We consider a family of smooth maps on an infinite cylinder which have invariant curves that are nowhere smooth. Most points on such a curve are buried deep within its spiked structure, and the outermost exposed points of the curve constitute an invariant subset which we call the "facade" of the curve. We find that for surprisingly many of the maps in the family, all points in the facades of th...

Dispersive liquid-liquid microextraction (DLLME) and spectrofluorimetry, coupled with chemometrics methods, are proposed in this work for the pre-concentration and determination of ofloxacin concentration in spiked human urine. Chloroform and acetonitrile were selected as the extraction and dispersive solvents by the one-variable-at-a-time process. The Box-Behnken design was used to optimize th...

A method for the simultaneous determination of sulfamethoxazole (SMX) and trimethoprim (TMP), based on a direct determination of SMX after diazotization and coupling with 2-naphthol by visible spectrophotometry and an indirect determination of TMP in the UV region by difference was developed. By the suggested procedure, it was possible to analyze SMX and TMP in pharmaceutical preparations witho...

A method for the simultaneous determination of sulfamethoxazole (SMX) and trimethoprim (TMP), based on a direct determination of SMX after diazotization and coupling with 2-naphthol by visible spectrophotometry and an indirect determination of TMP in the UV region by difference was developed. By the suggested procedure, it was possible to analyze SMX and TMP in pharmaceutical preparations witho...

Among the techniques of detection used in clinical chemistry, optical and electrochemical methods are especially attractive. However, except for glass electrodes for pH measurement, potentiometric electrochemical sensors (ionselective electrodes) gained general acceptance in clinical analyzers and in clinical instrumentation, respectively, only around 1970 (for reviews see 1-5). Here we report ...

The effect of the presence of metabolism-induced concentration correlations in the calibration samples on the prediction performance of partial least-squares regression (PLSR) models and mid-infrared spectra from Chinese hamster ovary cell cultures was investigated. Samples collected from batch cultures contained highly correlated metabolite concentrations as a result of metabolic relations. Ca...

The measurement process uncertainty is propagated through the use of a calibration curve. The magnitude and direction of this uncertainty depends on the choice of the controllable variable in producing the calibration curve; in other words, the design of the calibration experiment. In this paper this design is discussed in the context of Scheffe's approach to the uncertainties of a calibration ...

As the application for quantitative proteomics in the life sciences has grown in recent years, so has the need for more robust and generally applicable methods for quality control and calibration. The reliability of quantitative proteomics is tightly linked to the reproducibility and stability of the analytical platforms, which are typically multicomponent (e.g. sample preparation, multistep se...

Calibration in atomic-absorption spectrometry is achieved by means of a concentrationgradient chamber using a single concentrated standard solution. Calibration is rapid and extends over the entire working concentration range of the analyte, irrespective of the shape of the conventionally obtained calibration curve. No curve-fitting approximations are involved. With well-designed apparatus, dev...