A cleaner and simple spectrophotometric micro-fluidic procedure for copper determination using nitroso-R salt as chromogenic agent

A cleaner and simple spectrophotometric method using microflow analysis (muFA) was performed. It consisted of a T-junction with microcoil on a polymethyl methacrylate (PMMA) chip which was fabricated by laser ablation and a molded polydimethylsiloxane (PDMS) as top plate. The fabricated PMMA chip was integrated with light emitting diode (LED) as light source and spectrometer as detector. The proposed device was applied to determining copper in water samples using nitroso-R salt as chromogenic reagent at 495nm. It was found that the proposed muFA system was with less reagents and samples consumption with tiny waste generation. The relative standard deviation (R.S.D.) was less than 2% (n=11) with the percentage recovery of 98.0+/-1.7% (n=7). The linear range for determination of copper in water samples was over the range of 0.05-3.0mugmL(-1) with a correlation coefficient (r(2)) of 0.999. The limit of detection (3sigma) was 47ngmL(-1) with a sample throughput of 30h(-1).     

Simultaneous flow injection determination of ammoniacal nitrogen and chloride in industrial effluent water with a combined on-line gas diffusion/dialyser unit

An on-line gas diffusion/dialyser unit has been designed and incorporated into the manifold of a flow injection system for the simultaneous determination of two different species in a single sample injected into the FIA system. A fast and reliable fully automated two-component flow injection procedure has been carried out where a single sample (50 l industrial effluent water) is injected into a carrier stream and simultaneously gas diffused and dialysed in a single on-line gas diffusion/dialyser unit for the determination of ammonia and chloride, respectively. The results obtained for the ammoniacal nitrogen and chloride in industrial effluent water compared well with data obtained by standard methods. The relative standard deviation for industrial effluent water samples with concentrations of ammoniacal nitrogen in the range between 0.050 and 1 g/l and chloride from 0.127 to 2.531 g/l have been better than 1.0% for ammoniacal nitrogen and 0.5% for chloride, respectively. The proposed system could be attractive for routine analyses of industrial effluent water.     

Design of an optical sensor for indirect determination of isoniazid

The characterization of an optical sensor membrane is described for indirect determination of isoniazid. The sensing membrane was consisted of immobilized 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine (PDT) on a triacetylcellulose membrane. The procedure is based on the reaction of Fe(III) with isoniazid in the presence of PDT. Fe(III) is reduced by isoniazid to Fe(II) which forms a complex with PDT. The complex shows an absorption maximum at 558nm. By measuring the absorbance of the complex at this wavelength, isoniazid can be determined in the range of 0.62-6.15mugmL(-1). This method was applied to the determination of isoniazid in pharmaceutical formulation and enabled the determination of isoniazid in microgram quantities.     

Direct and precise determination of environmental radionuclides in solid materials using a modified Marinelli beaker and a HPGe detector.

A simple but precise detection method was studied for the determination of natural radionuclides using a conventional HPGe detector. A new aluminium beaker instead of a plastic Marinelli beaker was constructed and examined to reach radioactive equilibrium conditions between radon and its daughter elements without the escape of gaseous radon. Using this beaker fifteen natural radionuclides from three natural decay series could be determined by direct gamma-ray measurement and sixteen radionuclides could be determined indirectly after radioactive equilibrium had been reached. Analytical results from ground water were compared with those from conventional alpha spectroscopy and the results agreed well within 12% difference. Nitrogen gas purge was used to replace the surrounding air of the detector to obtain a stable background and reducing the interference of radon daughter nuclides in the atmosphere. The use of nitrogen purging and the aluminium Marinelli beaker results in an approximately tenfold increase of sensitivity and a decrease of the detection limit of 226Ra to about 0.74 Bq kg(-1) in soil samples.     

烘箱消解-镉铜还原法测定地表水中总氮

提出了烘箱消解-镉铜还原法测定地表水中总氮含量的方法。氮的浓度在7.637×10-4～1.375×10-2 mmol.L-1范围内与其吸光度呈线性关系,检出限(3S/N)为6.704×10-5 mmol.L-1。对人工海水、实验室自来水、海水和湖水中总氮进行测定,其回收率和相对标准偏差(n=6)分别在96.7%～101.3%和3.7%～3.9%之间。     

A semi-automatic alkaline peroxodisulphate method for the routine determination of total dissolved nitrogen in sea water

Nydahl's method for the determination of dissolved organic nitrogen (DON) in distilled water has been modified for the determination of total dissolved nitrogen (TDN) in sea water. Samples (9 cm³) are digested batch-wise with alkaline potassium peroxodisulphate solution. An improved buffering system permits the automatic measurement of the nitrate formed, and allows the analysis of 50–80 samples per day. DON may be determined as the difference between TDN and the sum of inorganic nitrogen species. The standard deviation of TDN determinations is 0.7 μg N dm^-3 at about 15 μg TDN dm^-3. The method is applied to a range of samples including tanker ballast water, oil platform production water, and zooplankton.     

Spectrophotometric determination of inorganic mercury (II) after preconcentration of its diphenylthiocarbazone complex on a cellulose column

A simple and a relatively green methodology have been developed for the preconcentration of mercury based on the adsorption of its diphenylthiocarbazone complex on a cellulose column. The effects of various parameters such as effect of acidity, eluting agents, stability of the column, sample volume, interfering ions, etc. have been studied in detail. The adsorbed complex could be easily desorbed using environmentally benign polyethylene glycol-400 and the concentration of mercury was determined using visible spectrophotometry. The calibration graph was linear in the range 0-2mugmL(-1) of mercury with a detection limit of 2mugL(-1) and the validity of the proposed method was checked by studying the recovery of mercury in spiked tap water, well water and sea water samples. The highest preconcentration factor achieved for quantitative recovery (>95%) of mercury (II) was 33 for a 500mL sample volume. The method was also applied to the analysis of mercury content in city waste incineration ash (CRM176). The relative standard deviation of the method was found to be 3.5%.     

Determination of ammonium in river water and sewage samples by capillary zone electrophoresis with direct UV detection

We developed capillary zone electrophoresis (CZE) with direct UV detection for determination of ammonium in environmental water samples. Ammonium in the samples was partly converted into ammonia in the alkaline background electrolyte (BGE) during migration and was detected by molecular absorption of ammonia at 190 nm in approximately 7 min. The limit of detection (LOD) for ammonium was 0.24 mg/l (as nitrogen) at a signal-to-noise ratio of three. The respective values of the relative standard deviation (RSD) of peak area, peak height, and migration time for ammonium were 2.1, 1.8, and 0.46%. Major alkali and alkaline earth metal ions coexisting in the samples did not interfere with ammonium determination by the proposed method. The proposed method determined ammonium in surface water and sewage samples. The results were compared to those obtained using ion chromatography (IC).     

Rapid and sensitive determination of ethylenediaminetetraacetic acid and diethylenetriaminepentaacetic acid in water samples by ion-pair reversed-phase liquid chromatography--electrospray tandem mass spectrometry

A new method is presented for the quantitative determination of ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA) from aqueous samples without an enrichment step. It consist of the formation of the Fe(III) complexes of EDTA and DTPA, liquid-chromatography with a volatile ion-pairing agent and determination by electrospray ionization-tandem mass spectrometry (ESI-MS/MS). Limits of quantification (LOQ) of 1.0 and 0.6 microgL(-1) for EDTA and DTPA were obtained, allowing the direct injection of most aqueous environmental samples without any preceding enrichment. With a more recent mass spectrometer, the LOQ could be further decreased by almost one order of magnitude. Parallel analysis of real samples by a standardized method employing enrichment, derivatization and GC-MS analysis yielded comparable results. The method was applied to the determination of both complexing agents in several wastewater, surface water and drinking water samples, showing that EDTA is an omnipresent contaminant in partially closed water cycles.     

Determination of uranium in tap water by ICP-MS

A fast and accurate procedure has been developed for the determination of uranium at microg L(-1) level in tap and mineral water. The method is based on the direct introduction of samples, without any chemical pre-treatment, into an inductively coupled plasma mass spectrometer (ICP-MS). Uranium was determined at the mass number 238 using Rh as internal standard. The method provides a limit of detection of 2 ng L(-1) and a good repeatability with relative standard deviation values (RSD) about 3% for five independent analyses of samples containing 73 microg L(-1) of uranium. Recovery percentage values found for the determination of uranium in spiked natural samples varied between 91% and 106%. Results obtained are comparable with those found by radiochemical methods for natural samples and of the same order for the certified content of a reference material, thus indicating the accuracy of the ICP-MS procedure without the need of using isotope dilution. A series of mineral and tap waters from different parts of Spain and Morocco were analysed.     

Kinetic photometric determination of copper at the nanograms per millilitre level in real samples

A highly sensitive and selective kinetic method is proposed for the determination of nanogram amounts of copper(II) based on its catalytic effect on the oxidation of 3-hydroxybenzaldehyde azine by potassium peroxydisulphase in an ammoniacal medium. The rate of the reaction is monitored spectrophotometrically at 465 nm and the method allows the determination of copper concentrations in the range 0.5–18 ng ml^?1 with a relative standard deviation of about 2%. The proposed method is virtually specific to copper and has been applied satisfactorily to its determination in a variety of food and industrial samples. A possible mechanism for the catalysed reaction is proposed.     

Determination of copper in white-metal bearing alloys

A method is proposed for the determination of copper in white-metal bearing alloys by direct controlled-potential electrolysis with a tantalum cathode at -0.32 V vs. SCE in a sulphate/bisulphate buffered electrolyte (pH 2) with fluoroboric acid and sodium tartrate as masking agents. Only Bi(III) interferes. Any co-deposited Bi can be corrected for by its spectrophotometric determination with Semi-Xylenol Orange after preconcentration with La(III) as carrier, from an ammoniacal solution containing the redissolved deposit. Any residual Cu(II) in the electrolyte is determined by spectrophotometry with 2,9-dimethyl-1, 10-phenanthroline. The standard deviation of this method has been found to be 0.03 mg (n = 12) and its relative standard deviation from 0.03 to 0.17%. It has been successfully used for referee analysis and certification of standard reference materials.     

Using blood hemoglobin for blood analysis

This paper demonstrates that the spectrophotometric properties of blood hemoglobin (Hb) can be used for the direct determination of biochemical compounds in blood. Glucose is used as a model, but the methodology can be applied to many other compounds (only a previous enzymatic reaction producing H(2)O(2) is needed). In order to develop the method, a model relating the Hb absorbance variation during the reaction with the glucose concentration has been developed to provide theoretical support for the method and to predict its application to other compounds. In addition, clear blood samples need to be prepared without pre-treatment and lateral reactions of H(2)O(2) with other blood constituents need to be blocked; this has been achieved with 100 : 1 v/v blood dilution in bi-distilled water and azide addition. The linear response range of the method can be fitted between 2 and 540 mg dL(-1) glucose relative to the original blood sample (RSD about 4%, 70 mg dL(-1)). The analyte concentration can be obtained by an absolute calibration method or by the standard addition method; both have been applied for direct glucose determination in several blood samples and good correlations with those obtained by an automatic analyzer have been obtained.     

Rapid and direct determination of glyphosate and aminomethylphosphonic acid in water using anion-exchange chromatography with coulometric detection

A simple, rapid, and low-cost coulometric method for direct detection of glyphosate and aminomethylphosphonic acid (AMPA) in water samples using anion-exchange chromatography and coulometric detection with copper electrode is presented. Under optimized conditions, the limits of detection (LODs) (S/N=3) were 0.038microgml(-1) for glyphosate and 0.24microgml(-1) for AMPA, without any preconcentration method. The calibration curves were linear and presented an excellent correlation coefficient. The method was successfully applied to the determination of glyphosate and AMPA in water samples without any kind of extraction, clean-up, or preconcentration step. No interferent was found in the water, like this, the recovery was, practically, 100%.     

Catalytic spectrophotometric determination of trace amounts of copper(II) with 3-hydroxy-2-naphthoic acid

A very sensitive catalytic spectrophotometric method for the determination of copper(II) concentrations as low as 0.06 ng/ml is described. This method is based on the oxidation of 3-hydroxy-2-naphthoic acid by hydrogen peroxide in ammoniacal medium, catalysed by copper(II). The results of an exhaustive study of interferences are given. The new method is applied to determination of copper in atmospheric aerosol samples. A qualitative study of the mechanism by means of electron paramagnetic resonance spectroscopy is also included.     

Large-volume injection electrothermal AAS combined with tungsten-treated pyrolytic graphite furnace: determination of cadmium in tap, snow and river water samples with phosphate modifier.

A large-volume (100 microl) injection-ETAAS with W-treated PG furnace combined with a phosphate modifier was applied to the determination of unpolluted levels of Cd in tap, snow and river-water samples. The limit of detection of 1.1 ng l(-1) was observed for a 4 w/v% NH4H2PO4 modifer. Matrix interference studies were tested for major ion species well found in fresh water. The direct determination of Cd in certified river water (12 +/- 2 ng l(-1)) was carried out and the observed value was in agreement with the certified one. The good recoveries of Cd added to real environmental water samples were also observed. This method was applied to the determination of Cd in unpolluted environmental water samples.     

Determination of aniline in environmental water samples by alternating-current oscillopolarographic titration

A new method for the determination of aniline in environmental water based on oscillopolarographic titration was presented in this paper. Several factors including the kind, concentration, and volume of acid, the dosage of potassium bromide, the temperature and concentration of concomitant substances were investigated in detail. The experimental results indicated that this method was simple, rapid, and sensitive. The linear range was 8.367×10-4 to 2.789×10-2 mol L-1, the relative standard deviation (R.S.D.) was lower than 0.96%, and the spiked recoveries of aniline in environmental water samples were in the range of 99.4-106.9% under the optimal conditions. The results indicated that the present method could be used as an alternative method for aniline determination in realworld water samples.     

Preparation and evaluation of a molecularly imprinted sol-gel material for on-line solid-phase extraction coupled with high performance liquid chromatography for the determination of trace pentachlorophenol in water samples

A highly selective imprinted amino-functionalized silica gel sorbent was prepared by combining a surface molecular imprinting technique with a sol-gel process for on-line solid-phase extraction-HPLC determination of trace pentachlorophenol (PCP) in water samples. The PCP-imprinted amino-functionalized silica sorbent was characterized by FT-IR, SEM, nitrogen adsorption and the static adsorption experiments. The imprinted functionalized silica gel sorbent exhibited high selectivity and offered a fast kinetics for the adsorption and desorption of PCP. The prepared sorbent was shown to be promising for on-line solid-phase extraction for HPLC determination of trace levels of PCP in environmental samples. With a sample loading flow rate of 5 ml min(-1) for 2 min, an enhancement factor of 670 and a detection limit (S/N = 3) of 6 ng l(-1) were achieved at a sample throughput of five samples h(-1). The precision (RSD) for nine replicate on-line sorbent extractions of 10 microgl(-1) PCP was 3.8%. The sorbent also offered good linearity (r = 0.9997) for on-line solid-phase extraction of trace levels of PCP. The method was applied to the determination of PCP in local lake water, river water and wastewater samples.     

Indirect ultraviolet determination of silver with nickelocyanide ion by flow injection analysis

A flow-injection method for the ultraviolet spectrophotometric determination of silver, based on its reaction with nickelocyanide ion, Ni(CN)²⁻₄, in ammoniacal buffer medium (pH 10) and subsequent measurement of the decrease in the absorption of the Ni(CN)²⁻₄ complex at 275 nm is described. The calibration graph is linear in the range 10–400 μm silver. At a sampling rate of about 60 samples h⁻¹ with 35 μl sample injections, precision was about 1% relative standard deviation. The proposed method was successfully applied to the determination of silver in some common silver minerals.