The determination of trace lead in drinking water by flow injection spectrophotometry

Lead is the non-essential trace element in the human body, and it has been confirmed that drinking water is one of the sources of lead in human body. In the research, based on the sensitive colour reaction of lead with I^?–EV⁺–PVA, a simple, sensitive, accurate and portable method for the determination of trace lead in drinking waters was proposed. Chemicals and physicals had been optimized in detail. The apparent molar absorption coefficient was up to 7.4 × 10⁵ mol L^?1 cm^?1. The developed method provided a linearity range over 5–80 μg L^?1. The regression deviation was between 0.71% and 2.33%. The 3σ detection limit was 0.9 μg L^?1. Close to the quantitation limit for the analyte the relative standard deviation was 1.10% (n = 10) at 40 μg L^?1. The method developed here for analysis of lead yielded results that were comparable with those of the GFAAS.     

Determination of triclosan,triclocarban and methyl-triclosan in aqueous samples by dispersive liquid–liquid microextraction combined with rapid liquid chromatography

In this study, dispersive liquid–liquid microextraction (DLLME) combined with ultra-high-pressure liquid chromatography (UHPLC)–tunable ultraviolet detection (TUV), has been developed for pre-concentration and determination of triclosan (TCS), triclocarban (TCC) and methyl-triclosan (M-TCS) in aqueous samples. The key factors, including the kind and volume of extraction solvent and dispersive solvent, extraction time, salt effect and pH, which probably affect the extraction efficiencies were examined and optimized. Under the optimum conditions, linearity of the method was observed in the range of 0.0500–100 μg L^?1 for TCS, 0.0250–50.0 μg L^?1 for TCC, and 0.500–100 μg L^?1 for M-TCS, respectively, with correlation coefficients (r²) > 0.9945. The limits of detection (LODs) ranged from 45.1 to 236 ng L^?1. TCS in domestic waters was detected with the concentration of 2.08 μg L^?1. The spiked recoveries of three target compounds in river water, irrigating water, reclaimed water and domestic water samples were achieved in the range of 96.4–121%, 64.3–84.9%, 77.2–115% and 75.5–106%, respectively. As a result, this method can be successfully applied for the rapid and convenient determination of TCS, TCC and M-TCS in real water samples.     

Nano TiO2-based preconcentration for the speciation analysis of inorganic selenium by using ion chromatography with conductivity detection

A simple, sensitive, and cost-effective analytical method was developed for the speciation analysis of inorganic selenium by combining a nano-TiO₂ preconcentration with an ion chromatography-conductivity detection (IC-CD) system. The experimental conditions for the simultaneous adsorption and desorption of Se(IV) and Se(VI) were carefully investigated. Under the established optimum condition, the Se(IV) and Se(VI) ions could been simultaneously adsorbed onto the nano-TiO₂ surface at pH 4.0, and then effectively desorbed by 0.1 M sodium hydroxide eluent. The adsorption process was fast and reached adsorption equilibrium within 10 min. The nano-TiO₂ also exhibited high adsorption capacity with 11.3 mg g^? 1 for Se(IV) and 8.34 mg g^? 1 for Se(VI). The enrichment factors for Se(IV) and Se(VI) were calculated to be 39 and 30, respectively, with sample volume of 50 mL. The detection limits (3σ) were 0.8 μg L^? 1 for Se(IV) and 0.4 μg L^? 1 for Se(VI), which were sensitive enough for the routine analysis of water and drink samples. The relative standard deviation was calculated to be < 4% (n = 6) for detection of 30 μg L^? 1 Se(IV) and 30 μg L^? 1 Se(VI). The results of the present work confirmed that our developed nano-TiO₂-IC-CD method could be applied for the detection of inorganic selenium species in tap water and drink samples with good recoveries in the range of 82%–108%.     

Development of a solid phase extraction method for the multielement determination of trace metals in natural waters including sea-water by FI-ICP-MS

An automated solid phase extraction method by flow analysis on-line inductively coupled plasma mass spectrometry (FI-ICP-MS) for the determination of cobalt, chromium, nickel, cadmium, manganese, zinc, copper and lead in sea-water and other natural waters is described. The system is based on retention of the analytes onto a minicolumn packed with a chelating resin, 1,5-bis (2-pyridyl)-3-sulphophenyl methylene thiocarbonohydrazide immobilized on aminopropyl-controlled pore glass, placed in the injection valve of a simple flow manifold. The effects of chemical and flow variables were investigated and selected as a compromise between sensitivity and sampling frequency. So, the sample solutions (adjusted to pH 8.0 ± 0.5) were passed through the column. After washing the column with water, the adsorbed metals were subsequently eluted into the plasma with 4% m/m nitric acid. Detection limits of the trace metals (180 s sample loading time at a sample flow rate of 0.7 mL min^? 1; sampling frequency 8.6 h^? 1) were 0.002 μg L^? 1 for Co, 0.057 μg L^? 1 for Cr, 0.117 μg L^? 1 for Ni, 0.004 μg L^? 1 for Cd, 0.210 μg L^? 1 for Mn, 0.260 μg L^? 1 for Zn, 0.030 μg L^? 1 for Cu and 0.020 μg L^? 1 for Pb, with enrichment factors between 2.2 and 6.8. The accuracy of the proposed method was checked with certified reference materials (CRMs) of sea-water SLEW 3, LGC6016 and CASS-5, river water SLRS-5 and fortified lake water TMDA-54.4. The results from the determination of these metals were in agreement with the certified values and recovery values ranged between 92.2 and 110.6%. The method was applied to the determination of these metal ions in sea-water samples collected in the Málaga Bay in order to realize a pilot study necessary to generate preliminary information on which to base a more detailed pollution study by heavy metals of the Bay.     

Determination of traces of Sb(III) using ASV in Sb-rich water samples affected by mining

Chemical speciation [Sb(V) and Sb(III)] affects the mobility, bioavailability and toxicity of antimony. In oxygenated environments Sb(V) dominates whereas thermodynamically unstable Sb(III) may occur. In this study, a simple method for the determination of Sb(III) in non acidic, oxygenated water contaminated with antimony is proposed. The determination of Sb(III) was performed by anodic stripping voltammetry (ASV, 1–20 μg L⁻¹ working range), the total antimony, Sb(tot), was determined either by inductively coupled plasma mass spectrometry (ICP-MS, 1–100 μg L⁻¹ working range) or inductively coupled plasma optical emission spectrometry (ICP-OES, 100–10,000 μg L⁻¹ working range) depending on concentration. Water samples were filtered on site through 0.45 μm pore size filters. The aliquot for determination of Sb(tot) was acidified with 1% (v/v) HNO₃. Different preservatives, namely HCl, L(+) ascorbic acid or L(+) tartaric acid plus HNO₃, were used to assess the stability of Sb(III) in synthetic solutions.The method was tested on groundwater and surface water draining the abandoned mine of Su Suergiu (Sardinia, Italy), an area heavily contaminated with Sb. The waters interacting with Sb-rich mining residues were non acidic, oxygenated, and showed extreme concentrations of Sb(tot) (up to 13,000 μg L⁻¹), with Sb(III) <10% of total antimony. The stabilization with L(+) tartaric acid plus HNO₃ appears useful for the determination of Sb(III) in oxygenated, Sb-rich waters. Due to the instability of Sb(III), analyses should be carried out within 7 days upon the water collection. The main advantage of the proposed method is that it does not require time-consuming preparation steps prior to analysis of Sb(III).     

Column solid phase extraction and determination of ultra-trace Au,Pd and Pt in environmental and geological samples

A new sorbent based on cysteine modified silica gel (SiG-cys) was prepared and studied for preconcentration and separation of noble metals Au(III), Pd(II), Pt(II), Pt(IV). Its extraction efficiency was examined by batch and column solid phase extraction procedures. Laboratory experiments performed showed that sorbent is characterized with high selectivity, permiting quantitative sorption (93–97%) of noble metals Au, Pd and Pt from acidic media 0.1–2 mol L^? 1 HCl and unsignificant sorption (less than 2%) for common base metals like Cu, Fe, Mn and Zn. The analytes retained on the sorbent are effectively eluted with 0.1 mol L^? 1 thiourea in 0.1 mol L^? 1 HCl and measured by ETAAS or ICP OES under optimal instrumental parameters. The sorbent showed high mechanical and chemical stability and extraction efficiency was not changed after 500 cycles of sorption/desorption. The sorbent was successfully applied in analyticals procedures for preconcentration and determination of Au, Pd and Pt in geological and soil samples. Detection limits (3σ criteria) achieved, depending on the instrumental methods used are: ETAAS (0.005 μg L^? 1 for Au in river and sea water, 0.002 μg g^? 1 for Au in copper ore and copper concentrate); ICP OES (0.03 μg L^? 1 for Pd and 0.06 μg L^? 1 for Pt in river and sea water, 0.006 μg g^? 1 for Pd in copper ore and copper concentrate and 0.002 μg g^? 1 for soluble Pt in soil). The accuracy of the procedures developed was confirmed by added/found method for sea and river water; by the analysis of national certified materials (copper ore and copper concentrate for Au and Pd) and by determination of the sum of soluble Pt(II) + Pt(IV) in spiked soil samples.     

Determination of gallium at trace levels using a spectrofluorimetric method in synthetic U–Ga and Ga–As solutions

A simple, easy to use and selective spectrofluorimetric method for the determination of trace levels of gallium has been developed. A new Schiff base, N-o-vanillidine-2-amino-p-cresol (OVAC) was synthesized and its fluorescence activity with gallium investigated. Based on this chelation reaction, a spectrofluorimetric method has been developed for the determination of gallium in synthetically prepared Ga–U and Ga–As samples buffered at pH 4.0 using acetic acid–sodium acetate. The chelation reaction between Ga(III) and N-o-vanillidine-2-amino-p-cresol was very fast, requiring only 30 min at room temperature to complex completely. The limit of detection (LOD) (3σ) for Ga(III) was 7.17 nM (0.50 μg L^?1), determined from the analysis of 11 different solutions of 20 μg L^?1 Ga(III).     

Determination of As in tobacco by using electrochemical hydride generation at a Nafion® solid polymer electrolyte cell hyphenated with atomic fluorescence spectrometry

In the present work, a novel solid polymer electrolyte hydride generation (SPE-HG) cell was developed. The home-made SPE-HG cell, mainly composed of three components (Nafion®117 membrane for separating and H⁺ exchanging, a soft graphite felt cathode and a Ti mesh modified by Ir anode), was employed for detecting As by coupling to atomic fluorescence spectrometry (AFS). The H⁺ generated by electrolysis of pure water in anode chamber transferred to cathode chamber through SPE, and immediately reacted with As^3 + to generate AsH₃. The relative mechanisms and operation conditions for hydride generation of As were investigated in detail. The developed cell employed water as an alternative of acid anolyte, with virtues of low-cost, more than 6 months lifetime and environment friendly compared with the conventional cell. Under the optimized conditions, the limit of determination of As^3 + for sample blank solution was 0.12 μg L^? 1, the RSD was 2.9% for 10 consecutive measurements of 5 μg L^? 1 As^3 + standard solution. The accuracy of the method was verified by the determination of As in the reference Tea (GBW07605) and the developed method was successfully applied to determine trace amounts of As in tobacco samples with recovery from 97% to 103%.     

Extraction and preconcentration of trace levels of cobalt using functionalized magnetic nanoparticles in a sequential injection lab-on-valve system with detection by electrothermal atomic absorption spectrometry

A new approach to performing extraction and preconcentration employing functionalized magnetic nanoparticles for the determination of trace metals is presented. Alumina-coated iron oxide nanoparticles were synthesized and used as the solid support. The nanoparticles were functionalized with sodium dodecyl sulfate and used as adsorbents for solid phase extraction of the analyte. Extraction, elution, and detection procedures were performed sequentially in the sequential injection lab-on-valve (SI-LOV) system followed by electrothermal atomic absorption spectrometry (ETAAS). Mixtures of hydrophobic analytes were successfully extracted from solution using the synthesized magnetic adsorbents. The potential use of the established scheme was demonstrated by taking cobalt as a model analyte. Under the optimal conditions, the calibration curve showed an excellent linearity in the concentration range of 0.01–5 μg L^?1, and the relative standard deviation was 2.8% at the 0.5 μg L^?1 level (n = 11). The limit of detection was 6 ng L^?1 with a sampling frequency of 18 h^?1. The present method has been successfully applied to cobalt determination in water samples and two certified reference materials.     

Assay of caffeoylquinic acids in Baccharis trimera by reversed-phase liquid chromatography

Baccharis trimera commonly named ‘carqueja’, is wide-spread in South America and are used as raw material for herbal medicines. A reversed-phase liquid chromatography (RP-LC) method coupled to diode array detector was developed for the analysis of caffeoylquinic acids (CQAs), the main compounds responsible for its digestive activity. The identity of the quinic acids was established by mass spectrometry and were them: 5-O-[E]-caffeoylquinic acid, 3,4-O-[E]-dicaffeoylquinic acid, 3,5-O-[E]-dicaffeoylquinic acid, 4,5-O-[E]-dicaffeoylquinic acid and a tricaffeoylquinic acid. The RP-LC method for the quantitation of the caffeoylquinic acids was validated according to ICH guidelines, based on the following parameters: linearity, selectivity, robustness, limits of detection and quantification, precision and recovery. Hydroalcoholic extracts were prepared by the maceration of the plant material with ethanol:water 1:1 (v/v) in a 0.1:25 g mL^?1 plant:solvent ratio in a water bath at 40 °C. Validation data indicated that the HPLC method proposed is suitable for the analysis of caffeoylquinic acids in B. trimera raw material. The results of the LOD and LOQ analyses for the 5-CQA were 4.1 μg mL^?1 and 12.5 μg mL^?1, respectively, 1.3 μg mL^?1, 3.9 μg mL^?1 for 4,5-diCQA and 1.7 μg mL^?1, 5.1 μg mL^?1 for triCQA. The levels of total CQAs ranged from 2.1 to 4.0 g% (w/w). The influence of season harvest and site collection was also evaluated and variations were observed in the results and can be related to phonologic phase, different locations, seasons and soil. Long term and photostability of plant material were carried out and was observed a stable behavior during the time of the experiments.     

Selective extraction of traffic-related antimony compounds for speciation analysis by graphite furnace atomic absorption spectrometry

Most traffic-related antimony air pollutants are derived from brake dust. Brake dust contains Sb₂S₃, used as a friction material in brake pads, and its high-temperature oxidation products, Sb₂O₃ or Sb₂O₄. Systematic investigations were carried out to find the most selective leaching conditions for these substances. First, solubility experiments of the pure potential compounds mentioned above were carried out. Then, the leaching of these compounds from home-made artificial dusts previously spiked with these compounds at the trace level was investigated. A 0.5 mol L^?1 citric acid solution proved to leach the whole Sb₂O₃ content while extracting less than 10% Sb₂S₃ and no Sb₂O₄ at all. It was found that Sb₂O₃ and Sb₂S₃ traces were soluble in a 6 mol L^?1 HCl solution, quantitatively and selectively. Graphite furnace atomic absorption spectrometry and hydride generation graphite furnace atomic absorption spectrometry methods were developed to determine the Sb content of the extracts. The proposed method proved to be applicable to settled dust containing traffic-related Sb compounds. The detection limits were 1.2 and 0.3 μg g^?1 for leaching by citric acid and HCl solution, respectively, which were adequate for Sb content determination in the urban dust studied. The reproducibility of the method expressed as relative standard deviation was about 7%. The results showed that the concentration of leachable Sb was 40 μg g^?1 in the settled dust of Budapest, about half of which corresponded to Sb₂O₃. The Sb₂O₄ content calculated as the difference of total and leachable fraction was about 10% with high uncertainty.     

Development of a new dispersive liquid–liquid microextraction method in a narrow-bore tube for preconcentration of triazole pesticides from aqueous samples

In the present work a new, simple, rapid and environmentally friendly dispersive liquid–liquid microextraction (DLLME) method has been developed for extraction/preconcentration of some triazole pesticides in aqueous samples and in grape juice. The extract was analyzed with gas chromatography–flame ionization detection (GC–FID) or gas chromatography–mass spectrometry (GC–MS). The DLLME method was performed in a narrow-bore tube containing aqueous sample. Acetonitrile and a mixture of n-hexanol and n-hexane (75:25, v/v) were used as disperser and extraction solvents, respectively. The effect of several factors that influence performance of the method, including the chemical nature and volume of the disperser and extraction solvents, number of extraction, pH and salt addition, were investigated and optimized. Figures of merit such as linearity (r² > 0.995), enrichment factors (EFs) (263–380), limits of detection (0.3–5 μg L^?1) and quantification (0.9–16.7 μg L^?1), and relative standard deviations (3.2–5%) of the proposed method were satisfactory for determination of the model analytes. The method was successfully applied for determination of target pesticides in grape juice and good recoveries (74–99%) were achieved for spiked samples. As compared with the conventional DLLME, the proposed DLLME method showed higher EFs and less environmental hazards with no need for centrifuging.     

Dual-signal anodic stripping voltammetric determination of trace arsenic(III) at a glassy carbon electrode modified with internal-electrolysis deposited gold nanoparticles

A glassy carbon electrode (GCE) modified with internal-electrolysis deposited gold nanoparticles (AuNPs_ied) was applied to sensitively and selectively detect As(III) by anodic stripping linear sweep voltammetry (ASLSV). The AuNPs_ied/GCE was prepared based on the redox replacement reaction between a supporting-electrolyte-free aqueous HAuCl₄ and a copper sheet in saturated KCl separated by a salt bridge. Under optimum conditions (0.5 M aqueous H₂SO₄, 300-s preconcentration at − 0.4 V), the ASLSV peak current for the As(0)–As(III) oxidation responded linearly to As(III) concentration from 0.02 to 3 μM with a limit of detection (LOD) of 0.9 nM (0.07 μg L^− 1) (S/N = 3), while that for the As(III)–As(V) oxidation was linear with As(III) concentration from 0.02 to 1 μM with a LOD of 4 nM (0.3 μg L^− 1) (S/N = 3). An appropriate high-scan-rate for ASLSV can enhance both the sensitivity and signal-to-noise ratio. This method was applied for analyses of As(III) in real water samples.     

Determination of NiII(3-OMe-salophene) in MCF7 and HT29 cancer cell lines using HR-CS-AAS and in serum albumin using LC with monolithic silica

A high-resolution continuum source atomic absorption spectrometric method was developed and validated for the determination of Ni^II(3-OMe-salophene) (a complex with anticancer activity in vitro) in MCF7 and HT29 cancer cell lines. The primarily most sensitive line 232.003 nm was selected for analysis. Compared to the standard nickel, the absorbance values obtained for Ni^II(3-OMe-salophene) complex was at least 93% at the upper end of linear range of the calibration curve. The use of common matrix modifiers including magnesium nitrate, palladium nitrate, ammonium hydrogen phosphate, lanthanum chloride and calcium nitrate brought no significant improvement in the GF AAS measurement. The dynamic linear working range of the calibration curve was found to be between 2.16 and 12.0 μg L^? 1 (ppb). This covers a concentration range of the complex from 0.036 μM to 0.204 μM. Typical coefficients of variation (n = 6) ranged from 0.2% to 6.7% for Ni in Ni^II(3-OMe-salophene). Detection and quantitation limits were 0.65 and 2.16 μg L^? 1 (ppb), respectively. The proposed method has been successfully applied to the analysis of Ni^II(3-OMe-salophene) complex in cell lines of breast cancer (MCF7) and colon cancer (HT29). However, being based on the determination of nickel in the salophene complex, the method was unsuitable for the quantitation of Ni^II(3-OMe-salophene) in serum albumin, which originally contains significant amount of nickel. For this purpose, a high performance liquid chromatographic method with a monolithic silica RP-18e column has been developed to quantitate the complex in serum albumin. The developed chromatographic method depends on detecting the whole complex in serum rather than the bounded nickel. A mobile phase consisting of 25 mM phosphate buffer pH 3/methanol (30:70, v/v) was pumped at a flow rate of 1 mL min^? 1. The eluted complex was monitored at a wavelength of 250 nm. The dynamic linear working range of the calibration curve for the developed LC method was found to be between 100 and 20,000 μg L^? 1 (0.23–46.18 μM). Detection and quantitation limits were 30 and 100 μg L^? 1 (ppb), respectively.     

Simultaneous determination of five commercial cationic dyes in stream waters using diatomite solid-phase extractant and multivariate calibration

A simple spectrophotometric method was developed for the simultaneous determination of five commercial cationic dyes at 2.0?8.5 μg L^?1 level after using diatomite as solid-phase extractant. The method is based on preconcentration of the five dyes on natural diatomite solid-phase extractant and on multivariate calibration using partial least squares method (PLS-1). Compared with commonly used chromatographic or electrophoretic methods the developed method is simple and sensitive. With enrichment factors between 89 and 96, diatomite outperformed zeolite and activated carbon for dyes preconcentration. Before preconcentration and using PLS-1 method, the cationic dyes were simultaneously analyzed with linear ranges of 0.18–4.5, 0.32–5.0, 0.23–4.5, 0.45–8.0 and 0.82–12.0 mg L^?1 for crystal violet, malachite green, methylene blue, safranine O, and thioflavin T, respectively. The detection limits of dyes were estimated using Lorber’s method and found to be within the range 43–245 μg L^?1. The proposed SPE/PLS-1 method was applied to spiked stream water samples with good accuracy (79–91%) and precision (RSD 1.8–7.3%) but with slightly lower enrichment factors (80–92).     

The investigation of the interactions between CdSe quantum dots and human serum albumin by resonance Rayleigh scattering and second-order scattering spectra

Human serum albumin (HSA) was the most abundant protein in human plasma and has significant physiological function. In Tris–HCl buffer solution (pH 7.4), water-soluble semiconductor CdSe quantum dots (QDs) reacted with HSA and the products resulted in a great enhancement of the intensity of resonance Rayleigh scattering (RRS) and second-order scattering (SOS). Based on this, a new method was developed to investigate the interactions between QDs and HSA. The parameters with regard to determination were optimized, and the reaction mechanism was discussed. Under optimal conditions, the increments of scattering intensity (ΔI) were directly proportional to the concentrations of HSA in the range of 0.4–48.0 μmol L^?1. The detection limits were 0.10 μmol L^?1 for RRS method and 0.25 μmol L^?1 for SOS method. The proposed method was sensitive, simple and rapid. It has been successfully applied to the determination of HSA in human urine samples. Analytical results obtained with this novel assay were satisfactory.     

UV-absorption and fluorimetric methods for the determination of alprazolam in pharmaceutical formulation

The development of UV and fluorescence spectrophotometric methods for the quantitative determination of alprazolam in dosage forms using As(III)?SDS system. The two simple and sensitive, spectrophotometric and spectrofluorimetric methods were developed for the determination of alprazolam (ALP) in tablets. These methods are based on formation of ALP?As(III) complex in the presence of SDS. The UV-spectrum of 30% methanolic solution of ALP (5 × 10^?5 M) at pH 6.5 (Mclivaine buffer) was run between 200 and 380 nm. The absorption spectrum of ALP exhibits two peaks with a λ_max. at 255 nm and a weak band at 325 nm. When the spectra of the drug were run at varying pH in the region 200–380 nm, one isosbestic point at 290 nm was observed, which indicated the presence of two ionic conditions in solution. The complex exhibited an absorption maximum at 265 nm and emission peak at 520 nm with respect to the excitation wavelength of 325 nm. The spectrophotometric method was found to be linear in 8.0–17.0 μg ml^?1 range with detection limit of 13.520 μg ml^?1, while 0.05–9.5 μg ml^?1 range was with detection limit of 1.048 × 10^?2 μg ml^?1 by spectrofluorimetric method. The mean percentage recovery of the added quantity was found to be 99.54 (spectrophotometric method) and 100.22 (spectrofluorimetric method) and the %RSD are lower than 0.478 and 0.296 determined spectrophotomerically and spectrofluorimtrically, respectively. This indicates that the proposed method is accurate. The apparent ionization constant of ALP was found to be 9.29. The spectra, experimental conditions were set followed by determination stoichiometry, stability constant and thermodynamic parameters of the As(III), Co(II), Ni(II), and Zn(II) complexes with ALP at pH 6.5. The proposed methods have been successfully applied to the assay of ALP in tablets and the results were statistically evaluated.     

Novel luminescent nanoparticles for DNA detection

Highly luminescent LaF₃:Ce³⁺/Tb³⁺ nanocrystals were successfully prepared and surface functionalized via Layer-by-Layer technology. These as-prepared nanocrystals are highly resistant to photobleaching and pretty dispersible in aqueous solution. Due to the efficient luminescence quenching of the nanocrystals by nucleic acids, a facile fluorescence quenching method was developed for the detection of trace amount of nucleic acids. Under optimal conditions, the fluorescence intensity was proportional to the DNA concentration over the range of 0.60–25.0 μg mL^?1 for calf thymus DNA (ct-DNA) and 0.60–30.0 μg mL^?1 for herring sperm DNA (hs-DNA), respectively. The corresponding detection limit is 0.21 μg mL^?1 for ct-DNA and 0.31 μg mL^?1 for hs-DNA, respectively. The results indicated that the reported method is simple and rapid with wide linear range. Also, the recovery and relative standard deviation of this method are reasonable and satisfactory.     

Copper(II)–neocuproine reagent for spectrophotometric determination of captopril in pure form and pharmaceutical formulations

A simple, rapid, sensitive and accurate spectrophotometric method for the determination of captopril in pure form and pharmaceutical formulations is developed. The procedure is based on the reaction of copper(II) with captopril in the presence of neocuproine (NC) (2,9-dimethyl-1,10-phenanthroline) reagent in acetate buffer at pH 5.0. Copper(II) is reduced easily by captopril to Cu(I)–neocuproine complex, which shows an absorption maximum at 448 nm. Beer’s law was obeyed in the concentration range 0.3–3.0 μg mL^?1 with a minimum detection limit (LOD) of 0.039 μg mL^?1 and a quantification limit (LOQ) of 0.129 μg mL^?1. For more accurate results, Ringbom optimum concentration ranges was 0.5–2.7 μg mL^?1. The apparent molar absorbtivity and Sandell sensitivity were calculated. The validity of the proposed method was tested by analyzing the pure and pharmaceutical formulations and compared well with those obtained by the official method and demonstrated good accuracy and precision.     

Electrochemical stripping analysis of cadmium on tantalum electrode

A tantalum electrode is reported as an alternative electrode for electrochemical stripping analysis for the first time. Several key operational parameters that influenced the electroanalytical signals were optimized, such as pH of the electrolyte, deposition potential and deposition time. The tantalum electrode yields well-defined and sharp stripping signals for trace cadmium analysis when combined with differential pulse anodic stripping voltammetry. Under the optimized condition the electrode shows good linear behavior in the examined concentration in the range of 20–200 μg L^?1 for cadmium, with a detection limit (3σ) of 0.57 μg L^?1 followed a 5-min deposition step under ? 1.3 V. It also shows good reproducibility with a relative standard deviation of 2.56% for ten consecutive measurements. The sensor was also employed for real sample determination and exhibited excellent performance compared with the result of inductively coupled plasma-mass spectrometry.