Diffusion coefficients at rotated microelectrodes

The limiting current for several electrode reactions at a rotated microelectrode is observed to vary with the two-thirds power of the diffusion coefficient at infinite dilution in accordance with the theories of TACHI, EISBNBERG, LIN, and others. However, the uncertainties involved in estimating diffusion coefficients at given ionic strength require, that for accurate work, the limiting currents for different electrode reactions be compared on the basis of electrode sensivity, k_ion= i₁/C, and without regard to the role of diffusion in the transport process. The method of LAITINEN AND KOLTHOFF using an electrode reaction with only linear diffusion is recommended for measuring diffusion coefficients at given ionic strength under conditions similar to those extant in voltammetry.     

Listeria monocytogenes: knowledge gained through DNA sequence-based subtyping, implications, and future considerations

The purpose of subtyping is to differentiate bacterial isolates beyond the classification of species or subspecies. Subtyping methods can be grouped into two broad categories based on the cellular components targeted: (1) phenotypic subtyping methods that differentiate isolates by the enzymes, proteins, or other metabolites expressed by the cell, and (2) molecular subtyping methods that discriminate isolates based on interrogation of nucleic acid sequences. The two major types of molecular subtyping methods include band-based methods based on fragment pattern data or DNA fingerprints, and methods that generate DNA sequence data. Molecular subtyping methods have shown that Listeria monocytogenes isolates can be classified into four genetic lineages or divisions. Although band-based molecular subtyping methods continue to serve as the gold standard for routine molecular subtyping of most clinically important foodborne pathogens, including L. monocytogenes, the explosion of recently completed and ongoing DNA sequencing projects, and thus available DNA sequence data, have stimulated efforts to develop highly discriminatory and high-throughput DNA sequence-based subtyping methods for L. monocytogenes. L. monocytogenes represents one of the most highly sequenced human pathogens; more than 20 genome sequences are currently available for this organism. This review provides an overview of the concepts behind subtyping and discusses the application of molecular subtyping methods, with an emphasis on DNA sequence-based subtyping methods to characterize L. monocytogenes.     

Simultaneous analysis of piperacillin and tazobactam in rabbits: application to pharmacokinetic study

A simple and rapid assay is developed for the simultaneous analysis of piperacillin and tazobactam in rabbit serum and tissue cage fluid (TCF). To eliminate endogenous interferences, a wavelength switch technique was applied, in which the programmable UV detector changed the monitoring wavelength from 218 to 254 nm at 10 min. After liquid-liquid extraction, sample analyses were performed on a C(18) column by gradient elution; the mobile phase consisted of acetonitrile and phosphate buffer (0.014 m, pH 2.4). Owing to the limited amount of rabbit TCF available, a cross-validation of a proxy matrix was evaluated. The relative standard deviation of the between- and within-batch precision of both compounds was less than 5.1%; the relative error of the between- and within-batch accuracy was less than 7.3%. The recoveries of both compounds in serum and TCF were larger than 80%. This assay was successfully applied to simultaneously analyze piperacillin and tazobactam in rabbit serum and TCF samples.     

4‐Chloro‐N‐(4‐cyano‐2‐nitro­phenyl)‐3‐nitro­benz­amide

The structure of the title compound, C₁₄H₇ClN₄O₅, comprises two nearly coplanar phenyl rings connected via an amido moiety.