Halogen Determination in Polymeric Waste of Electrical and Electronic Equipment: Overcoming Limitations in Sample Preparation

Abstract

Sample preparation of polymers for halogen determination requires special attention because they are difficult to bring into solution and due to the risk of analyte losses when using acid digestion. A method using microwave-induced combustion (MIC) was optimized for accurate determination of halogens in polymeric parts obtained in waste of electrical and electronic equipment. Results were compared with those by using microwave-assisted extraction (MAE) with alkaline solution and microwave-assisted wet digestion (MAWD) using concentrated nitric acid, which are common choices for sample preparation. In this particular case, the MAE method was not suitable and underestimated results were obtained, showing the necessity for the complete digestion. Even with the use of MAWD under high temperature and pressure, incomplete digestion and high acid content were obtained, which were unsuitable for analysis and resulted in poor recovery. Only by using MIC (diluted ammonia as absorbing solution) acceptable recoveries (95 to 104%) and agreement with certified values for the certified reference materials (CRMs) of polymers were obtained. Thus, a suitable method for all halogen to be determined by ion chromatography (IC) or inductively coupled plasma mass spectrometry (ICP-MS), with the exception of F, was obtained in agreement with the requirements by the Restriction of the Use of Certain Hazardous Substances (RoHS) European directive.

Challenges and trends for halogen determination by inductively coupled plasma mass spectrometry: A review

“…66 Regarding washing solutions, several studies have used alkaline solutions such as NH 4 OH and tetramethylammonium hydroxide (TMAH) that have been also used as a medium to prepare the standard calibration solutions. 22,49,52,[64][65][66][67][68][69][70][71][72] It has been reported that, when using 5% HNO 3 as a washing solution, 200 s were necessary for iodine counts to be reduced to 10% of their original value. When using 5% NH 4 OH as washing solution, only 20 s were necessary for iodine counts to return to the original value.…”

“…47,52,70,73 In this sense, several studies have used alkaline solutions such as NH 4 OH and TMAH as washing solutions for halogen determination by ICP-MS, as well as a medium to prepare the standard calibration solutions. 22,49,52,[64][65][66][67][68][69][70][71][72] Alternatively, the use of a 2% alcohol acidic solution 74 Another concern is regarding analyte stability during ICP-MS determination. Signal suppression and analyte losses when using acidic solutions can occur, especially for iodine.…”

“…NaOH, NH 4 OH, (NH 4 ) 2 CO 3 , and TMAH). 23,47,51,54,67,70,71,73,75,76 Another relatively common strategy is the addition of stabilizing agents to the digests prior to sample analysis. The addition of HCl or NaCl to the sample solution can be used to stabilize iodine as iodo-chloro complexes.…”