Rapid Monitoring Approach for Microplastics Using Portable Pyrolysis-Mass Spectrometry.

Microplastics (MPs) pollution has drawn increasing concern due to its widespread occurrence and potential risks in the environment. The reliable methods and instruments for fast analysis of microplastics (MPs) less than 5 mm are urgently needed. In this study, a new method based on custom-made portable pyrolysis-mass spectrometry (Pyr-MS) is developed, which enables rapid identification and mass related quantification of MPs. MPs are decomposed in the compact pyrolyzer and then directly analyzed in the portable MS by the chemical fingerprints of polymers including characteristic ions and their special ratio. It avoids the complex extraction and separation procedures of the pyrolysis/thermogravimetric-gas chromatography-mass spectrometry (Pyr/TGA-GC-MS), realizes the rapid analysis of MPs in 5 min, and thus can practically apply to a large number of MPs samples. In comparison to Fourier transform infrared spectroscopy (FT-IR) and Raman, this method is not limited by the shape, size, and color of MPs. Four common plastics including polyethylene (PE), polypropylene (PP), polystyrene (PS), and poly(methyl methacrylate) (PMMA) were investigated to verify the feasibility of this method. The environmental MPs samples collected from a beach were successfully identified and quantified, demonstrating the simplicity and practicality of this approach. The influence of plastics aging on the chemical fingerprints and the potential of mixed plastics detection by Pyr-MS are also assessed. The portable Pyr-MS could provide a promising tool for in-field analysis of MPs such as ship-based marine MPs surveys.

Portable Dielectric Barrier Discharge-Atomic Emission Spectrometer.

This paper describes the first demonstration of a portable dielectric barrier discharge-atomic emission spectrometer (DBD-AES). The instrument primarily consists of a miniature electro-thermal vaporizer (ETV), DBD, and optical signal acquisition units. It weighs only 4.5 kg and is powered by a 24 V DC battery with a maximum power consumption of 37 W. The accompanying software can be operated on a laptop computer. A specially designed quartz tube integrates the ETV unit with the DBD chamber. The effects of experimental parameters were investigated. The limit of detection (LOD) for mercury was 0.4 µg L-1 (1.2 pg) with a sampling volume of 3 µL. The instrument is applicable for multielement analysis, and the LODs ranged from 0.16 to 11.65 µg L-1 for Zn, Pb, Ag, Cd, Au, Cu, Mn, Fe, Cr, and As. The instrument was also validated by in-field analysis of seawater samples. The experimental results demonstrated the sensitivity, reliability, and practicality of the instrument.

A portable electromagnetic heating-microplasma atomic emission spectrometry for direct determination of heavy metals in soil.

In this work, electromagnetic heating was firstly explored as sample introduction approach in portable microplasma-atomic emission spectrometer to achieve the direct, rapid analysis of soil sample. The device primarily consists of an electromagnetic heating unit, a dielectric barrier discharge (DBD) excitation source and an optical signal acquisition unit. A W-boat was used as an electromagnetic heating medium and sample carrier, and copper coil spiraled around the tube was used as magnetic induction coil. With applying a voltage on copper coil, W-boat was electromagnetically heated to vaporize analyte-containing species for sample introduction into the microplasma. The portable battery-powered device is controlled by a miniature touch screen computer with the main advantages of small size (40.5 cm (l) × 30 cm (w) × 15 cm (h).), light weight (less than 7 kg), low-power consumption (the average power consumption is 118 W). By this method, Hg, Cd and Pb in soil were simultaneously analyzed within 4 min. Under the optimal conditions, the limits of detection for Hg, Cd and Pb in soils were 8.0 µg/kg, 17.8 µg/kg and 3.5 mg/kg, respectively, meeting the requirements for environmental quality standards for soils of China. Different types of CRM soils were analyzed, demonstrating good accuracy, stability and utility of this method. This technique could be a promising and powerful tool for on-site, rapid analysis of heavy metals in soil even other solid samples. Electromagnetic heating mode provides a good alternative for solid sampling to develop portable, miniaturized atomic spectrometers for solid sample analysis.

Rapid determination of cadmium in rice by portable dielectric barrier discharge-atomic emission spectrometer.

In this work, a home-made portable dielectric barrier discharge-atomic emission spectrometer (DBD-AES) was explored to the determination of heavy metal in foodstuffs. A rapid and simple method was developed for Cd determination in rice based on this instrument. Rice was pretreated with diluted acid dissolution without complex operations and apparatus. The detection time by DBD-AES is about 3 min and the total analysis time for rice sample is within 11 min. The effects of some key experiment parameters were investigated. The limit of detection was 11.9 µg kg-1 for Cd in rice, much lower than the maximum allowable level established by EC (200 µg kg-1). The practical performance of this method was demonstrated by analyzing real and CRM rice samples. With the portability of DBD-AES, the method is suitable for rapid and in-field analysis of Cd in rice. It will be a useful tool for the routine analysis of rice.