Fast liquid chromatography-tandem mass spectrometry methodology for the analysis of alkylphenols and their ethoxylates in wastewater samples from the tank truck cleaning industry

Analytical and Bioanalytical Chemistry - A fast methodology to quantify 4-tert-octylphenol (4-t-OP) and 4-nonylphenol (4-NP) and their mono- and di-ethoxylates was developed, validated, and applied...     

Potentiometric detection in UPLC as an easy alternative to determine cocaine in biological samples

The analytical methods which are often used for the determination of cocaine in complex biological matrices are a prescreening immunoassay and confirmation by chromatography combined with mass spectrometry. We suggest an ultra‐high‐pressure liquid chromatography combined with a potentiometric detector, as a fast and practical method to detect and quantify cocaine in biological samples. An adsorption/desorption model was used to investigate the usefulness of the potentiometric detector to determine cocaine in complex matrices. Detection limits of 6.3 ng mL^?1 were obtained in plasma and urine, which is below the maximum residue limit (MRL) of 25 ng mL^?1. A set of seven plasma samples and 10 urine samples were classified identically by both methods as exceeding the MRL or being inferior to it. The results obtained with the UPLC/potentiometric detection method were compared with the results obtained with the UPLC/MS method for samples spiked with varying cocaine concentrations. The intraclass correlation coefficient was 0.997 for serum (n =7) and 0.977 for urine (n =8). As liquid chromatography is an established technique, and as potentiometry is very simple and cost‐effective in terms of equipment, we believe that this method is potentially easy, inexpensive, fast and reliable. Copyright © 2014 John Wiley & Sons, Ltd.     

Suppression of analyte signal in inductively-coupled plasma/mass spectrometry and the use of an internal standard

The signal suppression of ⁹Be, ²⁷Al, ⁶⁴Zn, ⁸⁵Rb, ¹¹⁵In and ²⁰⁸Pb in the presence of increasing amounts of sodium chloride is studied. The suppression does not depend significantly on the analyte element considered. The use of ¹¹⁵In as internal standard thus allows correction for the matrix effect. It is shown that the suppressive effect decreases in the order CsCl>NaCl>NH₄Cl. The use of the internal standard also significantly improves the precision. The signal suppression is probably due largely to an increasing number of extracted ions resulting in a more pronounced space-charge effect.     

On some nonself mappings

Let X be a Banach space, let K be a non–empty closed subset of X and let T : K → X be a non–self mapping. The main result of this paper is that if T satisfies the contractive–type condition (1.1) below and maps ?K (?K the boundary of K) into K then T has a unique fixed point in K.     

Improved sample preparation for CE-LIF analysis of plant N-glycans

In view of glycomics studies in plants, it is important to have sensitive tools that allow one to analyze and characterize the N-glycans present on plant proteins in different species. Earlier methods combined plant-based sample preparations with CE-LIF N-glycan analysis but suffered from background contaminations, often resulting in non-reproducible results. This publication describes a reproducible and sensitive protocol for the preparation and analysis of plant N-glycans, based on a combination of the 'in-gel release method' and N-glycan analysis on a multicapillary DNA sequencer. Our protocol makes it possible to analyze plant N-glycans starting from low amounts of plant material with highly reproducible results. The developed protocol was validated for different plant species and plant cells.