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This study aimed to propose a mathematical method to investigate and optimize the simultaneous elimination process of multiple organic pollutants using the Fenton process. Hence, the treatment of rhodamine B (RB) and acid red 14 (AR14) dyes in their binary solution was studied. Multivariate curve resolution alternating least square (MCR-ALS), a novel chemometric method, was applied along with correlation constraints to resolute the UV-Vis spectrophotometric data, enabling quantification of investigated dyes despite a high spectral overlapping. Response surface methodology was adopted to assess the model and optimize individual and interactive effects of three independent factors (Fe2+, H2O2 and initial pH) on the simultaneous elimination of RB and AR14. The values of the regression coefficient for RB and AR14 were determined as 98.48 and 98.67 percent, respectively, revealing the reliability of the obtained polynomial models to predict decolorization efficiencies. Desirability function was employed to optimize the independent variables to attain the highest possible degradation performance for both dyes in their binary solution. At the optimum point of operation ([Fe2+] = 143.88 mg/L, [H2O2] = 126.89 mg/L and pH = 3.71), degradation efficiencies of RB and AR14 were found as 81.58% and 80.22%, respectively, which were nearly identical to the experimental results.

Comparative studies on esterification methods for the quantitative determination of fatty acids (FAs) were accomplished using a rotatable central composite design (RCCD). The effect of the three methylation methods on the isomerization of unsaturated fatty acids in gas chromatography analysis was also evaluated. The experimental design showed that the effect of both temperature and duration time of reaction on the recovery of methylation was significant. After optimization, the method was validated and the results for linearity, precision, and limit of detection (LOD) were presented. Methods were similar on account of the fatty acid methyl esters recovery (%) determined (91.30–96.44%). The acid-catalyzed procedures gave no isomerization of conjugated dienes and no artifacts, but artifacts were observed by using a methyl chloroformate reagent. Therefore, the optimized acid-catalyzed methylation process would be more convenient for polyunsaturated fatty acid analysis, whereas methyl chloroformate reagent would be an alternative for fast analysis.

The use of the efficient drug delivery systems in combinatorial or multi-drug treatment of complicated diseases for effective and target-specific delivery of therapeutic agents necessitates the use of the fast and reliable analytical techniques to reveal the true release profiles of the investigated drugs. The knowledge about the release kinetics of the drugs from different substrates and the effective parameters on this process can be obtained by mathematical modeling of release profiles which is a difficult and cost-effective task in multi-drug delivery processes because of the difficulty in the simultaneous determination of multiple release profiles. In this study, a kinetic-spectrophotometric analytical methodology has been proposed for the simultaneous determination of release profiles of Sumatriptan and Naproxen, two widely used drugs in migraine treatment which use MCR-ALS for the decomposition of the release data matrices. The obtained release profiles have been subjected to mathematical modeling for further determination of release mechanisms. It has been shown that the MCR-ALS effectively decomposes the data matrices (more than 97% of explained variance) and Korsmeyer–Peppas and Ritger–Peppas models can well describe the release behavior of drugs from the investigated substrate (R2 > 0.99 for both compounds and acceptable low SSE values).

The current study describes a simple method to determine four organophosphate insecticides (i.e., ethion, phosalone, diazinon, chlorpyrifos) and an isothiazolidine acaricide (i.e., hexyhiazox), as examples of pesticides in environmental water samples by stir bar sorptive extraction (SBSE). For this purpose, a self-magnetic nanocomposite monolithic (SMNM) kit coupled with high performance liquid chromatography-ultraviolet (HPLC-UV) spectroscopy was used. The size, morphology, and elemental distribution of synthesized SMNM kit were analyzed using field emission scanning electron microscopy (FESEM) coupled with energy dispersive X-ray (EDX) spectroscopy system, X-ray diffraction (XRD), and elemental mapping, respectively. An experimental design based on the central composite design (CCD) was used to optimize factors affecting SBSE. Under optimal experimental conditions, the limits of detection (LODs) were found to be in the range of 0.07 μg L−1 to 0.89 μg L−1. Linear ranges were 5-800 μg L−1 for ethion, hexythiazox, and chlorpyrifos, 1–1000 μg L−1 for phosalone, and 5–1000 μg L−1 for diazinon. The relative standard deviation (RSD%) did not exceed 5.48% and 6.45% for intraday and interday precisions, respectively. The enrichment factors (EFs) ranged from 15 to 39-fold (theoretical enrichment factor was 40-fold). The results showed that SMNM kit could enrich the above-mentioned pesticides effectively. The SMNMSBSE-HPLC-UV methodology was applied for the determination of pesticides in real water samples.

Drug delivery systems especially stimulus-responsive ones play an important role in medicinal chemistry because most of the cancer drugs have various side effects. In the present research, amine groups bonded to β-cyclodextrin (βCD) were used as a pH-sensitive cap for the cavities of magnetic mesoporous silica nanoparticles. In order to insert βCD cap on the cavities of magnetic mesoporous silica nanoparticles, a host which makes host–guest interaction with βCD was needed. Ethylene diamine chain was used as a host for βCD. Doxorubicin was loaded on Fe3O4@mSiO2@NH2 nanoparticles and then functionalized by βCD. In acidic media, the nitrogens of amine groups were protonated and the repellence among the chains gave rise to more and controlled drug release while in neutral media βCD all of the nitrogens had positive charge and these positive charges gave rise to repellence among chains. These interactions caused to open the chains, and βCD was released which in turn gave rise to the delivery of DOX. The amount of DOX loaded on the Fe3O4@mSiO2@NH2 nanoparticles surface was estimated by thermal gravimetric analysis. The results of drug delivery experiments were interesting which were investigated by ultraviolet–visible spectroscopy. To obtain the hydrodynamic diameter of Fe3O4@mSiO2@βCD, dynamic light scattering technique was used. Furthermore, the cytotoxicity of Fe3O4@mSiO2@βCD was also investigated.

The present study aims to present a new convenient sensor for heavy metals, based on aggregation of citrate-capped- N, N' biphenyl hydrazine 1, 2 dicarbothioamide (PHCA) - modified- (AuNPs). This paper reports a procedure for sensitive and selective spectrophotometric methods for simultaneous determination of mercury (Hg22+) and cadmium (Cd2+). For this aim multivariate data including kinetic spectra of AuNPs were collected during aggregation process. The characterization of AuNPs was performed by transmission electron microscopy (TEM) and Infra-Red (IR) spectroscopy. Partial least square (PLS) regression as an efficient multivariate calibration method was employed to make a connection between the surface plasmon resonance (SPR) spectra of the generated AuNPs. The number of PLS latent variables was optimized by leave-one-out cross-validation utilizing prediction residual error sum of square (PRESS). The linear range was in the range of 3.33 × 10-5 - 3.33 × 10-6 mol L-1 and 2.0 × 10-5 - 1.0 × 10-6 mol L-1, the detection limit was 1.21×10-7 and 0.5 ×10-7 mol L-1 (n=5) for Hg22+and Cd2+, respectively. This method used successfully for simultaneous determination of Hg22+ and Cd2+ in West Azerbaijan regional waters namely Zarineh / Simineh rivers and Urmia Lake.

In this work, a rapid, simple, and environmentally friendly method has been proposed for direct supramolecular microextraction of four organophosphate insecticides (ethion, phosalone, diazinon, chlorpyrifos) and an isothiazolidine acaricide (hexythiazox) in agricultural product samples prior to their determination by high-performance liquid chromatography-ultraviolet spectroscopy. These five target pesticides have been selected as models in combination with chemometrical optimization processing due to their high consumption in rice, cucumber, and tomato samples for pest control. Method is based on the extraction of pesticide residues from homogenized food sample in an aqueous media containing some tetrahydrofuran (THF) and decanoic acid (DeA). Effects of the experimental parameters, including THF volume, DeA content, salt concentration (as a measure of salting-out effect), and pH on extraction recoveries (ERs) and enrichment factors (EFs) were investigated and, then, the significant variables were optimized using central composite design (CCD) as chemometrical processing. At optimum conditions, this method has a linear response over the ranges of 0.10 to 1500 μg kg−1 for target analytes. Limits of detection (LOD) of this method were found to be in the range of 0.05 to 0.20 μg kg−1. Also, relative standard deviation (RSD) of the method was in the range of 3.45 to 12.27% and the enrichment factors ranged from 102- to 178-fold. The method was applied successfully for analysis of the pesticides in agricultural product samples.

Iodine as a mineral has great effects on public health; accordingly, there has been an urgent request for iodine selective and sensitive sensor. A colorimetric assay based on the anti-aggregation exclusive feature of gold nanoparticles is presented in this study. The proffered sensor was manufactured in regard to the interaction between thiosulfate and gold nanoparticles, and the forceful inactivation of thiosulfate by iodine. Different concentrations of iodine lead to differential inactivation of thiosulfate, which is in charge of obvious color alteration of AuNPs from blue to red. The quantification of iodine is acquired in relation to the alteration in the surface plasmon resonance absorption of the gold nanoparticles. Under the optimum condition, the limit of detection is 1.36 nmol L−1 with the linear range from 3 to 80 nmol L−1. Further utilization of the proposed colorimetric method to determine iodine in human serum presented satisfying consequence concerning selectivity and sensitivity.

The use of low-cost and eco-friendly adsorbents has been investigated as an ideal alternative to the current expensive methods of removing dyes from wastewater. In this study, not hydrolyzed poly(styrene-alternative-maleic anhydride) (PSMA) polymer have been used as new synthetic adsorbent to removal of acid red-14 dye from aqueous solutions (industrial wastes). Batch sorption studies have been carried out to determine the effect of agitation time, pH, adsorbent dose, and initial concentration of the sorbate and temperature. The effect of electrolyte interference such as $$ {\text{Na}}^{ + } $$ and $$ {\text{Cl}}^{ - } $$ on dyes removal efficiency was investigated. The acid red 14 dye showed maximal amount of sorption capacity as 5.12 mg/g at pH 6.1 and 25 °C. Equilibrium data were fitted with Langmuir and Freundlich isotherms to find the best fit, and it was found that the adsorption of this dye on adsorbents particles are monolayer and correspond to the Langmuir isotherm. Adsorption kinetics were investigated using pseudo-first-order and pseudo-second-order rate equations and kinetic data followed the pseudo-second-order rate equation for sorption of this dye on PSMA adsorbent. The application of adsorbents performance was tested with real samples which contain limit exceeded amount of foresaid dyes which had been taken from a Dyeing Factory. This study provides good background to development of dye removal in waste waters by polymeric sorbent.

Determination of pharmaceutical analytes has been subjected to many investigations, especially in transplantations in which accurate and precise detection of drugs is of importance. In this study, a simple and fast complexation reaction has been employed for simultaneous kinetic–spectrophotometric determination of two immunosuppressant drugs, mycophenolate mofetil and its active metabolite mycophenolic acid, which is based on the reaction between drugs and Fe(III) ions in the presence of sodium dodecyl sulfate as anionic surfactant by standard addition method. The effect of influential parameters including type of surfactant, concentration of Fe(III) ions and pH of the solution on the complexation reaction has been studied, and SDS was chosen as suitable surfactant, while reaction proceeds with 0.1 M Fe(III) at pH 4. Multivariate curve resolution-alternating least squares has been employed for analyzing the multiset data obtained from augmentation of resulting standard addition matrices. Values for limit of detection of method have been calculated as 4.88 and 1.62 µg mL−1 for mycophenolic acid and mycophenolate mofetil, respectively, and Beer’s law is obeyed over the concentration ranges 10–200 µg mL−1 for MPM and 50–250 µg mL−1 for MPA. The proposed method was successfully applied for determination of drugs in plasma serum samples. The accuracy and reliability of the method was further ascertained by recovery studies via standard addition procedure.

In this work a new method is presented for simultaneous colorimetric determination of morphine(MOR) and ibuprofen(IBU) based on the aggregation of citrate-capped gold nanoparticles (AuNPs). Citrate-capped gold nanoparticles were aggregated in the presence of morphine and ibuprofen. The difference in kinetics of AuNPs aggregation in the presence of morphine / ibuprofen was used for simultaneous analysis of morphine and ibuprofen. The formation and size of synthesized Au NPs and the aggregated forms were monitored by infra-Red (IR) spectroscopy and transmission electron microscopy (TEM) respectively.. By adding morphine or ibuprofen the absorbance was decreased at 520 nm and increased at 620 nm. The difference in kinetic profiles of aggregation was applied for simultaneous analysis of MOR and IBU using partial least square regression as an efficient multivariate calibration method. The number of PLS latent variables was optimized by leave-one-out cross-validation method using predicted residual error sum of square. The proposed model exhibited a high capability in simultaneous prediction of MOR and IBU concentrations in real samples. Our results showed linear ranges of 1.33â33.29 µg/mL (R2=0.9904) and 0.28â6.9 µg/mL (R2=0.9902) for MOR and IBU respectively with low detection limits of 0.15 and 0.03 µg/mL(S/N=5). Keywords: Morphine, Ibuprofen, Simultaneous determination, AuNps, Partial least squares

According to the intensive physical and mental risk of methamphetamine (crystal) on human, it is important to focus on the prevention of distribution and decrease of the usage of methamphetamine. In the current study, attempts was on the application of GC–MS analysis combined with chemometrics to present a classification model for methamphetamine samples seized in different regions of Iran. In this work, principal component analysis was not able to discriminate samples from different geographic regions. For the discrimination goal, partial least squares discriminant analysis (PLS-DA) and extended canonical variate analysis (ECVA) were utilized and a classification model was constructed to differentiate methamphetamine samples seized in three regions of Iran, i.e., south, west and central. PLS-DA showed good performance in calibration step; however, ECVA indicated better prediction ability. The difference of the classified samples can be because of difference in the synthetic root used in each of three investigated regions. Class sensitivity and selectivity for all three regions were excellent in ECVA model with nonsignificant misclassifications. Cross-validation and external validation using a test set confirmed the obtained classification model. Statistical results indicated a regional production/distribution pattern in the country.

Considering the need for detection of opioids, a colorimetric sensor array based on unmodified gold nanoparticles (AuNPs) was developed for the first time in order to sensitively detect and identify multiple structurally similar opioids including morphine, codeine, oxycodone, noroxycodone, thebaine, tramadol and methadone in aqueous media. Size dependency of assembly process encouraged us to employ AuNPs with four distinct particle sizes as sensing elements and visual differentiation tools to construct a colorimetric nanoarray. The target opioids seem to act as “molecular bridges”, shortening the interparticle distance and inducing the aggregation of AuNPs. This aggregation produces changes in both the color and UV–vis spectra of AuNPs generating a visual molecular fingerprint of each analyte. The cumulative array responses were differentiated by principal component analysis (PCA) and hierarchical cluster analysis (HCA) with 100% classification accuracy demonstrating the versatility of this simple nanoarray platform. Furthermore, color difference maps were created to provide a visual tool for classifications and semi-quantitative analysis without exploiting any statistical techniques. Finally, we demonstrated the ability of the constructed array to identify the various opioids in urine sample. The obtained results suggest that the proposed colorimetric nanoarray has promising perspective in the clinical toxicology and forensic cases for the on-spot detection of illegal drugs.

The formation of G-quadruplex (G4) structures in Human telomeric DNA (H-Telo) has been demonstrated to inhibit the activity of telomerase enzyme that is associated with the proliferation of many cancer cells. Accordingly, G-quadruplex structures have become one of the well-established targets in anticancer therapeutic strategies. And, the development of simple and selective detection platforms for G4 structures has become a significant focus of research in recent years. In this study, a simple "off-on" fluorometric method was developed for the selective detection of picomolar quantities of H-Telo G4 DNA based on a fluorescent cerium-based metal organic framework (Ce-MOF) conjugated with hemin to form the sensing probe, Hemin@Ce-MOF. The solvothermal synthesis of the Ce-MOF took advantage of 5-aminoisophtlalic acid (5AIPA) as the organic bridging ligand, (Ce2(5AIPA)3(DMF)2). Characterization of Ce-MOF and Hemin@Ce-MOF was performed by XRD, XPS, TEM, SEM, BET and FTIR techniques. The detection and quantification of the H-Telo was carried out through the adsorption/incorporation of hemin molecules on the pores and surface of Ce-MOF resulting in the fluorescent quenching of the system followed by the restoration of the fluorescence upon addition of H-Telo probably due to a competition between H-Telo and Ce-MOF to bind to hemin. The impact of the key variables including MOF quantity, hemin concentration and detection time was investigated and optimized. Under the optimized conditions, the developed probe provides a limit of detection (LOD) of 665 pM, linear dynamic range (LDR) of 1.6-39.7 nM and excellent selectivity towards H-Telo. Taken together, these results present a simple, novel and superior platform for the selective detection of H-Telo G4 DNA.

A sensitive and selective colorimetric method is presented for quantitative analysis of catechol based on the unmodified gold nanoparticles (AuNPs). In the absence of catechol, the addition of 4-mercaptophenyl boronic acid (MPBA) instigates the aggregation of AuNPs by Au–S covalent binding via self-dehydration condensation of boronic acid groups and causes a noticeable color alteration of AuNPs from wine red to blue. In the presence of catechol, boronic acid–diol binding is preferred than to the self-dehydration condensation. An increase in catechol concentration alleviates AuNPs aggregation by decreasing the amount of free MPBA, and solution color changes from blue to red. Therefore, the concentration of catechol can be detected with the naked eye or by an ultraviolet–visible spectrophotometer. Central composite design and response surface methodology were executed to evaluate interactions among variables. Due to the preference for the binding of 1,2-diol to boronic acid, this method showed high selectivity for catechol determination compared to dihydroxybenzene isomers with a linear response range of 0.87–56 µmol L−1 with a detection limit of 0.41 µmol L−1. The proposed colorimetric sensing method exhibits the advantage of no necessity for surface modification of AuNPs, avoids tedious separation processes and enables rapid assays. A highly sensitive sensing platform for catechol was established based on the anti-aggregation of AuNPs without prior modification through a competition reaction of boronic acid–diol binding between 4-mercaptophenyl boronic acid (MPBA) and catechol against the self-dehydration condensation of MPBA.

In this work, we developed a low-cost, rapid, simple and sensitive analytical method for the visual and fluorescence detection of arginine based on the inner filter effect (IFE) of gold nanoparticles (AuNPs) on the fluorescence of CdS quantum dots (QDs). The proposed sensing system consists of AuNPs and fluorescent CdS QDs, where CdS QDs function as fluorometric reporters, and AuNPs serve a dual function as fluorescence quenchers and colorimetric reporters in the probe. The fluorescence of L-cysteine capped CdS QDs was significantly quenched by citrate-stabilized AuNPs via the IFE. Upon addition of arginine the IFE of AuNPs on the fluorescence of CdS QDs was weakened and the fluorescence intensity was recovered, since arginine could induce the aggregation of AuNPs accompanied by a color change from red to blue, which resulted in turn-on of the IFE-decreased fluorescence of CdS QDs. Under the optimum conditions, the fluorescence intensity of the CdS QDs/AuNP system was proportional to the concentration of arginine in the range of 7–215 μg L−1, with a detection limit of 2.4 μg L−1. The sensing platform had been used for arginine detection in human serum and arginine injection samples with satisfactory results.

The electrochemical behavior of tramadol (TRA) on magneto layer double hydroxide (LDH)/Fe3O4@glassy carbon electrode (LDH/Fe3O4@GCE) was evaluated. Some theoretical thermodynamic and kinetic parameters were also determined using chronoamperometric and voltammetric methods. The ability of the modified electrode to determine trace amounts of TRA was studied using differential pulse voltammetry (DPV) as a sensitive electrochemical method. For characterizing and investigating the performance of LDH/Fe3O4@GCE, various methods including scanning electron microscopy (SEM), X-ray diffraction (XRD), cyclic voltammetry (CV), and DPV were used. The effect of pH, scan rate, and time on the voltammetric response of TRA were investigated. Under the optimized conditions, the anodic peak current was linear for the concentration of TRA in the range 1.0–200.0 μmol L−1 with the detection limit of 3.0 × 10−1 μmol L−1. This method was also successfully used to detect the concentration of TRA in human serum and urine samples.

A new convenient colorimetric sensor for fructose based on anti-aggregation of citrate-capped gold nanoparticles (AuNPs) is presented. 4-Mercaptophenylboronic acid (MPBA) induces the aggregation of AuNPs, leading to a color change from red to blue. Fructose as a potent competitor has strong affinity for MPBA and a borate ester is formed between MPBA and fructose. There is an obvious color change from blue to red with increasing the concentration of fructose. The anti-aggregation effect of fructose on AuNPs was seen by the naked eye and monitored by UV–vis spectra. Our results showed that the absorbance ratio (A 519 /A 640 ) was linear with fructose concentration in the range of 0.032–0.96 mmol/L ( R 2 = 0.996), with a low detection limit of 0.01 mmol/L (S/N = 3). Notably, a highly selective recognition of fructose was shown against other monosaccharide and disaccharide (glucose, mannose, galactose, lactose and saccharose). With anti-aggregation assays higher selectivity is achievable. The results of this work provide a rapid method for evaluating the quantitative analysis of fructose in human plasma at physiologically meaningful concentrations and at neutral pH. The proposed procedure can be used as an efficient method for the precise and accurate determination of fructose.

Au nanoparticles (AuNPs) are increasingly utilized as sensitive (bio) chemical probes due to their exceptional physicochemical properties and ease of functionalization. AuNPs, when functionalized with proper ligands, allow the development of highly selective colorimetric sensor. The aim of this paper was to discuss the usage of a reliable and sensitive colorimetric sensor, for sensing dissolved acetone based on the l-cysteine capped gold nanoparticles. The AuNPs were modified with l-cysteine through Au–S bonds. Acetone adsorbs on the surface of l-cysteine-AuNPs and induces the aggregation of AuNPs, due to the strong hydrogen-bonds formed between cysteine and acetone. Upon the addition of Acetone, the solution showed a color change from red to blue, which was also monitored by visible spectra. Under optimum conditions, acetone was detected at concentrations higher than 6.5 × 10−7 mol L−1, with a linear range from 1.0 × 10−6 to 6.1 × 10−5 mol L−1. The relative standard deviation for six replicates determinations of 2.0 × 10−5 mol L−1 of acetone was calculated to be 1.2 %.The selectivity was investigated by assaying some potentially interfering chemicals.

Reuse of polyethylene terephthalate (PET) bottles for storage of water and liquid food is so common in some countries of the world. However, it can result in the migration of plastic components or additives into the stored liquids and threatening of human health. In this respect, the present study developed a method for determination of endocrine disrupting chemicals (EDCs) that might be released from reused disposable plastic containers. The proposed method relied on the extraction of the phthalic acid esters (PAEs) and plastic additives by a self-magnetic nanocomposite monolithic (SMNM) kit and their determination by gas chromatography/mass spectroscopy (GC/MS). Extraction of the target analytes by the self-magnetic nanocomposite monolithic stir bar sorptive extraction (SMNMSBSE) method was optimized systematically by evaluating the effect of extraction time, ionic strength, stirring rate, desorption time and desorption solvent on the process. Analysis of different water and liquid food samples with various pH value and matrices unraveled that the acidic liquids and the samples stored at higher temperature have a greater chance of contamination by the released EDCs. Also, low-quality plastic bottles were found to release more plastic additives into the stored liquids. At the optimal conditions, the method demonstrated a linear response from 0.01 to 1000 µg L−1 and provided the limits of detection (LODs) of 0.008–1.000 µg L−1. Furthermore, the relative standard deviation (RSD) of the method did not exceed 10.05% and 8.12% for interday and intraday precision, respectively. In general, the results of this study indicated that the synthesized SMNM kit can effectively enrich the migrated plastic additives and the developed SMNMSBSE-GC/MS methodology is efficient for analysis of the target EDCs.

Driven by the need to detect narcotics, a new and simple colorimetric assay is presented for the sensitive and visual detection of morphine (MOR) and codeine (COD) using melamine modified gold nanoparticles (MA–AuNPs). Hydrogen-bonding interactions between melamine and the drugs induce aggregation of the AuNPs with a consequent color change from wine red to blue, which can be monitored by a UV-vis spectrophotometer or even the naked eye. Furthermore, we demonstrated the practicality of using mean centering of ratio spectra (MCRS) to remove the contribution of the reagent blank and obtain the net analyte signal in nanoparticle-based colorimetric assays, an aspect which appears to have received no attention to date. This procedure gives more accurate results than the conventional approach using the absorption ratio at maximum wavelength of the aggregated state to the dispersion state (Aagg/Adis). Comparison of the proposed method with the usual method reveals that MCRS slightly improves the figures of merit of the colorimetric assays. The systems exhibited a linear range from 0.07 to 3 μM for MOR and from 0.03 to 0.8 μM for COD using MCRS. Detection limits (3σ/m) of 17 and 9 nM were achieved for MOR and COD, respectively, which are much lower than the therapeutic plasma/serum concentrations and cutoff levels for opiates in urine samples set by the National Institute on Drug Abuse (NIDA). Furthermore, we demonstrate the application of the approach in biological fluids and pharmaceuticals, which suggests that the present assay could satisfy the requirements of clinical toxicology and forensic cases.

In this work, an application of mean centering of ratio spectra is proposed to the study of pollutant dyes degradation using Fenton reaction. Two-way kinetic-spectrophotometric data related to dye(s) mixtures degradation are divided into simulated kinetic profiles, mean centered and their ranks were monitored versus simulated dye degradation constant. For accurate dye degradation constant(s), the rank of resulted matrix will be reduced by one. By this search, all kinetic constants related to all included dyes are acquired. To find out which k values are related to the degradation of dye of interest, a preliminary deflation of data from its contribution is done and the procedure is repeated. By this search, the kinetic constant related to dye of interest will be omitted while others will be remained. The applicability of the proposed method was evaluated using model data. Finally, second-order kinetic-spectrophotometric data in the degradation of malachite green in the presence of crystal violet and methylene blue were analyzed by the proposed method as a real system.

In this work a new coacervative extraction method using pH-sensitive hydrogel has been developed for preconcentration and spectrophotometric determination of Cu (II) based on the complex formation with Zincon (2-carboxy-2″-hydroxy-5″-sulfoformazylbenzene) in water samples. In the extraction step, appropriate amounts of poly (styrene-alt-maleic anhydride), as a pH-sensitive hydrogel, was added into the aqueous solution, so a rather cloudy solution was formed. Organic and inorganic compounds having the potential to interact with polymer particles could be extracted into the organic phase. The surface area between the polymer particles and the aqueous sample becomes very large, so the equilibrium state is achieved quickly. After centrifuging, hydrogel-rich phase was sedimented in the bottom of sample tube. The sedimented phase was diluted with methanol and the absorbance of the solution was measured at 615 nm (λ max of the complex in hydrogel media). Central composite design (CCD) was performed at five levels to optimize the main experimental parameters including, concentration of hydrogel, HCl, Zincon and salting-out effect. Under the optimum conditions the linear analytical range was 5–500 ng mL−1 with a correlation coefficient of 0.991. The limit of detection was 3.4 ng mL−1. The proposed method is an efficient, rapid, simple and inexpensive microextraction technique and was successfully applied for the determination of copper in various water samples.

Synthesis and characterization of polyaniline-grafted poly(styrene-alt-maleic anhydride) (PANI-g-PSMA) was carried out to obtain conductive comb copolymers with highly improved processability. First, polyaniline (PANI) was prepared in nano-scale by chemical synthesis under ultrasonic irradiation. Then the poly(styrene-alt-maleic anhydride) (PSMA) was synthesized by free radical polymerization. Moreover, the PANI was grafted on the PSMA backbone to prepare a comb-like conductive copolymer for improving its processability as a new method. The products were characterized by Fourier transform infrared, ultraviolet–visible spectroscopy and X-ray diffraction patterns. Morphology of the samples was also investigated by scanning electron microscopy images. Finally, the solubility and conductivity of the products were studied, and it resulted in high solubility of the products in water and other common organic solvents in comparison to the pure PANI. Copyright © 2015 John Wiley & Sons, Ltd.

 A dispersive liquid-liquid microextraction (DLLME) process based on the complexation reaction of Cu(II) with diethyldithiocarbamate (DDTC) from aqueous solutions was investigated. The effect of various experimental parameters in the extraction such as, dispersive solvent, extracting solvent, the volume of extraction and disperser solvent, pH of the aqueous solution, ionic strength and extraction time were optimized using one variable at a time method, and the analytical charactristics of the method were obtained. Under the optimum conditions the calibration graph was linear over the range 0.01 to 0.1 μg mL-1 of Cu(II) ion with a correlation coefficient of 0.994. The limit of detection (S/N = 3) was 8.6 × 10-3 μg mL-1. Relative standard deviation (RSD) for 7 replicate determinations of 0.08 μg mL-1 Cu(II) was 3.3%. In this work, the concentration factor of 20 and also the improvement factor of 33 were reached. The interference effect of some anions and cations was also tested. The extraction method has been successfully applied to the determination of copper in human blood serum sample.

The importance of stereochemistry in chiral drugs is due to the different pharmacological behavior of enantiomers. Enantioseparation methods based on nanoparticles have gained interest recently. Different interactions of enantiomers with chiral nanoparticles encouraged us to determine the enantiomeric percentage of racemic mixtures with modified gold nanoparticles. In this work we applied L-cysteine capped gold nanoparticles (chiral environment) as a colorimetric sensor for enantio-selective detection of naproxen (NAP) racemic mixtures. The selective and rapid aggregation of modified gold nanoparticles in the presence of R-naproxen allowed us to construct a visual chiral sensor. The results were characterized by TEM, UV-visible, zeta potential and FT-IR measurements. L-Cysteine group functionalized gold nanoparticles (L-Cys-Au NPs) had a cooperative effect on visual inspection of R-naproxen in aqueous solution resulting in sensible changes in color and absorption specifications over S-naproxen. The effect can be monitored by the naked eye or using a UV-vis spectrometer. The developed method was utilized for the determination of enantiomeric percentage of racemic mixtures of NAP in aqueous and plasma samples with satisfactory results. Under optimum conditions, the chiral biosensor exhibited a good linear response to naproxen enantiomers in the concentration range of 10 to 200 μM with a limit of detection of 6.02 μM (S/N = 3). The relative standard deviation (R.S.D.) in water was 3.8% (n = 7).

Herein, a rapid, sensitive and selective approach for the colorimetric detection of dopamine (DA) was developed utilizing unmodified gold nanoparticles (AuNPs). This assay relied upon the size-dependent aggregation behavior of DA and three other structurally similar catecholamines (CAs), offering highly specific and accurate detection of DA. By means of this study, we attempted to overcome the tedious procedures of surface premodifications and achieve selectivity through tuning the particle size of AuNPs. DA could induce the aggregation of the AuNPs via hydrogen-bonding interactions, resulting in a color change from pink to blue which can be monitored by spectrophotometry or even the naked-eye. The proposed colorimetric probe works over the 0.1 to 4 μM DA concentration range, with a lower detection limit (LOD) of 22 nM, which is much lower than the therapeutic lowest abnormal concentrations of DA in urine (0.57 μM) and blood (16 μM) samples. Furthermore, the selectivity and potential applicability of the developed method in spiked actual biological (human plasma and urine) specimens were investigated, suggesting that the present assay could satisfy the requirements for clinical diagnostics and biosensors.

In the present work the removal of two azo dyes, methylene blue and methyl orange, from water using a synthesized hydrogel entitled poly (styrene-alt-maleic acid) is investigated. Superabsorbent hydrogel poly (styrene-alt-maleic anhydride) was prepared through a thermally initiated free-radical polymerization of styrene and maleic anhydride. The parameters affecting the adsorption of the studied dyes such as pH of the solution, hydrogel dose and contact time were investigated. The dye adsorption process was monitored spectrophotometrically. For this purpose the spectrophotometric linear range of both dyes were obtained and the removal experiments were done at the middle of the linear range. At the optimum conditions, 80–95 % of the mentioned dyes could be removed in less than 10 min which provides strong evidence of the potential of synthesized hydrogel for the application in azo dyes removal from water.

In this work a new synthetic hydrogel was applied to the synthesis of gold nanoparticles (GNPs). Poly(styrene-alt-maleic acid) pH-sensitive hydrogel, bearing negatively charged COO− groups, was used for this purpose. There was no need for the additional reducing agent and surfactant for the synthesis of GNPs. The optimum conditions for synthesis of the GNPs were obtained by studying the effects of pH and concentration of hydrogel. The structure, size and morphology of the synthesized GNPs were investigated by UV–vis spectra and transmission electron micrograph (TEM), respectively. In addition, the interactions between synthesized GNPs with several drugs such as acetaminophen (ACET), ascorbic acid (AA) and folic acid (FA) were studied. The results showed that the synthesized GNPs can be used as a new and highly efficient spectrophotometric sensor for the selective recognition and monitoring of three drugs in real samples such as serum samples. The sensitivity and selectivity of GNPs toward other drugs as potential interferents were also studied. The linear ranges for the spectrophotometric determination of ACET, AA and FA were calculated as well. Limit of detection (calculated as 3 times of standard deviation of blank) were obtained as 1.8 × 10−6 M, 2.7 × 10−7 M, 2 × 10−6 M for ACET, AA and FA, respectively. The proposed method was successfully used to the determination of ACET, AA and FA in various serum samples.

In this work we report an easy and simple green synthesis method for gold nanoparticles (GNPs) using willow tree bark extract. Willow tree bark includes aspirin, which acts as a reducing agent. In the present method, there is no need to add any stabilizing agent such as a surfactant to stabilize the synthesized GNPs. Therefore, as an alternative to chemical synthesis, the green synthesis of GNPs with willow tree bark extract is beneficial for its potential biological and medical applications. The optimum conditions for GNP synthesis were obtained by studying the pH and the amount of willow tree bark extract solution. The characteristics and morphologies of GNPs were investigated by UV-Vis spectroscopy and transmission electron microscopy. The interaction between the synthesized GNPs and cysteine was introduced as a new and high-potential colourimetric sensor for the selective recognition and monitoring of cysteine, among other amino acids. The sensitivity and selectivity of GNPs toward cysteine in comparison to other amino acids were studied.