Vol 71, No 4 (2016)

Pesticides are necessary for increasing agricultural productivity; however, their enormous use contaminates air, water and food. Among various organic pesticides, organochlorine pesticides (OCPs) are most persistent; and though their use is banned, they are still used illegally. In contrast to OCPs, organophosphorous pesticides are less persistent and used most extensively, while synthetic pyrethroid pesticides are the least toxic and used as insecticides. Extensive use of these pesticides is vulnerable to the ecosystem. Various extraction methods are used worldwide both by the regulatory bodies and private laboratories for the determination of multi-residue pesticides in leafy vegetables. This mini review presents an update on extraction procedure in gas chromatographic methods of pesticides analysis in various samples with special emphasis on leafy vegetables. We have covered six years of work from 2008–2013, discussing various extraction methods and their applications.

A method has been developed for the determination of trace amounts of seven nitrosoamines (N-nitrosodimethylamine, N-nitrosomethylethylamine, N-nitrosodiethylamine, N-nitrosopyrrolidine, N-nitrosodipropylamine, N-nitrosopiperidine, and N-nitrosodibutylamine) in food using gas-liquid chromatography with a mass-spectrometric detector. The optimum chromatographic conditions were selected: a DB-5MS column, temperature ramp rate 10 K/min from 40 to 250°C, carrier gas flow rate 1 mL/min. Conditions of the extraction of nitrosoamines from samples using microwave heating extraction followed by dispersive liquid-liquid microextraction, ensuring sufficient preconcentration and additional purification of the extract, have been optimized. The linearity ranges for nitrosoamines were (0.5–2.5)–25 µg/kg; the limits of detection were 0.1–0.5 µg/kg (signal-tonoise ratio 3). The method has been applied to the analysis of samples of sausage, smoked chicken meat, and smoked pork. The time of analysis is 1.5–2 h, the relative standard deviation of the results of analysis does not exceed 10%.

Humic substances (HS) have been extracted from fresh waters on macroporous adsorbents of different types, Amberlite XAD-8 resin and Bond Elute PPL solid-phase cartridge. Comparative analysis of the extracted samples by ultra-high resolution mass spectrometry demonstrated selectivity of the selected adsorbents to the components of the molecular assembly of HS: the XAD-8 resin has affinity to the higher oxidized aromatic compounds and PPL has affinity to substances of stronger aliphatic character and nitrogen-containing compounds. Because of this fact, a comparison of the molecular composition of HS isolated from various sources must be performed taking into account selective adsorption; therefore, it is necessary to compare the products extracted by the same adsorbent for correct interpretation.

Magnetic mesoporous silica was used for electrode modification and electro-oxidation of some cardiovascular drugs. The modified electrode was applied for detection of cardiovascular drugs using cyclic voltammetry, chronoamperometry, and differential pulse voltammetry. The modified electrode shows many advantages as an electrochemical sensor such as simple preparation method without using any specific electron transfer mediator or specific reagent, high sensitivity, excellent activity, short response time, long term stability and remarkable antifouling property toward for cardiovascular drugs and its oxidation product. Finally, the applicability of the sensor for determination of the selected drugs in human serum samples has been successfully demonstrated.

The analysis of published data shows that the results of the gas chromatographic determination of low-volatile polar aliphatic dicarboxylic acids are rather poorly reproducible. A considerable part of the published values of their retention indices appears to be erroneous. The experimental verification of the capabilities of gas chromatography and gas chromatography–mass spectrometry demonstrates that some of the compounds of this series (for example, glutaric acid) can be determined without decomposition; others are characterized by the formation of products of interaction with solvents (oxalic acid), and in some cases, the only detectable moieties are products of thermal degradation (citric acid).

In order to draw appropriate conclusions about the possible adverse biological effects of titanium dioxide nanoparticles (TiO₂—NPs), the so-called “dose?effect” relationship must be explored. This requires proper quantification of titanium in complex matrices such as animal organs for future toxicological studies. This study presents the method development for mineralizing TiO₂—NPs for analysis of biological tissues. We compared the recovery and quantification limits of the four most commonly used mineralization methods for metal oxides. Microwave-assisted dissolution in an HNO3–HF mixture followed by H₂O₂ treatment produced the best results for a TiO₂—NPs suspension, with 96 ± 8% recovery and a limit of quantification as low as 0.9 µg/L. This method was then used for the determination of titanium levels in tissue samples taken from rats. However, our tests revealed that even this method is not sensitive enough for quantifying titanium levels in single olfactory bulbs or hippocampus in control animals.