Sample preparation procedure for the determination of polycyclic aromatic hydrocarbons in petroleum vacuum residue and bitumen

This paper describes a novel method of sample preparation for the determination of trace concentrations of polycyclic aromatic hydrocarbons (PAHs) in high-boiling petroleum products. Limits of quantitation of the investigated PAHs in materials of this type range from tens of nanograms per kilogram to <20 μg/kg. The studies revealed that in order to separate most of interferences from the analytes without a significant loss of PAHs, it is necessary to use size exclusion chromatography as the first step of sample preparation, followed by adsorption using normal-phase liquid chromatography. The use of orthogonal separation procedure described in the paper allows the isolation of only a group of unsubstituted and substituted aromatic hydrocarbons with a specific range of molar mass. The lower the required limit of quantitation of PAHs, the larger is the scale of preparative liquid chromatography in both steps of sample preparation needed. The use of internal standard allows quantitative results to be corrected for the degree of recovery of PAHs during the sample preparation step. Final determination can be carried out using HPLC-FLD, GC-MS, or HPLC-UV–VIS/DAD. The last technique provides a degree of identification through the acquired UV–VIS spectra

Reversed-phase liquid chromatography coupled on-line to estrogen receptor bioaffinity detection based on fluorescence polarization

We describe the development and validation of a high-resolution screening (HRS) platform which couples gradient reversed-phase high-performance liquid chromatography (RP-HPLC) on-line to estrogen receptor α (ERα) affinity detection using fluorescence polarization (FP). FP, which allows detection at high wavelengths, limits the occurrence of interference from the autofluorescence of test compounds in the bioassay. A fluorescein-labeled estradiol derivative (E2-F) was synthesized and a binding assay was optimized in platereader format. After subsequent optimization in flow-injection analysis (FIA) mode, the optimized parameters were translated to the on-line HRS bioassay. Proof of principle was demonstrated by separating a mixture of five compounds known to be estrogenic (17β-estradiol, 17α-ethinylestradiol and the phytoestrogens coumestrol, coumarol and zearalenone), followed by post-column bioaffinity screening of the individual affinities for ERα. Using the HRS-based FP setup, we were able to screen affinities of off-line-generated metabolites of zearalenone for ERα. It is concluded that the on-line FP-based bioassay can be used to screen for the affinity of compounds without the disturbing occurrence of autofluorescence

Advances in mass spectrometry-based post-column bioaffinity profiling of mixtures

In the screening of complex mixtures, for example combinatorial libraries, natural extracts, and metabolic incubations, different approaches are used for integrated bioaffinity screening. Four major strategies can be used for screening of bioactive mixtures for protein targets—pre-column and post-column off-line, at-line, and on-line strategies. The focus of this review is on recent developments in post-column on-line screening, and the role of mass spectrometry (MS) in these systems. On-line screening systems integrate separation sciences, mass spectrometry, and biochemical methodology, enabling screening for active compounds in complex mixtures. There are three main variants of on-line MS based bioassays: the mass spectrometer is used for ligand identification only; the mass spectrometer is used for both ligand identification and bioassay readout; or MS detection is conducted in parallel with at-line microfractionation with off-line bioaffinity analysis. On the basis of the different fields of application of on-line screening, the principles are explained and their usefulness in the different fields of drug research is critically evaluated. Furthermore, off-line screening is discussed briefly with the on-line and at-line approaches

Preparation and use of maize tassels’ activated carbon for the adsorption of phenolic compounds in environmental waste water samples

The determination and remediation of three phenolic compounds bisphenol A (BPA), ortho-nitrophenol (o-NTP), parachlorophenol (PCP) in wastewater is reported. The analysis of these molecules in wastewater was done using gas chromatography (GC) × GC time-of-flight mass spectrometry while activated carbon derived from maize tassel was used as an adsorbent. During the experimental procedures, the effect of various parameters such as initial concentration, pH of sample solution, eluent volume, and sample volume on the removal efficiency with respect to the three phenolic compounds was studied. The results showed that maize tassel produced activated carbon (MTAC) cartridge packed solid-phase extraction (SPE) system was able to remove the phenolic compounds effectively (90.84–98.49 %, 80.75–97.11 %, and 78.27–97.08 % for BPA, o-NTP, and PCP, respectively) . The MTAC cartridge packed SPE sorbent performance was compared to commercially produced C18 SPE cartridges and found to be comparable. All the parameters investigated were found to have a notable influence on the adsorption efficiency of the phenolic compounds from wastewaters at different magnitudes

Single drop microextraction — Development, applications and future trends

Single drop microextraction (SDME) has emerged over the last 10-15 years as one of the simplest and most easily implemented forms of micro-scale sample cleanup and preconcentration. In the most common arrangement, an ordinary chromatography syringe is used to suspend microliter quantities of extracting solvent either directly immersed in the sample, or in the headspace above the sample. The same syringe is then used to introduce the solvent and extracted analytes into the chromatography system for identification and/or quantitation. This review article summarizes the historical development and various modes of the technique, some theoretical and practical aspects, recent trends and selected applications

Procedura przygotowania próbki do oznaczania wielopierścieniowych węglowodorów aromatycznych w produktach technicznych

W pracy opisano nową metodę przygotowania próbki w celu oznaczania śladowych zawartości wielopierścieniowych węglowodorów aromatycznych (WWA) w wysokowrzących produktach naftowych. Wartości granicy oznaczalności dla badanych WWA w materiałach tego typu mieściły się w przedziale od kilkudziesięciu ng/kg do poniżej dwudziestu ug/kg. Badania wykazały, że w celu oddzielenia większości zanieczyszczeń od analitów, bez ich znaczących strat, konieczne jest, w pierwszym etapie przygotowania próbki, zastosowanie chromatografii wykluczania (ang. Size exclusion chromatography - SEC) w skali semipreparatywnej albo preparatywnej. W kolejnym etapie zastosowano chromatografię adsorpcyjną w układzie faz normalnych, korzystnie, także w skali semipreparatywnej lub preparatywnej. Zastosowanie procedury rozdzielania ortogonalnego opisanego w pracy pozwala na wyizolowanie z badanego materiału jedynie grupy niepodstawionych w glowodorów aromatycznych w ściśle określonym zakresie masy molekularnej. Im niższa jest wymagana granica oznaczalności (LOQ) WWA, tym większą skalę preparatywnej chromatografii cieczowej należy zastosować w obu etapach wzbogacania próbki. Korzystne jest również zastosowanie metody dodatku wzorca, zapewniające analizę ilościową, skorygowaną o stopie odzysku WWA podczas etapu przygotowania próbki. Oznaczenie końcowe może być wykonane techniką HPLC-FLD albo GC-MS, przy czym w przypadku przygotowania próbki z zastosowaniem kolumn do preparatywnej chromatografii cieczowej, można do identyfikacji śladowych zawartości WWA, a take do wykonania oznaczenia, zastosować detektor UV-VIS/DAD, otrzymując widma UV-VIS oznaczanych analitów i dodatków możliwość ich identyfikacji na tej podstawie

Metal-coated fused silica fibers as a support for immobilized compounds yielding a volatile analyte (C2H4)

This paper presents the results of investigations of chemically modified fibers comprising an immobilized compound that yields ethene as the analyte in generated standard gaseous mixtures. Prior to chemical modification, the fibers were coated with a thin aluminum layer to improve their mechanical strength. Commercially available Al-coated fibers were used in this work. During thermal decomposition of the immobilized compound, reproducible quantities of the analyte per unit fiber length were obtained for all the investigated fibers (fiber diameter (microm)/outside diameter (microm) of the Al-coated fiber=110/146, 220/300, and 660/830), amounting to 0.685+/-0.032, 0.8300+/-0.0081, and 1.092+/-0.010 ng cm(-1), respectively. The proposed procedure can be used successfully for the generation of measured component of matrix-free reference materials