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Analytical Methods (v.4, #2)

Front cover (pp. 315-315).

Urine samples after oral administration of toremifene were investigated by liquid chromatography quadrupole time-of-flight tandem mass spectrometry (LC-QTOFMS) with accurate mass measurement. Two new metabolites were detected in positive full scan and targeted MS/MS experiments and their chemical structures were characterized as: 3-methoxy-4,4′-dihydroxy-toremifene and 4-hydroxy-N-oxide-toremifene. As the two metabolites could be detected in all urine samples during one week after intake, they should be potential biomarkers for monitoring the oral administration of toremifene in doping analysis.

Inside front cover (pp. 316-316).

Remote and automated detection of organic compounds in subsurface aquifers is crucial to superfund monitoring and environmental remediation. Current monitoring techniques use expensive laboratory instruments and trained personnel. The use of a filled tubular preconcentrator combined with a chemicapacitive detector array presents an attractive option for the unattended monitoring of these compounds. Five preconcentrator materials were exposed to common target compounds of subsurface remediation projects (1,1,2-trichloroethane, trichloroethylene, t-1,2-dichloroethylene, benzene, and perchloroethylene). Rapid heating of the tube caused the collected, concentrated effluent to pass over the surface of a chemicapacitive detector array coated with four different sorbent polymers. A system containing a porous ladder polymer and the sensor array was subsequently used to sample the analytes injected onto sand in a laboratory test, simulating a subsurface environment. With extended collection times, effective detection limits of 5 ± 3 ppbV for 1,1,2-trichloroethane and 145 ± 60 ppbV for benzene were achieved. Effects of the preconcentrator material structure, the collection time, and sensor material on the system performance were observed. The resultant system presents a solution for remote, periodic monitoring of chlorinated organic compounds and other volatile organic compounds in a soil matrix.

Contents list (pp. 317-330).

The reversible electrochemical modulation of fluorescence and selective sensing of ascorbic acid has been achieved using a DCIP-CA-CdTe QD system. Ascorbic acid could be detected over a linear range from 2.33 μM to 56.49 μM, with a detection limit of 0.50 μM.

Low field magnetic resonance techniques in the development of nanomaterials for biomedical applications by Carla J. Meledandri; Dermot F. Brougham (pp. 331-341).

In recent years there has been rapid progress in the development of nanomaterials, and in particular magnetic nanomaterials, for magnetic resonance imaging and other biomedical applications. Using selected highlights from recent literature we describe the magnetic resonance methods that are used to measure the effects of agents on image contrast. We also show how these methods offer new insight into magnetic order in the colloidal state, a critical factor for all biomedical applications.

Silver(I) ion detection in aqueous media based on “off-on” fluorescent probe by Chunwei Yu; Jun Zhang; Mingyu Ding; Lingxin Chen (pp. 342-344).

A novel and easily available fluorescent probe bearing naphthalimide and thiosemicarbazide groups has been designed. The probe H1 displays high selectivity and sensitivity to Ag⁺ over other metal ions in aqueous media.

Engineering a unimolecular multifunctional DNA probe for analysis of Hg²⁺ and Ag⁺ by Xiaoxiao He; Zhihe Qing; Kemin Wang; Zhen Zou; Hui Shi; Jin Huang (pp. 345-347).

We reported a unimolecular multifunctional DNA probe (UMDP) based on the ion-mediated conformation transformation of oligonucleotide, which can directly detect Hg²⁺ and Ag⁺ ions simultaneously.

Simultaneous determination of two important dopamine metabolites at physiological pH by voltammetry by S. Brillians Revin; S. Abraham John (pp. 348-352).

Simultaneous determination of two important dopamine metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), at physiological pH was demonstrated for the first time using the electropolymerized film of a 3-amino-5-mercapto-1,2,4-triazole modified glassy carbon electrode.

A new “capturer” for electrochemical detection of organophosphate pesticides: The hydroxylation and carbonylation carbonaceous nanospheres by Yan Wei; Ran Yang; Zheng Guo; Chao Gao; Lun Wang; Jin-Huai Liu; Xing-Jiu Huang (pp. 353-356).

The hydroxylation and carbonylation carbonaceous nanospheres (H/C-CNSs) were used in electrochemical detection of organophosphate pesticides (OPs) for the first time. H/C-CNSs were proven as a new sorbent for solid-phase extraction of OPs without the need for an external modification. Under the optimized conditions, OPs, such as methyl parathion, ethyl parathion, fenitrothion, and paraoxon, could be detected by differential pulse voltammetry (DPV) without any interference from other aromatic derivatives, showing a superior selective performance.

A new labelling reagent for glycans analysis by capillary electrophoresis-mass spectrometry by Cai Tie; Xin-Xiang Zhang (pp. 357-359).

In this work, a novel labelling reagent with multi-charges was designed and developed for glycans capillary electrophoresis-mass spectrometry (CE-MS) analysis. Glycans labelled with this reagent have multiple charges. The results showed that the separation efficiencies of glycans were improved and the sensitivities of large glycans were enhanced more than 10 fold.

A graphene oxide–rhodamine 6G nanocomposite as turn-on fluorescence probe for selective detection of DNA by Xue Wang; Shuhua Zhong; Yu He; Gongwu Song (pp. 360-362).

Indoor Air Quality (IAQ) can be significantly deteriorated by high levels of bioaerosols that may cause adverse health effects in building occupants. There is no standard method for the quantification of this kind of pollutants and several protocols and sampling devices are used. The aim of this work was to compare three commonly used portable air samplers available in the market. DUO SAS SUPER 360, SAMPL'AIR and SPIN AIR units were tested simultaneously for bacteria quantification in a laboratory room in realistic conditions. The results obtained showed that the SPIN AIR unit was the most precise and recovered a higher amount of colony-forming units; consequently this sampler seems to be better for indoor-air bioaerosol concentration measurements. Additionally, positive-hole correction can be avoided due to the SPIN AIR sampling head rotation mechanism. The mean bacterial concentration measured by the other two models was not significantly different. However, due to the high dispersion of the DUO SAS SUPER 360 results, many repetitions are necessary to obtain a reliable measure with this device.

Determination of amino acids and amines in mammalian decomposition fluid by direct injection liquid chromatography-electrospray ionisation-tandem mass spectrometry by Lisa M. Swann; Francesco Busetti; Simon W. Lewis (pp. 363-370).

A sensitive and selective analytical method utilising liquid chromatography-electrospray ionisation-tandem mass spectrometry (LC-ESI-MS/MS) operated in multiple reaction monitoring mode was developed for the semi-quantitative determination of 19 biogenic amines and amino acids in mammalian (porcine) decomposition fluid. The effect of the matrix on analyte response was initially investigated by diluting crude samples and by injecting various volumes in the LC-MS system. It was found that the matrix had little effect on analyte signal intensities when small volumes (0.1 to 1 μL) of crude samples or 1 : 10 diluted samples were injected into the LC-ESI-MS/MS system. The standard addition method was also investigated for quantitative assessment but proved unsuccessful, possibly due to poor ionisation of the electrospray interface at high analyte concentrations. Therefore a method using external calibration was used for semi-quantitative determination of the analytes in decomposition fluid. The LC-ESI-MS/MS method enabled identification of all target compounds as being present. In addition a 14-day cyclic trend in the concentrations of two amino acids, phenylalanine and tryptophan, was tentatively established. General increasing trends with respect to time and temperature were also observed for putrescine and indole.

Investigation of the optimal transient times for chronoamperometric analysis of diffusion coefficients and concentrations in non-aqueous solvents and ionic liquids by Linhongjia Xiong; Leigh Aldous; Martin C. Henstridge; Richard G. Compton (pp. 371-376).

We report the optimal transient times for chronoamperometric experiments in order to simultaneously determine accurate values of concentration (c) and diffusion coefficient (D), or alternatively the number of electrons passed (n) providing c is known. This is achieved by the analysis of the current-time transients resulting from potential steps for the oxidation of ferrocene in acetonitrile and the reduction of cobaltocenium in 1-ethyl-3-methylimidazolium bis(trifluoromethyl-sulfonyl)imide. The analysis is based upon Shoup and Szabo approximation, which has been reported to describe the current response over all time values to within an error of 0.5% [D. Shoup and A. Szabo, Journal of Electroanalytical Chemistry, 1982, 140, 237-245]. The error is quantified through comparing the resulting chronoamperometric data with simulation at all transient times. In addition, an alternative simple approach to the simultaneous determination of nc and D values is proposed by independently investigating the short and long time regimes of chronoamperometric transients. The chronoamperometry of hydrazine is investigated as a multielectron example process.

Application of ionic liquid matrices in spectral analysis of poly(lactide) - solid state NMR spectroscopy versus matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry by Beata Miksa; Marek Sochacki; Jan Libiszowski; Andrzej Duda; Wlodzimierz Ciesielski; Marek J. Potrzebowski (pp. 377-383).

The work presented here shows the complementarity of Solid State NMR (SS NMR) spectroscopy and Matrix-Assisted Laser Desorption/Ionization-time-of-flight (MALDI-TOF) mass spectrometry in spectral analysis of poly(l-lactide) (PLLA) using second-generation ionic liquid matrices (ILM II) prepared from N,N-diisopropylethylamine (DEA) and DHB (2,5-dihydroxybenzoic acid), IAA (3-indoleacrylic acid), and HABA (2-(4-hydroxyphenylazo) benzoic acid). The ¹³C cross-polarization (CP) magic angle spinning (CP/MAS) SS NMR technique was used to study the structure of ionic liquid matrices, their thermal stability, and the influence of ILM on the morphology of polymer. A comparison of MALDI-TOF spectra for samples prepared employing the dried droplet (DD) and the solvent free (SF) mode showed that the former approach gave better results (signal to noise ratio) very likely due to intimate contact between analyte and matrix domains. This hypothesis was verified by analysis of CP build-up curves for DHB–DEA–PLLA samples prepared employing both methods. We also showed that an alternative method of sample preparation based on the melting of ILM II together with a suspended polymer in the liquid matrix is unsatisfactory, particularly for those matrices which can undergo isomerization at higher temperatures (e.g., HABA–DEA and IAA–DEA).

Multivariate optimization of cloud point extraction for the simultaneous spectrophotometric determination of cobalt and nickel in water samples by Morteza Bahram; Somayeh Khezri (pp. 384-393).

In this paper a new and simple cloud point extraction (CPE) method has been developed for the preconcentration and simultaneous spectrophotometric determination of binary mixtures of cobalt and nickel in water samples, without prior separation steps. This method is based on the mean centering of ratio spectra. 1-nitroso-2-naphthol was used as the chelating agent and an anionic surfactant, sodium dodecyl sulfate (SDS), was used as extracting agent at room temperature. Central composite design (CCD) based response surface method (RSM) was applied for the optimization of main experimental parameters such as pH of solutions, concentration of the chelating agent, surfactant and salt. Under the optimum conditions the analytical characteristics of the method such as limit of detection, linear range, relative standard deviation (R.S.D.) and relative standard error (R.S.E.) were calculated. Calibration graphs were linear in the range of 5–300 and 10–320 ng mL⁻¹ with detection limits of 0.73 and 0.85 ng mL⁻¹ for Co(ii) and Ni(ii), respectively. The limit of quantification was 2.43 and 2.83 ng mL⁻¹ for Co(ii) and Ni(ii), respectively. The interference effect of some anions and cations was also tested. The method was successfully applied to the simultaneous determination of Co(ii) and Ni(ii) in water samples.

Using Zr doped TiO2 nanotubes for the pre-concentration and sensitive determination of bisphenol A prior to fluorescence spectrometry in water samples by Xuefeng Wang; Qingxiang Zhou; Mengxiao Zhai (pp. 394-398).

The present study focused on the investigation of the applicability of a new material, Zr doped TiO2 nanotubes, used as the solid phase extraction adsorbent for the enrichment of bisphenol A. The possible impacting parameters on the extraction such as the kind and volume of eluent, sample pH, sample flow rate, and sample volume were investigated in detail. Under the optimal extraction conditions, the proposed method had excellent linear range of 1–80 μg L⁻¹ and the LOD was 0.016 μg L⁻¹. The relative standard deviation at the concentration of 20 μg L⁻¹ (RSDs, n = 6) was 2.9%. Four different real water samples were used for validation, and the spiked recoveries were satisfactory in the range of 102.9–108.8%, and all these results indicated that Zr doped TiO2 nanotubes had much better extraction performance and would be widely used in the future.

Comparison of three high-flow single-stage impaction-based air samplers for bacteria quantification: DUO SAS SUPER 360, SAMPL'AIR and SPIN AIR by Marta Sánchez-Muñoz; María Muñoz-Vicente; Guillermo Cobas; Raquel Portela; Ricardo Amils; Benigno Sánchez (pp. 399-405).

Arsenic species and selected metals in human urine: validation of HPLC/ICPMS and ICPMS procedures for a long-term population-based epidemiological study by Jürgen Scheer; Silvia Findenig; Walter Goessler; Kevin A. Francesconi; Barbara Howard; Jason G. Umans; Jonathan Pollak; Maria Tellez-Plaza; Ellen K. Silbergeld; Eliseo Guallar; Ana Navas-Acien (pp. 406-413).

Exposure to high inorganic arsenic concentrations in drinking water has been related to detrimental health effects, including cancers and possibly cardiovascular disease, in many epidemiological studies. Recent studies suggest that arsenic might elicit some of its toxic effects also at lower concentrations. The Strong Heart Study, a large epidemiological study of cardiovascular disease in American Indian communities, collected urine samples and performed medical examinations on 4549 participants over a 10 year period beginning in 1989. We used anion-exchange HPLC/ICPMS to determine concentrations of arsenic species (methylarsonate, dimethylarsinate and arsenate) in 5095 urine samples from the Strong Heart Study. We repeated the chromatography on a portion of the urine sample that had been oxidised, by addition of H2O2, to provide additional information on the presence of As(iii) species and thio-arsenicals, and by difference, of arsenobetaine and other non-retained cations. Total concentrations for As, Cd, Mo, Pb, Sb, Se, U, W, and Zn were also determined in the urine samples by ICPMS. The dataset will be used to evaluate the relationships between the concentrations of urinary arsenic species and selected metals with various cardiometabolic health endpoints. We present and discuss the analytical protocol put in place to produce this large and valuable dataset.

Monitoring intracellular nitric oxide production using microchip electrophoresis and laser-induced fluorescence detection by Emilie R. Mainz; Dulan B. Gunasekara; Giuseppe Caruso; Derek T. Jensen; Matthew K. Hulvey; Jose Alberto Fracassi da Silva; Eve C. Metto; Anne H. Culbertson; Christopher T. Culbertson; Susan M. Lunte (pp. 414-420).

Nitric oxide (NO) is a biologically important short-lived reactive species that has been shown to be involved in a large number of physiological processes. The production of NO is substantially increased in immune and other cell types through the upregulation of inducible nitric oxide synthase (iNOS) caused by exposure to stimulating agents such as lipopolysaccharide (LPS). NO production in cells is most frequently measured via fluorescence microscopy using diaminofluorescein-based probes. Capillary electrophoresis with laser-induced fluorescence detection has been used previously to separate and quantitate the fluorescence derivatives of NO from potential interferences in single neurons. In this paper, microchip electrophoresis (ME) coupled to laser-induced fluorescence (LIF) detection is evaluated as a method for measurement of the NO production by Jurkat cells under control and stimulating conditions. ME is ideal for such analyses due to its fast and efficient separations, low volume requirements, and ultimate compatibility with single cell chemical cytometry systems. In these studies, 4-amino-5-methylamino-2′,7′-difluorofluorescein diacetate (DAF-FM DA) was employed for the detection of NO, and 6-carboxyfluorescein diacetate (6-CFDA) was employed as an internal standard. Jurkat cells were stimulated using lipopolysaccharide (LPS) to produce NO, and bulk cell analysis was accomplished using ME-LIF. Stimulated cells exhibited an approximately 2.5-fold increase in intracellular NO production compared to the native cells. A NO standard prepared using diethylamine NONOate (DEA/NO) salt was used to construct a calibration curve for quantitation of NO in cell lysate. Using this calibration curve, the average intracellular NO concentrations for LPS-stimulated and native Jurkat cells were calculated to be 1.5 mM and 0.6 mM, respectively

The effect of surfactant on headspace single drop microextraction for the determination of some volatile aroma compounds in citronella grass and lemongrass leaves by gas chromatography by Thanawat Jumepaeng; Devanand L. Luthria; Saksit Chanthai (pp. 421-428).

A rapid method for the determination of some volatile aromatic compounds (VACs), including citronellal, citronellol, neral, geranial, geraniol and eugenol in citronella grass and lemongrass leaves, was developed using surfactant as a surface tension modifier while performing headspace single drop microextraction (HS-SDME) prior to analysis by GC-FID. Experimental parameters were optimized, including type of single drop solvent, extraction temperature and time, enrichment time, sample volume, and salt and surfactant concentration. In this study, the effect of surfactants (SDS, Triton-X and CTAB) on the HS-SDME of VACs was investigated in detail. It was found that a small amount of SDS could contribute to decreasing the surface tension of liquid phase, resulting in an improvement of the extraction efficiency. The proposed method gave higher concentration factors (2.39–24.6 fold) of these VACs in real samples, and good recovery (97.6–109%) and precision (7–15% RSD). The advantage of this procedure is then recognized as green chemistry because its simple and cheap method with reduced analysis time and toxicity. The sample preparation can easily be applied to routine analysis of these VACs in citronella grass and lemongrass leaf samples.

Determination of malachite green and crystal violet in environmental water using temperature-controlled ionic liquid dispersive liquid–liquid microextraction coupled with high performance liquid chromatography by Zhen Zhang; Kai Zhou; Yuan-qin Bu; Zheng-jun Shan; Jing-fu Liu; Xiang-yang Wu; Liu-qing Yang; Zhong-lin Chen (pp. 429-433).

Temperature-controlled ionic liquid dispersive liquid–liquid microextraction (TC-IL-DLLME) was introduced to analyze malachite green (MG) and crystal violet (CV) in environmental water by coupling with high performance liquid chromatography (HPLC). In the method, 1-octyl-3-methylimidazolium hexafluorophosphate ([C8MIM][PF6]) and methanol were selected as appropriate extraction and dispersive solvents, respectively. Target compounds were extracted into the IL phase (dispersed completely in the aqueous phase) at a proper temperature. Several other parameters that could affect extraction performance were optimized, such as IL volume, sample pH, salinity, extraction time, temperature and centrifuging velocity. Under the optimum conditions (IL volume, 80 μL; sample pH, 4; salinity, 20% sodium chloride; extraction time, 50 min; temperature, 70 °C; centrifuging velocity, 1500 rpm), the established method offered: (i) good linear range (0.25–20 μg L⁻¹); (ii) low detection limits (MG, 0.086 μg L⁻¹; CV, 0.030 μg L⁻¹); (iii) good reproducibility (relative standard deviation, MG, 9.4%; CV, 7.6%; n = 5) and good recoveries (91.7% for MG and 97.2% for CV, respectively; n = 5); (iv) high enrichment factor (254 for MG, 276 for CV), which makes the method suitable to monitor low concentrations of MG and CV in aqueous systems.

Determination of vitamin B1 with 12-tungstophosphoric acid by resonance Rayleigh scattering method by Zhiping Cui; Shaopu Liu; Zhongfang Liu; Xiaoli Hu (pp. 434-438).

In pH 0–1.0 HCl medium, 12-tungstophosphoric acid (TP) could react with vitamin B1 (VB1) to form a 1 : 3 ion-association complex. As a result, new spectra of resonance Rayleigh scattering appeared and their intensities were enhanced greatly. The maximum wavelength was located at 335 nm. The scattering intensities were proportional to the concentration of VB1 in the range of 0.25–1.75 μg mL⁻¹. Therefore, a new method for the determination of VB1 was established. The method had high sensitivity and good selectivity, and the detection limit (3σ) was 0.94 ng mL⁻¹. It was applied to the determination of VB1 in urine samples and VB1 tablets, which showed that the results were consistent with those of the China pharmaceutical method. The recovery was between 97.3%–99.0%, and the relative standard deviation (RSD) was between 1.1%–3.4%. Furthermore, the optimum reaction conditions, the RRS spectra characteristics, the reaction mechanism and the reasons for enhancement of scattering were evaluated.

Mass spectrometric identification and characterization of new toremifene metabolites in human urine by liquid chromatography quadrupole/time-of-flight tandem mass spectrometry (LC-QTOFMS) by Jianghai Lu; Genye He; Xiaobing Wang; Youxuan Xu; Yun Wu; Ying Dong; Moutian Wu; Gangfeng Ouyang (pp. 439-443).

Multi-walled carbon nanotubes modified glassy carbon electrode for sensitive determination of ketoconazole by Joanna Borowiec; Lili Wei; Lihua Zhu; Jingdong Zhang (pp. 444-448).

The electrochemical behavior of ketoconazole (KC) on a multi-walled carbon nanotubes (MWCNTs)-modified glassy carbon (GC) electrode was investigated in this work. The result indicated that MWCNTs remarkably promoted the electrochemical response of KC on the GC electrode. To achieve a sensitive voltammetric determination of KC, experimental conditions such as solution pH, amount of MWCNTs, accumulation time as well as scan rate were systematically studied and optimized. Under optimized conditions, the differential pulse voltammetric (DPV) response on the MWCNTs-modified electrode was proportional to the KC concentration in the range of 1.0 × 10⁻⁶–3.0 × 10⁻⁵ mol L⁻¹ with a detection limit of 4.4 × 10⁻⁷ mol L⁻¹. Based on this MWCNTs-modified electrode, KC in a pharmaceutical drug (Ketoconazole^®) was successfully determined without requirement of complicated sample pretreatment.

New strategy to enhance the extraction efficiency of pyrethroid pesticides in fish samples using a modified QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) method by Fengyan Jia; Wenwen Wang; Juan Wang; Jungang Yin; Yongming Liu; Zhenbo Liu (pp. 449-453).

A novel method for the analysis of 6 pyrethroids in fish samples, based on the use of a modified QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) approach followed by gas chromatography (GC) method, is reported. In previous reports, it is surprising to find that only acetonitrile was used as the original QuEChERS extraction solvent. In the present work, the QuEChERS method was modified by replacing the traditional acetonitrile with isopropanol. It showed that the use of isopropanol improved the extraction efficiency of the QuEChERS. For the pyrethroids in the protein–matrix samples, the overall recoveries of 75.8–89.4% for the modified QuEChERS method are better than those of 68.9–84.8% for the original QuEChERS method. Fluorescence quenching spectra of BSA with pyrethroids showed that the strong binding interaction between pyrethroids pesticides and protein decreased the extraction efficiency of pyrethroids from fish samples. However, in the 80% (volume fraction) isopropanol aqueous solution, a slow protein denaturation might take place, which would cause the unfolding of protein and the release of pyrethroids. This resulted in the high extraction efficiency of pyrethroids from protein matrix samples. The method was used satisfactorily for the determination of 6 pyrethroid pesticides in spiked fish samples. This paper proposes a new strategy by slowing down the protein denaturation and releasing bound pesticides to enhance the extraction efficiency of pyrethroids in fish samples.

Nanostructured multi-walled carbon nanotubes derivate based on carbon paste electrode for potentiometric detection of Ag⁺ ions by Ting Zhang; Yaqin Chai; Ruo Yuan; Junxiang Guo (pp. 454-459).

A new hybrid material (B15C5-MWCNTs) has been used as a neutral carrier in a carbon paste electrode for the detection of silver. B15C5-MWCNTs were synthesized by grafting 4′-aminobenzo-15-crown-5 (B15C5) onto acid-functionalized multi-walled carbon nanotubes (MWCNT-COOH) through a short 2-carbon chain spacer. The silver carbon paste electrode can be prepared by simple mixing of B15C5-MWCNTs, graphite powder and paraffin oil. B15C5-MWCNTs were not only ion-to-electron transducers but also reactive materials. With 8.4 wt% B15C5-MWCNTs proportions, the electrodes exhibited a linear response ranging from 2.7 × 10⁻⁷ to 1.0 × 10⁻¹ M with a near Nernstian slope of 58.5 mV dec⁻¹. The proposed electrode displayed rapid response (∼15 s) and long-time stability. Moreover, the potentiometric responses could be carried out with a wide pH range of 3.0–9.0. Then, the response mechanism of the proposed electrode was investigated by using AC impedance. Finally, the developed electrode was successfully applied in the determination of silver ions in radiology films and chloride ions in water samples.

Monitoring of bovine serum albumin using ultrasensitive electrochemiluminescence biosensors based on multilayer CdTe quantum dots modified indium tin oxide electrodes by Meng Zhang; Mei Yan; Jinghua Yu; Shenguang Ge; Fuwei Wan; Lei Ge (pp. 460-466).

A novel method for the determination of bovine serum albumin (BSA) is proposed based on the electrochemiluminescence (ECL) of BSA with CdTe quantum dots (QDs) films. Thioglycolic acid (TGA) is used to cap CdTe colloidal solutions to obtain stable water-soluble QDs and intensive anodic ECL emission with a peak value starting from +1.2 V (vs. Ag/AgCl) in a carbonate bicarbonate buffer solution (pH 9.32) at an indium tin oxide (ITO) electrode. The ITO glass is modified with CdTe QDs by the layer-by-layer (LbL) self-assembly technique, which is immobilized into a homemade ECL flow chip and used as a receptor of the ECL sensor. The ECL intensity is correlated linearly with the concentration of BSA over the range of 1.0 × 10⁻⁹–1.0 × 10⁻⁶ g mL⁻¹ and 1.0 × 10⁻⁶–1.0 × 10⁻⁵ g mL⁻¹, and the detection limit is 5.48 × 10⁻¹⁰ g mL⁻¹. The relative standard deviation is 1.62% for 4.0 × 10⁻⁷ g mL⁻¹ BSA (n = 11). This simple and sensitive method reveals good reproducibility for ECL analysis. It puts forward a new efficient ECL method for the determination of BSA and opens new avenues for the application of QDs in ECL biosensors.

Multivariate calibration of near-infrared spectra by using influential variables by Xueguang Shao; Min Zhang; Wensheng Cai (pp. 467-473).

Near-infrared (NIR) spectral analysis usually needs to take advantage of multivariate calibration. However, not all the variables in the spectra have equal contributions to a calibration model. Identification of informative variables is a key step to build a high performance model. According to the influence of a variable on the calibration model, influential variable (IV) is defined and a method for identification of IVs is proposed in this work. In the method, a set of partial least squares (PLS) models are built using a subset of variables selected randomly by Monte Carlo re-sampling, and then the clustering of these models are investigated by means of principal component analysis. The variables that make the models grouping can be identified as the IVs. Finally, the PLS model built with the selected IVs is adopted as the calibration model. Five NIR spectral datasets are used to test the performance and applicability of the method. The results show that the identified IVs are reasonable and the calibration model is efficient enough to produce accurate and reliable predictions.

Mass spectrometric imaging as a high-spatial resolution tool for functional genomics: Tissue-specific gene expression of TT7 inferred from heterogeneous distribution of metabolites in Arabidopsis flowers by Andrew R. Korte; Zhihong Song; Basil J. Nikolau; Young Jin Lee (pp. 474-481).

Laser desorption/ionization (LDI) mass spectrometry imaging (MSI) was used to acquire chemical images of flavonoid metabolites on the surface of wild-type and mutant (tt7) Arabidopsis thaliana flowers. Flavonoids were localized to the petals and carpels of flowers, with tissue heterogeneity in the petals. Specifically, kaempferol and/or its glycosides were abundant in the distal region of petals and quercetin and its downstream flavonoids were highly enriched in the more proximal region of petals. As a result of a mutation in the TT7 gene which blocks the conversion of dihydrokaempferol to dihydroquercetin, the downstream metabolites, quercetin, isohamnetin, and their glycosides, were not observed in the mutant flowers. Instead, the metabolites in an alternative pathway, kaempferol and/or its glycosides, were as highly abundant on the proximal region of the petals as in the distal region. In addition, the combined flavonoid amounts on the proximal region of petals in the wild-type are almost equivalent to the amounts of kaempferol and/or its glycosides in the mutant. This strongly suggests that the expression of the TT7 gene is localized on the proximal part of the petal while the other genes in the upper stream pathway are evenly expressed throughout the petal. Most importantly, this work demonstrates MSI of metabolites can be utilized for the localization of gene expression.

Electrochemical sensor of 4-aminobutyric acid based on molecularly imprinted electropolymer by Xinyu Zheng; Ruiyu Lin; Xuechou Zhou; Lingling Zhang; Wenxiong Lin (pp. 482-487).

A simple and effective procedure based on a molecularly imprinted polymer (MIP) was developed for preparing a selective 4-aminobutyric acid (4-ABA) sensor. The sensitive layer was prepared by electropolymerization of o-phenylenediamine (o-PD) on a gold electrode in the presence of 4-ABA, which acts as a template. Cyclic voltammetry (CV), differential pulse voltammetry (DPV), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) measurements were used to monitor the process of electropolymerization. The molecularly imprinted sensor was tested by CV as well as DPV to verify the changes of redox currents of hexacyanoferrate. The concentration of 4-ABA in the range of 0.2–20.0 μmol L⁻¹ can be determined with a detection limit of 0.08 μmol L⁻¹ (defined as S/N = 3) under the optimum conditions. The MIP sensor shows high selectivity, sensitivity and reproducibility. The results from sample analysis indicate that the MIP-4-ABA sensor can be used for quantitative analysis.

A simple and sensitive colorimetric method for detection of mercury ions based on anti-aggregation of gold nanoparticles by Tingting Lou; Ling Chen; Chunrong Zhang; Qi Kang; Huiyan You; Dazhong Shen; Lingxin Chen (pp. 488-491).

A simple and sensitive method for the colorimetric detection of mercury ions (Hg²⁺) has been proposed by using anti-aggregation of gold nanoparticles (AuNPs) based on the co-ordination between thymine and mercury ions. The thymine can bind to the AuNPs through Au–N bonds and induce aggregation of AuNPs. In the presence of Hg²⁺, the thymine was released from the surface of AuNPs via the formation of a thymine-Hg²⁺ coordination complex, leading to the dispersion of AuNPs. The detection reagent can be simply prepared by mixing thymine with citrate-capped AuNPs. This method is not only cost-effective, but also avoids complicated surface modifications and tedious separation processes.

A novel electrochemical sensor based on boronic acid-functionalized multi-walled carbon nanotubes for astragaloside IV determination using ARS as the current indicator by Li Gu; Ying Liang; Tianshu Zhou; Xiaoshan Tang; Guoyue Shi (pp. 492-495).

Boronic acid functionalized multi-walled carbon nanotubes (MWCNTs) were prepared and used for sensitive and selective astragaloside IV determination through electrochemical methods using Alizarin Red S (ARS) as the current indicator.

Au NPs–Ni(OH)2–Cu nanocomposites enhanced electrochemical properties for detection of H2O2 by Xiaojun Zhang; Yan Huang; Liutao Yu; Guangfeng Wang; Bin Fang (pp. 496-501).

Ni(OH)2 nanoplates grown on Cu substrate were synthesized by a simple hydrothermal method. Au nanoparticles were dropped onto Ni(OH)2 nanoplates according to optimal ratio to get Au NPs–Ni(OH)2–Cu nanocomposites. These were characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and X-ray energy dispersive spectrometer (EDS). The electrode (Au NPs–Ni(OH)2–Cu/glassy carbon electrode) constructed by the composites was evaluated by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and typical amperometric response (i-t). Its wide linear range covered 2.5 μM to 1229.5 μM for the detection of peroxide hydrogen (H2O2), the optimized detection limit 0.3 μM (S/N = 3) and the response time was less than 3 s. Besides, the proposed electrode showed satisfactory selectivity, and good stability.

CPE–Paptode as a new technique for determination of dyes: application for determination of acid red 151 by A. Shokrollahi; A. Abbaspour; Z. Azami Ardekani; Z. Malekhosseini; A. Alizadeh (pp. 502-507).

In the present study, a new method for monitoring the signal after cloud point extraction (CPE) of dyes is introduced. The CPE–Paptode method was used to determine acid red 151, as an anionic dye. The method is based on the CPE of dye from aqueous solution, using Triton X-114, diluting the extracted surfactant-rich phase with ethanol and measuring the RGB parameters by special software written in visual basic (VB 6). Parameters, such as pH of the system, the concentration of the dye and surfactant, equilibration temperature and time, as effective parameters on the extraction efficiency and the determination of the dye, were investigated and optimized. Under the optimal conditions, the calibration curve was linear in the range of 0.5–19.0 mg L⁻¹. Preconcentration of a 15 mL sample gave an enhancement factor of 13.2 and a detection limit of 0.32 mg L⁻¹. In addition, the effects of some foreign species including cations, anions and dyes were investigated. The method was successfully applied to the determination of the acid red 151 content in aqueous solution. The results and the figure of merits of the proposed method were comparable with those of CPE–spectrophotometry.

Factorial and Doehlert designs in the optimization of a separation procedure using polyurethane foam as a solid phase extractant for platinum determination in ferrous matrices using inductively coupled plasma optical emission spectroscopy by Neyla Margarida Lopo de Araújo; Sérgio Luis Costa Ferreira; Hilda Costa dos Santos; Djane Santiago de Jesus; Marcos Almeida Bezerra (pp. 508-512).

A procedure for separation of platinum from ferrous matrices was developed using platinum sorption as chloride complexes on polyurethane foam, with subsequent determination by inductively coupled plasma optical emission spectrometry (ICP OES). The procedure was optimized using a two-level full factorial and Doehlert designs. Four variables (foam mass, shaking time, stannous chloride concentration and hydrochloric acid concentration) were regarded as factors in the extraction optimization. Results of the two-level full factorial design, 2⁴ with 16 runs based on Analysis of Variance (ANOVA) showed that only two factors (foam mass and shaking time) are statistically significant. Doehlert design was applied in order to determine the optimum conditions for platinum separation. The proposed procedure allowed platinum determination with a detection limit of 66 μg L⁻¹ and a precision, calculated as relative standard deviation (RSD), of 1.2% in a set of 10 measurements for a platinum concentration of 10.0 μg L⁻¹. The studied procedure was applied to platinum determination in several ferrous matrices (iron ores, pure iron and catalysts). Spike tests on iron ores and pure iron showed good performance in platinum recovery. The good accuracy of the proposed procedure was confirmed by analysis of an ore platinum standard reference material (SARM-7).

Rapid morphological characterization of isolated mitochondria using Brownian motion by Akilan Palanisami; Jie Fang; Thomas W. Lowder; Hawley Kunz; John H. Miller Jr (pp. 513-521).

Mitochondrial morphology has been associated with numerous pathologies including cancer, diabetes, obesity and heart disease. However, the connection is poorly understood—in part due to the difficulty of characterizing the morphology. This impedes the use of morphology as a tool for disease detection/monitoring. Here, we use the Brownian motion of isolated mitochondria to characterize their size and shape in a high throughput fashion. By using treadmill exercise training, mitochondria from heart and gastrocnemius of Balb/c mice were modulated in size and used to investigate the protocol. Consistent with previous reports, the heart mitochondria of untrained mice increased 5% in diameter immediately after a single bout of moderate exercise (1.091 ± 0.004 μm) as compared to completely sedentary controls (1.040 ± 0.022 μm). In addition, no change was observed in the size of gastrocnemius mitochondria (1.025 ± 0.018 μm), which was also in agreement with previous studies. The method was also successfully applied to smaller Saccharomyces cerevisiae mitochondria.

A study of techniques for the preservation of mercury and other trace elements in water for analysis by inductively coupled plasma mass spectrometry (ICP-MS) by Honway Louie; Choon Wong; Yi Jian Huang; Susan Fredrickson (pp. 522-529).

The storage of aqueous solutions in high density polyethylene (HDPE) bottles containing nitric acid (0.15 to 2.0% (v/v) was shown to be unsuitable for the preservation of dissolved mercury (Hg ²⁺) either as a single element or as part of a multi-element solution. At concentrations ranging from 0.05 to 10.0 ug l⁻¹ more than 10% of the dissolved mercury was lost within the first three days and up to 50% of the mercury was lost within nine days after solutions were prepared. However mercury was stable in the presence of hydrochloric acid (HCl) or sodium chloride (NaCl). Solutions of either 40 mg l⁻¹ NaCl in 0.15% (v/v) nitric acid (HNO3) or 0.01% (v/v) HCl in 1% (v/v) HNO3 were found to be effective for preserving mercury for more than 50 days. The stabilising mechanism is most likely the formation of HgCl4²⁻ complex ions that prevent the adsorption of mercury on the inner walls of the HDPE container. The elements Al, Ag, As, Ba, B, Cd, Cr, Co, Cu, Mn, Mo, Ni, Pb, Sb, Se, Tl, V and Zn were stable up to 12 months when preserved in 1.0 to 2.0% (v/v) nitric acid or a mixture of 1% (v/v) HNO3 plus 0.01% (v/v) HCl. The recommended acid combination for the preservation of mercury and multi-elements for the simultaneous determination by ICP-MS is 1% (v/v) HNO3 plus 0.01% (v/v) HCl. Chloride related polyatomic interferences in ICP-MS determination from this acid mixture were less than 0.1 ugl⁻¹ for all elements investigated, making it an ideal preservation medium for ICP-MS analysis.

A HPLC method for the quantification of butyramide and acetamide at ppb levels in hydrogeothermal waters by Gracy Elias; Earl D. Mattson; Jessica E. Little (pp. 530-533).

A quantitative analytical method to determine butyramide and acetamide concentrations at the low ppb levels in geothermal waters has been developed. The analytes are concentrated in a preparation step by evaporation and analyzed using HPLC-UV. Chromatographic separation is achieved isocratically with a RP C-18 column using a 30 mM phosphate buffer solution with 5 mM heptane sulfonic acid and methanol (98 : 2 ratio) as the mobile phase. Absorbance is measured at 200 nm. The limit of detection (LOD) for BA and AA were 2.0 μg L⁻¹ and 2.5 μg L⁻¹, respectively. The limit of quantification (LOQ) for BA and AA were 5.7 μg L⁻¹ and 7.7 μg L⁻¹, respectively, at the detection wavelength of 200 nm. Attaining these levels of quantification better allows these amides to be used as thermally reactive tracers in low-temperature hydrogeothermal systems.

Stereoselectivity of an enzyme-linked, immunosorbent assay for S-bioallethrin by Mengmeng Cao; Ming Li; Xu Yan; Minghua Wang (pp. 534-538).

A sensitive, specific, indirect and competitive enzyme-linked immunosorbent assay (ELISA) based on a polyclonal antibody (PcAb) for S-bioallethrin was developed. The hapten-bovine serum albumin (BSA) conjugate was used as an immunogen while the hapten-ovalbumin (OVA) conjugate was applied as a coating antigen. An anti-S-bioallethrin PcAb was obtained from immunized New Zealand white rabbits, and an ELISA for S-bioallethrin was developed. The inhibition standard curve of S-bioallethrin was obtained using optimized conditions (40% methanol, 0.5 mol L⁻¹ Na⁺, pH 6.5). The half-maximal inhibition concentration (IC50) was 0.089 μg mL⁻¹, and the limit of detection (LOD, IC10) was 0.0025 μg mL⁻¹. Very low cross-reactivity (CR) was found for allethrin and other pyrethroids. The CR for the stereoisomer demonstrates that the antibody has notable stereoselectivity for S-bioallethrin. Water and dust spiked with S-bioallethrin were analyzed by ELISA and acceptable recovery rates, 90.7% to 111.7%, were obtained. The ELISA results were confirmed by gas chromatography/electron capture detection (GC-ECD) and the proposed ELISA could be a highly sensitive, stereoselective, simple, rapid and inexpensive method for the detection of S-bioallethrin in environmental samples.

Determination of flavor components of rice bran by GC-MS and chemometrics by Maomao Zeng; Liangxiao Zhang; Zhiyong He; Fang Qin; Xueyan Tang; Xiaolin Huang; Honghong Qu; Jie Chen (pp. 539-545).

The flavor composition of rice bran was investigated using solid-phase microextraction (SPME), which was selected from four extraction methods. Additionally, static headspace extraction (SHS), accelerated solvent extraction (ASE) and simultaneous distillation extraction (SDE), followed by GC-MS analysis with the help of heuristic evolving latent projections (HELP) were also used. The effects of the most important factors, including fiber coating, extraction time, and temperature of SPME, on the flavor components of rice bran were studied. Qualitative analysis of the flavor components was obtained by a mass spectra similarity search using pure mass spectra resolved by HELP with the aid of automated mass spectral deconvolution and identification system (AMDIS) software and temperature-programmed retention indices (PTRIs), while quantitative analysis was conducted using the overall volume integration (OVI) technique. A total of 43 out of 76 compounds were tentatively identified, accounting for 82.76% of the total flavor compounds. The flavor compounds were mainly esters, alkanes, alcohols, ketones, aldehydes, and fatty acids, with a composition of 22.24%, 22.16%, 17.75%, 9.06%, 5.72%, and 4.18%, respectively. Together, these results indicate that analyzing the rice bran flavor profile may be more reasonable than solely monitoring free fatty acids for understanding, evaluating and controlling the instability of rice bran.

Comparison study on nucleosides and nucleotides in edible mushroom species by capillary zone electrophoresis by Feng-qing Yang; Rui Lv; Yong-lan Zhang; Zhi-ning Xia (pp. 546-549).

A capillary zone electrophoresis (CZE) method was developed for the simultaneous determination of four nucleosides (adenosine, guanosine, uridine and inosine) and three nucleotides (guanosine-5′-monophosphate (GMP), adenosine-5′-monophosphate (AMP) and uridine-5′-monophosphate (UMP)) in nine edible mushrooms including Lasiosphaera Seu Calvatia (puffball), Agrocybe aegerita, Boletus nigricans, Boletus fulvus, Tricholoma matsutake, edible tree fungus (Auricularia auricula), Tuckahoe (Poria cocos), white fungus (Tremella fuciformis) and Polyporus umbellatus. The results indicated that some of the tested mushroom species, such as tuckahoe, white fungus and Polyporus umbellatus, had no detectable nucleosides and nucleotides. Furthermore, only the nucleotide GMP can be detected in very small amounts in puffball and Boletus fulvus. In addition, puffball has a greater amount of total nucleosides as compared to other tested samples.

In vivo characterisation of a Nafion^®-modified Pt electrode for real-time nitric oxide monitoring in brain extracellular fluid by Niall J. Finnerty; Saidhbhe L. O'Riordan; Finbar O. Brown; Pier A. Serra; Robert D. O'Neill; John P. Lowry (pp. 550-557).

A Nafion^®-modified Pt sensor developed for real-time neurochemical monitoring in freely-moving animals has now been characterised in vivo for the detection of nitric oxide (NO). Experiments were undertaken to test sensitivity, selectivity and stability. In control experiments, local administration of aCSF resulted in a decrease in signal (42 ± 12 pA, n = 9), while systemic administration of saline caused a transient increase in signal (22 ± 3 pA, n = 9) from baseline levels. Local MD perfusions of known concentrations of NO (1 mM) and l-arginine (720 μM) caused significant increases in current (4 ± 1 nA (n = 7) and 271 ± 37 pA (n = 5) respectively) while systemic administration of the non-selective NOS inhibitor l-NAME produced a significant decrease in current (91 ± 19 pA, n = 4) compared to baseline levels. Confirmation that the sensor remained selective was achieved by injection of ascorbic acid (2 g kg⁻¹, i.p). The oxidation current showed no variation over the selected time interval of 60 min, indicating no deterioration of the polymer membrane. Finally, after an initial decrease in sensitivity (ca. 50%) within the first 24 h of implantation the Nafion^®-modified Pt sensor showed excellent stability under physiological conditions over extended periods (8 days) validating its use for continuous chronic in vivo recordings.

Chemiluminescence determination of primidone in pharmaceuticals and human fluids by Ali Mokhtari (pp. 558-563).

A chemiluminescence method using a flow injection system has been developed for the determination of primidone (PRI). The method is based on the fact that the weak chemiluminescence produced in the reaction of tris(1,10-phenanthroline)ruthenium(ii) and acidic Ce(iv) is enhanced in the presence of PRI. In this method, the detection limit and linear dynamic range were 0.43 μg mL⁻¹ and 0.5–20 μg mL⁻¹, respectively. In the developed method, the detection limit was lower than the therapeutic concentration of PRI. The relative standard deviation for six repeated measurements of 10.0 μg mL⁻¹ of PRI was 4.3%, and the sampling rate for analysis was 180 samples per hour. The proposed method was successfully applied to the analysis of commercial tablets containing the drug, and the results were in accordance with those obtained by the reference method. The proposed method was further applied to the determination of PRI in spiked human plasma and spiked saliva, and good recoveries were obtained for the quantification of PRI in saliva samples. In this work, the mean recovery of PRI in all matrices was 100.4 ± 4.8%.

Determination of elements in situ in green leaves by laser ablation ICP-MS using pressed reference materials for calibration by James Cizdziel; Kaixuan Bu; Piotr Nowinski (pp. 564-569).

Laser ablation (LA) was used with double focusing sector field inductively coupled plasma mass spectrometry (ICP-MS) for direct elemental analysis of green leaves from seven species of desert plants. Pressed leaf standards (n = 7) were used as matrix matched standards for calibration and quality assurance. Nine elements (Mg, Ca, Mn, Cu, Sr, Cd, Ba, Hg and Pb) were determined in low mass resolution (m/Δm ≈ 400). Data was collected for three ablation line scans starting from near the stem to the tip of the leaf. The 213 nm laser ablation system was operated at the full energy setting (100%), with a repetition rate of 20 Hz, a spot size of 100 μm, and a scan rate of 50 μm min⁻¹. Pressed cellulose was used for estimating detection limits, which were found to vary between 0.04 and 26 μg g⁻¹ for Pb and Ca, respectively. Results suggest that the calibration approach is feasible for some elements (Mg, Ca, Mn, Cu, Sr, Cd, Ba) but problematic for others (Pb, Hg). Although somewhat element dependent, desert willow, autumn sage and brittle bush tended to have the highest concentrations of the elements monitored. Overall, LA-ICP-MS is a useful method for quantifying (in situ) the distribution of many elements in plant leaves.

Validation of subsampling procedures and granulometry distribution uncertainty assessment in environmental soil analysis by Fulvia Risso; Riccardo Narizzano; Massimo Ottonelli; Alfredo Magherini; Michele Giampieri; Eugenio Carlini (pp. 570-574).

A scheme for validation of subsampling activities and assessment of granulometry distribution uncertainty has been developed. The study has been performed to ensure the representativity of the aliquot, the subsample, selected for the analytical procedure with respect to the field sample and final results. The procedure developed provides an easily accessible empirical method based on repeated measurements. The uncertainty and its consequences on analytical results have been evaluated. Different soil typologies have been tested.

First order speciation of vanadium and chromium in water samples by on-line continuous membrane separation hyphenated to inductively coupled plasma mass spectrometry by Xiao-yu Jia; Di-rong Gong; Yi Han; Tai-cheng Duan; Hang-ting Chen (pp. 575-580).

An on-line anion-exchange membrane separation system has been coupled to inductively coupled plasma mass spectrometry (ICP-MS) for the total vanadium(v) and chromium (Cr) determination and V(iv) and Cr(iii) species determination simultaneously. The positive charged V(iv) and Cr(iii) species have been efficiently separated from V(v) and Cr(vi), and selectively determined by the on-line electrodialyzer-ICP-MS. To determine the total concentrations of V and Cr in water samples, H2SO4 and Na2S2O3 were added to convert all vanadium and chromium species into their positive species, thus, V(v) and Cr(vi) in the samples were quantified by subtraction. The cool plasma and reaction gas can also be avoided as the severe interference from chloride, carbon and nitrogen-based molecular ion has been substantially suppressed by the anion-exchange membrane. The detection limits of the analytes were 0.02 μg L⁻¹ for V(iv) and 0.06 μg L⁻¹ for Cr(iii) with this on-line system, respectively, and the relative standard deviation (n = 10) of 10 μg L⁻¹ V(iv) and Cr(iii) were 3.7% and 2.1%, respectively. The developed method has been applied for the speciation of V and Cr in three water samples, with V(v) and Cr(iii) found as the main species in these samples. The accuracy and feasibility of this method have also been verified by spike tests and a certified reference material (CRM) of environmental water (GSBZ 50029-94) and a CRM of riverine water (GBW 08608), good recoveries have been obtained and the analytical results are also in good agreement with the certified values.

Back cover (pp. 581-582).

In a completely rational and designed approach, simultaneous determination of cyanazine and propazine in environmental and food samples was performed using a molecularly imprinted polymer modified carbon paste electrode (MIP–CPE) and partial least squares. The MIP–CPE designed is based on the theoretical studies functioned as a selective recognition element and pre-concentrator agent for cyanazine and propazine. Fractional factorial and central composite designs were performed to recognize, and subsequently optimize, the variables affecting the cathodic stripping voltammetric currents for the analytes. The important variables were identified to be accumulation potential with optimum values of −0.45 and −0.44 V and pH with optimum values of 2.40 and 2.34 for cyanazine and propazine, respectively. Exploration of the overall optimum conditions for simultaneous determination of cyanazine and propazine resulted in accumulation potential of −0.44 V and pH of 2.4. Dynamic linear ranges of 0.05–9.00 μmol L⁻¹ and 0.01–1.00 μmol L⁻¹ and detection limits of 0.010 and 0.001 μmol L⁻¹ were obtained for cyanazine and propazine, respectively. The results of the application of the proposed method on the simultaneous determination of cyanazine and propazine in foodstuffs and environmental samples were satisfactory.

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Analytical Methods (v.4, #2)