Ultra performance liquid chromatography tandem mass spectrometry performance evaluation for analysis of antibiotics in natural waters

An ultra performance liquid chromatography electrospray tandem mass spectrometry (UPLC/MS/MS) method was developed and validated for the determination of 17 antibiotics in natural waters in one single extraction and chromatographic procedure. Gradient separation conditions were optimised for 17 compounds belonging to five different antibiotic groups: quinolones (oxolinic acid, nalidixic acid, pipemidic acid, flumequine), fluoroquinolones (enoxacin, ciprofloxacin, norfloxacin, ofloxacin, enrofloxacin, sarafloxacin, danofloxacin, difloxacin, lomefloxacin), sulphonamides (sulphamethoxazole, sulphamethazine), nitro-imidazole (ornidazole) and diaminopyrimidine (trimethoprim). The separation of all compounds, obtained using a 1.7 μm particle size column (100 mm?×?2.1 mm), was achieved within 10 min time. Water samples were adjusted to pH 7 and extracted using Oasis hydrophilic–lipophilic balance (HLB) solid phase extraction cartridges. After elution with methanol and concentration, extracts were injected in a C18 column (Acquity UPLC BEH C18) and detected by tandem mass spectrometry. Average recovery from 100 ng L^?1 fortified samples was higher than 70% for most of the compounds, with relative standard deviations below 20%. Performances of the method (recoveries, detection limit, quantification limit and relative standard deviation) and matrix effects were studied, and results obtained showed that method was suitable for routine analysis of antibiotics in surface water. Samples analysis from Seine River (France) confirmed the interest of antibiotic contamination evaluation in that area.

Propagation of guided waves through weak penetrable scatterers

The scattering of a scalar wave propagating in a waveguide containing weak penetrable scatterers is inspected in the Born approximation. The scatterers are of arbitrary shape and present a contrast both in density and in wavespeed (or bulk modulus), a situation that can be translated in the context of SH waves, water waves, or transverse electric/transverse magnetic polarized electromagnetic waves. For small size inclusions compared to the waveguide height, analytical expressions of the transmission and reflection coefficients are derived, and compared to results of direct numerical simulations. The cases of periodically and randomly distributed inclusions are considered in more detail, and compared with unbounded propagation through inclusions. Comparisons with previous results valid in the low frequency regime are proposed.     

[1,5] Sigmatropic shifts in a 1,4-diphospholylbenzene

The central phenylene ring of 1,4-bis(3,4-dimethylphosphol-1-yl)benzene undergoes [1,5] shifts around both phospholyl rings above 150°C to give 1,4-bis(3,4-dimethyl-5H-phosphol-2-yl)benzene, which can be trapped by tolane, [CpFe(CO)₂]₂, or Mn₂ (CO)₁₀ to yield the corresponding bis-1-phosphanor-bornadiene, bis-phosphaferrocene, or bis-phosphacymantrene respectively.