Ultrasonic probes selection

FIGURE 2.34 Experimental setup used for the two modes of continuous ultrasound-assisted leaching and the possibilities of their coupling to other steps of the anal)dical process. One, two or three steps can he used in a single method. Abbreviations used are LC, leaching carrier PP, peristaltic pump UP, ultrasonic probe EC, extraction chamber WB, water bath W, waste SV, selection valve EX, extract E, eluent IV, injection valve SPC, solid-phase column DR, derivatization reagent RC, reaction coil and D, detector. (Reprinted from Luque-Garcia, J. L. and Luque de Castro, M. D., Trends Anal. Chem., 22, 41-47, 2003. With permission from Elsevier.)... 

Selective oxidation of diuron in a MeOH-water mixture Potentiostatic control 35 kHz cleaning bath and 20 kHz ultrasonic probe Sonication improves current efficiencies, mass transport rates, and depassivates the probe was reported to be a much more reliable and effective method of insonation 65... 

FIGURE 4.11 Experimental setup for the dynamic ultrasound-assisted extraction of phenolic compounds from olive leaves and alperajo (C, extraction coil EC, extraction chamber ER, extract reservoir HPLC, high-performance liquid chromatography LC, leaching carrier PC, personal computer PP, peristaltic pump SV, selection valve UP, ultrasonic probe WB, thermostatic water-bath). 

During the inspection of an unknown object its surface is scanned by the probe and ultrasonic spectra are acquired for many discrete points. Disbond detection is performed by the operator looking at some simple features of the acquired spectra, such as center frequency and amplitude of the highest peak in a pre-selected frequency range. This means that the operator has to perform spectrum classification based on primitive features extracted by the instrument. 

Then with the focused transducer activated, the probe was scanned across the weld area, under push-button control, to detect the lower edge of the unfused land. This point was then used as a datum to which all subsequent transducer positions were referred. If the operator was satisfied with the quality of signals obtained the automatic scanning facility was introduced. Most functions necessary to select the transducer and digitise and store the ultrasonic data were then performed automatically under micro-processor control. The sequence of such operations was as follows ... 

Both new compounds A and B gave satisfactory microanalyses and NMR spectra. Selected amino acids (R)- and (S)-alanine (Ala), (R)- and (S)-phenylglycine (PhGly) and (R)- and (S)- B-phenylalanine ( p-PhAla) as their sodium and potassium salts were dried in vacuo over phosphorus pentoxide prior to use and served as guest species. The host/guest ratio was 2 1 in deuteriochloroform solutions. Dissolution of solid salt was accomplished in an ultrasonic bath within 20 to 100 min. The host concentration was ca. 0.1 M. All the variable-temperature spectra were recorded with JEOL-JNM-4H-100 spectrometer at 100 MHz with TMS as internal standard and lock. The anomeric proton served as an NMR probe. The free energy of activation at the coalescence temperature was calculated from the expression 7 ... 

Accessibility for inspection should be reconciled with the selected inspection and destructive or non-destructive testing procedures (e.g. X-rays, ultrasonic, visual, probes, instruments, ete.). Probable expertise and availability of future maintenance personnel may govern selected maintenance requirements. The use of modular assemblies tailored to the requirements of eorrosion eontrol is recommended. 

The ultrasonic processor is designed to deliver constant amplitude (peak-to-peak displacement at the probe tip). As the resistance to the movement of the probe increases, so do the power requirements. The power supply senses these requirements, and automatically increases the amount of power delivered in order to maintain the selected excursion at the probe tip constant. 

Variable amplitude control Allows the ultrasonic vibrations at the probe tip to be set to any desired amplitude. Selected output level is clearly displayed on the screen. 

---