Simple HPLC method for simultaneous quantification of nicotine and cotinine levels in rat plasma after exposure to two different tobacco products

Purpose

Development and validation of a selective analytical method to accurately and precisely quantify nicotine and cotinine levels in rat's plasma after exposure to tobacco cigarettes and tobacco water-pipe.

Methods

An easy HPLC-Photodiode-Array Detection (PDA) method was developed and validated for simultaneous determination of nicotine and cotinine levels in plasma of 15 rats (10 rats after tobacco products exposure and 5 control rats). Nicotine and cotinine were extracted in one step from plasma using acetonitrile and concentrated to lowest volume using nitrogen stream.

Results

The developed method offered a rapid analysis time of 14 min with single step of analytes extraction from rat's plasma with recovery percentage range between 93 and 95% and excellent linearity with correlation factor more than 0.994 with analytical range between 50 and 1000 ng mL−1 and LOD of 25 ng mL−1 and 23 ng mL−1 for nicotine and cotinine, respectively. The analysis of rat's plasma after 28 days of exposure to tobacco cigarettes and tobacco water-pipe revealed that the average concentrations of 376 ng mL−1 for cotinine and 223 ng mL−1 for nicotine were obtained after tobacco cigarettes exposure, and 220 ng mL−1 for cotinine and 192 ng mL−1 for nicotine after tobacco water-pipe exposure.

Conclusion

Higher nicotine and cotinine levels were found in plasma after tobacco cigarettes exposure than water-pipe exposure which may have potential undesirable effects on passive smokers in both cases.

3D printed two-in-one on-capillary detector: Combining contactless conductometric and photometric detection for capillary electrophoresis

In this work, for the first time, a 3D printed two-in-one on-capillary detector, combining contactless conductometric detection (C⁴D) and photometric detection (PD), is fabricated for capillary electrophoresis (CE). The C⁴D Faraday shield (FS) is printed using electrically conductive composite polylactic acid (PLA) to minimize the stray capacitance. Non-conductive PLA is also used to print the insulator of FS to prevent the electrical conduction with two stainless steel electrodes. A novel collimator, consisting of two partially aligned pinholes, is printed by conductive material to collimate the light-emitting diode beam. The C⁴D detection has a signal-to-noise ratio of 1092 ± 2 for 200 μM potassium on a 25 μm id capillary. The PD detection shows excellent linearity with stray light down to 8% and an effective path length at 73% of a 75 μm id capillary. The analytical performance is demonstrated by CE separation and detection of cations. PD shows limits of detection (LODs) of 1.3, 0.9, and 1.7 μM for cobalt, copper and zinc, which are complexed with 4-(2-Pyridylazo) resorcinol, while C⁴D shows LODs of 1.2, 1.4, 21 and 2.6 μM for potassium, sodium, cobalt and zinc, respectively.

Optimization of background electrolyte composition for simultaneous contactless conductivity and fluorescence detection in capillary electrophoresis of biological samples

In this article, optimization of BGE for simultaneous separation of inorganic ions, organic acids, and glutathione using dual C⁴ D-LIF detection in capillary electrophoresis is presented. The optimized BGE consisted of 30 mM 2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid, 15 mM 2-amino-2-hydroxymethyl-propane-1,3-diol, and 2 mM 18-crown-6 at pH 7.2 and allowed simultaneous separation of ten inorganic anions and cations, three organic acids and glutathione in 20 min. The samples were injected hydrodynamically from both capillary ends using the double-opposite end injection principle. Sensitive detection of anions, cations, and organic acids with micromolar LODs using C⁴ D and simultaneously glutathione with nanomolar LODs using LIF was achieved in a single run. The developed BGE may be useful in analyses of biological samples containing analytes with differing concentrations of several orders of magnitude that is not possible with single detection mode.

Selectivity enhancement in capillary electrophoresis by means of two-dimensional separation or dual detection concepts

For the identification and quantification of analytes in complex samples, highly selective analytical strategies are required. The selectivity of single separation techniques such as gas chromatography (GC), liquid chromatography (LC), or capillary electrophoresis (CE) with common detection principles can be enhanced by hyphenating orthogonal separation techniques but also by using complementary detection systems. In this review, two-dimensional systems containing CE in at least one dimension are reviewed, namely LC-CE or 2D CE systems. Particular attention is paid to the aspect of selectivity enhancement due to the orthogonality of the different separation mechanisms. As an alternative concept, dual detection approaches are reviewed using the common detectors of CE such as UV/VIS, laser-induced fluorescence, capacitively coupled contactless conductivity (C⁴D), electrochemical detection, and mass spectrometry. Special emphasis is given to dual detection systems implementing the highly flexible C⁴D as one detection component. Selectivity enhancement can be achieved in case of complementarity of the different detection techniques.

Dual detection for non-aqueous capillary electrophoresis combining contactless conductivity detection and mass spectrometry

Coupling of two detectors is a powerful tool to enhance the overall analytical performance generating complementary information and overcoming the limitations of the single detectors. In this work, capacitively coupled contactless conductivity detection (C⁴D) and electrospray ionization mass spectrometry (ESI-MS) were coupled in conjunction with non-aqueous capillary electrophoresis (NACE). Non-aqueous electrolytes are highly compatible with ESI due to their volatility. Moreover, they exhibit low background conductivity, which is essential for the detection with C⁴D. A NACE-C⁴D-MS method was developed using an acetonitrile buffer containing 2 M HAc and 4 mM NH₄Ac as background electrolyte. The influence of the inner diameter of the separation capillary on the C⁴D was studied and taken into account. A capillary with 50 µm inner diameter was found to be best suited. The complementarity of the two detectors was shown by determining a sample mixture containing choline, thiamine, nitrate, and chloride as well as bromide and acetylcholine as internal standards. The C⁴D was the detector of choice for the inorganic ions, which were not detectable with the MS whereas the MS had much lower limits of detections for the organic biomolecules. The method was applied on an extract of a food supplement containing the model analytes.

Electrodeposition of Au nanoparticles on poly(diallyldimethylammonium chloride) functionalized reduced graphene oxide sheets for voltammetric determination of nicotine in tobacco products and anti-smoking pharmaceuticals

The principal objective of this study was to develop a sensitive and selective electrochemical sensor for nicotine detection based on a novel PDDA-RGO/Au nanocomposite.

Determination of Nicotine in Tobacco by Chemometric Optimization and Cation-Selective Exhaustive Injection in Combination with Sweeping-Micellar Electrokinetic Chromatography

Nicotine is a potent chemical that excites the central nervous system and refreshes people. It is also physically addictive and causes dependence. To reduce the harm of tobacco products for smokers, a law was introduced that requires tobacco product containers to be marked with the amount of nicotine as well as tar. In this paper, an online stacking capillary electrophoresis (CE) method with cation-selective exhaustive injection sweeping-micellar electrokinetic chromatography (CSEI-sweeping-MEKC) is proposed for the optimized analysis of nicotine in tobacco. A higher conductivity buffer (160 mM phosphate buffer (pH 3)) zone was injected into the capillary, allowing for the analytes to be electrokinetically injected at a voltage of 15 kV for 15 min. Using 50 mM sodium dodecyl sulfate and 25% methanol in the sweeping buffer, nicotine was detected with high sensitivity. Thus, optimized conditions adapted from a chemometric approach provided a 6000-fold increase in the nicotine detection sensitivity using the CSEI-sweeping-MEKC method in comparison to normal CZE. The limits of detection were 0.5 nM for nicotine. The stacking method in combination with direct injection which matrix components would not interfere with assay performance was successfully applied to the detection of nicotine in tobacco samples.

Present state of microchip electrophoresis: state of the art and routine applications

Microchip electrophoresis (MCE) was one of the earliest applications of the micro-total analysis system (μ-TAS) concept, whose aim is to reduce analysis time and reagent and sample consumption while increasing throughput and portability by miniaturizing analytical laboratory procedures onto a microfluidic chip. More than two decades on, electrophoresis remains the most common separation technique used in microfluidic applications. MCE-based instruments have had some commercial success and have found application in many disciplines. This review will consider the present state of MCE including recent advances in technology and both novel and routine applications in the laboratory. We will also attempt to assess the impact of MCE in the scientific community and its prospects for the future.