High-resolution time-of-flight mass spectrometry for suspect screening and target quantification of pharmaceuticals in river water.

The growing interest in screening and quantification of potential harmful pharmaceuticals in the environment requests multi-residue analytical techniques. Large-volume injection ultra performance liquid chromatography (LVI-UPLC) in combination with full-spectrum high-resolution mass spectrometry (HRMS) is a promising alternative for the state-of-the-art MS/MS instruments, because of its ability to analyse a virtually unlimited number of analytes thereby avoiding the time-consuming sample enrichment steps. We developed and fully validated an innovative analytical method for suspect screening and target quantification of a set of 69 pharmaceutical compounds in surface water based on LVI-UPLC coupled to a quadrupole time-of-flight (QTOF) MS. In a systematic research, we showed that optimal mass accuracy was obtained after centroiding the spectra. A novel suspect screening strategy was developed, assuring the detection of 95% of the pharmaceuticals spiked in surface water by modelling the variability of the signal intensity-dependent accurate mass error. A first screening of five Belgian river water samples revealed the occurrence of 30 pharmaceuticals (antibiotics, analgesics, antidepressants, alkylating agents, antiinflammatories, etc.). Concentrations between 17 ng/L up to 3.3 microg/L were subsequently measured by the validated target quantification.

Trace analysis of benzene, toluene, ethylbenzene and xylene isomers in environmental samples by low-pressure gas chromatography-ion trap mass spectrometry.

A rapid determination of benzene, toluene, ethylbenzene and the three xylene isomers (BTEX), including a nearly baseline separation of the xylene isomers in environmental samples within 1 min has been carried out using low-pressure gas chromatography-ion trap mass spectrometry (LP-GC-IT-MS). In order to evaluate the different parameters which may influence the performance of LP-GC-IT-MS, different column and mass spectral parameters were varied. Comparing LP-GC-IT-MS with the conventional equivalent, we obtained excellent detection limits as well as a good RSD of 8-13% in ition to a much shorter analysis time. In order to evaluate LP-GC-IT-MS for use in environmental samples, we determined BTEX in air.

Liquid chromatography-tandem mass spectrometry of some anabolic steroids.

In this paper a procedure is described for the analysis of 36 anabolic steroids, regularly found in kidney fat matrixes. After preparative HPLC is carried out, six fractions, containing the different steroids, were obtained. These fractions were then separated and on-line mass-analyzed, using APcI LC/MS. When used in tandem mass spectrometry (MRM) mode, it is possible to obtain detection limits below 1 ppb for all steroids and below 0.1 ppb for most of them. As such, it is possible to meet the regulations for detection of these anabolic steroids. To verify the influence of matrixes, real-world samples were analyzed in the same manner. This resulted in almost analog detection limits.

Measurement of the Surface Elasticity of an Adsorbed Monolayer by Continuous Surface Deformation

The elasticity of a monolayer adsorbed from a surfactant solution is considered by continuous surface deformation. For all kinds surface deformations a single relation between the elasticity and the effective time should be obtained (master curve). This effective time depends on the rate of deformation and on the kind of deformation. The relation between elasticity and effective time was proven experimentally for a decanoic acid solution at a concentration 10(-7) mol cm-3. The following surface deformations are considered: (i) expansion at a constant dilatation rate, (ii) compression at a constant dilatation rate, (iii) linear expansion, (iv) linear compression, and (v, vi) compression and expansion in a some what more complicated way. From these data the Gibbs elasticity and the diffusion relaxation time are obtained. These parameters are also obtained by longitudinal wave method of Lucassen-Van den Tempel. Both set of parameters are comparable. Finally the situation at a growing drop with constant flow rate is considered (Triton X-100) to show that also here the approach is followed.

Phenylglycidyl ether adducts of 2'-deoxycytidine and 2'-deoxyadenosine: Stability in solution and structure analysis by electrospray tandem mass spectrometry.

The adducts of phenylglycidyl ether with 2'-deoxyadenosine (dAdo) and 2'-deoxycytidine (dCyd) exhibit structural modifications. The N-1 adduct of dAdo underwent rearrangement to the N-6 adduct; the N-3 adduct of dCyd was deaminated to the corresponding 2'-deoxyuridine adduct. These structural modifications were studied by using liquid chromatography-electrospray tandem mass spectrometry, and kinetic data for both reactions are presented. The low energy (+) collision-activated dissociation spectra of the dAdo adducts allow the two positional isomers N-1 versus N-6 to be distinguished. The structure of the latter is independently proven by an extended NMR study. For the dCyd and 2'-deoxyuridine adducts, information about the alkylation site is found in the (-) collision-activated dissociation spectra. These spectra show the presence of an unexpected N-4-alkylated dCyd in addition to the two epimeric N-3 adducts.

Approach for an equation of state for adsorbed protein surfaces.

A surface equation of state for polymer interfaces is obtained by equating the chemical potentials of the solvent in the bulk and surface phases. This equation of state contains the fraction of the surface covered with polymer and the surface activity coefficient as parameters. These parameters may be obtained by measuring the thermodynamic modulus of elasticity. Moreover, if the amount of protein in the interface is known the degree of folding in the surface may be evaluated. The present theory was applied to adsorbed beta-lactoglobulin in surfaces. The results are in agreement with qualitative equations and results from other sources.