Dynamic microwave-assisted extraction combined with liquid phase microextraction based on the solidification of a floating drop for the analysis of organochlorine pesticides in grains followed by GC

A convenient,cost-effective and fast method using dynamic microwave-assisted extraction and liquid phase microextraction based on the solidification of a floating drop was proposed to analyze organochlorine pesticides in grains including rice,maize and millet.Twelve samples can be processed simultaneously in the method.During the extraction process,10%acetonitrile-water solutions containing 110μL of n-hexadecane were used to extract organochlorine pesticides.Subsequently,1.0 g sodium chloride was placed in the extract,and then centrifuged and cooled.The n-hexadecane drops containing the analytes were solidifi ed and transferred for determination by gas chromatography-electron capture detector without any further filtration or cleaning process.Limits of detection for organochlorine pesticides were 0.97–1.01μg/kg and the RSDs were in the range of 2.6%–8.5%.The developed technology has succeeded in analyzing six real grains samples and the recoveries of the organochlorine pesticides were 72.2%–94.3%.Compared with the published extraction methods,the developed method was used to analyze organochlorine pesticides in grains,being more environmentally friendly,which is suitable for the daily determination of organochlorine pesticides.

Dynamic Microwave-Assisted Extraction of Total Ginsenosides from Ginseng Fibrous Roots

A dynamic microwave-assisted extraction（DMAE） method is established for the extraction of total ginsenosides from ginseng fibrous roots. The extraction process has been simulated and its main affection factors（liquid/solid ratio K of solvent to ginseng powders（V/m）, irradiation time, irradiation temperature, extracting solution concentration, flow rate of solvent and microwave power） have been optimized by response surface methodology（RSM）. The optimum conditions of extraction are the liquid/solid ratio of 270 m L/g, the extraction temperature of 75 ℃, the extraction time of 35 min, ethanol concentration of 70%（V/V）, the solvent flow rate of 1.3 m L/min, and the microwave power of 500 W. The yield of ginsenosides obtained by the proposed DAME method is（15.0±0.7） %, which is well agreement with the yield predicted by the model. Compared with static microwave-assisted extraction, DMAE has a higher extraction yield and can avoid the degradation of ginsenoside.

Optimization and Control of Extractive Distillation with Heat Integration for Separating Benzene/Cyclohexane Mixtures

In this work, the extractive distillation with heat integration process is extended to separate the pressure-insensitive benzene-cyclohexane azeotrope by using furfural as the entrainer. The optimal design of extractive distillation process is established to achieve minimum energy requirement using the multi-objective genetic algorithm, and the results show that energy saving for this heat integration process is 15.7%. Finally, the control design is performed to investigate the system's dynamic performance, and three control structures are studied. The pressure-compensated temperature control scheme is proposed based on the first two control structures, and the dynamic responses reveal that the feed disturbances in both flow rate and benzene composition can be mitigated well.

Dynamic Microwave-assisted Extraction Online Coupled with QuEChERS for the Determination of Organophosphorus Pesticides in Cereals by Gas Chromatography

A rapid analytical method was first developed to detect organophosphorus pesticides(OPPs)in cereals,which used dynamic microwave assisted extraction(DMAE)coupled online with a modified quick,easy,cheap,effective,rugged,and safe(QuEChERS)method.Cereals samples were mixed with a certain amount of quartz,Ci8 and the primary second amine(PSA),and extracted successively with the acetonitrile-water solution(80%,VIV)under microwave irradiation.The obtained eluate was directly introduced into a collection tube containing NaCl and MgSO4.Finally,the supemate was evaporated and reconstructed,and determined by gas chromatographic spectrometry.Some factors affecting the experimental results were studied and optimized.The extraction and purification processes were carried out coinstantaneously and 12 samples could be treated in one step in 4 min.Low limits of tection(0.43—1.31 p.g/kg)for OPPs were obtained in cereals.The relative standard deviations(RSDs)were 2.1%—9.3%.The recoveries of OPPs ranged from 76.1%to 100.2%.By combining the advantages of DMAE with QuEChERS,the sample pretreatment process was simple to operate,with little amount of organic solvent.The whole extraction process was completed in a closed environment,therefore it was very appropriate for daily analysis of OPPs in cereals.

Extraction and application of the low dimensional dynamical component from underwater acoustic target radiating noise

Signal processing in phase space based on nonlinear dynamics theory is a new method for underwater acoustic signal processing. One key problem when analyzing actual acoustic signal in phase space is how to reduce the noise and lower the embedding dimen- sion. In this paper, local-geometric-projection method is applied to obtain fow dimensional element from various target radiating noise and the derived phase portraits show obviously low dimensional attractors. Furthermore, attractor dimension and cross prediction error are used for classification. It concludes that combining these features representing the geometric and dynamical properties respectively shows effects in target classification.