Current Analytical Chemistry - Volume 13, Issue 3, 2017

10.2174/157341101303170503175624

Background: Matrix-assisted laser desorption/ionization mass spectrometry imaging has proved to be a powerful tool in localization of endogenous molecules in thin tissue sections. Distributions of drug compounds following administration in experimental animal models can be spatially detected and superimposed upon histological images thereby identifying the tissue compartments involved in drug uptake, transfer and metabolism. Methods: A new instrumental setup consisting of a Thermo Scientific Q Exactive mass spectrometer and an AP SMALDI10 ion source was used for imaging data acquisition at 10-µm lateral resolution to provide details of the distribution of a bronchodilator, tiotropium, in a rodent model. Results: The extracted ion maps of tiotropium showed higher signal intensities in bronchioles compared to lung parenchyma, while the drug was absent in lymphoid nodes and blood vessels. The enhanced mass spectrometric image quality provided refined spatial distribution in comparison with data obtained on a Thermo Scientific MALDI LTQ Orbitrap XL mass spectrometer obtained at 30, 80 and 150 µm lateral resolution. Conclusion: The high spatial resolution images of administrated tiotropium in rat lung obtained by the AP SMALDI10 ion source have readily improved the localization of this drug, highlighting cellular level distributions from the airways to the parenchyma.

Background: In the last decades particular attention has been devoted to packaging materials to obtain the best conditions to store food and to preserve the organoleptic properties. Methods: In the present study samples of tomato sauce collected in different Italian markets and preserved in different packaging materials (glass, tin and multilayer plastic containers) were chemically characterized considering the content of anions (6 species), carotenoids (lycopene, sum of alpha- and beta- carotene), flavonoids (epicatechin and quercetin), metals (41 species), total polyphenols, vitamins (C and B-group), and volatile profile. Different analytical techniques were employed like GC and LC with different detectors (MS and DAD), ICP-MS and ICP-OES. All developed methods were validated and applied to different commercial products collected from local markets. Results: Multivariate statistical tools (Principal Components Analysis – Discriminant Analysis, PCA – DA, Ranking PCA and Partial Least Square – Discriminant Analysis, PLS – DA) were then applied to evaluate the effect played by the different packaging on the chemical profile of the samples. The multivariate strategy adopted allowed to identify markers able to discriminate samples stored in glass, tin or multilayer plastic containers. Conclusion: In both cases, the differences identified between the classes of samples can be ascribed to a double effect: 1) products stored in glass preserve their content in vitamins and other important nutrients or 2) storage in glass could force manufacturers to provide a product of better quality since the product is visible to the final consumer.

Background: In this work, a combined electrochemical approach has been developed for the purification and detection of chromium species in aqueous effluents. With this in mind, the technique of differential pulse voltammetry (DPV) using ultratrace graphite electrode was applied for the determination of hexavalent chromium during its elimination by an electrocoagulation (EC) process. Methods: The application of combined electrochemical techniques (differential pulse voltammetry (DPV) using ultratrace graphite electrode) for the determination of Cr(VI) in aqueous solutions during its treatment by EC process (aluminum electrodes) by applying 5 and 10 mA cm-2, was proposed. Cr(VI) was selected as target due to its presence in several industrial effluents, drinking water and tap water as well as in textile dyes and as anti-corrosion and conversion coatings. Results: The use of the DPV and UV-Vis for the monitoring of chromium concentration was tested during the EC process. A complete elimination of chromium in the solution was achieved by EC process. No increase on the removal efficiency of chromium was achieved, when an increase on applied current was applied. When low chromium concentrations were treated, complete removal was attained after 180 min, whereas at high concentrations, the elimination was achieved after 240 min. When chromium concentrations determined by DPV were compared with the determinations by UV-vis, some results are similar, principally at lower chromium concentrations (<2.5 mg L-1). However, higher concentrations of chromium were not determined by spectrophotometric approach, limiting the use of this method. Thus we may say that the DPV is a powerful electroanalytical method for determining hexavalent chromium in drinking water and effluents. Conclusion: The use of graphite ultratrace electrode was optimized to be employed as analytical approach for determining Cr(VI) removal efficiency during the EC process. The proposed procedure permits the monitoring of the elimination of chromium content in solutions by complexation method, reducing cost and analysis times required in other instrumental techniques. The combination of electroanalytical detection and EC procedures can be used in pilot plant remediation process to remove Cr(VI) because of efficacy and suitable use.

Background: This research had two purposes: first to verify if two enzyme biosensors developed by our research group for determining the Total antioxidant capacity (TAOC) and to determine the total polyphenol concentration (TPC) could correctly be used even in matrices such as commercial pharmaceutical supplements, as well as, earlier, have been used to analyze vegetables or food and feed based vegetables, only. The second was to determine whether there is a correlation between the values of TAOC and TPC, so measured, both in pharmaceutical supplements, analyzed in this work, and in several vegetables and food or feed based vegetables, analyzed with the same biosensors, but in our previous works. Methods: The two used amperometric biosensors are based on a Clark type electrode and on the enzyme superoxide dismutase, that for the measurement of the TAOC and on the tyrosinase enzyme, the one for the measurement of the TPC. Results: The results obtained showed that the first of these targets set has been largely achieved: TAOC and TPC can be effectively measured, with rapid biosensing methods, simple and also cheaper, in pharmaceutical supplements. The second objective showed that the correlation between TAOC and TPC certainly exists in vegetables and their derivatives, where the antioxidants consist essentially of polyphenols, while, in the pharmaceutical suppliers this correlation has been verified only in those commercial products based almost exclusively on vegetable products, while this correlation does not exist in more complex products, which contain molecules which of course have antioxidant compounds, but of kind also very different from those based only on vegetable antioxidants. Conclusion: The two enzymatic sensors have proven reliable and analytically suitable, also for applications in real matrices and the determination of total polyphenol concentration (TPC) can be considered a good indicator of the total antioxidant capacity (TAOC) and also but not always in pharmaceutical supplements.

Background: The aim of this work was to develop an efficient voltammetric method for rapid analysis and simultaneous determination of L-dopa and benserazide (Bz) in pharmaceutical formulations. To the best of our knowledge simultaneous electrochemical determination of the mentioned compounds based on an activated screen-printed carbon electrode (SPCE*) has not been reported in the literature, this paper being the first example of an electrochemically pre-treated disposable carbon sensor for the direct and simultaneous determination of L-dopa and Bz in pharmaceutical formulation Methods: Cyclic voltammetry (CV) was used to investigate the suitability of the SPCE* for the oxidation of L-dopa and Bz on the electrode surface in Britton-Robinson buffer solution (BRB) of pH 2.21. The validity of the proposed differential pulse voltammetry (DPV) method was successfully assessed for analysis of both drugs in a commercial pharmaceutical tablet formulation (Madopar). For comparison the determination of L-dopa and Bz in tablets was also carried out by a HPLC method. Results: Cyclic voltammetry studies showed that activated SPCE* lowers overpotentials and improve electrochemical behavior of L-dopa and Bz, compared to untreated SPCE. Under optimum differential pulse voltammetry conditions, the oxidation peak current of L-dopa in Britton-Robinson buffer solution of pH 2.21 showed a linear calibration range from 1x10-6 – 1x10-4 M with a limit of detection of 0.47x10-6 M. In case of Bz a linear calibration range from 6x10-6 M to 1x10-4 M and a detection limit of 2.6x10-6 M were obtained. Conclusion: In this work a simple and cost effective voltammetric method for the simultaneous determination of L-dopa and Bz in BRB solution of pH 2.21 was developed using activated SPCE. The current sensitivity and good limit of detection for L-dopa and Bz at the SPCE* prove its potential sensing applications for the determination of both compounds in Madopar pharmaceutical formulation with good recovery results. Some important advantages of the proposed method such as no need to use chemical modifiers and of sample pretreatment or any time-consuming extraction step prior to the drug assay and the disposability of the sensor strip that avoids poisoning from repeated use, along with its low cost, potential for miniaturization hold considerable promise for routine pharmaceutical analysis in evaluating the quality of some medicines in market places.

Background: Glutathione (GSH) is a water-soluble tripeptide which is contained in biological fluids (blood plasma, cell fluid) and plays an important role in redox processes in the organisms of humans and animals. The lack of GSH leads to oxidative stress in living cells and causes dangerous diseases. In this regard, the development of rapid and simple analytical methods to determine GSH in biological fluids is an important task. The purpose of the present paper was to explore the possibility of electrochemical determination of GSH using AuNPs-modified graphite electrodes to develop a sensitive voltammetric method. Methods: Electrochemical sensor (AuNP-GCE) for the determination of GSH in solutions was prepared by deposition of gold nanoparticles (5-15 nm) from Au-hydrosol at graphite electrode surface. Composition of electrodes was controlled using scanning electron microscopy and EDX-analysis (JSM 5500). Electrochemical behavior of GSH at graphite-based electrodes in alkaline medium was investigated using cyclic voltammetry (CV) by means of electrochemical analytical device TA-4 (Tomsk, Russia). Results: Electrocatalytic oxidation of GSH at AuNP-GCE occurs at +0.05 V (vs. silver chloride ref. electrode) in 0.1 M NaOH and is revealed from CV as an “inverse” current peak in the cathodic direction of potential scan. The sequence of electrode reactions has been suggested which includes oxidation of Au nanoparticles when potentials scanned towards positive direction up to 0.8 V and consequent GSH electrocatalytic oxidation by Au(I)-oxide during the backward potential scan represented as the “inverse” peak. Conclusion: Au-nanoparticles modified graphite electrode exhibits electrocatalytic activity towards GSH oxidation in alkaline medium. An “inverse” current peak in cathodic part of CVs can be used to determine concentration of GSH in a solution. The current of this peak linearly depends on GSH concentration in the interval 2-14 pM (detection minimum 0.7 pM) in supporting solution 0.1 M NaOH. The proposed method can be applied for determination of glutathione in biological fluids.

Background: In the modern clinical practice of TCM science, the formula Xihuang pill has been widely used as a remedy for the treatment of various tumors in clinical application. Due to the diversity of the manufacturers and relatively lower quality standards, the quality problem of Xihuang pill frequently resulted in unstable effect in clinical application. It is imperative to develop more effective and comprehensive quality control method capable of ensuring the safety and efficacy. The objective of our study is to introduce GC-FID/GC-MS for multiple components quantification and fingerprint description of the volatile oil in Xihuang pill. Methods: A GC-FID method was developed for a chemical fingerprint analysis of Xihuang pill, and gas chromatography coupled with mass spectrometry was applied for the identification of major components in the fingerprints. In order to systematically validate the method, specificity, precision, repeatability and stability were measured. Fingerprints data analysis was mainly performed by three pieces of original software, namely ‘Similarity evaluation system for chromatographic fingerprint of TCM’, SPSS and SIMCA-P+. The similarities of ten batches of Xihuang pill were characterized using cluster analysis, PCA and similarity analysis. Results: The Euclidean distance, cosine, and correlation coefficient of the 10 batches of Xihuang pill were greater than 0.89, which showed that samples from different batches were basically the same and consistent, despite some slightly differences of chemical indexes were found. The results of cluster analysis, PCA and similarity analysis were consistent with each other, and the principal component factors that had significant correlation with the similarity were analyzed. Combined with GC-MS, total of 22 volatiles among 32 separated ones were identified by searching spectra database and literatures, and their relative content was calculated by using peak area normalization method. Conclusion: The GC-FID fingerprint combined with a variety of statistical and stoichiometry approach could be readily utilized for comprehensive quality assessment and control of Xihuang pill.

Background: Mercury (Hg2+) ion which is one of the most toxic heavy metals, can pollute the environment and threaten human health due to its features of non-biodegradation and bioaccumulation. Therefore, the detecting of Hg2+ ion is very necessary and has received increasing interest among researchers. The aims of this study is to developed a simple, sensitive and selective fluorescence probe for Hg2+ ion detecting. Methods: In present work, we use boric acid as boron source, urea as the nitrogen source and citric acid monohydrate as the carbon source to synthesize boron and nitrogen co-doped carbon dots (BNCDs) by microwave heating method. At room temperature, different concentrations of Hg2+ ion were added into BNCDs solution. The fluorescence intensity of BNCDs was measured at an excitation wavelength of 360 nm. Results: In this study, the as-prepared BNCDs were characterized by multiple analytical techniques such as TEM, FT-IR, UV-vis absorption, XRD, XPS and fluorescence spectra. The BNCDs have exhibited high selectivity and sensitivity to Hg2+ ion with the detection limit of 2.3 nM. A good linear relationship was obtained between corresponding fluorescence intensity and the concentration of Hg2+ ion in the range of 0.0-22.0 μM (r = 0.996) under the optimal conditions. According to the UV-vis absorbance of BNCDs have a small blue shift with the increasing concentration of Hg2+ ion, the Stern- Volmer quenching constant (KSV) value decreasing with the rising of temperature, the lifetime of BNCDs have no change in the presence of different concentrations of Hg2+ ion, the quenching mechanism of the BNCDs-Hg2+ system appears to be mainly static quenching. Conclusion: The BNCDs were faultlessly synthesized by the microwave heating method in a short time, which was expedient and low cost. The as-prepared BNCDs could be used as a highly sensitive flourescent probe for the quantitative and selective determination of Hg2+ ion. The quenching mechanism between BNCDs and Hg2+ ion was primarily static quenching. This proposed method could be viewed as a fundamental exemplification for a specific nanosensing system towards heavy metal ions in biomedicine and environmental fields.

Background: The safety and level of heavy metal ions in the traditional Chinese medicine has become an important topic. Most of the metal ions are carcinogens and lead to serious health concerns by producing free radicals. It is of great significance to develop simple and effective methods to determine heavy metal ions. The aim of this paper is to develop a CE-indirect UV method for the analysis of the four heavy metal ions for Chinese medicine Shuanghuanglian oral liquid. Methods: The alternative CE method for separation and test of metal ions was developed in this paper, which can help control the safety and level of heavy metal ions in traditional Chinese medicine Shuanghuanglian oral liquid. And the developed HPCE method showed superior analytical performance, including high sensitivity and good selectivity. Results: The experimental conditions of the CE separation method were: 5s hydrodynamic injection at 0.5 psi, 20 kV applied voltage, and UV detection at 218 nm. The results show that the migration time of all the four heavy metal ions was less than 6 min. The calibration curves for four heavy metal ions were linear in the range of 0.5-35 μg mL-1 with linear correlation coefficients of 0.9984-0.9999. The limits of detection were in the range of 0.08-0.61 μg mL-1 along with the recoveries of 93.0% to 109.5%. Conclusion: A simple, rapid and sensitive HPCE method has been developed to separate four heavy metal ions including Cd2+, Cr3+, Cu2+ and Zn2+ in traditional Chinese medicine Shuanghuanglian oral liquid. The comprehensive analysis performance is satisfactory. The proposed HPCE method provides shorter analysis time and lower detection limit. The results demonstrated that the developed CE method can be potentially applied as an good alternative for quality control of TCM.

Background: Food products and pharmaceuticals prepared with American red cranberries are gaining importance in our society due to some healthy effects on humans. However, some concerns have arisen on the evaluation of authenticity of red cranberry extracts as well as on the detection of possible adulterations with less expensive fruits like grapes or blueberries, which do not contain the appropriate polyphenols for having the desired bioactivity. This fact reveals the importance of developing analytical methodologies for the characterization of natural extracts to deal with authentication issues regarding the fruit of origin. Methods: HPLC-UV polyphenolic fingerprints of pure cranberry extracts and cranberry-based extracts adulterated with grape at different percentages were obtained and analyzed by chemometric methods (principal component analysis and partial least square regression). Results: Preliminary studies of HPLC-UV polyphenolic fingerprints by principal component analysis showed that the sample extracts were clearly distributed depending on the extent of adulteration with grape. Data was then further treated by partial least square regression to determine the percentages of grape contamination. It was found that even mixture samples containing low percentages of grape could be distinguished from genuine cranberry extracts. Besides, results obtained were highly satisfactory, with overall quantification errors lower than 5%. Conclusion: The proposed HPLC-UV method resulted in an excellent approach to carry out the authentication of cranberry-based products relying on polyphenolic fingerprints.

Background: Volatile organohalogen compounds (VOX) are a group of environmental pollutants that risk the quality of drinking water. These compounds are characterized by certain acute and chronic toxicities, possessing mutagenic properties. Because of these potential risks factors that these compounds cause, the maximum allowable concentrations (MACs) have been established by respective organizations. The abundance of VOX, their potential hazards and legislation are driving factors to develop analytical procedures for their determination in water samples. Objective: The aim of the study is to develop greener DLLME technique for VOX determination in water samples, incorporating extraction solvent lighter than water. To achieve this goal the design of new extraction device is required. Methods: The DLLME-GC-ECD procedure was developed to perform an analysis of water samples in order to determine VOX. The sample preparation step was performed by applying the solvent lighter than water (pentane). Results: The best results regarding sample preparation are obtained when 70 µL of pentane is used as extractant solvent, 0.5 mL acetone is used as dispersive solvent. The analytical procedure is characterized by good analytical performance with limit of detection within 0.0010 - 0.30 µg L-1 and precision within 2.4 - 6.6% range. Conclusion: Dispersive liquid-liquid microextraction is a suitable technique for determination of VOX. The newly designed extraction device is suitable for extraction of organic compounds as the area of polymeric parts is greatly reduced in comparison to similar home-made extraction devices. It allows for application of pentane - solvent lighter than water and safer in use than carbon disulfide.