Application of CE-MS to examination of black inkjet printing inks for forensic purposes.

The potential of capillary electrophoresis coupled to mass spectrometry with electrospray ion source and time of flight analyser (CE-ESI-TOF-MS) in the analysis of inkjet inks was investigated. The developed and validated method allowed reliable and repeatable analysis of black inkjet inks extracted from printouts. Over a dozen inkjet printouts printed on various printer models from different manufacturers were analysed under selected conditions to determine the variation of chemical composition of inks between different brands and types. It was ascertained that the developed method is capable of revealing qualitative differences between ink samples. For most of the investigated inks, the studies showed the presence of a characteristic mass spectrum originating from the surfactant or polymer. The mass distribution of the additive is distinctive for some inkjet ink producers, and allows for group identification of inks. The results showed the strength of the CE-ESI-TOF-MS method as an effective technique for forensic purposes, requiring a small amount of inkjet ink samples and giving analytical information that is useful in the identification of compounds

Microwave-assisted hydrolysis and extraction of tricyclic antidepressants from human hair

The objective of this research was to develop, optimize, and validate a modern, rapid method of preparation of human hair samples, using microwave irradiation, for analysis of eight tricyclic antidepressants (TCADs): nordoxepin, nortriptyline, imipramine, amitriptyline, doxepin, desipramine, clomipramine, and norclomipramine. It was based on simultaneous alkaline hair microwave-assisted hydrolysis and microwave-assisted extraction (MAH–MAE). Extracts were analyzed by high-performance liquid chromatography with diode-array detection (HPLC–DAD). A mixture of n-hexane and isoamyl alcohol (99:1, v/v) was used as extraction solvent and the process was performed at 60°C. Application of 1.0 mol L−1 NaOH and microwave irradiation for 40 min were found to be optimum for hair samples. Limits of detection ranged from 0.3 to 1.2 μg g−1 and LOQ from 0.9 to 4.0 μg g−1 for the different drugs. This enabled us to quantify them in hair samples within average therapeutic concentration ranges

Mesoporous carbon-containing voltammetric biosensor for determination of tyramine in food products

A voltammetric biosensor based on tyrosinase (TYR) was developed for determination of tyramine. Carbon material (multi-walled carbon nanotubes or mesoporous carbon CMK-3-type), polycationic polymer—i.e., poly(diallyldimethylammonium chloride) (PDDA), and Nafion were incorporated into titania dioxide sol (TiO(2)) to create an immobilization matrix. The features of the formed matrix were studied by scanning electron microscopy (SEM) and cyclic voltammetry (CV). The analytical performance of the developed biosensor was evaluated with respect to linear range, sensitivity, limit of detection, long-term stability, repeatability, and reproducibility. The biosensor exhibited electrocatalytic activity toward tyramine oxidation within a linear range from 6 to 130 μM, high sensitivity of 486 μA mM(−1) cm(−2), and limit of detection of 1.5 μM. The apparent Michaelis–Menten constant was calculated to be 66.0 μM indicating a high biological affinity of the developed biosensor for tyramine. Furthermore, its usefulness in determination of tyramine in food product samples was also verified. [Figure: see text] ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s00216-016-9612-y) contains supplementary material, which is available to authorized users