Subject(s)
Benzene Derivatives/analysis , Benzene Derivatives/radiation effects , Chromatography, Gas/trends , Microwaves , Calibration , Chromatography, Gas/instrumentation , Chromatography, Gas/methods , Gases/chemistry , Naphthalenes/analysis , Naphthalenes/radiation effects , Sensitivity and SpecificityABSTRACT
Microwave energy is an alternative energy source that is receiving a considerable amount of attention from researchers for a wide spectrum of applications. The fundamentally different method of transferring energy from the source to the sample is the main benefit of utilizing microwave energy; by directly delivering energy to microwave-absorbing materials, conventional issues such as long heating periods, thermal gradients, and energy lost to the system environment can be minimized or avoided. Furthermore, the penetrating capacity of microwave allows volumetric heating of samples. These attributes of microwave energy make utilizing it very attractive for industrial applications as an alternative to conventional processing methods. The reality is otherwise however, and limited literature is found in any given area of work. Despite the lack of focus, in most published cases, the utilization of microwave energy has produced improved results compared to conventional methods with reduced heating times or reaction temperatures. This review provides a general overview of reported applications of microwave energy in the open literature. It also attempts to summarize the results obtained for various common uses and highlights some applications that have not gathered as much attention as anticipated.
Subject(s)
Food Preservation/methods , Microwaves , Catalysis , Ceramics/chemistry , Cooking/methods , Desiccation/methods , TemperatureABSTRACT
The use of microwave energy as a heating source for the field-based headspace sampling and the subsequent determination of various volatile organic compounds (VOCs) using a field-portable HAPSITE gas chromatograph-mass spectrometer has been evaluated. A significant advantage in time reduction has been observed when using microwave energy when compared to conventional resistive-based heating. Such time savings are critical in field operations involving equipment such as the HAPSITE where non-routine sampling is commonly performed and very quick turnaround time is usually needed. Further, the technology also showed significant improvements in terms of sensitivity, thus suggesting its applicability to a broader range of compounds and detection levels than current technologies.
Subject(s)
Environmental Monitoring/instrumentation , Environmental Monitoring/methods , Microwaves , Organic Chemicals/analysis , Equipment Design , Gas Chromatography-Mass Spectrometry/instrumentation , Gas Chromatography-Mass Spectrometry/methods , Sensitivity and Specificity , VolatilizationABSTRACT
The use of microwave-assisted extraction has gained wide acceptance as a powerful tool for the recovery of environmental contaminants and their subsequent analysis. This paper reviews the historical and fundamental basis of the technology. It also provides a cursory review of the current state-of-the-art and literature (2000-2006) in the area of environmental analysis in addition to providing a critical review of the level of efforts being devoted to its further development.
Subject(s)
Environmental Pollutants/analysis , Microwaves , AnimalsABSTRACT
Response surface methodology (RSM) was applied to predict optimum conditions for microwave-assisted extraction-a MAP technology-of saponin components from ginseng roots. A central composite design was used to monitor the effect of ethanol concentration (30-90%, X(1)) and extraction time (30-270 s, X(2)) on dependent variables, such as total extract yield (Y(1)), crude saponin content (Y(2)), and saponin ratio (Y(3)), under atmospheric pressure conditions when focused microwaves were applied at an emission frequency of 2450 MHz. In MAP under pre-established conditions, correlation coefficients (R (2)) of the models for total extract yield and crude saponin were 0.9841 (p < 0.001) and 0.9704 (p < 0.01). Optimum extraction conditions were predicted for each variable as 52.6% ethanol and 224.7 s in extract yield and as 77.3% ethanol and 295.1 s in crude saponins, respectively. Estimated maximum values at predicted optimum conditions were in good agreement with experimental values.
Subject(s)
Microwaves , Panax/chemistry , Plant Extracts/chemistry , Plant Roots/chemistry , Saponins/isolation & purification , Ethanol , Saponins/analysisABSTRACT
A Microwave-Assisted Process (MAP is a Trade-Mark of Her Majesty the Queen in Right of Canada as represented by the Minister of the Environment) solvent extraction procedure was used in conjunction with GC-MS analysis to investigate the chemical composition of dried and live cockroaches. The main components extracted were classified into four groups: sterols. fatty acids and their esters, long chain alkanes and fused aromatic hydrocarbons.
