Liquid chromatography-mass spectrometry and liquid chromatography-tandem mass spectrometry determination of N-methylpyrrolidinone in riverine biofilms

A rugged procedure utilizing reversed-phase liquid chromatography with positive-ion electrospray ionization mass spectrometry (LC-MS) along with tandem MS is described for the quantification and confirmation of N-methylpyrrolidinone (NMP) in methanolic extracts of riverine biofilm. The LC-MS method provided a 100-fold improvement in detection limits (2 ng g(-1) with a repeatability of 80-95% based on triplicate analyses) compared to a conventional LC-UV detection procedure and was applicable to quantitative analysis of biofilm samples with little or no clean up. Under low-energy collision induced dissociation (CID) conditions (17 V, laboratory frame of reference, with argon as the collision gas), two product-ions of the [M+H]+ ion were formed at m/z 69 [MH-CH3NH2]+ and m/z 58 [MH-CH3NCH]+ with relative abundances of 30% and 5%, respectively. These CID transitions were used to demonstrate that biofilm uptake of a photocatalytically-generated mixture of NMP was rapid once acclimation was achieved.     

Picosecond laser ablation of nano-sized WTi thin film

Interaction of an Nd:YAG laser, operating at 532 nm wavelength and pulse duration of 40 ps, with tungsten-titanium (WTi) thin film (thickness, 190 nm) deposited on single silicon (100) substrate was studied. Laser fluences of 10.5 and 13.4 J/cm² were found to be sufficient for modification of the WTi/silicon target system. The energy absorbed from the Nd:YAG laser beam is partially converted to thermal energy, which generates a series of effects, such as melting, vaporization of the molten material, shock waves, etc. The following WTi/silicon surface morphological changes were observed: (i) ablation of the thin film during the first laser pulse. The boundary of damage area was relatively sharp after action of one pulse whereas it was quite diffuse after irradiation with more than 10 pulses; (ii) appearance of some nano-structures (e.g., nano-ripples) in the irradiated region; (iii) appearance of the micro-cracking. The process of the laser interaction with WTi/silicon target was accompanied by formation of plasma.     

Comparison of high- and low-resolution electrospray ionization mass spectrometry for the analysis of naphthenic acid mixtures in oil sands process water

The oil sands regions of Northern Alberta, Canada, contain an estimated 1.7 trillion barrels of oil in the form of bitumen, representing the second largest deposit of crude oil in the world. A rapidly expanding industry extracts surface-mined bitumen using alkaline hot water, resulting in large volumes of oil sands process water (OSPW) that must be contained on site due to toxicity. The toxicity has largely been attributed to naphthenic acids (NAs), a complex mixture of naturally occurring aliphatic and (poly-)alicyclic carboxylic acids. Research has increasingly focused on the environmental fate and remediation of OSPW NAs, but an understanding of these processes necessitates an analytical method that can accurately characterize and quantify NA mixtures. Here we report results of an interlaboratory comparison for the analysis of pure commercial NAs and environmental OSPW NAs using direct injection electrospray ionization mass spectrometry (ESI-MS) and high-pressure liquid chromatography/high-resolution mass spectrometry (HPLC/HRMS). Both methods provided very similar characterization of pure commercial NA mixture; however, the m/z selectivity of HPLC/HRMS was essential to prevent substantial false-positive detections and misclassifications in OSPW NA mixtures. For a range of concentrations encompassing those found in OSPW (10-100 mg/L), both methods produced linear response, although concentrations of commercial NAs above 50 mg/L resulted in slight non-linearity by HPLC/HRMS. A three-fold lower response factor for total OSPW NAs by HPLC/HRMS was largely attributable to other organic compounds in the OSPW, including hydroxylated NAs, which may explain the substantial misclassification by ESI-MS. For the quantitative analysis of unknown OSPW samples, both methods yielded total NA concentrations that correlated with results from Fourier transform infrared (FTIR), but the coefficients of determination were not high. Quantification by either MS method should therefore be considered semi-quantitative at best, albeit either method has substantial value in environmental fate experiments where relative concentration changes are the desired endpoints rather than absolute concentrations.     

The development and assessment of high‐throughput mass spectrometry‐based methods for the quantification of a nanoparticle drug delivery agent in cellular lysate

The safe use of lipid‐based drug delivery agents requires fast and sensitive qualitative and quantitative assessment of their cellular interactions. Many mass spectrometry (MS) based analytical platforms can achieve such task with varying capabilities. Therefore, four novel high‐throughput MS‐based quantitative methods were evaluated for the analysis of a small organic gene delivery agent: N,N‐bis(dimethylhexadecyl)‐1,3‐propane‐diammonium dibromide (G16‐3). Analysis utilized MS instruments that detect analytes using low‐resolution tandem MS (MS/MS) analysis (i.e. QTRAP or linear ion trap in this work) or high‐resolution MS analysis (i.e. time of flight (ToF) or Orbitrap). Our results indicate that the validated fast chromatography (FC)‐QTRAP‐MS/MS, FC‐ LTQ‐Orbitrap‐MS, desorption electrospray ionization‐collision‐induced dissociation (CID)‐MS/MS and matrix assisted laser desorption ionization‐ToF/ToF‐MS MS methods were superior in the area of method development and sample analysis time to a previously developed liquid chromatography (LC)‐CID‐MS/MS. To our knowledge, this is the first evaluation of the abilities of five MS‐based quantitative methods that target a single pharmaceutical analyte. Our findings indicate that, in comparison to conventional LC‐CID‐MS/MS, the new MS‐based methods resulted in a (1) substantial reduction in the analysis time, (2) reduction in the time required for method development and (3) production of either superior or comparable quantitative data. The four new high‐throughput MS methods, therefore, were faster, more efficient and less expensive than a conventional LC‐CID‐MS/MS for the quantification of the G16‐3 analyte within tissue culture. When applied to cellular lysate, no significant change in the concentration of G16‐3 gemini surfactant within PAM212 cells was observed between 5 and 53 h, suggesting the absence of any metabolism/excretion from PAM212 cells. Copyright © 2014 John Wiley & Sons, Ltd.     

Unprecedented Biodegradable Cellulose-Derived Polyesters with Pendant Citronellol Moieties: From Monomer Synthesis to Enzymatic Degradation

Levoglucosenone (LGO) is a cellulose-derived molecule that is present commercially on a multi-ton/year scale. Taking advantage of the α,β-conjugated ketone of LGO, a new citronellol-containing 5-membered lactone (HBO-citro) was synthesized through a one-pot two-step pathway involving oxa-Michael addition and Baeyer-Villiger oxidation. The solvent-free treatment of HBO-citro with NaBH₄ at room temperature led to the full reduction of the lactone moiety which gave a novel fully renewable triol monomer having a citronellol side chain (Triol-citro). Noticeably, by simply changing the reducing agent, temperature and reaction duration, the partial reduction of HBO-citro can be achieved to yield a mixture of 5- and 6-membered Lactol-citro molecules. Triol-citro was chosen to prepare functional renewable polyesters having citronellol pendant chains via polycondensation reactions with diacyl chlorides having different chain lengths. Good thermal stability (T_d5% up to 170 °C) and low glass transition temperatures (as low as −42 °C) were registered for the polyesters obtained. The polymers were then hydrolyzed using a commercial lipase from Thermomyces lanuginosus (Lipopan^® 50 BG) to assess their biodegradability. A higher degradation profile was found for the polyesters prepared using co-monomers (acyl chlorides) having longer chain lengths. This is likely due to the decreased steric hindrance around the ester bonds which allowed enhanced accessibility of the enzyme.     

Laser induced mixing in multilayered Ti/Ta thin film structures

The possibility of interlayer mixing in a Ti/Ta multilayer system, induced by laser irradiation, was the main purpose of these experiments. Ti/Ta multilayer system, consisting of ten alternating Ti and Ta thin films and covered by slightly thicker Ti layer, was deposited on Si (100) wafers to a total thickness of 205 nm. Laser irradiation was performed in air by picoseconds Nd:YAG laser pulses in defocused regime with fluences of 0.057 and 0.11 J cm^?2. Laser beam was scanned over the 5?×?5 mm surface area with different steps along y-axes. Structural and compositional characterisation was done by auger electron spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy, and scanning electron microscopy. Laser processing at lower fluence caused only oxidation of the top Ti layer, despite of the number of applied laser pulses. Interlayer mixing was not observed. Application of laser pulses at fluence of 0.11 J cm^?2 caused partial and/or complete ablation of deposited layers. In partially ablated regions considerable mixing between Ti and Ta films was registered.     

Optimization of solid-phase microextraction for the gas chromatographic-mass spectrometric determination of synthetic musk fragrances in water samples

Described is a solid-phase microextraction-gas chromatography-mass spectrometric procedure for the determination of three polycyclic musk fragrances (galaxolide, tonalide, celestolide) and a nitro musk fragrance (musk ketone) in natural river water. Both classes of the musk fragrances could be extracted reproducibly from water samples with a recovery in the range of 45-50% and relative standard deviation of 11-18% for fragrances at 25-260 ng/l levels. Detection limits were between 14 and 22 ng/l. To achieve this reproducibility it was necessary to use an internal standard, pentachloronitrobenzene, for all substances. Best recoveries were achieved with polydimethylsiloxane (PDMS)-divinylbenzene fibers (compared to recoveries obtained with PDMS, polyacrylate or carboxen fibers) and extraction times of 45 min at 30 degrees C, with no need for attainment of equilibrium conditions. The latter was achieved at about 2 h. For Elbe River water, in the vicinity of Magdeburg, no matrix effects were observed. While the average levels of celestolide and musk ketone for samples investigated were below the detection limits, 14 and 22 ng/l, respectively, and for tonalide below the limit of quantification, 22 ng/l, the ambient levels of galaxolide in the Elbe River were 117 ng/l.