ABSTRACT
Microplastics is known to be ubiquitous in aquatic environment. Quantification of microplastics in natural waters is an important problem of analytical chemistry, the solution of which is needed for the assessment of water quality and potential risks for water inhabitants and consumers. Separation methods play a key role in the correct quantification of microplastics in natural waters. In the present study the applicability of countercurrent chromatography to the continuous-flow separation and preconcentration of microplastics from water samples in rotating coiled column (RCC) using water-oil systems has been demonstrated for the first time. The effect of column rotation speed and mobile phase (water) flow rate on the retention of the stationary (oil) phase in RCC is studied. The retention parameters of 10 vegetable and 2 synthetic oils are determined. Castor, olive, rapeseed, soybean, linseed, sesame, and sunflower oils are found to be applicable to the separation of microplastics from water samples using RCC. Taking as example polyethylene microparticles of different size (40-63, 63-100, and 100-250 µm), the high recovery of microplastics (about 100 %) from aqueous phase into castor and rapeseed oils is shown. The method has been proven to be efficient for the separation of microplastics from simulated fresh and sea natural waters. It may be perspective not only for the quantification of microplastics in natural waters but as well as for the purification of wastewaters containing microplastics.
ABSTRACT
A novel approach to the elemental analysis of crude and diesel oil permitted preconcentration of trace elements is presented. An oil sample is continuously pumped through the rotating coil column as a mobile phase while an aqueous nitric acid solution is retained as a stationary phase. Two phases are kept well mixed and agitated but there is no emulsion on the interface at chosen conditions. Preliminary investigation of features of stationary phase retention of two-phase liquid systems (oil/oil products-aqueous solution) in rotating coil column has been shown. Special features of CCC give an opportunity to vary the volume of oil samples to be analyzed from 10 mL to 1 L or more. Trace metals are preconcentrated into 10 mL of stationary aqueous acidic phase which pumped out of the column for analysis can be easily determined with inductively coupled plasma mass spectrometry (ICP-MS) without additional sample preparation. Optimal concentration in the stationary phase of nitric acid for preconcentration of elements from oil by CCC has been investigated. Combination of CCC with ICP-MS gives the possibility to develop a rapid, reliable and accurate method of trace metal including rare earth elements (REE) determination in crude oils and oil products. Combination of preconcentration method by CCC and highly sensitive determination method (ICP-MS) for quantitative detection of the trace elements (without any additional sample preparation) has been suggested for the first time.
