Simultaneous Screening of Major Flame Retardants and Plasticizers in Polymer Materials Using Pyrolyzer/Thermal Desorption Gas Chromatography Mass Spectrometry (Py/TD-GC-MS).

This study was conducted with the aim of achieving the simultaneous screening of various additives in polymer materials by utilizing a solvent-free pyrolyzer/thermal desorption gas chromatography mass spectrometry (Py/TD-GC-MS) method. As a first step to achieve this goal, simultaneous screening has been examined by selecting major substances representing plasticizers and flame retardants, such as short chain chlorinated paraffins (SCCPs), decabromodiphenyl ether (DecaBDE), hexabromocyclododecane (HBCDD), and di(2-ethylhexyl) phthalate (DEHP). A quantitative MS analysis was performed to check for the peak areas and sensitivities. Since Py/TD-GC-MS is fraught with the risk of thermal degradation of the sample, temperatures during the analytical process were finely tuned for securing reliable results. The instrumental sensitivity was confirmed by the S/N ratio on each component. The detection limits of all components were less than 50 mg/kg, which are sufficiently lower than the regulatory criteria. With regard to reproducibility, a relative standard deviation (RSD) of about 5% was confirmed by employing a spike recovery test on a polystyrene polymer solution containing mixed standard solution (ca. 1000 mg/kg). In conclusion, the results obtained in this study indicate that Py/TD-GC-MS is applicable for the screening of major flame retardants and plasticizers in real samples with sufficient reproducibility at regulatory levels.

Degradation of SARS-CoV-2 specific ribonucleic acid in samples for nucleic acid amplification detection.

The degradation of SARS-CoV-2 specific ribonucleic acid (RNA) was investigated by a numerical modeling approach based on nucleic acid amplification test (NAAT) results utilizing the SmartAmp technique. The precision of the measurement was verified by the relative standard deviation (RSD) of repeated measurements at each calibration point. The precision and detection limits were found to be 6% RSD (seven repeated measurements) and 94 copies/tube, respectively, at the lowest calibration point. RNA degradation curves obtained from NAAT data on four different temperatures were in good agreement with the first-order reaction model. By referring to rate constants derived from the results, the Arrhenius model was applied to predict RNA degradation behavior. If the initial RNA concentration was high enough, such as in samples taken from infected bodies, the NAAT results were expected to be positive during testing. On the other hand, if initial RNA concentrations were relatively low, such as RNA in residual viruses on environmental surfaces, special attention should be paid to avoid false-negative results. The results obtained in this study provide a practical guide for RNA sample management in the NAAT of non-human samples.

Photometric Screening of Tetrabromobisphenol A in Resin Using Iron(III) Nitrate/Hexacyanoferrate(III) Mixture as a Colorimetric Reagent.

This study aims to provide a simple way to identify the possibility of tetrabromobisphenol A (TBBPA) present in polymers without the need for complicated separation with expensive equipment. Since the presence of phenolic hydroxyl groups is known to be identifiable by the reduction of Fe3+ to Fe2+ in a ferric coloring reagent, the possibility of TBBPA being present in a polymer can be screened by a photometric measurement. A mixed solution of iron(III) nitrate and potassium hexacyanide(III) acid was used as a ferric coloring reagent. With this method, the concentration of TBBPA can be estimated from the photometric absorbance corresponding to the depth of the blue color produced by reduction of the ferric reagent in the presence of Fe(NO3)3. The limit of detection (LOD) was determined to be approximately 2 mg/kg using the Student's t-test (99% confidence), and a reproducibility of approximately 3% was determined by the relative standard deviation (RSD) from measurements of calibration samples (n = 7). Furthermore, TBBPA in actual polymer samples was screened without the need for any complex processing steps. Because this colorimetric method measures TBBPA by detecting phenolic groups, it may overestimate the TBBPA concentration in the presence of other similar phenolic substances. Nonetheless, this simple colorimetric method should help to quickly identify the presence of TBBPA in various polymers.

Simple Colorimetric Determination of Phthalates in Polymers by Dye Formation.

This paper describes a simple method for quantifying phthalates via the conversion of anhydrous phthalates to a dye. The phthalate was hydrolyzed with sodium hydroxide and dehydrated to form phthalic anhydride, which was converted to a marker, namely fluorescein, by reaction with resorcinol. Concentrated sulfuric acid was used as the catalyst. The presence of a phthalate was determined by absorbance spectrophotometry. The detection limit of this method for di(2-ethylhexyl) phthalate was 0.1 µmol, and the relative standard deviation with respect to reproducibility was approximately 10% (n = 3). For other phthalates, namely diisobutyl phthalate, dibutyl phthalate, bis(butylbenzyl) phthalate, di-n-octyl phthalate, diisononyl phthalate, and diisodecyl phthalate, the absorbance deviation was less than 20%, which is within the acceptable range for screening purposes. Because the phthalates were hydrolyzed to enable colorimetric determination, the identification of individual phthalates is beyond the scope of this method. However, this simple colorimetric method can easily be used to determine the total amount of phthalates in real samples at the sub-micromolar level, by converting the phthalates to dyes. The applicability of this method was investigated by analyzing actual samples containing various phthalates. The quantitative results were almost the same as those obtained by using a conventional gas chromatographic method.

Evaluating Phthalate Contaminant Migration Using Thermal Desorption⁻Gas Chromatography⁻Mass Spectrometry (TD⁻GC⁻MS).

This study describes a methodology for evaluating regulatory levels of phthalate contamination. By collecting experimental data on short-term phthalate migration using thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS), the migration of di(2-ethylhexyl) phthalate (DEHP) from polyvinyl chloride (PVC) to polyethylene (PE) was found to be expressed by the Fickian approximation model, which was originally proposed for solid (PVC)/liquid (solvent) migration of phthalates. Consequently, good data correlation was obtained using the Fickian approximation model with a diffusion coefficient of 4.2 × 10-12 cm²/s for solid (PVC)/ solid (PE) migration of DEHP at 25 °C. Results showed that temporary contact with plasticized polymers under a normal, foreseeable condition may not pose an immediate risk of being contaminated by phthalates at regulatory levels. However, as phthalates are small organic molecules designed to be dispersed in a variety of polymers as plasticizers at a high compounding ratio, the risk of migration-related contamination can be high in comparison with other additives, especially under high temperatures. With these considerations in mind, the methodology for examining regulatory levels of phthalate contamination using TD-GC-MS has been successfully demonstrated from the viewpoint of its applicability to solid (PVC)/solid (PE) migration of phthalates.

Development of a screening method for phthalate esters in polymers using a quantitative database in combination with pyrolyzer/thermal desorption gas chromatography mass spectrometry.

Seven phthalate esters (di-isobutyl phthalate (DIBP), di-n-butyl phthalate (DBP), benzylbutyl phthalate (BBP), di-(2-ethylhexyl) phthalate (DEHP), di-n-octyl phthalate (DNOP), di-isononyl phthalate (DINP) and di-isodecyl phthalate (DIDP)) were analyzed by pyrolyzer/thermal desorption-gas chromatography/mass spectrometry (Py/TD-GC/MS), the retention index and relative response factor (RRF) relative to DEHP was calculated for each compound and used to construct a quantitative database (qDB). This qDB enables normalization of the retention time and response factor of each phthalate ester between any laboratory simply by analyzing an n-alkane solution and DEHP standard material. This allows for easy calculation of the phthalate ester content of samples without preparation of calibration curves. The efficacy of this qDB method was verified by performing a quantitative analysis of phthalate esters at 4 different laboratories that showed actual retention times were within ±0.012 min of the estimated retention times for all compounds at all laboratories. Similarly, the mean recovery rate (n = 6) at each laboratory was within 79-113%. Quantitative analysis was also performed on 30 real samples using both the qDB method and the Py/TD-GC/MS method set forth in IEC62321-8, which involves the preparation of 1-point calibrations to perform quantitative analysis. The difference in quantitative results between the methods was approximately within ±200 mg/kg for compounds in the concentration region of <2000 mg/kg.

Screening of phthalates in polymer materials by pyrolysis GC/MS.

A study on the rapid identification of phthalates in polymer materials has been conducted by employing gas chromatography-mass spectrometry coupled with a pyrolyzer (Py-GC/MS). Since Py-GC/MS does not require any complex solvent-extraction process, a rapid screening of phthalates should be possible. In this study, polymer samples were directly introduced into the pyrolyzer in order to thermally extract phthalates from the polymer under specific heating conditions. By optimizing the Py-GC/MS parameters, a sequential testing cycle of 35 min per sample was feasible without causing any major decomposition of the base materials. Thus, a rapid screening of over 20 samples per day was achieved without any time constraints by effectively utilizing specifically prepared reference polymer sheets for quality control. Py-GC/MS was found to be suitable and effective for identifying phthalates in polymer materials.