Development of lithium attachment mass spectrometry - knudsen effusion and chemical ionisation mass spectrometry (KEMS, CIMS)

Knudsen effusion mass spectrometry: Current and future approaches

RATIONALE

Knudsen effusion mass spectrometry (KEMS) has been a powerful tool in physical chemistry since 1954. There are many excellent reviews of the basic principles of KEMS in the literature. In this review, we focus on the current status and potential growth areas for this instrumental technique.

METHODS

We discuss (1) instrumentation, (2) measurement techniques, and (3) selected novel applications of the technique. Improved heating methods and temperature measurement allow for better control of the Knudsen cell effusive source. Accurate computer models of the effusive beam and its introduction to the ionizer allow optimization of such parameters as sensitivity and removal of background signals. Computer models of the ionizer allow for optimized sensitivity and resolution. Additionally, data acquisition systems specifically tailored to a KEMS system permit improved quantity and quality of data.

RESULTS

KEMS is traditionally utilized for thermodynamic measurements of pure compounds and solutions. These measurements can now be strengthened using first principles and model-based computational thermochemistry. First principles can be used to calculate accurate Gibbs energy functions (gefs) for improving third law calculations. Calculated enthalpies of formation and dissociation energies from ab initio methods can be compared to those measured using KEMS. For model-based thermochemistry, solution parameters can be derived from measured thermochemical data on metallic and nonmetallic solutions. Beyond thermodynamic measurements, KEMS has been used for many specific applications. We select examples for discussion: measurements of phase changes, measurement/control of low-oxygen potential systems, thermochemistry of ultrahigh-temperature ceramics, geological applications, nuclear applications, applications to organic and organometallic compounds, and thermochemistry of functional room temperature materials, such as lithium ion batteries.

CONCLUSIONS

We present an overview of the current status of KEMS and discuss ideas for improving KEMS instrumentation and measurements. We discuss selected KEMS studies to illustrate future directions of KEMS.

Screening analysis of RoHS directive hazardous substances (phthalate esters and bromodiphenyl ethers) by novel mass spectrometry using soft ionization

In 2013, the European Union expanded the list of hazardous substances contained in the RoHS Directive. In addition, certain phthalate esters, such as dibutyl phthalate (DBP), butyl benzyl phthalate (BBP), di-2-ethylhexyl phthalate (DEHP) and diisobutyl phthalate (DIBP), will be categorized as RoHS-prohibited substances starting from July 2019. Although pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) is a promising analytical method for the screening of phthalate esters, we have developed a novel soft-ionization MS method that is quantitative as well as faster and more convenient for this purpose. The sample was measured three times, after providing the calibration curve using a powdery standard material of SPEX. The data collection time is 5 min, and continuous measurements are completed within 8 min per sample. The mass spectrum was corrected by dividing the intensity by the sample weight. For the coefficient of variation, DBP was 2.9%, BBP was 3.4%, DEHP was 3.6%, and good reproducibility was observed. Precise analyses of phthalate esters using traditional methods can require solvent extraction times of up to 24 h as well as special techniques. Therefore, a screening method that can be easily carried out by anyone within ten minutes is very attractive.