However, in 50 male patients with cirrhosis of the liver, blood-ammonia levels increased from already elevated fasting levels (mean, 1.56 mg NH3/litre) to much higher peak concentrations (mean, 3.7 mg NH3/litre) at 15 min, followed by a slow decrease reflecting impaired hepatic urea synthesis.
Cao  performed modification of zinc oxide using silica and trimethyl siloxane (TMS). The finest particles of ZnO were obtained by calcination of the precursor zinc carbonate hydroxide (ZCH). ZHC was obtained in a process of precipitation from substrates such as zinc sulfate heptahydrate (ZnSO4·7H2O), ammonium solution (NH4OH) and ammonium bicarbonate (NH4HCO3). The surface of the ZCH was then successively modified by an method using TEOS and hexamethyldisilazane (HMDS) in water. The ZHC functionalized in this way was calcined, to obtain ultrafine particles of ZnO. Modification of the ZnO particles made possible a solution to the problem of their agglomeration. Functionalization of the ZnO surface with an inorganic compound (silica) reduced the photocatalytic action of the oxide, while the organic compound (HMDS) increased the compatibility of the ZnO with an organic matrix. The highly transparent modified zinc oxide surface was found to provide excellent protection against UV radiation, which represents a significant advantage of the use of these modifying agents. A schematic representation of the synthesis of surface-modified ZnO ultrafine particles using an modification method is shown in .
In processes of synthesis of nanopowders based on precipitation, it is increasingly common for surfactants to be used to control the growth of particles. The presence of these compounds affects not only nucleation and particle growth, but also coagulation and flocculation of the particles. The surfactant method involves chelation of the metal cations of the precursor by surfactants in an aqueous environment. Wang  obtained nanometric zinc oxide from ZnCl2 and NH4OH in the presence of the cationic surfactant CTAB (cetyltrimethylammonium bromide). The process was carried out at room temperature, and the resulting powder was calcined at 500 °C to remove residues of the surfactant. The product was highly crystalline ZnO with a wurtzite structure and with small, well-dispersed spherical nanoparticles in size of 50 nm. It was found that CTAB affects the process of nucleation and growth of crystallites during synthesis, and also prevents the formation of agglomerates.