Microwave Instruments: Green Machines for Green Chemistry?

Abstract

In this column, the authors discuss the ease of using microwave ovens for various activities in the undergraduate chemistry laboratory and suggest a few models of microwave systems for readers to consider.

Greening the organic chemistry laboratory: a comparison of microwave-assisted and classical nucleophilic aromatic substitution reactions

“…In one study (39), the authors report that the time and yield of their own previously developed synthesis of 2-chloromethylbenzothiazole from ortho-aminothiophenol and polyphosphoric acid, which gives a reasonable yield of 62% after 8 h of reflux at 180°C, improves to a 90% yield with only 10 min of microwave irradiation. Thus, for select reactions, higher yields, faster reaction times, and the ability to minimize the use of hazardous organic solvents has begun to establish microwaveassisted procedures as a leader in green chemistry techniques (40). The present experiment thus provides the impetus for students to research the microwave effect (41) as well as the 12 principles of green chemistry (42).…”

The Accumulation of Nutrients and Contaminants in Aromatic Plants Grown in a Hydroponic System

“…Sample preparation for ICP-MS analysis 0.250g ± 0.0001 g of fresh samples where weighted with analytical balance in Teflon recipients, then 8 ml concentrated ultrapure HNO 3 (65%) and 2 ml H 2 O 2 30% were added and were subjected to mineralization by microwave digestion (30 min.) with ETHOS UP microwave digestion system, then the clear solutions were transferred quantitatively into the volumetric flasks (50 mL) and made up with Milli-Q ultrapure water (2 repetitions) (Milestone ETHOS UP Digestion Apps, Zovinka and Stock 2010) The Agilent Series ICP-MS spectrometer with quadrupole analyzer 7700x and MassHunter Workstation software (Agilent Technologies) was used in the analysis of the two varieties of basil and peppermint variety after acidic digestion (65% ultrapure nitric acid). The calibration curve was performed with ICP-MS multi-element calibration standard (1000 mg/L of Fe, K, Ca, Na, Mg; 100 mg/L of Sr; 10 mg/L of Ag, Al, As, Ba, Be, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Sb, Se, Tl, V, Zn, Th, U in 5% HNO3) (Sannac et al, 2017;Pacquette et al, 2015;Liba et al, 2014)…”

Microwave co-pyrolysis of sewage sludge and rice straw

“…Compared with conventional heating, microwave heating is environmentally friendly and well-established and reduces energy consumption and reaction time [13]. Besides, microwave heating does not directly contact the heated materials [14].…”