Current Analytical Chemistry - Volume 16, Issue 3, 2020

Introduction: A molecular imprinting is one of the fascinating modification methods that employ molecules as targets to create geometric cavities for recognition of targets in the polymeric matrix. This method provides a broad versatility to imprint target molecules with different size, three-dimensional structure and physicochemical features. In contrast to the complex and timeconsuming laboratory surface modification procedures, this method offers a rapid, sensitive, inexpensive, easy-to-use, and selective approach for the diagnosis, screening and monitoring disorders. Owing to their unique features such as high selectivity, physical and chemical robustness, high stability, low-cost and reusability of this method, molecularly imprinted polymers have become very attractive materials and been applied in various applications from separation to detection. Background: The aims of this review are structured according to the fundamentals of molecularly imprinted polymers involving essential elements, preparation procedures and also the analytical applications platforms. Finally, the future perspectives to increase the development of molecularly imprinted platforms. Methods: A molecular imprinting is one of the commonly used modification methods that apply target as a recognition element itself and provide a wide range of versatility to replica other targets with a different structure, size, and physicochemical features. A rapid, easy, cheap and specific recognition approach has become one of the investigation areas on, especially biochemistry, biomedicine and biotechnology. In recent years, several technologies of molecular imprinting method have gained prompt development according to continuous use and improvement of traditional polymerization techniques. Results: The molecularly imprinted polymers with excellent performances have been prepared and also more exciting and universal applications have been recognized. In contrast to the conventional methods, the imprinted systems have superior advantages including high stability, relative ease and low cost of preparation, resistance to elevated temperature, and pressure and potential application to various target molecules. In view of these considerations, molecularly imprinted systems have found application in various fields of analytical chemistry including separation, purification, detection and spectrophotometric systems. Conclusion: Recent analytical methods are reported to develop the binding kinetics of imprinted systems by using the development of other technologies. The combined platforms are among the most encouraging systems to detect and recognize several molecules. The diversity of molecular imprinting methods was overviewed for different analytical application platforms. There is still a requirement of more knowledge on the molecular features of these polymers. A next step would further be the optimization of different systems with more homogeneous and easily reachable recognition sites to reduce the laborious in the accessibility in the three-dimensional polymeric materials in sufficient recognition features and also better selectivity and sensitivity for a wide range of molecules.

Background: Sartans are mostly used as a part of combination with additional medicines in the therapy of essencial hypertension. Preferred combinations are ARB and thiazide diuretics (Hydrochlorothiazide (HCT) and Chlorthalidone (CHL)) or ARB and calcium antagonists. The number of sartans mostly prescribed by specialists is only seven - Candesartan (CDS), Eprosartan (EPS), Irbesartan (IBS), Losartan (LOS), Olmesartan (OMS), Telmisartan (TMS) and Valsartan (VLS). Methods: The widespread use of sartans in the treatment of hypertension requires reliable methods of analysis. Bulk drugs and pharmaceutical preparations should be analyzed to ensure the quality of the medicinal products reaching patients. On the other hand, the analysis of drugs in biological fluids aims to trace and improve patient care by adjusting the therapeutic doses of drugs. According to our knowledge, a review devoted to the analysis of sartans was published in 2014. Results: Spectral methods are widely used in the analysis of bulk drugs and pharmaceutical dosage forms due to their relatively simple procedures, low reagent and sample consumption, speed, precision and accuracy combined with accessibility and comparatively low cost of common apparatus. Many papers for determination of sartans in bulk drugs and pharmaceutical preparations based on liquid chromatographic techniques were published in the available literature. Among these methods, HPLC takes the leading place but UPLC and HPTLC are also present. Conclusion: The widespread use of sartans in the treatment of hypertension requires reliable methods of analysis. Bulk drugs and pharmaceutical preparations should be analyzed to ensure the quality of the medicinal products reaching patients. On the other hand, the analysis of drugs in biological fluids aims to trace and improve patient care by adjusting the therapeutic doses of drugs. Since 2014, many articles have been published on the sartans analysis and this provoked our interest to summarize the latest applications in the analysis of sartans in pharmaceutical formulations and biological media. Articles published from 2014 to 2018 are covered.

Background: This work reports a green analytical method for the determination of organic environmental pollutants using nano-liquid chromatography with a self-made column for rapid, sensitive, inexpensive and efficient analysis of BTX pollutants in water. The applications of monolithic nanoscale columns for quantitative analysis of environmental real samples are very limited in the literature. Methods: A capillary column containing a composite of multi-walled carbon nanotubes incorporated into a lauryl methacrylate-co-ethylene dimethacrylate porous monolithic polymer was fabricated for the determination of BTX pollutants in real water samples. Results: Baseline separation was accomplished at 0.4 μL/min flow rate with UV-detection set at 208 nm. Under the optimum conditions, the calibration curves were validated over the range of 1.0-500 μg/L with R2 more than 0.9992. The detection limits of benzene, toluene, o-xylene and m/p-xylene were 0.25, 0.05, 0.075 and 0.05 μg/L, respectively. After a simple extraction process with a theoretical preconcentration factor equal to 200, the recovery values in Milli-Q, tap and sea water samples were found to be ranged from 84.85 to 97.84% with %RSD less than 7.5. Furthermore, we reported a comparison between our prepared composite column with a commercial C18 silica based column which is the most used in such analytical field. Each column demonstrated its advantages from different analytical aspects. Conclusion: The application of monolithic columns and nano-scale LC for routine analysis of environmental samples is very promising as the use of monolithic capillary columns offers several advantages over conventional scale particulate packed columns.

Background: Hydrogen (H) and Carbon (C) are major elements that occur in various materials, including organic matter. The identification and analysis of C and H are necessary for several fields. LIBS is an excellent method for such analysis because it is rapid, and can be conducted remotely. The technique has been employed for the analysis of H in zircaloy metals. However, few studies on the emission characteristics of H and C in various gases have been undertaken because of the difficulty of identifying H and C using standard LIBS techniques. In this work, the emission characteristics of H and C were studied using pulsed CO2 LIBS. H and C elements were obtained from ethanol vapor. Various gas environments were employed, including Nitrogen (N2), Argon (Ar), and Helium (He) gases, in order to study the stability of the laser-induced plasma, the plasma lifetime, and the excitation mechanisms of H and C. Methods: The LIBS system used in this work consisted of a pulsed TEA CO2 laser (Shibuya SQ 2000), pulse generator, and optical multichannel analyzer. In this work, the laser with a wavelength of 10.6 μm, pulse duration of 200 ns, and pulse energy of 3 J, was used as the irradiation source. The laser energy used was 1.5 J. The laser was irradiated, and focused, using a 200 mm zinc selenide (ZnSe) lens, onto a metal surface in order to initiate and induce a luminous plasma. The sample used in this study was ethanol vapor, obtained from ethanol (99.5%, Merck). For this purpose, 10 mL ethanol was poured into a glass beaker, and this was placed into a closed chamber that could be evacuated by ambient gases including N2, Ar, and He gases. Results: Identification of H emission line has been successfully carried out using this present technique demonstrated in various gases including N2, Ar, and He. From the results, it was observed that in N2 gas, the Hα I 656.3 nm emission line was clearly expressed, with a wide, full-width halfmaximum, and quite a low emission intensity. Conclusion: The emission characteristics of H and C in laser-induced plasma, produced in various ambient gases, including N2, Ar, and He, were studied. The emission spectra of Hα and Hβ were expressed clearly, with high intensity and low background emission, in He, while they were broad and had high background emissions in N2 and Ar. Based on the time-resolved emissions, the Hα emission had a longer lifetime in Ar and He. It was assumed that the metastable atoms of Arand He were predominant in the excitation process of H and C. The characteristics of the H and C emissions in various gases are important in selecting a suitable ambient gas for the study of light atomic emission in the medical field, which mostly deals with organic materials containing H, C, and oxygen.

Background: Diclofenac (DCF) is an important widely used non-steroidal antiinflammatory drug. Disposal of expired formulation, excretion from administered dose, the poor performance of sewage treatment process, contributes to its frequent detection in environment. Analysis of DCF in environmental sample requires time consuming pretreatment, extraction steps. Though, UV absorption analysis of DCF is simple but spectral interference of soil organic matter is a problem. The aim of this paper is to establish appropriate partial least square chemometric model for DCF quantitation through variable selection, and validation of analytical method through multivariate figure of merit analysis. Methods: Spectral data of DCF spiked soil solution is recorded and variants of partial least squares (PLS) regression viz., backward-interval PLS (biPLS), synergy-interval PLS (siPLS) and genetic algorithm (GA) based PLS models (GA-PLS) are developed from autoscaled and 2nd order differential spectrum. Prediction fidelity of the selected models was evaluated from a blind-folded semi-synthetic spectral data. The method was validated through figures of merit estimates, such as selectivity, analytical sensitivity, limits of detection and quantitation. Results: The siPLS model developed offered the minimum root mean square error of crossvalidation (RMSECV) of 0.1896 mg/l and 0.1910 mg/l for autoscaled data (9 variables) and derivative spectra (12 variables), respectively. Refinement of the derivative spectrum with GA offered a simplified model (RMSECV:0.1712, 10 variable). Conclusion: The GA based variable selection for PLS regression analysis offers robust analytical tool for DCF in environmental samples. Further research is warranted to model variable interference in spectral data unknown to analyst in priori.

Objective: Ten racemic 3,4-dihydropyrimidin-2(1H)-ones and 3,4-dihydropyrimidin- 2(1H)-thiones were separated by liquid chromatography on Chiralcel®OD-H column containing cellulose tris(3, 5-dimethylphenylcarbamate). Methods: The enantioseparation was carried out using Chiralcel®OD-H polysaccharide-type chiral stationary phase to resolve such enantiomers under normal-phase mode. Results: Complete separations of the 3,4-dihydropyrimidin-2(1H)-ones and 3,4-dihydropyrimidin- 2(1H)-thiones derivatives with good resolution (RS= 1.04-2.80) were achieved within a short time (10-15 min). Conclusion: An optimal baseline separation (Rs> 1.5) was achieved using Chiralcel®OD-H under normal-phase mode. Structure-retention relationships have also been discussed.

Background: Pesticides are increasingly used in agriculture and households, but they are also considered a major pollutant to the environment. Carbofuran (CAR; 2,3-dihydro-2,2- dimethylbenzofuran-7-yl methylcarbamate) is a widely used pesticide due to its effectiveness on soybean aphids. Objectives: A simple and green method was suggested for the extraction and determination of CAR in different matrices. Methods: A diazotization reaction involving the use of the drug compound metoclopramide was utilized in this study. A red dye product, which was formed from the diazotization coupling between CAR and diazotized metoclopramide (DMCP), was extracted using cloud point extraction with the nonionic surfactant Triton X-114 and measured at a wavelength of 515 nm. Results: The linearity of the extracted method was over a concentration range of 0.1-0.5 μg/mL (r2 = 0.996) for CAR with a detection limit of 0.064 μg/mL and enrichment factors of about 148 folds for CAR. The mean recovery percentage was in the range of 99-102% for water and soil samples with precision (RSD%) of less than 0.4%. Conclusion: The described method was effectively utilized in the simultaneous extraction of CAR from water and soil samples.

Background: This manuscript focuses on Novel multivariate UV-chemometric method and HPLC-QbD method for simultaneous determination of Vardenafil (VR) and Dapoxetine (DP) in active pharmaceutical ingredient and their marketed formulation. To the best of our knowledge, there is no literature data on multivariate methods for the same. Methods: The spectrophotometric data were processed by CLS, PCR, PLS and MLR methods in order to determine the active substances, without prior separation from tablet marketed formulation. Analytical figures of merit, such as sensitivity, selectivity, analytical sensitivity, LOD, and LOQ were determined. In HPLC-QbD, four critical factors were selected after screening and boxbehnken design was applied for optimization. Twenty-five experiments were done, and a quadratic model was used for all response variables. Desirability plot, surface plot, design space, and three-dimensional plots were calculated. Results: For Chemometrics, wavelength range selected was 202 nm - 326 nm at 2 nm intervals, hence 59 wavelength points were selected in such a way that minimum RMSEC and RMSECV values were obtained at multiple wavelengths. HPLC-QbD optimized conditions were; Phenomenex C8 column (250 x 4.6 mm, 5 μm), acetonitrile: buffer (ammonium acetate buffer at pH 2.7 with acetic acid) (40:60, v/v) as a mobile phase at flow rate of 0.9 mL/min, 239 nm wavelength and 20°C temperature. Conclusion: The developed methods were validated and successfully applied for simultaneous determination of VR and DP in tablet dosage form. The results obtained by UV-Chemometric methods were statistically compared with an HPLC-QbD method, which concludes both the methods can apply for tablet analysis.

Background: The first highly sensitive, rapid and specific green microemulsion liquid chromatographic (MELC) method was established for the simultaneous estimation of fluticasone propionate (FLU) and azelastine HCl (AZL) in the presence of their pharmaceutical dosage form additives (phenylethyl alcohol (PEA) and benzalkonium chloride (BNZ)). Methods: The separation was performed on a C18 column using (o/w) microemulsion as a mobile phase which contains 0.2 M sodium dodecyl sulphate (SDS) as surfactant, 10% butanol as cosurfactant, 1% n-octanol as internal phase and 0.3% triethylamine (TEA) adjusted at pH 6 by 0.02 M phosphoric acid; with UV detection at 220 nm and programmed with flow rate of 1 mL/min. Results: The validation characteristics e.g. linearity, lower limit of quantification (LOQ), lower limit of detection (LOD), accuracy, precision, robustness and specificity were investigated. The proposed method showed linearity over the concentration range of (0.5-25 μg/mL) and (0.1-25 μg/mL) for FLU and AZL, respectively. Besides that, the method was adopted in a short chromatographic run with satisfactory resolution factors of (2.39, 3.78 and 6.74 between PEA/FLU, FLU/AZL and AZL/BNZ), respectively. The performed method was efficiently applied to pharmaceutical nasal spray with (mean recoveries ± SD) (99.80 ± 0.97) and (100.26 ± 0.96) for FLU and AZL, respectively. Conclusion: The suggested method was based on simultaneous determination of FLU and AZL in the presence of PEA and BNZ in pure form, laboratory synthetic mixture and its combined pharmaceutical dosage form using green MELC technique with UV detection. The proposed method appeared to be superior to the reported ones of being more sensitive and specific, as well as the separation was achieved with good performance in a relatively short analysis time (less than 7.5 min). Highly acceptable values of LOD and % RSD make this method superior to be used in quality control laboratories with of HPLC technique.

Background: Gold nanoparticles (Au NPs) are normally prepared using standard gold (III) trichloride which is much expensive and irritant. This work is aimed at demonstrating simple and low-cost synthesis of Au NPs from the reused traditional gold leaf which is cost-free and less toxic. Methods: The reused gold leaf was donated by the local temple. It was digested and used as the precursor for the preparation of the Au NPs by Turkevich method. Poly (vinyl alcohol) (PVA) was employed as a stabilizer. The as-prepared Au NPs were applied for the colorimetric determination of creatinine in urine without any sample pretreatment. Results: Long-term stability of the gold colloids was achieved for at least 3 months. Morphology and purity of the as-prepared Au NPs were the same as the ones prepared from standard gold (III) salt and standard gold foil. Colorimetric response of the Au NPs was linear to the standard creatinine up to 200 mg L-1. The limit of detection (0.16 mg L-1 or 1.41 μM) was enough sensitive for urinary creatinine detection in patients with kidney disease. Good recoveries (97-108%) and fast analysis time (3 min) were achieved. The developed method was successfully validated against the HPLC method. Conclusion: Facile and cost-effective synthesis of the Au NPs from the reused traditional gold leaf, was accomplished. The as-prepared Au NPs were successfully applied for the determination of urinary creatinine with high sensitivity and selectivity.

Background: Paederia scandens (Lour.) Merrill, belonging to the Rubiaceae family, was one of the Traditional Chinese Medicines that has been generally used to treat aches and pains, inflammation, bacillary dysentery, piles and rheumatic arthritis. The four iridoid glycosides that Paederosidic acid, Paederoside, Paederosidic acid methyl ester, and Asperuloside from Paederia scandens are considered to be the main bioactive constituents. However, their pharmacokinetics and action mechanisms of these iridoid glycosides still remain unknown. In this study, a method of simultaneous determination of four iridoid glycosides components in rat plasma with LC-MS/MS has been established and successfully applied to a pharmacokinetic study in rats, which would be favourable for further exploration. Methods: In this study, a sensitive, rapid, accurate bioanalytical method of simultaneous determination of four iridoid glycosides components from Paederia scandens extract in rat plasma with LCMS/ MS has been established. It is easy and rapid for LC-MS/MS to accurately separate and simultaneously quantify the analytes because of its high sensitivity, selectivity and accuracy. This validated method was successfully applied to a pharmacokinetic study in rats with intravenous and oral administrations of Paederia scandens extract. Results: The resulting data are fully satisfied for the selectivity and the sensitivity. Their lower limit of quantitation are in 0.25-0.5 ng/mL. Intra- and interday precisions were less than 15.0% with accuracy in the range of -15.0% to 15.0%. In the stability measurements including repeated Freeze-thaw, 4 hours at 4°C, 24 hours at 4°C, and 30 days at -80°C, the variations between the measurements and the nominated values of these compounds in plasma were detected to be less than 15.0%. The extraction recoveries of the compounds were from 85.4% to 105.6%. The bioavailability (F) of the four iridoid glycosides were 1.74% to 3.36%. Conclusion: In summary, a simple, rapid, precise, and sensitive LC-MS/MS method has been established and validated to determine the four iridoid glycosides from Paederia scandens extract in rat plasma, which was successfully applied to pharmacokinetic study in rats. The information obtained from the study will facilitate further exploration on Paederosidic acid, Paederoside, Paederosidic acid methyl ester as well as Asperuloside and these may provide valuable pharmacokinetic reference for human applications.

Background: Graphene quantum dots (GQD) is a new member of carbon nanomaterial that has attracted increasing attention owing to its better chemical inertness, low cytotoxicity, large specific surface area, cheap cost, suitable conductivity and excellent biocompatibility. Methods: Electrochemical behaviors of this modified electrode were studied by cyclic voltammetry and electrochemical impedance spectroscopy. Electrochemical investigations of Nafion/Hb/GQD/ CILE were carried out with electrochemical parameters calculated. Results: In the phosphate buffer solution with a pH value of 5.0, good linear relationships between the catalytic reduction current and the concentration of substrate were got for TCA (6.0~100.0 mmol·L-1), NaNO2 (2.0~12.0 mmol·L-1) and H2O2 (6.0~30.0 mmol·L-1). The proposed method was applied to NaNO2 concentration detection in soak water from picked vegetables with satisfactory results. Conclusion: This Nafion/Hb/GQD/CILE had a good bioelectrocatalytic activity to different substrates such as trichloroacetic acid, NaNO2 and H2O2 reduction with the advantages including wide detection range, low detection limit and good stability. Therefore, the application of GQD in electrochemical sensor was extended in this paper.

Background: Biocompatible and easily available immobilization matrix is vital for the construction of enzyme-based biosensor. Methods: Reed membrane was selected as a novel immobilization matrix to construct an optical phenol biosensor. Tyrosinase from mushroom was immobilized in a reed membrane using glutaraldehyde as a cross-linker. The detection scheme was based on the measurement of the color intensity of the adduct resulting from the reaction of 3-methyl-2-benzothiazolinone hydrazone (MBTH) with the quinone produced from the oxidation of phenol by tyrosinase. The performance of such method including specificity, sensitivity, repeatability and practical use were validated. Results: The prepared biosensor demonstrated optimum performance at pH 6-7, temperature of 40°C and a linear response in the phenol concentration range of 5-100 μM. It also showed good operation stability for repeated measurements (over 200 times) and good storage stability after it had been kept at 4°C for 2 months. Conclusion: Reed membrane is a novel matrix for immobilization of enzyme. The prepared biosensor permits good sensitivity, reproducibility and stability. It is anticipated that reed membrane is a promising solid support for fabricating other enzyme-based biosensors.

Background: Punica granatum L. (pomegranate) is one of the oldest edible fruits used for the treatment of countless diseases. The bioactivity of this fruit is mainly related to tannins, especially elagitannins. P.granatum fruit peel dried extracts (PPDEs) are widely marketed today and the lack of accessible quality control methods is a key to the variable and questionable quality of these products. Objective: To develop a miniaturized spectrophotometric method for quantification of tannins in commercial PPDEs. Method: Spectrophotometric method using Folin-Ciocalteu reagent was developed and validated for quantification of total polyphenols and polyphenols not adsorbed by hide powder in 17 samples of commercial PPDEs. Tannins content was calculated by the difference between total polyphenols and polyphenols not adsorbed by hide powder contents and expressed as pyrogallol. The UV/Visible microplate spectrophotometer was operated at 760 nm. Results: The developed miniaturized method was precise, accurate, selective and linear, and has no rotational or translational matrix effect. This method significantly reduced the cost of the analysis: 82.2% with reagents, 84.7% in electricity consumption, and 56.3% in the total analysis time. The wide variability in tannins contents in commercial PPDEs (<1% to 14.20%) shows the importance of quality control, ensuring the therapeutic effect and safety of the extracts. Conclusion: A miniaturized spectrophotometric method was successfully developed and fully validated, being appropriate for quantification of tannins of PPDEs in quality control routine analysis, as it showed to be a simple and cheaper method.

Background: The magnetic nanocomposites are very important as a reusable sorbents for the extraction of Cd(II) and other toxic metals from water samples. Methods: The Ag/MgO@Fe3O4 nanocomposite was synthesized by the coprecipitation method and characterized by the XRD, EDX, SEM, UV-vis spectroscopy and FTIR. This nanocomposite was used to extract Cd(II) from water samples prior to its quantitative analysis with FAAS. Different variables, i.e. pH, temperature, amount of nanosorbent, adsorption/desorption and dilution were optimized. Results: The method was successfully applied to determine Cd(II) in real water samples with excellent recoveries (98%). The present method has lower detection (0.29) and quantification limit (0.97 ng mL-1). Conclusion: The Ag/MgO@Fe3O4 nanocomposite based magnetic extraction is a simple, fast, reproducible, less expansive and efficient technique for the Cd(II) extraction in water samples. The developed sorbent can be recycled and reused (20 times).

Background: Recently, Derris scandens, a Thai herbal medicine with anti-inflammatory activity, is widely used as beverage and supplementary food. When the traditional medicine is a choice for health therapy, the simple and reliable equipment is required to control the suitable consuming amount of the active component. Objective: To develop the electrochemical sensor for genistein determination in Derris scandens with high sensitivity and rapid operation. Methods: An in-house screen-printed electrochemical sensor consisting of a three-electrode system was developed for genistein determination. A silver/silver chloride (Ag/AgCl) reference electrode, a carbon counter electrode and a carbon working electrode were prepared on a 0.3-mm-thick plastic substrate by the screen-printing technique using conductive ink. The dimensions of each sensor were 2.5x1.0 cm. Only 50 μL of sample solution was required on this device for the determination of genistein concentration by rapid response square wave voltammetry. Results: The oxidation peak of genistein appeared with good response in acidic media at a peak potential of 0.6 V. Moreover, the signal was enhanced by modifying the conductive carbon ink with cobalt( II) phthalocyanine. Under the optimized conditions, the linear range was found to be 2.5-150 μM and the detection limit was 1.5 μM. Moreover, the small volume extraction was successfully developed without any further pre-concentration. This proposed method was applied to determine genistein in Derris scandens with satisfying results. Conclusion: The proposed method is promising as an alternative method for genistein determination with facile and fast analysis.