The Double Face of Ketamine—The Possibility of Its Identification in Blood and Beverages

The purpose of this study was to develop and validate a high-sensitivity methodology for identifying one of the most used drugs—ketamine. Ketamine is used medicinally to treat depression, alcoholism, and heroin addiction. Moreover, ketamine is the main ingredient used in so-called “date-rape” pills (DRP). This study presents a novel methodology for the simultaneous determination of ketamine based on the Dried Blood Spot (DBS) method, in combination with capillary electrophoresis coupled with a mass spectrometer (CE-TOF-MS). Then, 6-mm circles were punched out from DBS collected on Whatman DMPK-C paper and extracted using microwave-assisted extraction (MAE). The assay was linear in the range of 25–300 ng/mL. Values of limits of detection (LOD = 6.0 ng/mL) and quantification (LOQ = 19.8 ng/mL) were determined based on the signal to noise ratio. Intra-day precision at each determined concentration level was in the range of 6.1–11.1%, and inter-day between 7.9–13.1%. The obtained precision was under 15.0% (for medium and high concentrations) and lower than 20.0% (for low concentrations), which are in accordance with acceptance criteria. Therefore, the DBS/MAE/CE-TOF-MS method was successfully checked for analysis of ketamine in matrices other than blood, i.e., rose wine and orange juice. Moreover, it is possible to identify ketamine in the presence of flunitrazepam, which is the other most popular ingredient used in DRP. Based on this information, the selectivity of the proposed methodology for identifying ketamine in the presence of other components of rape pills was checked.     

DFT B3LYP/6-311+G* calculation study of a new nonclassical mechanism of electrophilic functionalization of aromatic C–H bond via aryl cation formation

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Magneto-Thin-Layer Chromatography as a Tool for the Analysis of Plant Extracts

JPC – Journal of Planar Chromatography – Modern TLC - As it was presented in our previous works, applying external magnetic field during chromatogram development results in changes of...     

Substituent effect on inter-ring interaction in paracyclophanes

Molecular Diversity - The theoretical calculations, namely multipole-derived charge analysis, quantum theory of atom in molecules, and non-bonding interaction (NCI), were performed for...     

Weak interactions in furan dimers

Dimers of furan, 2,3-dihydrofuran, 2,5-dihydrofuran and tetrahydrofuran were investigated with the use of theoretical methods to determine the interactions that keep the molecules together. The QTAIM and NCI methods confirmed that for furan dimers the C–H?O hydrogen bond and stacking interactions can form the dimers with similar energy. For 2,3-dihydrofuran, 2,5-dihydrofuran and tetrahydrofuran, the decisive mechanism of dimer formation is the stacking interaction between the furan rings.     

Maximum weight edge-constrained matchings

Practical questions arising from (for instance) biological applications can often be expressed as classical optimization problems with specific, new features. We are interested here in the version of the maximum weight matching problem (on a graph G) obtained by (1) defining a set F of pairs of incompatible edges of G and (2) asking that the matching contains at most one edge in each given pair. Such a matching is called an odd matching. The graph T(F)=(V_F,F), where V_F is the set of edges of G occurring in at least one pair of F, is called the trace-graph of G and F.We motivate the introduction of the maximum weight odd-matching (abbreviated as Odd-MWM) problem and study its complexity with respect to two parameters: the type of graph G and the graph class T to which T(F) belongs.Our contribution includes:

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A proof that Odd-MWM is NP-complete for 3-degree bipartite graphs when T(F) is a matching (i.e. when T is the class of 1-regular graphs), even if the weight function is constant.

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A proof that Odd-MWM is NP-complete (for 3-degree bipartite graphs as well as for any larger class) if and only if T is a class of graphs with unbounded induced matching. Otherwise, Odd-MWM is polynomial.

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A (Δ(T(F))+1)-approximate algorithm for Odd-MWM on general graphs. This algorithm becomes a χ(T(F))-approximate algorithm when the graph class T admits a polynomial algorithm for minimum vertex coloring.

     

The shape of the potential energy curves for NHN(+) hydrogen bonds and the influence of non-linearity

The potential energy curves for proton motion in NHN(+) hydrogen bonds have been calculated to investigate whether different methods of evaluation give different results: for linear H bonds most curves calculated along the NH direction are, as expected, identical with those along NN; for intramolecular H bonds it is very important to take into account the non-linearity and the potential energy curve calculated along the NH direction can be very far from the curve correctly describing the proton transfer. Other factors which influence the proton-transfer process are steric hindrance and presence of anions which modify the proton motion. In the analysis of the proton transfer process it is very important to take changes in the structure of the rest of the molecule into account, which is connected with exchange of energy with the surroundings. Comparison of adiabatic and non-adiabatic curves shows that they are significantly different for very bent hydrogen bonds and for hydrogen bonds with steric constraints for which the proton transfer process must be accompanied with relaxation of the whole molecule. Comparison of the potential-energy curves for compounds with very short H bonds emphasizes that the term 'strong H bond' needs to be qualified. For intermolecular H bonds shortening of the bond is connected with linearization. But for intramolecular H bonds the NN distance cannot be used as the only measure of H bond strength.     

Digital microfluidics for cell-based assays

We introduce a new method for implementing cell-based assays. The method is based on digital microfluidics (DMF) which is used to actuate nanolitre droplets of reagents and cells on a planar array of electrodes. We demonstrate that this method is advantageous for cell-based assays because of automated manipulation of multiple reagents in addition to reduced reagent use and analysis time. No adverse effects of actuation by DMF were observed in assays for cell viability, proliferation, and biochemistry. A cytotoxicity assay using Jurkat T-cells was performed using the new method, which had approximately 20 times higher sensitivity than a conventional well plate assay. These results suggest that DMF has great potential as a simple yet versatile analytical tool for implementing cell-based assays on the microscale.