Injected cerium

Magnesium-based additives are commonly employed to treat boiler furnace area fouling and corrosion conditions. They are injected into heavy fuel oil or other combustible material. Cerium is superior in action to magnesium salts, however, because an equivalent weight of cerium increases the melting point of the deposit more than that of magnesium. 

There are no available human data for transfer of cerium from the pregnant mother to the fetus. In studies with pregnant mice, Naharin et al. (1969) found that about 0.006 of the l44Ce citrate injected into the mother was transferred to the fetus. These studies were in agreement with those of Sternberg (1962) in which 0.003 to 0.03 of the cerium injected into guinea pig mothers was transferred to their fetuses after 24 hours. 

Cember, H. (1962). Lung Cancer in Rats from Intratracheally Injected Radioactive Cerium as litCeF3 and li4CeCl3, Report No. NYO-10056 (National Technical Information Service, Springfield, Virginia). 

Thomas, R. L., Scott, R. T. and McClellan, R. O. (1971). Influence of carrier cerium on retention and tissue distribution of injected 144Ce in the rat, page 86 in Fission Product Inhalation Program Annual Report 1970-1971, Report No. LF-44 (Lovelace Foundation, Albuquerque, New Mexico). 

Methods for determination of thiol drugs (i.e., captopril [21-25], penicillamine [26-28], hydrochlorothiazide [24, 25, 29, 30], and tiopronin [31, 32]) have been developed. These methods are based on CL from a cerium (IV) oxidation system sensitized by adequate fluorophores such as quinine and rhodamine B. By using HPLC-coupled CL-flow-injection analysis method, tiopronin and its metabolite 2-mercaptopropionic acid in human urine were sensitively determined with the detection limits of 0.8 and 1 pM, respectively [32],... 

Trace metals have been measured in various tissues by ICP-MS to investigate Alzheimer s disease [249-252]. Various sample preparation and processing approaches have been used, including flow injection analysis and extraction. Al, Si, and Sn levels were reported to be higher than in healthy tissue, whereas zinc and selenium concentrations were lower. In the temporal cortex there were also reductions of cesium and cerium concentrations. The mechanisms responsible and the key elements remain incompletely understood. 

Aly et al. [73] proposed a rapid and sensitive flow-injection chemilu-minometric method for the determination of three phenothiazine derivatives fluphenazine hydrochloride, levomepromazine hydrochloride and trimeprazine tartrate. The method was based on the chemiluminescence (CL) induced by the oxidation of the drugs with cerium (Ce(IV)) in an acidic medium. The CL intensity was greatly enhanced when rhodamine B was used as a sensitizer in the case of levomepromazine hydrochloride and trimeprazine tartrate. The linear dynamic ranges were 0.5-90 pg/mL for... 

For the reaction of the column effluent with the cerium(IV) reagent, instead of a simple injection loop, Fields et al. used a solid-bed reactor with a volume of 2.8 mL. This relatively large volume is necessary to allow the required reaction time of at least two minutes for the oxidation of nitrite ions with cerium(IV). While the reaction of nitrite ions with cerium(IV) is comparatively slow, the maximum fluorescence yield with iodide is obtained in less than ten seconds. On the other hand, the reaction kinetics with thiosulfate appears to be completely different. As seen in the respective diagram in Fig. 6-21, this reaction is characterized by a fast rise of the fluorescence yield within a short time, which increases as the reaction product from Eq. (191), tetrathionate, also reacts slowly with cerium(IV). 

Fig. 6-22. Analysis of nitrite, thiosulfate, and iodide upon application of fluorescence detection after derivatization with cerium(IV). — Separator column Vydac 302 IC eluent 0.001 mol/L KHP + 0.01 mol/L Na2S04 pH 5.5 with Na2B407 flow rate 1 mL/min detection fluorescence after reaction with cerium(IV) injection volume 100 pL solute concentrations 0.5 ppm nitrite, 1.1 ppm thiosulfate, and 1.5 ppm iodide (taken from [37]).

Fig. 6-23. Analysis of monovalent cations with indirect fluorescence detection. — Separator column 100 mm x 3.2 mm I.D. ION-210 eluent 10-5 mol/L cerium(III) sulfate flow rate 1 mL/min detection indirect fluorescence injection volume 20 gL solute concentrations 0.16 ppm sodium (1), 0.15 ppm ammonium (2), 0.21 ppm potassium (3), 0.71 ppm rubidium (4), and 1.2 ppm cesium (5) (taken from [41]).

Rao, Y., Zhang, X., Luo, G., and Baeyens, W. R. G. Chemiluminescence flow-injection determination of furosemide based on a rhodamine 6G sensitized cerium (IV) method. Anal. Chim. Acta 396(2-3) 273-277,1999. 

Thus a subanalgesic dose of La3+ significantly potentiated morphine analgesia after intracerebroventricular (i.c.v.) injection, while at higher doses both La3+ itself and another Ca blocker, cerium produced analgesia. On a molar basis, La3+ was approximately one-tenth as potent as morphine. Surprisingly, the effects of La3+ were antagonized by naloxone but a flat dose-response curve was obtained. 

Using small quantities of additives, such as cerium oxide, incorporated in the fuel or injected into the exhaust ahead of the particulate trap. The additive, when collected on the filter with the particulate, allows the particulate to bum at normal exhaust temperatures to form carbon dioxide and water. This system is insensitive to sulphur and can be used with current European diesel fuel containing 500 PPM of sulphur. 

The relative role of thorium (and especially cerium) was never established. In mona-zite-processing workers exposed again to a mixture of rare earth elements and thorium, slight effects on peripheral lymphocytes and on liver function were found (Farid and Con-ibear 1983, Serio 1983). On the other hand, Thampi et al. (2002) have not observed differences between newborns from high-level natural radiation (HLNR) and natural-level natural radiation (NLNR) areas with respect to chromosome aberrations and constitutional anomalies, nor was there any association with the background radiation levels. The injection of considerable amounts of thorotrast in diagnostic medicine without apparent acute effects is another indication of the absence of shortterm effects (Ishikawa et al. 1999). 

P. Martinez-Jimenez, M. Gallego, and M. Valcarcel, Indirect Atomic Absorption Determination of Cerium and Lanthanum by Flow Injection Analysis Using an Air-Acetylene Flame. At. Spectrosc., 6 (1985) 137. 

K. H. Al-Sowdani and A. Townshend, Simultaneous Spectrofluorimetric Determination of Cerium (III) and Cerium (IV) by Flow Injection Analysis. Anal. Chim. Acta, 179 (1986) 469. 

In conclusion, the observed complete conversions of NH3 and NO under excess ammonia conditions (> 200 °C) indicates great potential of cerium zeoUte. With ammonia applied in excess over NO, a stoichiometric amoimt of NH3 converts NO completely, and the excess NH3 will be simply converted to N2 by oxygen. With a certain shortage of NH3, a shghtly lower NO conversion may be obtained, but ammonia will be exhausted in the NO reduction anyway. This flexibility in ammonia feed concentration makes an approximate reductant injection control appUcable in practice. Under the present reaction conditions, an excess of ammonia up to 30 % is maximally allowed without ammonia slip. However, the effects of the reaction conditions, e.g., the space velocity, the presence of water or SO2, should be further examined to estimate such a "maximum ammonia excess value" in practice. 

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