Linear Range Of Calibration Curve Research Articles

A simple and sensitive LC-MS/MS method for the determination of loganic acid in rat plasma and its pharmacokinetic analysis.

Loganic acid is an iridoid compound extracted from Gentianaceae plant Gentiana macrophylla Pall. It can effectively inhibit inflammation and tumor migration and has antioxidant activity. In this paper, we establish a simple, fast, sensitive and validated LC-MS method with the purpose of quantification of loganic acid in rat plasma with gliclazide as an internal standard (IS). Methanol was used to precipitate the protein in the plasma sample, and a C18 column (2.1 × 50 mm, 1.7μm) was used for the separation of the target compound. Meanwhile, 0.1% formic acid water-methanol was employed as the mobile phase. Multiple reaction monitoring detection mode was adopted in detection with m/z 375.1 > 213.2 for loganic acid and m/z 322.1 > 169.9 for the IS, respectively, in negative ion scan mode. The linear range of calibration curve was 5.77-11,540.00 ng/ml, and the lower limit of detedtion was 2.89 ng/ml. The inter-day and intra-day precision and accuracy were <15% for lower limit of quantitation, low, middle and high quality control samples. This method was successfully used for the pharmacokinetic study of loganic acid in rat plasma at a dose range of 50-150 mg/kg for oral administration and 2mg/kg for intravenous administration. The pharmacokinetic results showed that the oral bioavailability of loganic acid was low (2.71-5.58%).

Multiplexed Anodic Stripping Voltammetry Detection of Heavy Metals in Water Using Nanocomposites Modified Screen-Printed Electrodes Integrated With a 3D-Printed Flow Cell.

In this study, we present multiplexed anodic stripping voltammetry (ASV) detection of heavy metal ions (HMIs)—As(III), Cd(II), and Pb(II)—using a homemade electrochemical cell consisting of dual working, reference and counter screen-printed electrodes (SPE) on polyimide substrate integrated with a 3D-printed flow cell. Working and counter electrodes were fabricated by the screen-printing of graphite paste while the Ag/AgCl paste was screen-printed as a reference electrode (Ag/AgCl quasi-reference electrode). The working electrodes were modified with (BiO)2CO3-reduced graphene oxide (rGO)-Nafion [(BiO)2CO3-rGO-Nafion] and Fe3O4 magnetic nanoparticles (Fe3O4MNPs) decorated Au nanoparticles (AuNPs)-ionic liquid (IL) (Fe3O4-Au-IL) nanocomposites separately to enhance HMIs sensing. Electrochemical detection was achieved using square wave ASV technique. The desired structure of the flow electrochemical cell was optimized by the computational fluid dynamic (CFD). Different experimental parameters for stripping analysis of HMIs were optimized including deposition time, deposition potential and flow rate. The linear range of calibration curves with the sensing nanocomposites modified SPE for the three metal ions was from 0–50 μg/L. The limits of detection (S/N = 3) were estimated to be 2.4 μg/L for As(III), 1.2 μg/L for Pb(II) and 0.8 μg/L for Cd(II). Furthermore, the homemade flow anodic stripping sensor platform was used to detect HMIs in simulated river water with a 95–101% recovery, indicating high selectivity and accuracy and great potential for applicability even in complex matrices.

A Novel Surfactant Sensitized Fluorescent Sensor for Co(II) Based on Nitrogen Doped Carbon Quantum Dots

A novel nitrogen-doped carbon quantum dots (N-CDs) were prepared by the microwave irradiation method. The fluorescence quenching effect of Co(II) on the N-CDs was studied in the sodium dodecyl sulfate (SDS) medium and the fluorescence quenching was sensitized in the SDS. The linear range of calibration curve for the determination of Co(II) was 0.17µg/mL-11.8µg/mL and the limit of detection was 0.052µg/mL. The method has been applied for the determination of Co(II) in samples with satisfactory results.

Quantitative detection of ricin in beverages using trypsin/Glu-C tandem digestion coupled with ultra-high-pressure liquid chromatography-tandem mass spectrometry.

The toxic protein of ricin has drawn wide attention in recent years as a potential bioterrorism agent due to its high toxicity and wide availability. For the verification of the potential anti-terrorism activities, it is urgent for the quantification of ricin in food-related matrices. Here, a novel strategy of trypsin/Glu-C tandem digestion was introduced for quantitative detection of ricin marker peptides in several beverage matrices using isotope-labeled internal standard (IS)-mass spectrometry. The ricin in beverages was captured and enriched by biotinylated anti-ricin polyclonal antibodies conjugated to streptavidin magnetic beads. The purified ricin was cleaved using the developed trypsin/Glu-C tandem digestion method and then quantitatively detected by ultra-high-pressure liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) with isotope-labeled T7A and TG11B selected as IS.The use of trypsin/Glu-C digestion allows shorter peptides, which are more suitable for MS detection, to be obtained than the use of single trypsin digestion.Under the optimized tandem digestion condition, except for T7A in the A-chain, two resulting specific peptides of TG13A, TG28A from the A-chain and two of TG11B, TG33B from the B-chain were chosen as novel marker peptides with high MS response. The uniqueness of the selected marker peptides allows for unambiguous identification of ricin among its homologous proteins in a single run. The MS response of the four novel marker peptides is increased by more than 10 times compared with that of individual corresponding tryptic peptides. Both the marker peptides of A-chain T7A and B-chain TG11B were selected as quantitative peptides based on the highest MS response among the marker peptides from their individual chains. The limit of detection (LOD) of ricin is 0.1ng/mL in PBS and 0.5ng/mL in either milk or orange juice. The linear range of calibration curves for ricin were 0.5-300ng/mL in PBS, 1.0-400ng/mL in milk, and 1.0-250ng/mL in orange juice. The method accuracy ranged between 82.6 and 101.8% for PBS, 88.9-105.2% for milk, and 95.3-118.7% for orange juice. The intra-day and inter-day precision had relative standard deviations (%RSD) of 0.3-9.4%, 0.7-8.9%, and 0.2-6.9% in the three matrices respectively. Furthermore, whether T7A or TG11B is used as a quantitative peptide, the quantitative results of ricin are consistent. This study provides not only a practical method for the absolute quantification of ricin in beverage matrices but also a new strategy for the investigation of illegal use of ricin in chemical weapon verification tasks such as OPCW biotoxin sample analysis exercises.

Potential Cytotoxicity, Pharmacokinetics, and Excretion Properties of Sapindoside B from the Seeds of Nigella sativa var. hispidula.

The seeds of Nigella sativa var. hispidula are widely used in food preparation by the Uighur people in western China. Recently, series of oleanane triterpenoid saponins were extracted from the seeds of Nigella sativa var. hispidula, especially α-hederin as representative that exhibited strong antitumor activity. Compared to α-hederin, sapindoside B has just 1 more terminal xylopyranose in the 3-O position and displays similar effects against various human cancer cell lines with cisplatin. Considering this potential cytotoxic activity, a reliable LC-MS/MS method was developed to quantify sapindoside B in rat plasma, urine, and feces. Chromatographic separation was conducted on an Agilent Zorbax SB-Aq (3.0 × 150 mm, 3.5 µm) column via an isocratic elution procedure with acetonitrile and water containing 0.1% formic acid. Mass spectrometric detection was coupled with an electrospray ionization source in the MRM mode. The linear range of calibration curves was 15 ~ 3000 ng/mL in plasma/urine and 30 ~ 3000 ng/g in feces. The intra-day and inter-day precision was less than 11.1%, and accuracy ranged from 92.2% to 108.7%. The proposed method was validated and shown to be reliable, precise, and accurate and was successfully applied to its pharmacokinetics and excretion studies. Sapindoside B exhibited dosage-dependent pharmacokinetics in the range of 2.5 mg/kg to 12.5 mg/kg, and only about 2% of intravenous dose of sapindoside B was excreted by the feces and urine in its unchanged form over 48 h. These results provide further data support for evaluating the druggability of sapindoside B.

Determination of Lisinopril in Bulk and Pharmaceutical Formulations by Cloud Point Extraction—A Green Method

A sensitive and eco-friendly method was developed for the spectrophotometric determination of Lisinopril (LSP) in bulk and pharmaceutical formulations by cloud point extraction technique. The method was based on the formation of a blue-colored coordination complex between Lisinopril (LSP) and Cobalt Thiocyanate (CTC) at a suitable pH. The Complex in aqueous medium was extracted into surfactant layer by cloud point extraction using a non-ionic surfactant Triton X-114 and then the surfactant layer was dissolved in a suitable volume of ethanol and the amount of Lisinopril was determined spectrophotometrically at a wavelength of 625 nm. The conditions like concentration of the drug, concentration of CTC and of Triton X-114, PH, etc. were optimized by OFAT (One Factor At a Time) method. The linear range of calibration curve was 1 - 6 μg/ml and the linear regression equation with a correlation coefficient of 0.99996 was y = 0.0021 + 0.084x. Preconcentration and enrichment factors were found to be 100 and 3.12 respectively, achieving the detection limit of 0.0588 μg/ml. The proposed method was successfully applied for the determination of LSP in the drug formulations. The obtained values were in agreement with the values as quoted by the manufacturers.

APPLICATION OF RESPONSE SURFACE MODELING FOR OPTIMIZATION AND DETERMINATION OF MALONDIALDIALDEHYDE BY VORTEX-ASSISTED DISPERSIVE LIQUID-LIQUID MICROEXTRACTION AND GC-FID

An analytical method based on vortex-assisted dispersive liquid-liquid microextraction and gas chromatography-flame ionization detection is presented for the extraction and determination of malondialdehyde (MDA) in blood plasma of human. Various parameters affecting the extraction efficiency such as type and volume of extraction and dispersive solvents, vortex and centrifuge times, volume, ionic strength and pH of the sample solution were evaluated using, one-variable-at-a-time and response surface methodology. In order to optimize the MDA extraction and determination, seven factors in five- levels were used for design of experiments (DOE), slider optimum extraction condition, this method showed linear range of calibration curve between 10-1150 mu g L--(1). The detection limit of the proposed method was found to be 0.8 mu g L(-1 )with a relative standard deviation better than 5.5 (n=10) for blood serum samples. Enrichment factor was calculated to be 175 fold and the total analysis time including microextraction was about 13 min. The method was successfully applied for the analysis of MDA in blood plasma of human.

Application of response surface methodology to optimize pipette tip micro-solid phase extraction of dyes from seawater by molecularly imprinted polymer and their determination by HPLC

In this paper, a novel pipette tip micro-solid phase extraction based on molecularly imprinted polymer as a selective sorbent was developed and applied for extraction, pre-concentration and high-performance liquid chromatographic determination of trace amounts of malachite green (MG), rhodamine B (RB), methyl orange (MO) and acid red 18 (AR) dyes in seawater samples. Different parameters affecting the extraction efficiency such as type and volume of eluent solvent, sample volume, number of cycles of extraction and desorption, amount of sorbent and pH of the sample solution were evaluated using one-variable-at-a-time and response surface methodology. In order to optimize dyes extraction, seven factors in three levels were used for Box–Behnken experimental design. Under optimum extraction condition, pH of sample solution was 3.1 for MG, 3.0 for RB, 7.1 for MO and 6.1 for AR; volume of eluent solvent (HCl, 0.5 mol L−1) was 200 µL; volume of the sample solution was 10 mL (for MG) and 4 mL (for RB, MO and AR); the concentration of triton X-114 was 0.085 (MG), 0.10 (RB), 0.08 (MO) and 0.075 (AR) % v/v; the number of extraction cycles was 10 (MG), 6 (RB), 5 (MO) and 7 (AR); the number of elution cycles was 10, 6, 5 and 9, respectively, for MG, RB, MO and AR; NaCl concentration was 0.4 mol L−1; and amount of MIP was 2.0 mg for all dyes. The linear range of calibration curves was 0.5–250.0 µg L−1 for malachite green and methyl orange and 0.5–150.0 µg L−1 for both rhodamine B and acid red 18. The detection limits calculated to be 0.083, 0.10, 0.12 and 0.17 µg L−1 for MG, RB, MO and AR, respectively. The developed protocol was successfully used for determination of dyes in seawater of Chabahar Bay. The mean recoveries were ranged between 76.1 and 97.3% by mean relative standard deviations of 1.2–7.1%.

Fundamental Study of Behaviors of In-Source Collision Induced Dissociation and Shifting the Linear Range of Calibration Curves of Various Drugs and the Metabolites Used for Therapeutic Drug Monitoring

Therapeutic drug monitoring (TDM) is a clinical practice that designs personalized medication for patients with blood concentrations of the drug. TDM approach is used for many drugs, including immunosuppressant, antifungal, antiarrhythmic, and anti-cancer drugs. Combination therapies are often adopted in TDM. Liquid chromatography tandem mass spectrometry (LC-MS/MS) is a useful analytical method in such cases. However, the development of a simultaneous LC-MS/MS analytical method is difficult owing to the differences in MS sensitivity and the therapeutic range of each drug. In order to avoid saturation of the detector, in-source collision induced dissociation (CID) was used to reduce the ion inlet. In this study, we investigated the in-source CID behavior of 13 compounds of drugs and metabolites in TDM practice. As a result, all compounds provided a sharp reduction of ion inlet over the threshold ion guide voltage. In addition, a shift to the higher concentration of the calibration range was observed according to such changes. The intensity and linearity data in this study that all 13 drugs could be analyzed under in-source CID conditions simultaneously. These results might be useful for TDM of combination therapy in clinical practice.

A Deep Eutectic Solvent as an Extraction Solvent to Separate and Preconcentrate Parabens in Water Samples Using in situ Liquid-Liquid Microextraction

In this study, an in situ deep eutectic solvent-liquid-liquid microextraction method together with high performance liquid chromatography was developed for the determination of parabens in aqueous sample. The hydrophobic deep eutectic solvent, formed in situ by the DL-menthol and decanoic acid was used as the extraction solvent. Various parameters affecting the extraction efficiency including the composition of deep eutectic solvent, temperature of sample solution, extraction time, solution pH and salt concentration were investigated and optimized. Under the optimum conditions, the linear range of calibration curves was in the range of 3-1000 ng mL-1. The limits of detection and limits of quantification were in the range of 0.6-0.8 and 2.0-2.5 ng mL-1, respectively. The relative standard deviations were less than 7.2% for both intra-day and inter-days analysis. Finally, the proposed method was successfully applied to determine four parabens in environmental water samples with acceptable recoveries.

Multifunctional Bismuth Oxychloride/Mesoporous Silica Composites for Photocatalysis, Antibacterial Test, and Simultaneous Stripping Analysis of Heavy Metals.

The increasing complexity of environmental pollution nowadays poses a severe threat to the public health, which attracts considerable attentions in searching for nanomaterials of multiproperty. In this study, mesoporous silica of KIT-6-encapsulated bismuth oxychloride (BiOCl), an intrinsically multifunctional material exhibiting bunched structure in the composites, are facilely prepared under hydrothermal conditions. Subsequently, the produced materials of multifunctionality were applied for photocatalysis, antibacterial test, and simultaneous determination of heavy metals including lead and cadmium. A combination of physiochemical characterizations have revealed that the BiOCl–KIT-6 composites exhibit enlarged yet refined surface morphology contributing to the improved photocatalytic ability with a band gap of 3.06 eV at a molecular ratio of 8Bi–Si. Moreover, the antibacterial activities of our BiOCl–KIT-6 composites were explored, and possible antimicrobial mechanism related to the production of reactive oxygen species was discussed. Furthermore, a sensitive electrochemical determination of heavy metals of lead and cadmium using square-wave anodic stripping voltammetry was also achieved. The composites-modified glassy carbon electrode displays a linear range of calibration curve from 0.2 to 300 μg/L with a detection limit of 0.05 μg/L (Pb2+) and 0.06 μg/L (Cd2+), respectively.

Application of central composite design for methyl red dispersive solid phase extraction based on silver nanocomposite hydrogel: Microwave assisted synthesis

In this study microwave irradiation was used to synthesis the silver nanocomposite hydrogel and the usefulness as an adsorbent for the preconcentration, extraction and determination of methyl red (MR) from water by dispersive solid phase extraction method was evaluated. For this purpose, silver nanocomposite hydrogel (SNH) was synthesized and characterized by thermo-gravimetric (TG) analysis, FT-IR, TEM and SEM images. The effects of some important variables such as centrifuge time (min), the pH of the methyl red solution, amount of adsorbent (g), acetone volume (mL) and chloroform volume (mL) on methyl red removal were studied using central composite design (CCD) and the optimum experimental conditions were evaluated by the desirability function (DF) combined response surface methodology (RSM). Under the optimal experimental conditions, the detection limit was found to be 1.4μgmL−1 for MR adsorption. The limit of quantification and the linear range of calibration curve were 4.6μgmL−1 and 0.1–25μgmL−1, respectively.

Solid-phase extraction disk based on multiwalled carbon nanotubes for the enrichment of targeted pesticides from aqueous samples.

A sensitive method for the determination of six varying polarity pesticides (imidacloprid, acetamiprid, carbendazim, simazine, linuron, and tebufenozide) based on a solid-phase extraction disk with multiwalled nanotubes is proposed.A dispersion of multiwalled nanotubes in a surfactant aqueous solution (Triton X-100) was used for the preparation of the solid-phase extraction disk. The effect of surfactant on the functional groups of multiwalled nanotubes was examined by applying temperature-programmed desorption. It was found that this treatment increased the amount of oxygen groups of treated multiwalled nanotubes comparing with untreated ones. The factors that may influence the adsorption and recovery such as the kind and volume of eluent, volume, flow rate and pH of sample were investigated and optimized. Under the optimized conditions, the maximal enrichment factors for low polar pesticides are ranging from 4000 to 4985 and for more polar are 2250 and 2750. The linear range of calibration curves was 10-500ng/L with correlation coefficient higher than 0.9960, and the detection limit was 6.2-23.7ng/L. Finally optimized method was applied for determination trace level of five out of six pesticides in tap and river water samples with good recovery.

Simultaneous quantification of four metabolites of sulfur mustard in urine samples by ultra-high performance liquid chromatography-tandem mass spectrometry after solid phase extraction

Four HD urinary metabolites including hydrolysis metabolite thiodiglycol (TDG), glutathione-derived metabolite 1,1′-sulfonylbis[2-S-(N-acetylcysteinyl)ethane] (SBSNAE), as well as the β-lyase metabolites 1,1′-sulfonylbis[2-(methylsulfinyl)ethane] (SBMSE) and 1-methylsulfinyl-2-[2-(methylthio) ethylsulfonyl]ethane (MSMTESE) are considered as important biomarkers for short-term retrospective detection of HD exposure. In this study, a single method for simultaneous quantification of the four HD metabolites in urine samples was developed using ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC–MS/MS). The four urinary metabolites were simultaneously extracted from urinary samples using a solid phase extraction (SPE) method with high extraction recoveries for all four metabolites varied in the range of 71.1–103% followed by UHPLC–MS/MS analysis. The SPE is simple and high effective only requiring 0.1mL of urinary samples and 0.5h time consuming. The problem of previous co-elution of TDG and SBSNAE in UHPLC was well solved, and complete separation of TDG, SBSNAE, SBMSE and MSMTESE from SPE-processed urine matrix was obtained to increase specificity and sensitivity. A full method validation was performed for each analyte in urine matrix. The linear range of calibration curves for the four analytes were respectively from 0.50–500ngmL−1 for TDG and SBSNAE, 0.05–500ngmL−1 for SBMSE and MSMTESE with coefficient of determination value (R2) ≥0.990. The limit of detection was 0.25ngmL−1 for TDG and SBSNAE, 0.01ngmL−1 for SBMSE and MSMTESE spiked in normal urine. The intra/inter-day precision for each analyte at three QC levels had relative standard deviation (%RSD) of ≤10.3%, and the intra/inter-day accuracy ranged between 88.0–108%. This developed method allows for simultaneous and trace measurement of four HD urinary metabolites within one single determination with the lowest usage amount of urine samples over all previous methods This study provides a useful tool for early diagnosis and monitoring of HD poisoning for medical treatment with high confidence, avoiding the need for application of several analysis methods.

Ultrasonically accelerated synthesis of silver nanocomposite hydrogel based on salep biopolymer: application in Rhodamine dye adsorption

Silver nanocomposite hydrogel (SNH) based on poly(acrylic acid) grafted onto salep was prepared without initiator and under just 2 min ultrasonic irradiation for the first time. The SNH was then applied as an adsorbent for Rhodamine removal from aqueous solution. The SNH adsorbent was characterized by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy images and X-ray photoelectron spectroscopy. A 24 full factorial central composite design, a linear mathematical model representing the influence of different variables and their interactions, was successfully employed for experimental design and analysis of the results. Analysis of variance demonstrated that Rhodamine adsorption significantly increased with increases in the amount of adsorbent, extraction time, stirring rate of the solution and Rhodamine volume as donor phase volume, but slightly decreased with an increase in temperature and pH of Rhodamine solution. The adsorption behaviors showed that the adsorption kinetics were in good agreement with a pseudo-second-order model for Rhodamine removal from aqueous solution. Thermodynamic studies revealed the feasibility and exothermic nature of the system. Adsorption mechanism was studied through two important adsorption isotherm models (Langmuir and Freundlich models). Under the optimal experimental conditions, the detection limit was found to be 0.94 µg mL−1 for Rhodamine adsorption. The limit of quantification and the linear range of calibration curve were 3.14 µg mL−1 and 1.00–10.98 µg mL−1, respectively.

Simultaneous quantification of soman and VX adducts to butyrylcholinesterase, their aged methylphosphonic acid adduct and butyrylcholinesterase in plasma using an off-column procainamide-gel separation method combined with UHPLC-MS/MS.

This work describes a novel and sensitive non-isotope dilution method for simultaneous quantification of organophosphorus nerve agents (OPNAs) soman (GD) and VX adducts to butyrylcholinesterase (BChE), their aged methylphosphonic acid (MeP) adduct and unadducted BChE in plasma exposed to OPNA. OPNA-BChE adducts were isolated with an off-column procainamide-gel separation (PGS) from plasma, and then digested with pepsin into specific adducted FGES*AGAAS nonapeptide (NP) biomarkers. The resulting NPs were detected by UHPLC-MS/MS MRM. The off-column PGS method can capture over 90% of BChE, MeP-BChE, VX-BChE and GD-BChE from their respective plasma materials. One newly designed and easily synthesized phosphorylated BChE nonapeptide with one Gly-to-Ala mutation was successfully reported to serve as internal standard instead of traditional isotopically labeled BChE nonapeptide. The linear range of calibration curves were from 1.00-200ngmL-1 for VX-NP, 2.00-200ngmL-1 for GD-NP and MeP-NP (R2≥0.995), and 3.00-200ngmL-1 for BChE NP (R2≥0.990). The inter-day precision had relative standard deviation (%RSD) of <8.89%, and the accuracy ranged between 88.9-120%. The limit of detection was calculated to be 0.411, 0.750, 0.800 and 1.43ngmL-1 for VX-NP, GD-NP, MeP-NP and BChE NP, respectively. OPNA-exposed quality control plasma samples were characterized as part of method validation. Investigation of plasma samples unexposed to OPNA revealed no baseline values or interferences. Using the off-column PGS method combined with UHPLC-MS/MS, VX-NP and GD-NP adducts can be unambiguously detected with high confidence in 0.10ngmL-1 and 0.50ngmL-1 of exposed human plasma respectively, only requiring 0.1mL of plasma sample and taking about four hours without special sample preparation equipment. These improvements make it a simple, sensitive and robust PGS-UHPLC-MS/MS method, and this method will become an attractive alternative to immunomagnetic separation (IMS) method and a useful diagnostic tool for retrospective detection of OPNA exposure with high confidence. Furthermore, using the developed method, the adducted BChE levels from VX and GD-exposed (0.10-100ngmL-1) plasma samples were completely characterized, and the fact that VX being more active and specific to BChE than GD was re-confirmed.

A novel and label-free immunosensor for bisphenol A using rutin as the redox probe

In this work, a new and label-free electrochemical immunosensor for sensitive detection of bisphenol A was reported. MWCNTs and gold nanoparticles (AuNPs) were modified on glassy carbon electrode surface to enhance current response. The Anti-BPA was immobilized on the modified electrode through AuNPs. Rutin was used for the first time as the redox probe to construct electrochemical immunosensor of bisphenol A. The peak current change due to the specific immuno-interaction between anti-BPA and BPA on the modified electrode surface was utilized to detect bisphenol A. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) were employed to trace the assembly process of the electrochemical immunosensor. Experimental factors affecting the sensitivity of the immunosensor were examined in terms of incubation time and pH of phosphate buffer solution (PBS). Under optimized conditions, the linear range of calibration curve based on the relationship between current response and BPA concentration was from 1.0×10−8–1.0×10−6M with detection limit of 8.7×10−9M (S/N=3). The proposed immunosensor showed good reproducibility, selectivity, stability and was successfully applied to the determination of BPA in real sample.

Sorptive thin film microextraction followed by direct solid state spectrofluorimetry: A simple, rapid and sensitive method for determination of carvedilol in human plasma

A poly acrylate-ethylene glycol (PA-EG) thin film is introduced for the first time as a novel polar sorbent for sorptive extraction method coupled directly to solid-state spectrofluorimetry without the necessity of a desorption step. The structure, polarity, fluorescence property and extraction performance of the developed thin film were investigated systematically. Carvedilol was used as the model analyte to evaluate the proposed method. The entire procedure involved one-step extraction of carvedilol from plasma using PA-EG thin film sorptive phase without protein precipitation. Extraction variables were studied in order to establish the best experimental conditions. Optimum extraction conditions were the followings: stirring speed of 1000 rpm, pH of 6.8, extraction temperature of 60 °C, and extraction time of 60 min. Under optimal conditions, extraction of carvedilol was carried out in spiked human plasma; and the linear range of calibration curve was 15–300 ng mL−1 with regression coefficient of 0.998. Limit of detection (LOD) for the method was 4.5 ng mL−1. The intra- and inter-day accuracy and precision of the proposed method were evaluated in plasma sample spiked with three concentration levels of carvedilol; yielding a recovery of 91–112% and relative standard deviation of less than 8%, respectively. The established procedure was successfully applied for quantification of carvedilol in plasma sample of a volunteer patient. The developed PA-EG thin film sorptive phase followed by solid-state spectrofluorimetric method provides a simple, rapid and sensitive approach for the analysis of carvedilol in human plasma.

Magnetic molecularly imprinted polymer nanoparticles for selective extraction of copper from aqueous solutions prior to its flame atomic absorption determination

This paper describes a pre-concentration procedure using magnetic molecularly imprinted polymer (MMIP) nanoparticles for the extraction of copper(II) from aqueous samples prior to its atomic absorption determination. Cu–morin complex was used as template molecule which was chemically bonded to MMIP nanoparticles. MMIP nanoparticles were characterized by scanning electron microscopy as well as Fourier transform infrared spectroscopy. The extraction conditions including pH value, adsorption and desorption time, temperature, amount of ligand and ionic strength of the sample matrix were studied and optimized. The method showed good extraction recoveries (≥96%) with relative standard deviation below 3.4% for real samples. The linear range of calibration curve was between 5–1000 μg/L with a correlation coefficient (r 2) of 0.996. The detection limit was 0.5 μg/L. The method was suitable for the determination of trace copper in drinking water samples.

A novel fluorescent chemosensor for safranine T based on calixarene-1,3-diacyl hydrazone

A novel surfactant sensitized fluorescent chemosensor for safranine T (ST) based on calixarene-1,3-diacyl hydrazone (CADH) in sodium dodecyl sulfate (SDS) medium was investigated. The fluorescence intensity of CADH was quenched by ST due to the formation of weak fluorescent inclusion complex (ST-CADH), and the fluorescence quenching (ΔF=FCADH−FST-CADH) was sensitized in SDS. Under the optimal conditions, the linear range of calibration curve for the determination of ST was 0.02–3.00μg/m and the detection limit estimated 0.015μg/mL with RSD 2.2% (n=3, c=1.0μg/mL). The mechanism of determination was discussed with the fluorescence quenching type, the inclusion of CADH with ST and surfactant sensitized effect. This method has been applied for the detection of ST in real samples with satisfactory results.