Metal analysis in polymers using tandem LA-ICP-MS/LIBS: eliminating matrix effects using multivariate calibration

Abstract

Nowadays, metal analysis in polymers is experiencing growing interest due to increased environmental regulations and the need for sustainable polymer recycling strategies. Quick and reliable analyses are required to fulfill the demands of today's industry. Due to the high chemical inertness of most polymers, traditional solution-based analysis is often not an option and solid-sampling techniques such as Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) or Laser Induced Breakdown Spectroscopy (LIBS) have to be employed as an alternative. These, however, are typically prone to matrix effects and for each polymer type a separate reference material with known concentration may be required -an approach which is obviously not suitable if the polymer type is not even known. To overcome these difficulties, a tandem LA-ICP-MS/LIBS procedure coupled with statistical analysis has been used in this study. LIBS is known to be especially prone to matrix effects -which has been used as a benefit here. Complete broadband LIBS spectra with a wealth of information have been used as signatures for the investigated polymer types (polyimide, polymethylmethacrylate and polyvinylpyrrolidone) to serve the purpose of reducing matrix effects. While LIBS allowed the detection of alkali metals and alkali earth metals even at lower concentrations, LA-ICP-MS was used simultaneously for the analysis of other trace metals in the mg g À1 regime. Na, Sr, Co, In, and Pt were used as exemplary analytes at concentrations ranging from as low as 0.1 mg g À1 up to 300 mg g À1. Using the combined dataset of all three polymer types (in total 23 samples), multivariate calibration models could be constructed for all elements of interest.Validation was performed using a set of 22 external samples showing relative average deviations from their actual elemental content of 4.4%, but not more than 9.6%.

Improved plasma stoichiometry recorded by laser ablation ionization mass spectrometry using a double‐pulse femtosecond laser ablation ion source

“…LA‐ICP‐MS is among the most widespread laser‐based analytical technique due to its accurate quantification, high reproducibility, and low limits of detection. Today, various hybrid systems commercially exist that integrate both LA‐ICP‐MS and LIBS instrumentation to extend the measurement capabilities for the chemical analysis of solids 17–20 …”

“…Today, various hybrid systems commercially exist that integrate both LA-ICP-MS and LIBS instrumentation to extend the measurement capabilities for the chemical analysis of solids. [17][18][19][20] The application of a pulsed laser system to probe the analyte of interest has many advantages, as structures down to tens of nanometers can be targeted, layered materials can be chemically profiled by consecutive laser pulses, and sample contamination via handling can be minimized as no mechanical or chemical contact is required during preparation, among others. 9,21,22 With the replacement of, e.g., nanosecond or picosecond laser systems with powerful and stable ultra-fast pulsed femtosecond laser systems, the analytical capabilities and figures of merit of all laser-based measurement techniques have improved significantly, including, e.g., minimized matrix effects and element fractionation effects due to the absence of laser plasma plume interaction, improvement of spatial resolution due to reduced heat dissipation, increased reproducibility of measurements, enhanced ionization and stoichiometry, among others.…”

Measure of polymer performance based on correlated physical parameters

“…Multivariate analysis based on principal component analysis and clustering on physical parameters data is quite common. 5,6 However, a drawback of this approach is that effect of dopant levels on correlations between parameters is not captured and quantified since dopant information is not explicitly included as part of the data analysis.…”

“…Data on the physical parameters is obtained by using doping agents at different concentration levels (e.g., ammonium dihydrogen phosphate) during polymer preparation. Multivariate analysis based on principal component analysis and clustering on physical parameters data is quite common 5,6 . However, a drawback of this approach is that effect of dopant levels on correlations between parameters is not captured and quantified since dopant information is not explicitly included as part of the data analysis.…”

Combined LA-ICP-MS/LIBS: powerful analytical tools for the investigation of polymer alteration after treatment under corrosive conditions

“…Broadband LIBS spectra have, for example, already been used for the classification of different polymer types 37,38 . The aerosol generated in the ablation process is measured with LA-ICP-MS and provides data about the inorganic sample constituents 39 . Attributes making LA-ICP-MS attractive for the analysis of trace elements in solid samples are the high sensitivity, reaching LODs in the range of μg•g −1 to ng•g −1 , the large dynamic working range and the capability for multi-elemental analysis 40,41 .…”