are present, the digestion is often incomplete and therefore the reproducibility depends strongly on the type of polymer and additives used. A promising alternative technology that allows for the direct analysis of these polymers without digestion is laser ablation ICP-MS. Due to a lack of available reference materials and the presence of matrix dependent effects, a precise calibration cannot be obtained. In order to compensate for the matrix dependent effects the use of internal standardization is necessary. In this study the correlation between the carbon released during the ablation process and the 13 C signal detected by ICP-MS and its use as an internal standard are investigated. For this purpose, twenty-one virgin polymer materials are ablated; the released carbon is determined and correlated with the corresponding integrated 13 C signal. The correlation resulted in a direct relationship between the ablated carbon and 13 C signal demonstrating the potential ability to neglect at least some of the matrix dependent and transport effects which occur during the laser ablation of virgin polymers.

Quantitative elemental analysis of polymers through laser ablation – inductively coupled plasma by using a dried droplet calibration approach, DDCA

“…Among these additives, metals and metalloids play a very important role and their content and distribution may influence the polymers behavior. 1,2,3,4,5,6 Nevertheless, an important number of regulations must be complied because some elements can be harmful to consumers and/or the environment. Therefore, there is a growing interest in developing analytical methods to carry out elemental analysis of polymers.…”

“…Besides, the atomization and ionization processes are separated in space and time thus giving rise to a mitigation of matrix effects and, hence, quantification without the absolute need for matrix-matched calibration standards is possible. However, this technique shows 4 restricted lateral resolution (on the order of mm) and requires certain conditions related with the vacuum level, the sample shape and its dimensions. 9 Nowadays, elemental analysis of polymers can be carried out using spectroscopic techniques such as inductively coupled plasma optical emission spectroscopy (ICP-OES) or mass spectrometry (ICP-MS).…”

“…Unfortunately, in most of the cases lengthy dissolution protocols must be applied, that may cause sample contamination and losses of volatile components. 10,11 Laser ablation (LA) coupled to ICP-OES or ICP-MS allows the direct determination of additives in polymers with minimal or no sample preparation. 1,2,10,12 However, severe matrix and fractionation effects may be observed when working with nanosecond pulsed lasers.…”

“…10,11 Laser ablation (LA) coupled to ICP-OES or ICP-MS allows the direct determination of additives in polymers with minimal or no sample preparation. 1,2,10,12 However, severe matrix and fractionation effects may be observed when working with nanosecond pulsed lasers. 1,13 Although femtosecond lasers are promising devices, 14 several methods have been proposed to mitigate these phenomena as, for instance, an external calibration using solid certified reference materials as standards.…”

“…11,15,16,17 Unfortunately, the sample ablation yield depends strongly on the type of polymer and, hence, it is still difficult to find suitable solid standards. 10,18,19 In order to compensate for changes in the sample ablated mass as a function of the matrix, 20 an element acting as internal standard (IS) can be selected. 20,21[ Carbon has been suggested as a good candidate because of its known concentration in polymers and its uniform distribution within the samples.…”