Ultrasound-assisted emulsification microextraction with solidification of floating organic droplet (USAEME-SFOD) has been applied to isolate hormones and other emerging contaminants from groundwater samples. Simultaneously with the extraction process, derivatization in the matrix was carried out using acetic anhydride. Quantification of studied organic pollutants was done through gas chromatography mass spectrometry (GC-MS). Hormones included β-estradiol (E2), estrone (E1), and diethylstilbestrol (DES). Other compounds belonged to groups of pharmaceuticals (diclofenac (DIC)), antiseptics (triclosan (TRC)), preservatives (propylparaben (PP) and butylparaben (BP)), sunscreen agents (benzophenone (BPH), and 3-(4-methylbenzylidene)camphor (3MBC)), repellents (N,N-diethyltoluamide (DEET)), industrial chemicals (bisphenol A (BPA), 4-t-octylphenol (4OP), 4-n-nonylphenol (4NP)). A non-toxic and inexpensive 1-undecanol was successfully used as the extraction solvent. Volume of extractant and derivatization agent, ionic strength, and time of extraction were optimized. Very low limits of detection (LoD) ranging from 0.01 to 5.9 ng/L were obtained. Recoveries ranged from 90% to 123%, with relative standard deviation being lower than 17%. The developed procedure was used to determine target compounds in groundwater collected at municipal waste landfills as well as in groundwater from wells distant from sources of pollution.
The paper presents comparison of results of impulse response spectral analysis that has been obtained using a method based on cross-correlation with results obtained using classical FFT. The presented non-Fourier method is achieved by correlating the analyzed signal and reference single-harmonic signals and using Hilbert transform to obtain an envelope of cross-correlation. The envelope of crosscorrelation makes it possible to calculate appropriate indicator and make its plot in frequency domain as a spectrum. The spectrum obtained this way has its advantage over the FFT that the spectral resolution does not depend on duration of signal. At the same time, the spectral resolution can be much greater than spectral resolution resultant from FFT. Obtained results show that presented non-Fourier method gives frequency readout more accurate in comparison to FFT when the impulse response is a short-time signal e.g. few dozen of miliseconds lasting.
The paper presents the use of the autocorrelation function for the description of vibrations and the problems connected with. The proposed method is based on the analysis of vibration signal recorded for machine during its operations using an analytic form of the autocorrelation function. The parameters are obtained using a curve fitting procedure. To keep a quality of parametric representation of considered vibration, only the curve fitting causes a determination coefficient over 0.90 is taken into consideration. Therefore, the autocorrelation functions are submitted for the fast Fourier transform to be helped, in determination of number of the dominant harmonic components. Also, the analytic form and parameters of power spectral density has been also calculated. Finally, the set of parameters has been collected to describe the selected fragment of vibration of the simple rotating machine. The influence of duration of analyzed vibration on the parameters values is also examined in this work.
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