Cyclic activation analysis

Instrumental Neutron Activation Analysis (INAA) was applied to the determination of the platinum metals as part of a study of their uptake, accumulation and toxicity in plants. Long irradiations are described for iridium, osmium and ruthenium determinations in specially grown plant materials. An interference in the determination of platinum in plant matrices by this method is reported also. Short irradiations, utilising thermal and epithermal fluxes are investigated for rhodium and palladium determinations, with further studies using cyclic activation analysis. 

Figure 3, Cyclic activation analysis. Variation of induced activity with time and cycle number. Key T, cycle period tj, time of irradiation U, time between end of irradiation and start of count tc, time of counting and t ,, time between end of counting and start of irradiation. The detected radiations at each counting period are summed to give a cumulative detector response, Dc, over the total experimental time. Dc is maximized when = t , and tf = tc = T/2 ( See reference 17...

CINAA cyclic instrumental neutron activation analysis... 

In the course of determinations of trace element concentrations in nails of a group of carpenters by cyclic instrumental neutron activation analysis (CINAA) using the PCA (principal component analysis256-259) method, the silver concentration in nails was determined260 to be 0.027 0.037 pgg-1. The mean concentration of gold was 0.010 pgg-1. Nails can be used as a dietary and environmental exposure monitor261-267. 

GINAA Cyclic instrumental neutron activation analysis is used to determine very short lived isotopes. The sample is irradiated for a short time, rapidly transferred to a detector for counting the entire process repeated for a number of cycles with the gamma-ray spectrum recorded from each cycle accumulated to yield a cumulative spectrum. 

The nondestructive instrumental (INAA) and destructive radiochemical (radiochemical neutron activation analysis — RNAA) procedures of this method are discussed later in this chapter. Specific problems, such as chain decays, cyclic activation, and interferences, as well as typical appKcations have recently been discussed by Alfassi (2001) and the references therein. 

Elson, C.M., Ackman, R.G. and Chatt, A. (1983) Determination of selenium, arsenic, iodine and bromine in fish, plant and mammalian oils by cyclic instrumental neutron activation analysis. J. Am. Oil Chem. Soc. 60, 829-832. 

Sia, J., Yee, H.-B., Santos, J. and Abdurrahman, M. (2010) Cyclic voltammetric analysis of antioxidant activity in cane sugars and palm sugars from Southeast Asia. Food Chem., 118, 840-846. 

The research activity here presented has been carried out at the N.D.T. laboratory of l.S.P.E.S.L. (National Institute for Occupational Safety and Prevention) and it is aimed at the set up of the Stress Pattern Analysis by Measuring Thermal Emission technique [I] applied to pressure vessels. Basically, the SPATE system detects the infrared flux emitted from points resulting from the minute temperature changes in a cyclically stressed structure or component. 

The acylation of enamines derived from cyclic ketones, which can lead to the acyl ketone or ring expansion (692-694), was studied by NMR and mass spectroscopic analysis of the products (695,696). In a comparative study of the rates of diphenylketene addition to olefins, a pronounced activation was observed in enamines (697). Enamine N- and C-acylation products were obtained from reactions of Schiff s bases (698), vinylogous urethanes (699), cyanamides (699), amides (670,700), and 2-benzylidene-3-methylbenzothiazoline (672) with acid chlorides, anhydrides, and dithio-esters (699). 

This aminium radical salt in aqueous solution in the form of solvated radical salt is very stable and will not polymerize acrylonitrile even with CeHsCOONa to form the corresponding benzoate. Therefore, we believe that in the nucleophilic displacement, there must be some intermediate step, such as intimate ion pair and cyclic transition state, which will then proceed the deprotonation to form the active aminium radical ion [14], as shown in Scheme 1. The presence of the above aminomethyl radical has also been verified [15] through ultraviolet (UV) analysis of this polymer formed such as PAN or PMMA with the characteristic band as the end group. 

Cyclic voltammetry (adsorption, monolayers) Potentiodynamic polarisation (passivation, activation) Cathodic reduction (thickness) Frequency response analysis (electrical properties, heterogeneity) Chronopotentiometry (kinetics)... 

An example of a separation primarily based on polar interactions using silica gel as the stationary phase is shown in figure 10. The macro-cyclic tricothecane derivatives are secondary metabolites of the soil fungi Myrothecium Verrucaia. They exhibit antibiotic, antifungal and cytostatic activity and, consequently, their analysis is of interest to the pharmaceutical industry. The column used was 25 cm long, 4.6 mm in diameter and packed with silica gel particles 5 p in diameter which should give approximately 25,000 theoretical plates if operated at the optimum velocity. The flow rate was 1.5 ml/min, and as the retention time of the last peak was about 40 minutes, the retention volume of the last peak would be about 60 ml. 

Reaction progress kinetic analysis offers a reliable alternative method to assess the stability of the active catalyst concentration, again based on our concept of excess [e]. In contrast to our different excess experiments described above, now we carry out a set of experiments at the same value of excess [ej. We consider again the proline-mediated aldol reaction shown in Scheme 50.1. Under reaction conditions, the proline catalyst can undergo side reactions with aldehydes to form inactive cyclic species called oxazolidinones, effectively decreasing the active catalyst concentration. It has recently been shown that addition of small amounts of water to the reaction mixture can eliminate this catalyst deactivation. Reaction progress kinetic analysis of experiments carried out at the same excess [e] can be used to confirm the deactivation of proline in the absence of added water as well to demonstrate that the proline concentration remains constant when water is present. 

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