Liquid chromatography with triple-quadrupole or quadrupole-time of flight mass spectrometry for screening and confirmation of residues of pharmaceuticals in water

LC–MS–MS has been performed with triple-quadrupole (QqQ) and quadrupole-time of flight (Q-ToF) instruments and has been used for screening and confirmation of pharmaceuticals in surface, drinking, and ground water. Screening was based on monitoring of one specific MS–MS ion of the target compounds. Confirmation of the identity of the pharmaceuticals was based either on the monitoring of two specific MS–MS ions and calculation of the ratio of their intensities, or on the exact masses of MS–MS product ions obtained for a molecular ion by use of LC–Q-ToF MS. The set of pharmaceuticals included four analgesics (acetylsalicylic acid, diclofenac, ibuprofen, and paracetamol), three antibiotics (sulfamethoxazole, erythromycin, and chloramphenicol), five blood-lipid regulators and beta-blockers (fenofibrate, bezafibrate, clofibric acid, bisoprolol, and metoprolol), and the anti-epileptic drug carbamazepine. Limits of quantification ranged from 5 to 25 ng L^–1. Fifty-six samples were analysed and residues of the pharmaceuticals were detected in almost all surface and groundwater and in some drinking water samples. The identity of the compounds could be confirmed by use of both QqQ- and Q-ToF-based LC–MS–MS. However, the latter technique has the distinct advantage that a large number of pharmaceuticals can be screened and confirmed at low concentrations (1–100 ng L^–1) in one run.     

A survey of literature on automated storage and retrieval systems

Automated Storage and Retrieval Systems (AS/RSs) are warehousing systems that are used for the storage and retrieval of products in both distribution and production environments. This paper provides an overview of literature from the past 30 years. A comprehensive explanation of the current state of the art in AS/RS design is provided for a range of issues such as system configuration, travel time estimation, storage assignment, dwell-point location, and request sequencing. The majority of the reviewed models and solution methods are applicable to static scheduling and design problems only. Requirements for AS/RSs are, however, increasingly of a more dynamic nature for which new models will need to be developed to overcome large computation times and finite planning horizons, and to improve system performance. Several other avenues for future research in the design and control of AS/RSs are also specified.     

A marginalistic value for monotonic set games

In this paper we characterize a value, called a marginalistic value, for monotonic set games, which can be considered to be the analog of the Shapley value for TU-games. For this characterization we use a modification of the strong monotonicity axiom of Young, but the proof is rather different from his.     

Synthesis of flexibilene,a naturally occurrring 15-membered-ring diterpene

A total synthesis of the naturally occurring 15-membered ring diterpene, flexibilene, was accomplished using a titanium-induced cyclization of the keto-aldehyde 3,37,11-tetramethyl- 15-oxohexadeca-4E,7E,11E-trienal as the key step.     

STATIC and TIME-RESOLVED FLUORESCENCE OF AN AMPHIPHILIC FLAVIN IN AEROSOL OT REVERSED MICELLES

Spectral and time-resolved fluorescence studies have been carried out on N(3)-undecyllumi-flavin dispersed in reversed micelles composed of the surfactant sodium di(2-ethylhexyl) sulfosuccinate (Aerosol OT, AOT), various amounts of water and n -heptane as continuous phase. The fluorescence spectral properties (spectral distribution, quantum efficiencies and lifetimes) as function of the water to AOT molar ratio suggest that the flavin occupies a position within the surfactant boundary layer in close contact with water. The fluorescence anisotropy exhibits biexponential decay with a short (0.3 ns) and a longer (1.6–2.4 ns) correlation time. The contribution of the short component increases with the growth of the droplet providing evidence for enhanced flexibility of the flavin in the interfacial layer.     

Isostructural triazenido complexes of first row transition metals. Part 1. Synthesis and properties of (η5-C5H5)(L)(RN3R) FeII,L = PPh3, P(OMe)3, P(OPh)3 or CO

Summary The complexes ( ⁵-C₅H₅)L(RN₃R)Fe, where L = PPh₃, P(OMe)₃, P(OPh)₃ or CO and R,R=p-MeC₆H₄ orp-ClC₆H₄, have been prepared by reaction of suitable iron halides with Ag(RN₃R). The mechanism of formation of the Fe(RN₃R) group is thought to involve, initially, an Fe-Ag bond. The bonding mode of the triazenido ligand is chelating in a six coordinate configuration. The spectroscopic results are discussed in relation to variations in the environment of the metal atom.     

Ab initio Calculations on the thermal ring closure of acrolein

The electrocyclic reaction which interconverts acrolein and oxetene is investigated by ab initio calculations, using a 4-31G basis set. Like the transition state of the thermal ring closure of cisbutadiene, the transition state of this reaction shows a torsion of about 18 ° around the central bond, in spite of the absence of H-H repulsion. The resulting oxetene is 43 kcal/mol endothermic with regard to acrolein. The calculated activation energies for ring closure and -opening are 3.4 and 1.0 eV. The conformational result of the ring opening reaction is discussed.