Enrichment and quantification of 18 polycyclic aromatic hydrocarbons from intermediates for plastics production by a generic liquid chromatography column switching

The polycyclic aromatic hydrocarbon concentration in plastic products is regulated in (European Union) No. 1272/2013. However, this only covers the end products and not intermediate substances. Therefore, a generic method was developed to analyze the polycyclic aromatic hydrocarbons listed by the Environmental Protection Agency and the European Union. This method is based on direct large volume injection from solutions of plastic additives followed by liquid chromatography coupled to fluorescence detection. The additives Irganox 1010, ureido methacrylate, and cetyl methacrylate 1618F were used as examples for method development. Two serially coupled columns allowed the matrix to be removed on the first column and the analytes to be separated on the second column. The columns were connected by an intermediate valve. The valve allowed the matrix to be diverted after the first column and water to be dosed upstream of the second column via an additional pump. This allowed samples in aqueous or organic media to be focused at the column head. An injection volume of 100 μl and online aqueous dilution of 1:3 led to a limit of detection below 1 ng/ml for 15 polycyclic aromatic hydrocarbons. Moreover, concentrations between 1.6 and 10.3 ng/ml were found in the three plastic additives.

A Toolbox for the Determination of Nitroaromatic Explosives in Marine Water, Sediment, and Biota Samples on Femtogram Levels by GC-MS/MS

To determine the amount of the explosives 1,3-dinitrobenzene, 2,4-dinitrotoluene, 2,4,6-trinitrotoluene, and its metabolites in marine samples, a toolbox of methods was developed to enhance sample preparation and analysis of various types of marine samples, such as water, sediment, and different kinds of biota. To achieve this, established methods were adapted, improved, and combined. As a result, if explosive concentrations in sediment or mussel samples are greater than 10 ng per g, direct extraction allows for time-saving sample preparation; if concentrations are below 10 ng per g, techniques such as freeze-drying, ultrasonic, and solid-phase extraction can help to detect even picogram amounts. Two different GC-MS/MS methods were developed to enable the detection of these explosives in femtogram per microliter. With a splitless injector, limits of detection (LODs) between 77 and 333 fg/µL could be achieved in only 6.25 min. With the 5 µL programmable temperature vaporization-large volume method (PTV-LVI), LODs between 8 and 47 fg/µL could be achieved in less than 7 min. The detection limits achieved by these methods are among the lowest published to date. Their reliability has been tested and confirmed by measuring large and diverse sample sets.

A novel chromatographic separation method for rapid enrichment and isolation of novel flavonoid glycosides from Sphaerophysa salsula

Flavonoid glycosides exist widely in medicine herbs and often used as nutraceuticals because of their excellent bioactivity and low toxicity. For accurate quality control and bioactivity assessment of Sphaerophysa salsula, a rapid and productive method to isolate flavonoid glycosides is needed. Therefore, this work reports the development of a novel comprehensive strategy based on an online middle-pressure chromatography and preparative high-performance liquid chromatography for rapid enrichment and separation of flavonoid glycosides from S. salsula. First, the flavonoid glycosides were enriched using an online middle-pressure chromatographic column containing stationary middle chromatogram isolated phase. During this process, the high-volume injection of the extracting solution was realized by an empty precolumn positioned before the main chromatographic tower. Then, the compounds were separated through preparative high-performance liquid chromatography with Megress C18. As a result, one new flavonol 3-O-glycoside (2) and two known flavonol 3-O-glycosides (1, 3) were targetedly isolated from S. salsula. The content of compounds 1-3 in S. salsula was 0.09, 0.11, and 0.18 wt%, respectively. Comparing to traditional enrichment and separation methods, our technique offers significantly shorter sample pretreatment time as well as high reproducibility. We believe that our separation method has a strong potential to be used for the processing of other medicinal plants.

Rugged Large Volume Injection for Sensitive Capillary LC-MS Environmental Monitoring

A rugged and high throughput capillary column (cLC) LC-MS switching platform using large volume injection and on-line automatic filtration and filter back-flush (AFFL) solid phase extraction (SPE) for analysis of environmental water samples with minimal sample preparation is presented. Although narrow columns and on-line sample preparation are used in the platform, high ruggedness is achieved e.g., injection of 100 non-filtrated water samples did not result in a pressure rise/clogging of the SPE/capillary columns (inner diameter 300 μm). In addition, satisfactory retention time stability and chromatographic resolution were also features of the system. The potential of the platform for environmental water samples was demonstrated with various pharmaceutical products, which had detection limits (LOD) in the 0.05–12.5 ng/L range. Between-day and within-day repeatability of selected analytes were <20% RSD.

Comparison of QuEChERS official methodologies for the analysis of pesticide residues on Colombian fruit by GC-MS

Surveys of pesticide residues in fruit are important to demonstrate conformity with strict regulations of newly open markets for export of exotic fruit. Multi-residue methods are tools to ensure compliance with regulations and both the CEN and the AOAC have versions of QuEChERS that are used effectively as mainstream methods. The aim of this study was to assess their performance and pick the optimum one for this particular application using GC-MS. The use of graphitised carbon black (GCB) to improve clean-up was assessed. Optimisation of large volume injection (LVI) and implementation of concurrent back-flushing was needed in order to improve sensitivity at a low concentration levels for 33 pesticides (0.01 mg kg(-1)). Cleaner total ion current (TIC) profiles were obtained with the CEN method. Recoveries of most of the pesticides showed statistical differences (α = 0.05) when GCB was used in the AOAC method, unlike the CEN method. In general, GCB/no GCB use for CEN clean-up gave good, very similar results for all fruit, though some pesticides showed some adsorption on the GCB surface. The CEN general method was preferred since acceptable recoveries (> 80%) and RSD (< 20%) can be achieved for all analytes.

Elimination pathways of cyclosarin (GF) mediated by β-cyclodextrin in vitro: pharmacokinetic and toxicokinetic aspects

Cyclodextrins (CD) are promising small molecular scavengers showing favourable degradation of extremely toxic organophosphorus compounds (OP) such as tabun (GA), soman (GD) or cyclosarin (GF). For β-CD derivatives as potential OP antidotes with low intrinsic toxicity it is of great interest to completely understand the modes of interaction of both compounds in terms of OP detoxification. The mechanisms of CD action are not completely understood which prompted us to investigate the interactions of GF and β-cyclodextrin (β-CD) as model compounds. Using positive electrospray ionization mass spectrometry (ESI/MS), the formation of covalent conjugates of β-CD with O-cyclohexylmethylphosphonate (CHMP) residue was detected for the first time and was examined in vitro. With a newly developed LC-MS method the formation of O-cyclohexylmethylphosphonic acid (CHMPA) (i.e. GF hydrolysis) and covalent CHMP-β-CD conjugates was analyzed. Compared to water, tris(hydroxymethyl)aminomethane (TRIS) reduced the formation of covalent conjugates but amplified formation of CHMPA. Depending on experimental conditions the degradation of GF by β-CD may be preferably catalytic or stoichiometric. For illustrating different possible reaction pathways a scheme was established that could support the idea of β-CD acting as an artificial enzyme. These results provide an important insight into the β-CD mediated detoxification pathways of GF.

Parametric evaluation for programmable temperature vaporization large volume injection in gas chromatographic determination of polybrominated diphenyl ethers

This work is a thorough investigation on the major operating parameters of the programmable temperature vaporization (PTV) inlet used for gas chromatographic injection, including injection mode and volume, inlet temperature, vent and purge flow rates. The results clearly demonstrate the advantage of large volume injection in enhancing the detection of polybrominated diphenyl ethers (PBDEs). Partial loss of injected PBDEs occurred during solvent venting and due to incomplete sample transfer. Such loss was minimized by lowering the initial inlet temperature and vent flow and elevating the final inlet temperature. The results show that 50 mL/min vent flow, as low as 0 degrees C initial and higher than 300 degrees C final inlet temperatures produced the relatively high responses. Two mass spectrometric parameters were also evaluated. Indoor dust, lake sediment and human placenta tissue samples were analyzed to demonstrate reliability and sensitivity improvement of the PTV large volume injection.