No abstract

In this study, we experimentally investigated the effect of charged particles generated from an alternating current glow discharge in liquids and the ability of these particles to synthesize silver nanoparticles. The measurement of the pH and electrical conductivity in liquids was performed to study the interface reactions and transfer of species from plasmas to liquids. Solutions of sodium hydroxide, de-ionized water, sodium nitrate, and silver nitrate were used in this study. We determined that the pH of de-ionized water and sodium hydroxide solutions was reduced to 4.0 during the discharge. However, the pH of nitrate salts evolved in two opposite stages, with an initial reduction within 3 min from the start of the discharge and a subsequent increase to alkaline values. The results also showed that spherical silver nanoparticles were generated in the silver nitrate solutions under the discharge. These results indicate that alternating current glow discharge generates both positive ions and free electrons when in contact with a liquid, leading to complex chemical transformations. This suggests that the proposed approach can be used for noble nanoparticle synthesis.

Simvastatin, a pro-drug lactone, forms the open carboxylic acid as a major metabolite that inhibits the activity of 3-hydroxy-3-methylglutaryl coenzyme A reductase. Simvastatin and the acid in plasma were quantified by a gas chromatography/mass spectrometry/selected ion monitoring (GC/MS/SIM) method. These drugs were separated by solid-phase extraction and independently converted into a 1,3-diol-type compound. This compound reacted with ferroceneboronic acid to yield the cyclic boronate that gave satisfactory mass spectra for GC/MS/SIM measurements. The serum was dominated by the molecular ion appearing as the base peak, thereby leading to a sensitive and selective assay. The calibration curves for simvastatin and the acid were linear in their concentration range of 0.1-10 ng ml-1, where the values of coefficient of variation for both drugs were below 8%, except for the value of 11% for simvastatin at a concentration of 0.1 ng ml-1. The quantification limit for both drugs was 0.1 ng ml-1 on the basis of a signal-to-noise ratio of 4:1.

In this study, we report the influence of pH level in HAuCl4 solution on the size and shape of gold nanoparticles synthesized by an alternating current glow discharge on liquid. The results indicate there have three distinct groups in the size/shape of gold nanoparticles due to varying pH, one at pH ≤ 8, one at pH 9 and the other at higher than 9. At pH ≤ 8, single spherical gold nanoparticles with an average size of 5.7 nm and coral-shaped clusters aggregated from these gold nanoparticles were formed after 10 min of alternating current glow discharge on liquids. In the case of pH 9, spherical AuNPs with the size of 120 nm and coral-shaped clusters with the size up to 100 nm were generated after 10 min of discharge. At pH ≥ 10, roughly spherical gold nanoparticles with an average size of 100 nm (at pH 10) to 30.6 nm (at pH 13) were generated after 10 min of discharge. There has a decrease in the average size of gold nanoparticles when pH increases from 10 to 13. Our findings open a new way to control the size/shape of gold nanoparticles synthesized by plasma over liquid via pH control in the precursor solution.

Metabolic pathways of simvastatin (MK-733), a lactone prodrug of an inhibitor of HMG-CoA reductase, were elucidated in male rats, using the [14C]-labelled compound. Evidence has been obtained for hydrolysis of simvastatin and its metabolites at their 2,2-dimethylbutyryl moieties. Metabolites identified in plasma were 2,2-dimethylbutyric acid (DMB), 2,2-dimethyl-3-hydroxybutyric acid (DMHB) and an open chain hydroxy acid of simvastatin: metabolites identified in urine were DMHB, a glucuronide and the glycine conjugate of DMB. They were characterized by gas chromatography/electron impact and chemical ionization mass spectrometry as phenacyl or pertrimethylsilylated derivatives. The structures of the metabolites and the aglycone of the glucuronide were confirmed as phenacyl esters by comparison of their chromatographic data and mass spectra with those of the phenacyl derivatives of authentic compounds.