Sediment extraction and clean-up for organic phosphorus analysis by electrospray ionization tandem mass spectrometry

A method to prepare NaOH sediment extracts for organic P compound analysis with electrospray ionization tandem mass spectrometry (ESI-MS-MS) was developed on natural samples. Ion exchange, rotary evaporation and mass cut-off filtering proved to be suitable for sample preparation. Samples were analyzed with ESI-MS-MS, and reproducibility and repeatability of the method was calculated. In addition, ³¹P-nuclear magnetic resonance spectroscopy (³¹P NMR) was used to measure recovery of different P compound groups such as orthophosphate (Ortho-P), orthophosphate monoesters (Monoester-P), orthophosphate diesters (Diester-P) and pyrophosphates (Pyro-P).

The developed sample preparation method resulted in an easy-to-spray liquid for the ESI-MS-MS instrumentation. The overall P recovery was 65% and ³¹P NMR showed that Diester-P, possibly in the form of DNA, was apparently lost through the filtering step most likely due to their size. Variances in the total intensities of the MS scans (relative standard deviation (R.S.D.) 35–54%) were for about 50% due to repeated MS runs. Covariances of the peaks in the MS spectra were calculated to be for about 30% due to the sample preparation procedure. Finally, with the ESI-MS-MS approach, 11 peaks in the mass spectra were found likely to represent phosphate containing compounds.     

Biomaterials for molecular electronics development of optical biosensor for retinol

Molecular electronics involves expertise from several branches of science. Various biomaterials and electronics are involved in the fabrication of such devices. While passive biomaterials are involved in anchoring the active biomolecules, the latter are involved in switching and/or signal transduction. In the present investigation we have used a glass-capillary-based approach to design a biosensor for retinol. The sensing element is retinol-binding protein (RBP). The affinity of retinoic-acid-horseradish peroxidase (conjugate) to RBP is tested using a surface plasmon resonance technique. A simple photomultiplier-tube-based system is exploited to monitor the chemiluminescent signal generated upon reaction of hydrogen peroxide and luminol with the conjugate bound to RBP. The photomultiplier tube is directly coupled to a computer for data logging.     

Using a Bootstrap Method to Choose the Sample Fraction in Tail Index Estimation

Tail index estimation depends for its accuracy on a precise choice of the sample fraction, i.e., the number of extreme order statistics on which the estimation is based. A complete solution to the sample fraction selection is given by means of a two-step subsample bootstrap method. This method adaptively determines the sample fraction that minimizes the asymptotic mean-squared error. Unlike previous methods, prior knowledge of the second-order parameter is not required. In addition, we are able to dispense with the need for a prior estimate of the tail index which already converges roughly at the optimal rate. The only arbitrary choice of parameters is the number of Monte Carlo replications.     

The enzyme thermistor—A realistic biosensor concept. A critical review

This review describes principles and features of thermal biosensors and microbiosensors in flow injection analysis. Examples are given that illustrate the great versatility and excellent operational stability offered by thermal biosensors. The examples are mostly from work with the original type of enzyme thermistor operating with an enzyme column, but there will also be work described involving miniaturised devices including thermal lab-on-chip constructions and other types of sensing materials, such as MIPs (molecularly imprinted polymers) for both affinity and catalytic reactions. Several recently presented thermal biosensor concepts are reviewed including a thermal–electrochemical hybrid sensor for lactose based on immobilised cellobiose dehydrogenase. Another recent method is the determination of fructose using a fructose-6-phosphate kinase column. Operation with complex sample matrices such as blood, plasma and milk and how to avoid non-specific temperature effects are considered.     

Can One Hear the Composition of a Drum?

This note is related to the famous question raised by Mark Kac and concerning the determination of the shape of the drum by the eigenvalues of its governing equation. Here, we allow the drum to be composed by several different types of membranes and we consider the problem of hearing the composition of the drum, starting from the eigenvalues of numerical approximations of the related equation. Some key tools, taken from asymptotic linear algebra, are reported and extended, and allow somehow to answer to the question in the positive.     

Computerized potentiometric stripping analysis for the determination of cadmium,lead, copper and zinc in biological materials

Two different types of tinned mussels and a bovine liver reference sample have been analyzed for Zn, Cd, Pb and Cu by means of computerized potentiometric stripping analysis and atomic absorption spectrometry. The samples were digested by two different procedures, one employing nitric acid only and the other employing nitric and perchloric acids. It is shown that computerized stripping analysis can be used in samples containing high concentrations of electroactive organic nitro compounds, without sample deoxygenation.     

Determination by the enzyme thermistor of cellobiose formed on degradation of cellulose

A calorimetric assay procedure for the determination of cellobiose has been developed. The cellobiose is hydrolyzed by β-glucosidase and the glucose formed is measured calorimetrically by an enzyme thermistor containing co-immobilized glucose oxidase and catalase. The system was optimized with regard to the arrangement of the enzymes, the pH-dependence of the separate enzymic steps, and of the total system. By placing the β-glucosidase in a precolumn that could be switched in and out of the flow through the enzyme thermistor, both cellobiose and glucose present in the sample could be determined. The performance with standard solutions and with crude samples from cellulose degradation experiments was investigated.     

Computerization of quality control tests of liquid chromatography media

A dual microcomputer system is described for quality control tests of chromatography media at medium speed (time resolution 1 s). One dedicated microcomputer handles real-time control and measurement in a multi-experiment situation. The other computer is a personal computer that handles setting-up of experiments and evaluations. A special, simple high-level language is implemented through an interpreter in the dedicated computer. Precautions against loss of data and the design of reliable and easy-to-use operating procedures are discussed. The results in terms of performance, economy and computer familiarity from daily use of the system during three years are also given.     

Fluorimetric method for the determination of uranium in natural waters

A method is described for the fluorimetric determination of uranium in natural waters. The limit of detection is 0.3 ppM. Ion-exchange is used to preconcentrate the uranium by a factor of 22 and separate it from quenching ions in the sample. The fluorescence is measured in a medium that is 1.35M in both sulphuric and phosphoric acids. The uranyl ions are excited by radiation of wavelength 280 nm and bandwidth 40 nm. The emitted signal is scanned from 470 to 510 nm. After spiking of the sample solution with a small volume of standard uranium solution, the fluorescence signal is scanned again and the uranium content of the sample calculated from the two readings. The coefficient of variation is 8.5% for determinations of U in a synthetic water sample having a uranium content of 1.9 ppM. Destruction of organic matter in the eluates gives 0.1 ppM detection limit.     

Differentiation of human serum samples by surface plasmon resonance monitoring of the integral glycoprotein interaction with a lectin panel

Bacterial infection and inflammation result in massive changes in serum glycoproteins. These changes were investigated by the interaction of the saccharide glycoprotein moiety with lectins. A panel of eight lectins (Canavalia ensiformis, Bandeiraea simplicifolia BS-I, Arachis hypogaea, Phytolacca americana, Phaseolus vulgaris, Artocarpus integrifolia, Triticum vulgaris and Pisum sativum) was used to differentiate human serum glycoproteins obtained from patients with various bacterial infections. Lectin functionalised sensing layers were created on gold-coated wafers and lectin-glycoprotein interactions were monitored by surface plasmon resonance. The interaction of the lectin panel with serum glycoproteins produces unique patterns. Principal component analysis (PCA) was used to analyse the patterns. The actual panel of eight lectins enabled discrimination between sera obtained from patients sick with bacterial infection and healthy patients. Extended lectin panels have the potential to distinguish between types of bacterial infection and identify specific disease state.