Evaluation of the QuEChERS sample preparation approach for the analysis of pesticide residues in olives

This paper describes the use of a quick, easy, cheap, effective, rugged, and safe (QuEChERS) method for extraction and cleanup of 16 pesticide residues of interest in olives and olive oil. These products contain a high lipid content, which can adversely affect pesticide recoveries and harm traditional chromatographic systems. For extraction, the main factors (oil and water content) were studied and optimized in experiments to maximize pesticide recoveries. Dispersive SPE with different sorbents was also investigated to minimize matrix coextractives and interferences. For analysis, a new automated DSI device was tested in GC-MS to avoid nonvolatile coextractives from contaminating the instrument. LC-MS/MS with positive ESI was used for those pesticides that were difficult to detect by GC-MS. The final method was validated for olives in terms of recoveries, repeatabilities, and reproducibilities using both detection techniques. The results demonstrated that the method achieved acceptable quantitative recoveries of 70-109% with RSDs < 20% for DSI-GC-MS and 88-130% with RSDs < 10% for LC-MS/MS, and LOQ at or below the regulatory maximum residue limits for the pesticides were achieved.     

Study of posttranslational non-enzymatic modifications of collagen using capillary electrophoresis/mass spectrometry and high performance liquid chromatography/mass spectrometry

The depository effects that occur in slowly metabolized proteins (typically glycation) are very difficult to assess, owing to their extremely low concentration in the protein matrix. Collagen accumulates reactive metabolites through reactions that are not regulated by enzymes. A typical example of these non-enzymatic changes is glycation (the Maillard reaction, the formation of advanced glycation end products), resulting from the reaction of the oxo-group of sugars with the epsilon-amino group of lysine and arginine. Collagen samples (type I) as a test protein were incubated separately with glucose, ribose and malondialdehyde. Collagen was fragmented with cyanogen bromide and then digested with trypsin. This peptide digest was separated by CE, CE-MS/MS, and HPLC-MS/MS. An ion trap MS was used and MS conditions were optimized for both methods. These on-line CE-MS/MS and HPLC-MS/MS couplings made it possible to discover specific modifications such as (N(epsilon)-(carboxymethyl)-lysine) in the precise location in the structure of collagen corresponding to posttranslational non-enzymatic modifications. A new CE-MS/MS technique for peptide analysis was developed, and applied in the identification of posttranslational modifications in slowly metabolized test proteins.     

Synthesis of second-generation sansalvamide A derivatives: novel templates as potential antitumor agents

We report the synthesis of 34 second-generation Sansalvamide A derivatives. San A derivatives have unique anticancer properties and target multiple cancers, including colon, pancreatic, breast, prostate, and melanoma. As novel templates, the derivatives described herein explore the role of stereochemistry, amide bond geometry, transannular hydrogen bonding, and polarity on antitumor potency. Testing the chemotherapeutic activity of these derivatives against multiple cancer cell lines will provide clear structural motifs and identify conformational space that is important for cytotoxicity. The 34 compounds presented are divided into six series, where five series involve the insertion of D-amino acids in conjunction with four structural features at each of the five positions of the macrocycle. The sixth series involves comparison between all L- and all D-amino acid derivatives with N-methyls placed at each position around the macrocyclic core. The four structural features explored in conjunction with D-amino acids include N-methyl amino acids, aromatic amino acids, polar amino acids, and hydrophobic alkyl amino acids.     

Headspace solid-phase microextraction of phthalic acid esters from vegetable oil employing solvent based matrix modification

A new solvent-free analytical procedure based on headspace solid-phase microextraction (SPME) coupled to gas chromatography employing an electron capture detector (GC/ECD) or alternatively a mass spectrometric detector (GC/MSD) has been developed for the determination of phthalic acid esters (dimethyl-[DMP], diethyl-[DEP], di-n-butyl-[DnBP], butylbenzyl-[BBP], di-2-ethylhexyl-[DEHP] and di-n-octyl [DnOP] phthalate) in vegetable oils. Four different fiber coatings were evaluated, among them polydimethylsiloxane with a thickness of 100 μm appeared to be the best choice for allowing extraction of the whole group of analytes. Various solvents were tested as sample matrix modification agents with the aim to facilitate the transfer of esters with low vapour pressure (DEHP and DnOP) from oil matrix into the headspace. The addition of methanol resulted in optimal set-up applicable for all phthalate esters. Temperature control and the way of sample stirring were recognized as critical points of the whole procedure. Primarily, because shaking rather than stirring of the sample is carried out using a CombiPal multipurpose sampler, the automation of the SPME method employing this instrument was found to be not fully suitable for efficient stripping of phthalates from the oil matrix into the sample headspace. Nevertheless, the optimized manual SPME method, encompassing GC/ECD or GC/MSD for the separation and detection of target analytes, offers a unique solution and showed acceptable performance characteristics: linear response in the range of 0.5-2 mg kg⁻¹ and repeatability expressed as R.S.D. between 14 and 23% at the spiking level of 2 mg kg⁻¹.     

Ruggedness and other performance characteristics of low-pressure gas chromatography-mass spectrometry for the fast analysis of multiple pesticide residues in food crops

Low-pressure gas chromatography-mass spectrometry (LP-GC-MS) using a quadrupole MS instrument was further optimized and evaluated for the fast analysis of multiple pesticide residues in food crops. Performance of two different LP-GC-MS column configurations was compared in various experiments, including ruggedness tests with repeated injections of pesticides in matrix extracts. The tested column configurations employed the same 3 m x 0.15 mm i.d. restriction capillary at the inlet end, but different analytical columns attached to the vacuum: (A) a 10 m x 0.53 mm i.d., 1 microm film thickness RTX-5 Sil MS column; and (B) a 10 m x 0.25 mm i.d., 0.25 microm film thickness DB-5MS column. Under the optimized conditions (compromise between speed and sensitivity), the narrower analytical column with a thinner film provided slightly (<1.1-fold) faster analysis of <5.5 min separation times and somewhat greater separation efficiency. However, lower detection limits for most of the tested pesticides in real extracts were achieved using the mega-bore configuration, which also provided significantly greater ruggedness of the analysis (long-term repeatability of analyte peak intensities, shapes, and retention times). Additionally, the effect of the increasing injection volume (1-5 microl) on analyte signal-to-noise ratios was evaluated. For the majority of the tested analyte-matrix combinations, the increase in sensitivity caused by a larger injection did not translate in the same gain in analyte detectability. Considering the costs and benefits, the injection volume of 2-3 microl was optimal for detectability of the majority of 57 selected pesticides in apple, carrot, lettuce, and wheat extracts.     

Capturing and prioritizing students’ requirements for course design by embedding Fuzzy-AHP and linear programming in QFD

Customer requirements play a vital and important role in the design of products and services. Quality Function Deployment (QFD) is a popular, widely used method that helps translate customer requirements into design specifications. Thus, the foundation for a successful QFD implementation lies in the accurate capturing and prioritization of these requirements. This paper proposes and tests the use of an alternative framework for prioritizing students’ requirements within QFD. More specifically, Fuzzy Analytic Hierarchy Process (Fuzzy-AHP) and the linear programming method (LP-GW-AHP) based on Data Envelopment Analysis (DEA) are embedded into QFD (QFD-LP-GW-Fuzzy AHP) in order to account for inherent subjectivity of human judgements. The effectiveness of the proposed framework is assessed in capturing and prioritizing students’ requirements regarding courses’ learning outcomes within the process of an academic course design. Sensitivity analysis evaluates the robustness of the prioritization solution and implications for course design specifications are discussed.     

Benzene elimination from reformate gasoline by high pressure hydrogenation in a fixed-bed reactor

The reduction of benzene from benzene-rich real gasoline fractions has been studied in a high-pressure fixed-bed reactor using a Pt/TiO₂ catalyst. It was found that the yield of this process decreases with the toluene content in the feedstock, but it is independent of the kind of the saturated hydrocarbons. This revised version was published online in August 2006 with corrections to the Cover Date.     

Graftlike interpolymer complexes from poly(2‐vinylpyridine) and end‐sulfonic acid polystyrene and polyisoprene: Intermediates to noncovalently bonded block copolymer‐like micelles

The complexation between narrow molecular weight distribution poly(2‐vinylpyridine) (P2VP) and polystyrene (suPS) or polyisoprene (suPI) end‐functionalized with one sulfonic acid group was examined in tetrahydrofuran dilute solutions by a combination of static and dynamic laser light scattering. Both apparent weight‐average molecular weight (M_w,app) and hydrodynamic radius (R_h) of the complexes exhibited a maximum at a certain molar ratio of suPS chains to P2VP monomeric units. This indicated that the P2VP backbone may be saturated by the grafted end‐functionalized chains because of repulsion between the grafted chains. By changing the molar mass of P2VP from 100,000 to 30,000 g/mol, the values of M_w,app and R_h decreased. When suPI was used instead of suPS, similar trends were observed. In the latter case, it was possible to prepare block copolymer‐like micelles by transferring the P2VP/suPI blend solutions in decane, which is a selective solvent for PI. The non‐covalent‐bonded polymeric micelle characteristics were investigated as a function of sulfonic acid/2‐vinylpyridine units ratio as well as temperature. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2454–2461, 2003     

Thermomechanical Properties of Carbon Nanocomposites PEGDA Photopolymers

In this work, UV-curable resin poly (ethylene glycol) diacrylate (PEGDA) was reinforced with three different types of nanofillers: pristine graphene (G), multiwalled carbon nanotubes (MWNTs), and a hybrid of MWNTs and graphene 70/30 in mass ratio (Hyb). PEGDA was mixed homogenously with the nanofiller oligomer by shear mixing and then photopolymerized, affording thin, stable films. The thermomechanical properties of the afforded nanocomposites indicated the superior reinforcing ability of pristine graphene compared with MWNTs and an intermediate behavior of the hybrid.