Determination of cyclic volatile methylsiloxanes in sludge samples collected from To Lich River, Hanoi, Vietnam

Abstract

Cyclic volatile methylsiloxanes (cVMSs) are synthesis chemicals used widely in consumer products such as building materials, households, electrical and medical devices, and personal care products. Due to being used in many applications, cVMSs are released into various micro-environments. Recently, the pollution level of cVMSs in the environment including sewage sludge has been gradually concerned. In this work, four typical cVMSs: hexamethylcyclotrisiloxane (D3), octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylhexasiloxane (D6) were measured in 20 sludge samples collected from a sewage river (To Lich River) in Ha Noi metropolitan by using the gas chromatography-tandem mass spectrometry (GC-MS) method. The method detection limits (MDLs) and the method qualification limits (MQLs) of cVMSs in sewage sludge were a range of (1.20-3.00) ng/g-dw (dry weight) and (3.60-9.00) ng/g-dw, respectively. Recoveries of the surrogate compound (tetrakis-(trimethyl siloxane)-silane: M4Q) in blank and real samples were from (89.4 to 112) % (RSD: 9.2 %). The total concentrations of cVMSs in sewage sludge samples from To Lich River ranged from (260 to 13,800) ng/g-dw. Among the studied cVMSs, D5 was found at the highest levels in a range of (150-6,040) ng/g-dw. To our knowledge, this is the first report on the occurrence of cVMSs in sewage sludge samples in Ha Noi as well as Vietnam. The results indicate that the distribution of cVMSs in environments is significantly high and further studies should be conducted.

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