Determination of polycyclic aromatic hydrocarbons in marine sediments by high-performance liquid chromatography after microwave-assisted extraction with micellar media.
A simple and rapid method is developed for extraction and determination of polycyclic aromatic hydrocarbons (PAHs) in marine sediments. The procedure was based on the microwave-assisted extraction of PAHs in marine sediment samples using a micellar medium of Polyoxyethylene 10 lauryl ether as extractant. Two-level factorial designs have been used to optimize the microwave extraction process. The analysis of extracts has been carried out by HPLC with UV detection. Fortified sediments gave an average recovery between 85.70 and 100.73%, with a relative standard deviation of 1.77-7.0% for PAHs with a ring number higher than three.
Microwave-Assisted Extraction as an Alternative to Soxhlet, Sonication, and Supercritical Fluid Extraction
Microwave-assisted extraction (MAE), Soxhlet, sonication, and supercritical fluid extraction (SFE) were compared in their ability to extract 95 compounds listed in U.S. Environmental Protection Agency Method 8250. Freshly spiked soil samples and 2 standard reference materials were extracted with hexane-acetone (1 + 1) by MAE and Soxhlet extraction, with methylene chloride-acetone (1 + 1) by sonication extraction, and with supercritical carbon dioxide modified with 10% methanol by SFE. Results indicate that MAE is a promising extraction technique. Of 94 compounds for which we are reporting data, 51 compounds gave MAE recoveries of >80% ; 33, 50-79% ; 8, 20-49% ; and 2, 80% ; 32, 50-79% ; 8, 20-49% ; and 4, 80% ; 25, 50-79% ; 4, 20-49% ; and 2, 80% ; 37, 50-79% ; 12, 20-49%, and 8, 70%) with acetonitrile at 115°C.
Turbine blade temperature calculation and life estimation - a sensitivity analysis
Abstract The overall operating cost of the modern gas turbines is greatly influenced by the durability of hot section components operating at high temperatures. In turbine operating conditions, some defects may occur which can decrease hot section life. In the present paper, methods used for calculating blade temperature and life are demonstrated and validated. Using these methods, a set of sensitivity analyses on the parameters affecting temperature and life of a high pressure, high temperature turbine first stage blade is carried out. Investigated uncertainties are: (1) blade coating thickness, (2) coolant inlet pressure and temperature (as a result of secondary air system), and (3) gas turbine load variation. Results show that increasing thermal barrier coating thickness by 3 times, leads to rise in the blade life by 9 times. In addition, considering inlet cooling temperature and pressure, deviation in temperature has greater effect on blade life. One of the interesting points that can be realized from the results is that 300 hours operation at 70% load can be equal to one hour operation at base load.