A carbon paste electrode modified with poly(methylene disulfide) nanoparticles for anodic stripping voltammetric determination of silver(I).

Poly(methylene disulfide) nanoparticles (PMDSNPs) were synthesized and characterized by FTIR, FESEM, EDX, and TGA. The nanomaterial was used to modify a carbon paste electrode to obtain a sensor for differential pulse anodic stripping voltammetric analysis of silver ion. The silver ions are accumulated on the modified electrode by reduction at a potential of -0.3 V. This is followed by the quantitation of adsorbed Ag(I) by differential pulse anodic stripping voltammetry. Under optimized conditions, the electrode has a dynamic range in the 3.0 × 10-12 to 1.0 × 10-9 mol L-1 Ag(I) concentration range, and the detection limit is 1.0 × 10-13 mol L-1. The relative standard deviation (for n = 6) is 1.8%, this showing good reproducibility. The method was successfully applied to the determination of Ag(I) in spiked tap and river waters and tea leaves. The results were in good agreement with those obtained by inductively coupled plasma optical emission spectrometry. Graphical abstract Graphical presentation of synthesis of poly(methylene disulfide) nanoparticles (PMDSNPs) and their use as a modifier in a carbon paste electrode (MCPE). Differential pulse anodic stripping voltammograms of the MCPE for silver ion are compared with those of the bare CPE.

Hollow Fiber Liquid Based Microextraction of Nalidixic Acid in Urine Samples Using Aliquat 336 as a Carrier Combined with High-Performance Liquid Chromatography.

A new and simple hollow fiber liquid-phase microextraction was used in conjunction with HPLC for the extraction and quantitative determination of nalidixic acid (NA) in human urine samples. This study considers this technique an alternative to common methods of hollow fiber microextraction based on pH gradient and electromembrane extraction of NA in human urine samples. In this research, the drug was extracted from the source phase (donor phase) into a modified organic phase with Aliquat 336 (hydrophobic ion-pair reagent) as a carrier able to impregnate pores of the hollow fiber. In this study, the effects of several factors were tested on the extraction efficiency of the drug. Under optimum conditions, the linearity of the method was observed over the range 0.05-2.0 µg mL(-1) with a correlation coefficient of r = 0.9983. The results of tests on the method determined a good sensitivity with a limit of detection of 0.008 µg mL(-1). The intra-day relative standard deviation (n = 9) for 0.8 µg mL(-1) was 6.2%, and the inter-day relative standard deviation (n = 5) for 0.8 µg mL(-1) was 5.6%. This new strategy was successfully applied to analyze a real urine sample with satisfactory results.

Resonance Rayleigh scattering method for determination of 2-mercaptobenzothiazole using gold nanoparticles probe.

A sensitive, simple and novel method was developed to determine 2-mercaptobenzothiazole (2MBT) in water samples. This method was based on the interaction between gold nanoparticles (AuNPs) and 2MBT followed by increasing of the resonance Rayleigh scattering (RRS) intensity of nanoparticles. The change in RRS intensity (ΔIRRS) was linearly correlated to the concentration of 2MBT over the ranges of 5.0-100.0 and 100.0-300.0 µg L(-1). 2MBT can be measured in a short time (5 min) without any complicated or time-consuming sample pretreatment process. Parameters that affect the RRS intensities such as pH, concentration of AuNPs, standing time, electrolyte concentration, and coexisting substances were systematically investigated and optimized. Interference tests showed that the developed method has a very good selectivity and could be used conveniently for determination of 2MBT. The limit of detection (LOD) and limit of quantification (LOQ) were 1.0 and 3.0 µg L(-1), respectively. Relative standard deviations (RSD) for 20.0 and 80.0 µg L(-1) of 2MBT were 1.1 and 2.3, respectively. Possible mechanisms for the RRS changes of AuNPs in the presence of 2MBT were discussed and the method was successfully applied for the analysis of real water samples.

Determination of thiram using gold nanoparticles and Resonance Rayleigh scattering method.

A sensitive, simple and novel method was developed to determine thiram fungicide in water and plant samples. This method was based on the interaction between gold nanoparticles (AuNPs) and thiram fungicide followed by increasing of the Resonance Rayleigh scattering (RRS) intensity of nanoparticles. The change in RRS intensity (∆IRRS) was linearly correlated to the concentration of thiram over the range of 1.0-200.0µgL(-1). Thiram can be measured in a short time (4min) without any complicated or time-consuming sample pretreatment process. Parameters that affect the RRS intensities such as pH, concentration of AuNPs, standing time, electrolyte concentration, and coexisting substances were systematically investigated and optimized. Interference tests showed that the developed method has a very good selectivity and could be used conveniently for the determination of thiram. The limit of detection (LOD) and limit of quantification (LOQ) were 0.3 and 1.0µg L(-1), respectively. Relative standard deviations (RSD) for 20.0 and 80.0µg L(-1) of thiram were 3.0 and 1.1, respectively. Possible mechanisms for the RRS changes of AuNPs in the presence of thiram were discussed and the method was successfully applied for the analysis of spiked real water samples and fresh plant samples such as tomato and cucumber.

Resonance Rayleigh scattering method for determination of ethion using silver nanoparticles as probe.

A simple, novel and sensitive method was developed to determine ethion insecticide in water samples. This method was based on the interaction of ethion with silver nanoparticles (AgNPs) and quenching of the resonance Rayleigh scattering (RRS) intensity. The change in RRS intensity (ΔIRRS) was linearly correlated to the concentration of ethion over the range of 10.0-900.0 µg L(-1). Ethion can be measured in a short time (3 min) without any complicated or time-consuming sample pretreatment process. Parameters that affect the RRS intensities such as pH, concentration of AgNPs, standing time, electrolyte concentration, and coexisting substances were systematically investigated and optimized. Interference tests showed that the developed method has a very good selectivity and could be used conveniently for determination of ethion. The limit of detection (LOD) and limit of quantification (LOQ) were 3.7 and 11.0 µg L(-1), respectively. Relative standard deviations (RSD) for 15.0 and 60.0 µg L(-1) of ethion were 4.1 and 0.2, respectively. Possible mechanisms for the quenching of RRS of AgNPs were discussed and the method was successfully applied for the analysis of spiked real water samples.

Ultrasound-assisted solid phase extraction of nitro- and chloro-(phenols) using magnetic iron oxide nanoparticles and Aliquat 336 ionic liquid.

A novel and sensitive ultrasound-assisted solid phase extraction (UASPE) method for pre-concentration and determination of ultra-trace amounts of nitrophenols and chlorophenols in water samples was demonstrated. Four hazardous phenolic compounds in water samples were extracted and monitored by high performance liquid chromatography. The results demonstrated that in the presence of Aliquat 336 (ALQ), magnetic iron oxide nanoparticles (MIONPs) were quite efficient in the adsorption and pre-concentration of traces of analytes. MIONPs were synthesized and characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The important parameters influencing the extraction efficiency were studied and optimized. The separation and pre-concentration steps were fast and completed in 10 min. Acetonitrile was used for the desorption of target analytes. Under optimum adsorption conditions, a linear range between 0.015 and 100 µg L(-1) (R(2)≥0.997), and limits of detections (LODs) ranging from 0.005 to 0.041 µg L(-1) were obtained. Enrichment factors in the range of 76-195 were achieved and relative standard deviations (%RSDs) were less than 10.0 (n=3) for the target analytes. The analytical method was successfully applied for environmental water samples such as tap water and river water. The recoveries varied within the range of 70-119% confirming the good performance of the method in various water samples. The results showed that the proposed method is a rapid, convenient and feasible technique for the determination of nitrophenols and chlorophenols in aqueous samples.

Solid phase extraction-preconcentration and high performance liquid chromatographic determination of 2-mercapto-(benzothiazole, benzoxazole and benzimidazole) using copper oxide nanoparticles.

This study introduces a novel method of solid phase extraction (SPE), preconcentration and HPLC determination of 2-mercaptobenzimidazole (2MBI), 2-mercaptobenzoxazole (2MBO) and 2-mercaptobenzothiazole (2MBT) from an aqueous solution by a SPE cartridge loaded with copper oxide nanoparticles. Results demonstrated that copper oxide nanoparticles are quite efficient for extraction and preconcentration of trace amounts of these mercaptans at room temperature. The study also investigated the effects of parameters such as pH, buffer and its volume, electrolyte concentration, flow rate of the test solution, composition and volume of the desorbing solvent, accepted tolerable volume, amount of adsorbent, reusability of cartridges and evidence of some co-existing species on extraction and determination of the above mentioned mercaptans. The method showed good linearity for determination of these mercaptans in the range of 0.01-10 µg mL(-1) with regression coefficients better than 0.9969. The limits of detection (LODs) evaluations were 0.0021, 0.0027 and 0.0019 µg mL(-1) for 2MBT, 2MBO and 2MBI, respectively. The relative standard deviations (RSDs) for 0.2 µg mL(-1) and 5 µg mL(-1) of the measured mercaptans were below 3.04% and 4.23%, respectively. Ramin Power Plant (3000 MW, Ahvaz, Iran) cooling water containing some 2MBT (as corrosion inhibitor) was used as the real sample. Recovery tests with spiked levels of 2MBT, 2MBI and 2MBO were carried out and satisfied results were obtained.

Carbon paste electrode modified with cuo-nanoparticles as a probe for square wave voltammetric determination of atrazine.

BACKGROUND: Atrazine (ATZ) is a widely used herbicide in most countries because of its low cost and good selectivity. The concentration of ATZ that the EPA considers safe to consume in drinking water is 3 ppb. Therefore, recently, there have been concerns about its determination in trace levels. This compound is not electro-active, so in this research indirect electrochemical method for its detection in low levels was proposed. OBJECTIVES: The main aim of this study is the indirect determination of ATZ in water samples by voltammetry using nano-particle modified electrode. MATERIALS AND METHODS: A nano-CuO modified carbon paste electrode (NMCPE) is constructed and its application for indirect square wave voltammetric (SWV) detection of ATZ is reported. The sensing performance mechanism of the nano-CuO modified carbon paste electrode toward atrazine is due to complexation of the analyte with Cu (II) ion. The peak current for copper (II) reduction decreases with increase in the ATZ concentration and is monitored for its determination. Instrumental and chemical parameters influencing the detection of ATZ were optimized. RESULTS: The results revealed that decrease in peak current was proportional to ATZ concentration over the range of 5-75 ng/mL. The limit of detection (LOD) and limit of quantification (LOQ) were 2 ng/mL and 5.6 ng/mL (n = 20), respectively. The relative standard deviation (n = 10) for the determination of 10 and 50 ng/mL of ATZ solution was estimated as 4.9% and 4.2 %, respectively. CONCLUSIONS: This easily fabricated electrode together with the fast and sensitive SW voltammetry was successfully applied for the determination of concentration of ATZ at trace levels, in different water samples.

Removal, preconcentration and spectrophotometric determination of picric acid in water samples using modified magnetic iron oxide nanoparticles as an efficient adsorbent.

A simple, fast and sensitive spectrophotometric method is developed for removal, preconcentration and determination of trace amounts of picric acid in water samples. Magnetic iron oxide nanoparticles (MIONPs) were synthesized and characterized by transmission electron microscopy (TEM). The magnetic nanoparticles were coated with cetyltrimethylammonium bromide (CTAB) and were applied for fast separation, preconcentration and spectrophotometric determination of picrate anion (the ion of picric acid) in an aqueous solution. The separation, preconcentration procedure is fast and will be completed in 2min. Methanol is used for desorption of adsorbed picrate anion. The effects of important parameters such as pH of aqueous medium, CTAB dosage, adsorbent amount, temperature, electrolyte concentration, desorbing solvent and interfering ions on the adsorption of picrate anion were investigated. The method showed good linearity for the determination of picric acid in the concentration range of 0.02-1.00µgmL-1 with a regression coefficient of 0.999. The limit of detection (LOD) is obtained to be 0.007µgmL-1. The relative standard deviation (RSD) for 0.03µgmL-1 and 0.8µgmL-1 of picric acid were 3.98% and 1.97% respectively. Picric acid was separated, preconcentrated and determined successfully in spiked samples of Karoon River water.

Solid phase extraction-spectrophotometric determination of salicylic acid using magnetic iron oxide nanoparticles as extractor.

This method shows a novel, fast and simple solid phase extraction-spectrophotometric procedure for preconcentration and determination of salicylic acid (SA) in blood serum using magnetic iron oxide nanoparticles (MIONs) as extractor. It is shown that the novel magnetic nano-adsorbent is quite efficient for fast adsorption of SA at 25 degrees C. Various parameters affecting the adsorption of SA on MIONs, such as pH of solution, type, volume and concentration of desorbing reagent and amount of adsorbent and matrix effects, have been investigated. The calibration graph for the determination of SA was linear in the range of 0.025-1.250microgmL(-1). The limit of detection (LOD) based on three times the standard deviation of the blank (3S(b)) was 5.5x10(-3)microgmL(-1) (n=10) for SA. The intra-day precision (R.S.D.) was below 10.1% and inter-day R.S.D. was less than 17.5%, while accuracy (relative error R.E.) was within +/-3.6 determined from quality control samples for salicylic acid (SA) which corresponded to requirement of the guidance of Food and Drug Administration (FDA). The preconcentration factor of 100 was achieved in this method. The proposed procedure has been successfully applied to the determination of SA in blood serum.

Solid phase extraction and spectrophotometric determination of trace amounts of thiocyanate in real samples.

A simple, selective and rapid method for solid phase extraction and spectrophotometric determination of thiocyanate using a manganese (III) tetrakis (p-sulfonatophenyl) porphyrin, [Mn (TPPS) OAC] bound to Amberlite IR-400 has been developed. The influence of pH, amount of solid phase, sample matrix, type and amount of eluting agent and flow rates i.e. variables affecting the efficiency of the extraction system were evaluated and conditions of the sample, eluting solution and active phase were optimized. The maximal capacity was found to be as 1.16 microg mL(-1) for 1200 mL. Thiocyanate ions can be eluted quantitatively with 8 mL 0.3 M ferric chloride. The enrichment factor was 150. The linear range of the determination is between 0.4-2.0 microg mL(-1) for preconcentration method with a limit of detection of 2.8 ng mL(-1). The method has been successfully applied for determination of trace amounts of thiocyanate in tap water, saliva sample and a synthetic mixture.

Square-wave voltammetric (SWV) determination of Captopril in reconstituted serum and pharmaceutical formulations.

A simple, fast and sensitive square-wave voltammetric (SWV) method for the determination of trace amounts of Captopril in pharmaceutical formulation and reconstituted serum is reported. A three-electrode system containing the static mercury drop electrode (SMDE) working electrode, Pt auxiliary electrode and Ag/AgCl reference electrode was used throughout. Sodium sulfite was used as both supporting electrolyte and oxygen removing agent. No nitrogen purging is needed for oxygen removal from sample solution. Calibration graph showed good linearity in the concentration range of 0.5-50.0mugmL(-1) of Captopril and regression coefficient of 0.9957 is obtained. R.S.D. for eight replicate measurements and LOD of the proposed method are 1.2% and 6.28 x 10(-3)mugmL(-1), respectively. The effect of various parameters (equilibration time, scan increment, pulse height, drop size, frequency and sodium sulfite concentration) on the determination were investigated. The procedure was successfully applied to the determination of Captopril in pharmaceutical formulation and reconstituted serum.