Nafion-multi-walled Carbon Nanotubes Supported Tris(bipyridyl)iron(II) for Nicotine Detection

This work reports an electrochemical sensing framework for nicotine determination based on glassy carbon electrode (GC) immobilized with Fe(bpy)₃²⁺ (where bpy is 2,2’-bipyridyl) supported by Nafion and multi-walled carbon nanotubes (Nf-MWCNTs). Fe(bpy)₃²⁺ immobilized Nf-MWCNTs modified GC (GC/Nf-MWCNTs/Fe(bpy)₃²⁺) manifests stable redox peaks, characteristics of Fe(bpy)₃²⁺. The GC/Nf-MWCNTs/Fe(bpy)₃²⁺ exhibits effective electrochemical oxidation of nicotine, diminishing the overpotential relative to GC/Nf-MWCNTs. The limit of detection is 0.1 μM (experimentally observed) with two different linear calibration ranges between 0.1 to 600 μM and 600 to 3000 μM. Electrocatalytic responses observed at GC/Nf-MWCNTs/Fe(bpy)₃²⁺ indicate superior performance for nicotine determination with acceptable selectivity, stability, and reproducibility. Additionally, the nicotine present in real samples such as beedi and tobacco are also analyzed with satisfactory recovery percentages.     

The spectrophotometric and titrimetric determination of gold with ferroin as reagent

A spectrophotometric and a photometric titration method in a two-phase system for the determination of gold with ferroin is reported. Both methods are rapid and reproducible with an accuracy of ±1%. In the spectrophotometric determination Co²⁺, Cu²⁺, Ni²⁺ , Fe³⁺, Zn²⁺, Mn²⁺ and Cr³⁺ do not interfere with the determination of gold and Pt⁴⁺, Pd²⁺, Hg²⁺, Ir⁴⁺ and Os⁴⁺ can be tolerated up to a ratio of 1:1. The titrations can also be carried out in the presence of a number of diverse ions, e.g. Ni²⁺, Cu²⁺, Co²⁺, Fe³⁺, Zn²⁺, Cr³⁺, Mn²⁺, without interference; the platinum metals and Hg²⁺ cause interference but, by the use of the spectrophotometric procedure, this can be reduced.     

Standard addition method applied to the urinary quantification of nicotine in the presence of cotinine and anabasine using surface enhanced Raman spectroscopy and multivariate curve resolution

In this work, urinary nicotine was determined in the presence of the metabolite cotinine and the alkaloid anabasine using surface enhanced Raman spectroscopy and colloidal gold as substrate. Spectra were decomposed using the multivariate curve resolution-alternating least squares method, and pure contributions were recovered. The standard addition method was applied by spiking urine samples with known amounts of the analyte and relative responses from curve resolution were employed to build the analytical curves. The use of multivariate curve resolution in conjunction with standard addition method showed to be an effective strategy that minimized the need for reagent and time-consuming procedures. The determination of the alkaloid nicotine was successfully accomplished at concentrations 0.10, 0.20 and 0.30 μg mL⁻¹ and total error values less than 10% were obtained.     

Study on Determination of Trace Nickel in Water Samples after Separation/enrichment using Microcrystalline Phenolphthalein Loaded with Chelate

The paper presents a novel method for the separation/enrichment of trace Ni²⁺ using microcrystalline phenolphthalein loaded with chelate prior to the determination by spectrophotometry. The effects of different parameters, such as the dosages of phenolphthalein and sodium diethyldithiocarbamate (DDTC), various salts and acidity on the enrichment yield of Ni²⁺ have been investigated to select the experimental conditions. The possible enrichment mechanism of Ni²⁺ was discussed. The results showed that under the optimum conditions, Ni²⁺ could be quantificationally adsorbed on the surface of microcrystalline phenolphthalein in the form of the chelate precipitate of Ni(DDTC)₂, while K⁺, Na⁺, Ca²⁺, Mg²⁺, Zn²⁺, Fe²⁺, Al²⁺, Pb²⁺ and Cd²⁺ could not be adsorbed at all. Therefore, Ni²⁺ was completely separated from the above metal ions in the solution. A new method for the separation/enrichment and determination of trace nickel using microcrystalline phenolphthalein loaded with chelate was established. The proposed method has been successfully applied to the determination of Ni²⁺ in various water samples, and the results agreed well with those obtained by FAAS method.     

Determination of Hg in water and wastewater samples by CV-AAS following on-line preconcentration with silver trap

An online mercury preconcentration and determination system consisting of cold vapor atomic absorption spectrometry (CV-AAS) coupled to a flow injection (FI) method was studied. The method was developed involving the determination of ng/L levels of mercury retained on the silver wool solid sorbent. Experimental conditions such as sample volume, flow rate, stability of the column and effect of foreign ions on the determination of trace amounts of mercury were optimized. The detection limit is 3 ng/L and dynamic range 10–250 ng/L require only 50 mL of sample. The relative standard deviations (RSD) of the determinations are below 4%. The presence of common metal ions, such as K+, Na⁺, Cu²⁺, Pb²⁺, Fe³⁺, Ni²⁺, and Mn²⁺, does not interfere with the measurement of mercury by this method. The method was successfully applied to the determination of mercury in water and wastewater samples.     

2,2′,3,4-Tetrahydroxy-3′-sulpho-5′-nitroazobenzene for spectrophotometric determination of aluminium in pharmaceutical suspensions and granite

A selective and sensitive new spectrophotometric method has been developed for the determination of aluminium. 2,2′,3,4-Tetrahydroxy-3′-sulpho-5′-nitroazobenzene (tetrahydroxyazon SN) formed an orange chelate with aluminium at pH 4. Molar absorptivity of the complex in 1:2 is 5.46 × 10⁴ l mol⁻¹ cm⁻¹ at 479 nm. The method obeys Beer's law in the range of 0.005-1.079 μg ml⁻¹. The determination of aluminium is not interfered with by earth alkaline, alkaline elements, rare earth elements, halides, phosphates, sulphates, urea, ascorbic acid, Sn²⁺, Sr²⁺, Cr³⁺, Cd²⁺, Hg²⁺, or Mn²⁺. The proposed method is rapid and simple, and it has been successfully applied to the determination of aluminium in certified pharmaceutical suspension and granite.     

A selective electromembrane extraction of uranium (VI) prior to its fluorometric determination in water

A novel method for the selective electromembrane extraction (EME) of U⁶⁺ prior to fluorometric determination has been proposed. The effect of extraction conditions including supported liquid membrane (SLM) composition, extraction time and extraction voltage were investigated. An SLM composition of 1% di-2-ethyl hexyl phosphonic acid in nitrophenyl octyl ether (NPOE) showed good selectivity, recovery and enrichment factor. The best performance was achieved at an extraction potential of 80 volts and an extraction time of 14 minutes Under the optimized conditions, a linear range from 1 to 1000 ng mL⁻¹ and LOD of 0.1 ng mL⁻¹ were obtained for the determination of U⁶⁺. The EME method showed good performance in sample cleanup and the reduction of the interfering effects of Mn²⁺, Zn²⁺, Cd²⁺, Ni²⁺, Fe³⁺, Co²⁺, Cu²⁺, Cl⁻ and PO₄³⁻ ions during fluorometric determination of uranium in real water samples. The recoveries above 54% and enrichment factors above 64.7 were obtained by the proposed method for real sample analysis.     

DPASV Method for Determination of Trace Concentrations of Manganese in Non-Buffered Chloride Solutions by Addition of Cyanide as a Masking Agent

 A highly sensitive, selective, and rapid differential pulse anodic stripping voltammetric method at HMDE is described for the determination of trace concentrations of Mn²⁺. The determination of Mn²⁺ in non-buffered chloride solution is seriously disturbed by the presence of Ni²⁺, Co²⁺, Cr³⁺, Zn²⁺ and Cu²⁺ due to intermetallic compound formation. The procedure is based on the addition of low amounts of cyanide as a masking agent. The interference of < 20 μgL⁻¹ of Ni²⁺, Co²⁺ and Cr³⁺ and < 75 μgL⁻¹ of Cu²⁺ and Zn²⁺ can thus be avoided, as the formed cyanide complexes prevent intermetallic compound formation during the short accumulation period. Thus, the addition of cyanide greatly improves the DPASV determination of manganese in non-buffered medium. A comparison between the determination of Mn²⁺ in the presence of a mixed cyanide/non-buffered chloride and in the ammoniacal buffer solution shows that the peak current of manganese in the presence of cyanide is four times higher with the same peak potential. The proposed method is shown to be applicable for the Mn²⁺ determination in both ground and tap water. A good agreement is obtained between the results by DPASV and AAS. Received May 14, 1999. Revision May 25, 2000.     

Qualitative and quantitative 1H NMR spectroscopy for determination of divalent metal cation concentration in model salt solutions,food supplements,and pharmaceutical products by using EDTA as chelating agent

This paper introduces an ¹H NMR method to identify individual divalent metal cations Be²⁺, Mg²⁺, Ca²⁺, Sr²⁺, Zn²⁺, Cd²⁺, Hg²⁺, Sn²⁺, and Pb²⁺ in aqueous salt solutions through their unique signal shift and coupling after complexation with the salt of ethylenediaminetetraacetic acid (EDTA). Furthermore, quantitative determination applied for the divalent metal cations Ca²⁺, Mg²⁺, Hg²⁺, Sn²⁺, Pb²⁺, and Zn²⁺ (limit of quantification: 5–22 μg/ml) can be achieved using an excess of EDTA with aqueous model salt solutions. An internal standard is not required because a known excess of EDTA is added and the remaining free EDTA can be used to recalculate the quantity of chelated metal cations. The utility of the method is demonstrated for the analysis of divalent cations in some food supplements and in pharmaceutical products.     

Determination of caesium microamounts by isotope dilution with substoichiometric separation

Selectivity of isotope dilution analysis with substoichiometric separation for caesium determination has been investigated. Caesium can be extracted with a substoichiometric amounts of bis 1,2-dicarbollylcobaltate in nitrobenzene in the presence of dibenzo-18-crown-6. The method is selective. Other metal ions (K⁺, Na⁺, Mg²⁺, Ca²⁺, Fe³⁺, Al³⁺) do not interfere.     

Stopped-flow kinetic determination of a binary mixture: Simultaneous determination of europium and cerium

A kinetic method is proposed for the simultaneous determination of europium(II) and cerium(III), based on their inductive action on the Cr(VI)-iodide redox reaction in weak acidic medium. The reaction rate was followed by the stopped-flow spectrophotometric technique using starch-iodine complex as indicator. The method can be used for the determination of europium and cerium after reduction with zinc metal powder in the concentration ranges 0–2.1 and 0–1.8 g/ml, respectively. The detection limits are 0.015 g/ml Eu and 0.010 g/ml Ce. 100 to 1000 times higher concentrations of other rare earth metal ions and Th⁴⁺, Al³⁺, Mn²⁺, Hg²⁺, Co²⁺, Ni²⁺, Cu²⁺, Pb²⁺ do not interfere. The method is applied to the determination of europium and cerium in a synthetic sample and in barium yttrium fluoride fluorescent material, with relative standard deviation of about 4%.     

Improved sensitivity for some [corrected] metal ions by use of sulfide in the Belousov-Zhabotinskii oscillating reaction

A highly sensitive method for the determination of trace amounts of transition metal ions by use of sulfide in the Belousov-Zhabotinskii (B-Z) oscillating chemical reaction is proposed. The use of sulfide increased strongly the sensitivity of the B-Z reaction for transition metal ions, such as Ag⁺, Pb²⁺, Hg²⁺, Cd²⁺, Cu²⁺,and Bi³⁺. Results showed that the variational ratio of oscillating period (P_R) is linearly proportional to the negative logarithm of concentration of metal ions. The detection limit is down to 10⁻¹² mol L⁻¹. Various influencing factors on the determination were also examined.     

Extraction-photometric determination of vanadium(V) with N-hydroxy-N-m-tolyl-N′-(2-methyl-5-chloro)phenyl-p-toluamidine hydrochloride in the presence of acetic,monochloroacetic, and phenylacetic acids

N-Hydroxy-N-m-tolyl-N′-(2-methyl-5-chloro)phenyl-p-toluamidine hydrochloride (HTMCPTH), a monobasic and bidentate chelating agent which reacts with vanadium(V) in carboxylic acid media to develop a blue-violet complex, has been employed as a highly selective reagent for extraction and direct photometric determination of the metal. Solvent extraction experiments indicate that from aqueous acetic acid (1.0–10.0 M), monochloroacetic acid (0.1–10.0 M), and phenylacetic acid (at pH 0.5–6.0) vanadium(V) is quantitatively extracted into chloroform. Almost all common ions including Fe³⁺, Cu²⁺, Ni²⁺, Co²⁺, Mn²⁺, Cr³⁺, Ti⁴⁺, Zr⁴⁺, and Mo⁶⁺ do not interfere with the proposed method. The procedure has been utilized for accurate determination of vanadium in standard steels.     

Complexometric and spectrophotometric determination of thorium(IV), cerium(III), and uranium(VI), using quinizarin sulphonic acid after separation with ion-exchange resins

A method is described for the complexometric EDTA-titration and spectrophotometric determination of Th⁴⁺ Ce³⁺, and UO₂²⁺ in binary or ternary mixtures after primary separation with ion-exchange resin. As indicator or coloring agent, quinizarin sulphonic acid is used. The EDTA titration gives accurate results with Th⁴⁺ and Ce³⁺ only, but the spectrophotometric method proved to be suitable for determination of small quantities of the metal ions.     

On-line preconcentration and simultaneous determination of heavy metal ions by inductively coupled plasma-atomic emission spectrometry

A flow injection analysis system for on-line preconcentration and simultaneous determination of Bi³⁺, Cd²⁺, Co²⁺, Cu²⁺, Fe³⁺, Ni²⁺, Pb²⁺ and Zn²⁺ in aqueous samples by inductively coupled plasma (ICP)-atomic emission spectrometry with a charge coupled detector is described. The preconcentration of analytes is accomplished by retention of their chelates with sodium diethyldithiocarbamate in aqueous solution on a solid phase containing octadecyl silica in a minicolumn. Methanol, as eluent, is introduced into the conventional nebulizer of the ICP instrument. The effects of different parameters, including preconcentration flow rate (equal to sample flow rate (SR)), eluent flow rate (ER), weight of solid phase (W) and eluent loop volume (EV), were optimized by the super-modified simplex method. The optimum conditions were evaluated to be SR 7.2 ml min⁻¹, ER 3.5 ml min⁻¹, W of 100 mg and EV of 0.8 ml. An enrichment factor of 312.5 for each analyte was obtained. The detection limits of the proposed method for Bi³⁺, Cd²⁺, Co²⁺, Cu²⁺, Fe³⁺, Ni²⁺, Pb²⁺ and Zn²⁺ were evaluated as 1.3, 1.0, 0.8, 0.3, 14.7, 0.5, 5.5 and 0.1 ng l⁻¹, respectively. The effect of several metal ions on percent recovery was also studied. The method was applied to the recovery of these heavy metals from real matrices and to the simultaneous determination of these cations in different water samples.     

Spectrophotometric microdetermination of iron(III) by tris-pyrrolidone(5)-hydroxamato(2)-chelate

The optimum conditions for the spectrophotometric determination of iron(III) with neutrial tris-PIH-chelate are: pH = 5, λ = 430 nm, PIH concentration 2 × 10⁻² M, and iron (III) concentration (0.6–3.3) × 10⁻⁴ M. Under these conditions the suggested method conforms to Beer's law and the molar absorptivity is 2800. The relative accuracy is ±0.48% based upon evaluation from the calibration curve and ±1.02% based upon algebraic equations. The precision is ±0.53% as deviation from the mean, and 0.69% as SD.The suggested method suffers from no interference from Fe²⁺, Al³⁺, Cr³⁺, Pb²⁺, Hg²⁺, Cd²⁺, Ni²⁺, Co²⁺, Zn²⁺, Mn²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Mg²⁺, Ag⁺, F⁻, and tartrate, but interference is caused by U⁶⁺, V⁵⁺, Mo²⁺, Cu²⁺, (in larger concentrations) or by oxalate and citrate. The method may be used either as a sensitive spectrophotometric or visual method.     

Study on Determination of Trace Copper by Spectrophotometry after Flotation Separation Using Microcrystalline Adsorption System

The paper presents a novel method for the flotation separation of Cu²⁺ using microcrystalline adsorption system prior to the determination by spectrophotometry. The effects of different parameters, such as the dosages of NH₄SCN and octadecyl trimethyl ammonium bromide (OTMAB), various salts on the flotation yield of Cu2+ have been investigated to select the optimum experimental conditions. The possible flotation separation mechanism of Cu²⁺ was discussed. The results showed that under the optimum conditions, octadecyl trimethyl ammonium bromide cation (OTMAB⁺) reacted with SCN^‐ to produce the microcrystalline matter (Ms‐M) of (OTMAB⁺·SCN^‐), the water‐insoluble ternary association complex of [Cu(SCN)₄] (OTMAB)₂ which produced by Cu²⁺ and SCN^‐, OTMAB⁺ was quantificationally adsorbed on the surface of Ms‐M of (OTMAB²⁺·SCN^‐) and was floated above water phase, the liquid‐solid phases were formed with clear interface. In this condition, K⁺, Na⁺, Ca²⁺, Mg²⁺, Al³⁺, Fe²⁺, Mn²⁺, Ni²⁺, Cd²⁺ and Co²⁺ could not be floated. Therefore, Cu²⁺ was separated completely from the above metal ions. A new method of determination of trace copper by flotation separation was established. The proposed method has been successfully applied to the determination of Cu²⁺ in plating waster water, and the results agreed well with AAS method. The recoveries were 93.3%～107.8%, and the RSD was 1.9%～2.1%.     

Study on Spectrophotometric Method for Determination of Bismuth after Flotation Separation Using Microcrystalline Adsorption System

The paper presents a novel method for the flotation separation of Bi³⁺ using microcrystalline adsorption system prior to the determination by spectrophotometry. The effects of different parameters, such as the dosages of KI and dodecyl trimethyl ammonium bromide (DTMAB), various salts and acidity etc. on the flotation yield of Bi³⁺ have been investigated to select the optimum experimental conditions. The possible flotation separation mechanism of Bi³⁺ was discussed. The results showed that under the optimum conditions, dodecyl trimethyl ammonium bromide cation (DTMAB⁺ ) reacted with I^? to produce themicrocrystalline matter (Ms‐M) of (DTMAB⁺·I^?), the water‐insoluble ternary association complex of (DTMAB)₃[BiI₆] which produced by Bi³⁺ and I^?, DTMAB⁺ was quantificationally adsorbed on the surface of Ms‐M of (DTMAB⁺·I^?) and was floated above water phase, the liquid‐solid phases were formed with clear interface. In this condition, K⁺, Na⁺, Ca²⁺, Mg²⁺, Co²⁺, Ni²⁺, Mn²⁺, Zn²⁺, Fe²⁺ and Al³⁺ could not be floated. Therefore, Bi³⁺ was separated completely from the above metal ions. A new method for flotation separation and determination of bismuth using microcrystalline adsorption system was established. The proposed method has been successfully applied to the determination of Bi³⁺ in bismuthiferous drug samples, and the results agreed well with those obtained by pharmacopoeia method. The recoveries were 94.1%～106.8%, and the RSD was 1.5%～2.3%.     

Nanometer-sized alumina coated with chromotropic acid as solid phase metal extractant from environmental samples and determination by inductively coupled plasma atomic emission spectrometry

A method for solid phase extraction of trace metals such as Cd²⁺, Cr⁶⁺, Cu²⁺, Fe³⁺, Mn²⁺, Ni²⁺, Pb²⁺ and Zn²⁺ using nanometer-sized alumina coated with chromotropic acid prior to determination by inductively coupled plasma atomic emission spectrometry (ICP-AES) has been developed. Various influencing parameters on the separation and preconcentration of trace metals, pH, flow rate, sample volume, amount of adsorbent, concentration of eluent and sorption kinetics have been studied. The detection limits for Cd²⁺, Cr⁶⁺, Cu²⁺, Fe³⁺, Mn²⁺, Ni²⁺, Pb²⁺ and Zn²⁺ were found to be 0.14, 0.62, 0.22, 0.54, 0.27, 0.28, 0.53 and 0.38 ng ml^− 1, respectively. The adsorption capacity of the solid phase adsorption material is 10.3, 11.3, 14.5, 16.4, 15.1, 11.7, 15.4 and 16.8 mg g^− 1 for Cd²⁺, Cr⁶⁺, Cu²⁺, Fe³⁺, Mn²⁺, Ni^2+, Pb²⁺ and Zn²⁺, respectively. The preconcentration factor was obtained in the range of 50-100 for all studied metal ions. Coexisting ions over a high concentration range have not shown any significant effects on the determination of aforesaid metal ions. The accuracy of the proposed method was tested by standard reference materials (NIST 1643e: water, NIST 1573a: tomato leaves and NIST 1568a rice flour) and natural waters and the results obtained were in good agreement with the certified values.     

Study on Separation/Enrichment and Determination of Mercury(II) using Microcrystalline Thymolphthalein Loaded with Ternary Association Complex

The paper presents a novel method for the separation/enrichment of Hg²⁺ using microcrystalline thymolphthalein loaded with ternary association complex prior to the determination by spectrophotometry. The effects of different parameters, such as the dosages of KI and dodecyl trimethyl ammonium bromide (DTAB) and thymolphthalein, various salts and acidity etc. on the enrichment yield of Hg²⁺ have been investigated to select the experimental conditions. The results showed that in the presence of 1.0 g NaCl, when the dosage of 0.1 M KI solution was 1.50 mL and 5.0 × 10⁻³ M dodecyl trimethyl ammonium bromide (DTAB) solution was 1.50 mL respectively, the water‐insoluble ternary association complex of (DTAB)₂(HgI₄) which produced by Hg²⁺ and I⁻, DTAB cation (DTAB⁺) was quantificationally absorbed on the surface of microcrystalline thymolphthalein Therefore, Hg²⁺ was separated completely from Zn²⁺, Mn²⁺, Ni²⁺, Co²⁺, Fe³⁺, Al³⁺, Pb²⁺, Bi³⁺ and Cr³⁺ etc. by contolling acidity. The possible enrichment mechanism of Hg²⁺ was deduced. The proposed method has been successfully applied to the determination of Hg²⁺ in the sample of industrial waster water, and the results agreed well with the dithizone method. The recoveries were 94.5%∼106.5%, and the RSD was 2.0%∼2.8%.