Determination of microplastic content in seafood: An integrated approach combined with the determination of elemental contaminants.

A method for the determination of microplastic (MP) content in seafood is proposed based on the selective digestion of seafood without the degradation of MP. A simple approach was developed using diluted acid with microwave-assisted wet digestion. The following parameters were evaluated: nitric acid concentration (0.5 to 14.4 mol L-1), digestion temperature (180 to 220 °C), irradiation program holding time (10 to 30 min), MP particle size (0.3 to 5 mm), and the seafood mass (0.5 to 2 g). To develop a reliable method for the determination of MP amount, up to 2 g of an in natura seafood sample were spiked with a known amount of MP (100 mg of mixed MP). Suitable conditions were obtained using 1 mol L-1 HNO3 at 200 °C (10 min holding time). Digests were filtered and the plastic content was gravimetrically determined. The heating program was 20 min, which represents a significant reduction in the time normally reported in the literature for MP analysis (from few hours up to 3 days). The proposed method allowed gravimetric determination of eight plastic types (polyethylene terephthalate, polystyrene, expanded polystyrene, polypropylene, high and low density polyethylene, polycarbonate and polyvinyl chloride) with particle size ≥0.3 mm. Up to 2 g of an in natura seafood sample (shark species, acoupa weakfish, tuna fish, trahira, and pink shrimp) were efficiently digested, which opened the possibility of using the proposed digestion method for determining elemental contaminants (Al, As, Ca, Cd, Co, Cr, Cu, Fe, Hg, La, Mg, Mn, Mo, Ni, Pb, and Zn). Thus, as the main feature of the proposed digestion method is the possibility of determining MP and elemental contaminants using the same digestion protocol, saves time and reagents and provides accurate and precise information about different classes of marine pollutants (MP and elemental contaminants).

Determination of elemental impurities in poly(vinyl chloride) by inductively coupled plasma optical emission spectrometry.

In this work, a method for poly(vinyl chloride) (PVC) analysis by inductively coupled plasma optical emission spectrometry (ICP-OES) was developed. Samples were digested by microwave-induced combustion (MIC) and thirteen elements (Ba, Cd, Co, Cu, Fe, Mg, Mn, Mo, Ni, Pb, Sr, V and Zn) were determined by ICP-OES. Operational conditions of MIC were investigated allowing quantitative determination of all the analytes and suitable results were achieved using a 3 mol L(-1) HNO3 solution. Microwave-assisted wet digestion (MAWD) using closed quartz vessels and a single reaction chamber microwave digestion system (MAWD-SRC), were also evaluated for PVC digestion for results comparison. All the evaluated sample preparation methods were considered suitable for PVC digestion but MIC was preferable due to the possibility of using diluted HNO3 instead of concentrated reagents and due to the better digestion efficiency. The residual carbon content (RCC) in digests obtained by MIC was significantly lower in comparison with the values obtained after MAWD and by MAWD-SRC. Accuracy for the proposed method was better than 94% for all analytes by comparison of results with those obtained by neutron activation analysis (NAA). Using MIC, it was possible to digest a relatively high sample mass (500 mg) and up to 8 samples in less time (25 min) in comparison with MAWD and MAWD-SRC (about 60 min for both methods). The efficiency of digestion by MIC was higher 99% and lower limits of detection (as low as 0.1 µg g(-1)) were obtained avoiding the use of concentrated acids that is of great concern according to the current green chemistry recommendations.

Study and determination of elemental impurities by ICP-MS in active pharmaceutical ingredients using single reaction chamber digestion in compliance with USP requirements.

In this work a method for active pharmaceutical ingredients (APIs) digestion using the single reaction chamber (SRC-UltraWave™) system was proposed following the new recommendations of United States Pharmacopeia (USP). Levodope (LEVO), primaquine diphosphate (PRIM), propranolol hydrochloride (PROP) and sulfamethoxazole (SULF) were used to evaluate the digestion efficiency of the proposed method. A comparison of digestion efficiency was performed by measuring the carbon content and residual acidity in digests obtained using SRC and in digests obtained using conventional microwave-assisted digestion system (Multiwave(TM)). Three digestion solutions (concentrated HNO3, aqua regia or inverse aqua regia) were evaluated for digestion of APIs. The determination of Cd, Ir, Mn, Mo, Ni, Os, Pb, Pd, Pt, Rh, Ru was performed using inductively coupled plasma mass spectrometry (ICP-MS) in standard mode. Dynamic reaction cell (DRC) mode was used for the determination of (51)V, (52)Cr, (53)Cr, (63)Cu and (65)Cu in order to solve polyatomic ion interferences. Arsenic and Hg were determined using chemical vapor generation coupled to ICP-MS (FI-CVG-ICP-MS). Masses of 500mg of APIs were efficiently digested in a SRC-UltraWave™ system using only HNO3 and allowing a carbon content lower than 250mg L(-1) in final digests. Inverse aqua regia was suitable for digestion of sample masses up to 250mg allowing the determination of Ir, Pd, Pt, Rh and Ru. By using HNO3 or inverse aqua regia, suitable recoveries were obtained (between 91 and 109%) for all analytes (exception for Os). Limits of quantification were in agreement with USP requirements and they ranged from 0.001 to 0.015µg g(-1) for all elemental impurities (exception for Os). The proposed method was suitable for elemental impurities determination in APIs and it can be used in routine analysis for quality control in pharmaceutical industries.