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Analytica Chimica Acta (v.590, #2)

Editorial Board (pp. co1).

Contents (pp. iii-iv).

Calendar of forthcoming meetings (pp. n3).

Editorial Board (pp. co1).

Calendar of forthcoming meetings (pp. n3).

Contents (pp. iii-iv).

Fast and sensitive trace analysis of malachite green using a surface-enhanced Raman microfluidic sensor by Sangyeop Lee; Junghyun Choi; Lingxin Chen; Byungchoon Park; Jin Burm Kyong; Gi Hun Seong; Jaebum Choo; Yeonjung Lee; Kyung-Hoon Shin; Eun Kyu Lee; Sang-Woo Joo; Kyeong-Hee Lee (pp. 139-144).

A rapid and highly sensitive trace analysis technique for determining malachite green (MG) in a polydimethylsiloxane (PDMS) microfluidic sensor was investigated using surface-enhanced Raman spectroscopy (SERS). A zigzag-shaped PDMS microfluidic channel was fabricated for efficient mixing between MG analytes and aggregated silver colloids. Under the optimal condition of flow velocity, MG molecules were effectively adsorbed onto silver nanoparticles while flowing along the upper and lower zigzag-shaped PDMS channel. A quantitative analysis of MG was performed based on the measured peak height at 1615cm⁻¹ in its SERS spectrum. The limit of detection, using the SERS microfluidic sensor, was found to be below the 1–2ppb level and this low detection limit is comparable to the result of the LC-Mass detection method. In the present study, we introduce a new conceptual detection technology, using a SERS microfluidic sensor, for the highly sensitive trace analysis of MG in water.

Keywords: Microfluidic sensor; Malachite green; Surface-enhanced Raman spectroscopy; Lab on a chip; Trace analysis

Autocorrelation infrared analysis of mineralogical samples: The influence of user controllable experimental parameters by Adam J. Blanch; Jamie S. Quinton; Claire E. Lenehan; Allan Pring (pp. 145-150).

Autocorrelation infrared (ACIR) analysis is based upon the application of the autocorrelation functioncorr(α,ω′)=∫−∞∞α(ω+ω′)α(ω)dω to standard Fourier transform infrared (FTIR) transmission spectra. We present a rigorous examination of the effect of experimental parameters such as dilution ratio, spectral resolution, grinding time and pressing conditions upon the ACIR analysis of haematite. Results were found to vary by less than 4.5% irrespective of sample preparation, instrumental and data collection parameters. For a series of perovskite samples, the relationship between the measured effective linewidth and material composition appears to be reproducible, even though the absolute magnitudes of Δcorr values do not. Our results further indicate that the ACIR technique is indeed valid for comparative analysis of synthetic sample sequences that vary slightly in composition or structural state, provided that primary spectra are all recorded by the same instrument.

Keywords: Autocorrelation analysis; Infrared spectroscopy; Haematite; Iron oxide; Minerals; Perovskites

Flow injection analysis of imidacloprid in natural waters and agricultural matrixes by photochemical dissociation, chemical reduction, and nitric oxide chemiluminescence detection by Anthony F. Lagalante; Peter W. Greenbacker (pp. 151-158).

A flow injection analysis (FIA) to quantify imidacloprid was developed based upon (1) ultraviolet (254nm) photochemical dissociation of imidacloprid to produce nitrite, (2) chemical reduction of the nitrite to nitric oxide by iodide in acid, (3) removal of gas-phase nitric oxide from the aqueous stream using a membrane separator, and (4) detection of the nitric oxide by chemiluminescent reaction with ozone. The cross-reactivity of imidacloprid with eight metabolites of imidacloprid was determined using a commercial ELISA kit and the FIA method. While the ELISA kit demonstrated varying degrees of cross-reactivity, cross-reactivity in the FIA method was observed for only the N-nitro and N-nitroso metabolites. The optimized analytical FIA method, FIA provides a linear response in imidacloprid concentration over four orders of magnitude, has a limit of detection of 5.6pmol (1.5ng) of imidacloprid, and exhibits an inter-day precision of 0.4%. Spike-recoveries by FIA demonstrated excellent recovery of imidacloprid in natural waters, hemlock xylem fluid, honey, and grapes with little to no interference from the matrix.

Keywords: Cross-reactivity; Enzyme-linked immunosorbent assay; Hemlock; Imidacloprid; Insecticides; Flow injection analysis; Grapes; Honey; Metabolites; Natural waters; Nitric oxide chemiluminescence; Nitrite

Enhancement in sample preconcentration by the on-line incorporation of cloud point extraction to flow injection analysis inside the chemiluminescence cell and the determination of total serum bilirubin by Chao Lu; Guanqun Song; Jin-Ming Lin; Carmen W. Huie (pp. 159-165).

The on-line incorporation of cloud point extraction (CPE) to flow injection analysis (FIA) was previously based on the use of a cotton-packed column to entrap the analyte-containing surfactant aggregates after salt-induced CPE, and then the preconcentrated analyte was eluted into a separate detection cell for subsequent chemiluminescence (CL) detection ( via the peroxyoxalate CL reaction). In the work, the on-line CPE/FIA technique was improved by the following: (1) sample preconcentration and CL detection were both carried out directly inside the collection column, thus avoiding the decrease in detection sensitivity due to sample dispersion and dilution, and (2) CL detection was performed through the reaction between nitrite and hydrogen peroxide, which is compatible with aqueous samples and should allow for chemical excitation to occur more efficiently inside the collection column. In addition to more effective sample preconcentration, the CL detection of the entrapped analytes directly inside the collection column, i.e., a unique heterogeneous microenvironment in which analyte-containing surfactant aggregates were embedded within the densely packed filtering material, may also contribute to the overall increase in CL intensity (e.g., a CL enhancement factor of ca. 1000). Under optimum experimental conditions, the calibration curve was found to be linear for the CL detection of bilirubin (5 to 120μgL⁻¹), the limit of detection (S/N=3) was 1.8μgL⁻¹, and the R.S.D. was ca. 2.6% ( n=30) for 20μgL⁻¹ bilirubin. Good agreements were obtained for the determination of total bilirubin in certified reference human serum samples between the present approach and an established clinical method.

Keywords: On-line cloud point extraction; Chemiluminescence inside the collection column; Flow injection analysis; Total bilirubin; Human serum

Cloud point extraction applied to casein proteins of cow milk and their identification by mass spectrometry by Aline Soriano Lopes; Jerusa Simone Garcia; Rodrigo Ramos Catharino; Leonardo Silva Santos; Marcos Nogueira Eberlin; Marco Aurélio Zezzi Arruda (pp. 166-172).

This work describes the optimization of a cloud point extraction (CPE) method for casein proteins from cow milk samples. To promote phase separation, polyoxyethylene(8) isooctylphenyl ether (Triton^® X-114) and sodium chloride (NaCl) were used as nonionic surfactant and electrolyte, respectively. Using multivariate studies, four major CPE variables were evaluated: Triton^® X-114 concentration, sample volume, NaCl concentration, and pH. The results show that surfactant concentration and sample volume were the main variable affecting the CPE process, with the following optimized parameters: 1% (w/v) Triton^® X-114 concentration, 50μL of sample volume, 6% (w/v) NaCl concentration and extractions carried out at pH 7.0. At these conditions, 923±66 and 67±2μgmL⁻¹ of total protein were found in the surfactant-rich and surfactant-poor phases, respectively. Finally, matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) was then used to evaluate those target proteins (α_s1-casein, α_s2-casein and β-casein) separation as well as to check the efficiency of the extraction procedure, making a fingerprint of those target proteins possible.

Keywords: Milk; Protein; Cloud point; Extraction; Matrix-assisted laser desorption ionization-time of flight mass spectrometry

Analysis of brain distribution and biliary excretion of a nutrient supplement, gastrodin, in rat by Lei-Chwen Lin; Yen-Fei Chen; Tong-Rong Tsai; Tung-Hu Tsai (pp. 173-179).

Gastrodin is a bioactive constituent of rhizome in Gastrodia elata Blume (Orchidaceae) The aim of this study is to develop a rapid and sensitive liquid chromatographic method coupled to microdialysis sampling system to measure the unbound of gastrodin in rat blood, brain and bile. Microdialysis probes were simultaneously inserted into the jugular vein, brain striatum and bile duct of each anesthetized rat for sampling after the administration of gastrodin (100 or 300mgkg⁻¹) through the femoral vein. Separation of unbound gastrodin from various biological fluids was applied to an RP-select B column (250mm×4.6mm i.d., 5μm). The mobile phase consisted of acetonitrile–50mM potassium dihydrogen phosphate buffer–triethylamine (5:95:0.1, v/v/v, adjusted to pH 2.5 with orthophosphoric acid) with a flow rate of 1mLmin⁻¹. The UV detector wavelength was set at 221nm. Fifteen minutes after the administration, the gastrodin reached the peak concentration in brain and bile. In addition, the results indicate that gastrodin penetrates the blood-brain barrier (BBB) and goes through hepatobiliary excretion.

Keywords: Gastrodia elata; Blume; Gastrodin; Hepato-biliary excretion; Microdialysis; Pharmacokinetics

Analysis of brain distribution and biliary excretion of a nutrient supplement, gastrodin, in rat by Lei-Chwen Lin; Yen-Fei Chen; Tong-Rong Tsai; Tung-Hu Tsai (pp. 173-179).

Keywords: Gastrodia elata; Blume; Gastrodin; Hepato-biliary excretion; Microdialysis; Pharmacokinetics

Simultaneous determination of citrus limonoid aglycones and glucosides by high performance liquid chromatography by Amit Vikram; G.K. Jayaprakasha; Bhimanagouda S. Patil (pp. 180-186).

High performance liquid chromatography (HPLC) method has been developed for simultaneous quantification of limonoid aglycones and glucosides on a reversed phase C₁₈ column using a binary solvent system, coupled with diode array detector. Seven limonoids such as limonin, nomilin, isolimonic acid, ichangin, isoobacunoic acid, limonin 17-β-d glucopyranoside and deacetyl nomilinic acid 17-β-d glucopyranoside were separated and detected at 210nm. Furthermore, limonoids were separated, identified and quantified in four varieties of citrus fruits and seeds using developed method. Limonin and limonin glucoside were found to be the predominant limonoid aglycone and glucoside, respectively, in all tested samples. The sensitivity of the method was found to be 0.25–0.50μg for tested limonoids.

Keywords: Liquid chromatography; Method development; Limonoid aglycones; Limonoid glucosides

Simultaneous determination of citrus limonoid aglycones and glucosides by high performance liquid chromatography by Amit Vikram; G.K. Jayaprakasha; Bhimanagouda S. Patil (pp. 180-186).

Keywords: Liquid chromatography; Method development; Limonoid aglycones; Limonoid glucosides

Extraction and determination of papaverin in pericarpium papaveris using aqueous two-phase system of poly(ethylene glycol)–(NH₄)₂SO₄ coupled with high-performance liquid chromatography by Qing Cao; Shehong Li; Chiyang He; Kean Li; Feng Liu (pp. 187-194).

Based on aqueous two-phase system (ATPS) of poly(ethylene glycol) (PEG)–(NH₄)₂SO₄, a simple pretreatment approach was developed for the extraction and determination of papaverin in pericarpium papaveris. The influence factors on phase behavior of the ATPS and partition behavior of papaverin was investigated, and partition mechanism based on the hydrophobic interaction between PEG and analyte molecules was proposed. Under the optimal conditions, the extraction efficiencies for papaverin were 93–96%, and the recoveries of the added standard were 97–106% with relative standard deviations of 1.8–2.5%. Combined with a high-performance liquid chromatography (HPLC) method, this extraction technique has been successfully applied to the determination of papaverin in pericarpium papaveris with the detection limit of 2ngmL⁻¹ and the linear range of 0.10–10μgmL⁻¹. Compared with the conventional liquid–liquid extraction or solid-phase extraction, this method was more environmentally benign, more cost effective and much simpler due to the direct injection of the upper phase into HPLC system.

Keywords: Extraction; Papaverin; Paricarpium papaveris; Aqueous two-phase system; High-performance liquid chromatography

Comparative validation of amisulpride determination in pharmaceuticals by several chromatographic, electrophoretic and spectrophotometric methods by Robert Skibiński; Łukasz Komsta; Hanna Hopkała; Izabela Suchodolska (pp. 195-202).

Nine accurate methods for determination of amisulpride in tablets: reversed phase high pressure liquid chromatography (RP-HPLC), aqueous capillary electrophoresis (CE), non-aqueous CE, normal phase (NP) and reversed-phase (RP) high performance thin layer chromatography (HPTLC) with densitometry and videodensitometry, and direct and derivative UV spectrophotometry were developed and validated. The HPLC was carried out using Nova-Pak C8 column and mobile phase consisted of acetonitrile–methanol–phosphate buffer pH 4.50 (15:5:80, v/v/v) with flow rate 1 mL min⁻¹and UV detection at 225 nm. The moclobemide was used as the internal standard. CE was performed using75μm×82cm fused silica capillary (65 cm effective), the internal standard was quetiapine. Detection was carried out at 225 nm. For aqueous analysis, the 30 mM phosphate buffer pH 6.00, 30 kV voltage and 30° C temperature were chosen, non-aqueous determination was performed with ammonia acetate 1 mM in acetonitrile–methanol (1:1, v/v), 30 kV voltage and 25° C temperature. NP-HPTLC was carried out using HPTLC silicaF254 plates, developed with hexane–ethanol–propylamine (5:5:0.1, v/v/v) through 9 cm distance. RP-HPTLC was developed with HPTLC RP8F254 plates, with mobile phase of tetrahydrofuran-phosphate buffer pH 3.50 (4:6, v/v), distance 4.5 cm. Both analyses were performed in horizontal chambers and scanned with densitometer at 275 nm or videodensitometer at 254 nm. UV spectrophotometry was carried out in methanol, using 224 nm for direct assay and 258 nm (D1) for derivative assay. The precision and accuracy of all the methods were complexively compared. The highest accuracy was observed in RP-HPTLC, the highest precision was achieved in non-aqueous CE method. The differences were not significant, so all the elaborated methods can be used in routine analysis.

Keywords: Amisulpride; Analysis; Pharmaceutical formulations; High pressure liquid chromatography; Capillary electrophoresis; Thin layer chromatography; Densitometry; Videodensitometry; Spectrophotometry

Influence of electronic and steric effects on stability constants and electrochemical reversibility of divalent ion complexes with glycine and sarcosine by Ignacy Cukrowski; Helder M. Marques; Tumaini S. Mkwizu; Philemon P. Magampa; Claudette Serge (pp. 203-216).

Cd^II complexes with glycine (gly) and sarcosine (sar) were studied by glass electrode potentiometry, direct current polarography, virtual potentiometry, and molecular modelling. The electrochemically reversible Cd^II–glycine–OH labile system was best described by a model consisting of M(HL), ML, ML₂, ML₃, ML(OH) and ML₂(OH) (M=Cd^II, L=gly) with the overall stability constants, as log β, determined to be 10.30±0.05, 4.21±0.03, 7.30±0.05, 9.84±0.04, 8.9±0.1, and 10.75±0.10, respectively. In case of the electrochemically quasi-reversible Cd^II–sarcosine–OH labile system, only ML, ML₂ and ML₃ (M=Cd^II, L=sar) were found and their stability constants, as log β, were determined to be 3.80±0.03, 6.91±0.07, and 8.9±0.4, respectively. Stability constants for the ML complexes, the prime focus of this work, were thus established with an uncertainty smaller than 0.05 log units. The observed departure from electrochemical reversibility for the Cd–sarcosine–OH system was attributed mainly to the decrease in the transfer coefficient α. The MM2 force field, supplemented by additional parameters, reproduced the reported crystal structures of diaqua-bis(glycinato-O,N)nickel(II) and fac-tri(glycinato)-nickelate(II) very well. These parameters were used to predict structures of all possible isomers of (i) [Ni(H₂O)₄(gly)]⁺ and [Ni(H₂O)₄(sar)]⁺; and (ii) [Ni(H₂O)₃(IDA)] and [Ni(H₂O)₃(MIDA)] (IDA=iminodiacetic acid, MIDA= N-methyl iminodiacetic acid) by molecular mechanics/simulated annealing methods. The change in strain energy, Δ U_str, that accompanies the substitution of one ligand by another (ML+L′→ML′+L), was computed and a strain energy Δ U_str=+0.28kcalmol⁻¹ for the reaction [Ni(H₂O)₄(gly)]⁺+sar→[Ni(H₂O)₄(sar)]⁺+gly was found. This predicts the monoglycine complex to be marginally more stable. By contrast, for the reaction [Ni(H₂O)₃IDA]+MIDA→[Ni(H₂O)₃MIDA]+IDA, Δ U_str=−0.64kcalmol⁻¹, and the monoMIDA complex is predicted to be more stable. This correlates well with (i) stability constants for Cd–gly and Cd–sar reported here; and (ii) known stability constants of ML complex for glycine, sarcosine, IDA, and MIDA.

Keywords: Glycine; Sarcosine; Iminodiacetic acid; N; -Methyl iminodiacetic acid; Stability constants; Molecular modelling; Polarography; Potentiometry; Cadmium; Nickel; Virtual potential

Micellar effect on the sensitivity of spectrophotometric Mo(VI) determination based on the formation of gallic acid complex providing evidence for the polyoxoanion structure of molybdate ions by Senay Taşcıoğlu; Olcay Şendil; Şivekar Beyreli (pp. 217-223).

In this study effects of anionic (sodium dodecyl sulfate, SDS), cationic (cetyltrimethylammonium bromide, CTAB) and nonionic (Triton X-100, TX100) micelles on the sensitivity of spectrophotometric molybdenum(VI) (Mo) determination based on the formation of a binary complex with gallic acid (GA) were investigated.Micellar CTAB was found to enhance the formation of Mo–GA complex. SDS micelles exerted an inhibitory effect while TX100 micelles had no effect on the complex formation. By the optimization of experimental conditions, the determination limit of the method suggested in the literature was lowered from 5.2×10⁻⁵ to 4.6×10⁻⁶ and to 5.7×10⁻⁷M, in the absence and presence of CTAB, respectively.The mechanism of the effect of CTAB was investigated by spectrophotometric titrations and it was concluded that CTAB did not form a ternary complex with Mo and GA. The stoichiometry of the complex, deduced from the results of spectrophotometric titrations, provided evidence for the formation of para-Mo₇O₄⁶⁻ polyanions at pH 4.5, indicating to the formation of a charge transfer complex between these ions and GA in micellar medium.

Keywords: Molybdenum(VI); Gallic acid; Cetyltrimethylammonium bromide; Micellar effects; Spectrophotometric Mo(VI) determination; Polyoxomolybdate

Novel indirect enzyme-linked immunosorbent assay (ELISA) method to detect Total E. coli in water environment by Na Wang; Miao He; Han-Chang Shi (pp. 224-231).

In order to establish ELISA (enzyme-linked immunosorbent assay) method to detect Total E. coli in water environment, E. coli multi-characters antigens in water environment were prepared according to the characters of kinds of E. coli serotypes, including antigen of whole cell, antigen of disrupted whole cell, somatic antigen, flagellar antigen and fimbrial antigen. Total E. coli polyclonal antibodies were obtained from the New Zealand rabbits immunized with these five antigens, respectively. Antibodies generated in this research are with high titers and good purity, can conjugate with antigens, specifically, stably and strongly. Indirect ELISA shows the titers of antibody of whole cell and antibody of disrupted whole cell are both over 1×10⁵. The cross-reactivity of the antibody is from 12 to 30% which indicate the specificity of the antibody against Total E. coli. Based on these antibodies, we established indirect ELISA method to detect Total E. coli in water environment. The matrix effects were studied and the results show that there is no significant influence by all the factors. The ELISA result shows that the detection limitation could be 10⁴CFU (colony forming units) L⁻¹. The indirect ELISA method developed in this study is well suited for Total E. coli analysis in real water samples as a rapid screen method.

Keywords: Total; E. coli; Multi-characters antigen; Polyclonal antibody; Water environment; Immunoassay

Novel indirect enzyme-linked immunosorbent assay (ELISA) method to detect Total E. coli in water environment by Na Wang; Miao He; Han-Chang Shi (pp. 224-231).

Keywords: Total; E. coli; Multi-characters antigen; Polyclonal antibody; Water environment; Immunoassay

First approach to radionuclide mixtures quantification by using plastic scintillators by A. Tarancón; J.F. García; G. Rauret (pp. 232-238).

Recent studies have evaluated the capability of plastic scintillation (PS) as an alternative to liquid scintillation (LS) in radionuclide activity determination without mixed waste production. In order to complete the comparison, we now assess the extent to which PS can be used to quantify mixtures of radionuclides and the influence of the diameter of the plastic scintillation beads in detection efficiency.The results show that the detection efficiency decreases and the spectrum shrink to lower energies when the size of the plastic scintillation beads increases, and that the lower the energy of the beta particle, the greater the variation takes place. Similar behaviour has been observed for beta–gamma and alpha emitters.Two scenarios for the quantification of mixtures are considered, one including two radionuclides (¹⁴C and⁶⁰Co) whose spectra do not overlap significantly, and the other including two radionuclides (¹³⁷Cs and⁹⁰Sr/⁹⁰Y), where the spectra of one the isotopes is totally overlapped by the other The calculation has been performed by using the conventional window selection procedure and a new approach in which the selected windows correspond to those with lower quantification errors. Relative errors obtained using the proposed approach (less than 10%) are lower than those of the conventional procedure, even when a radionuclide is completely overlapped, except for those samples with extreme activity ratios that were not included in the window optimization process.

Keywords: Plastic scintillation; Radionuclide mixtures; Mixed waste; Mixture quantification; Scintillator beads diameter

First approach to radionuclide mixtures quantification by using plastic scintillators by A. Tarancón; J.F. García; G. Rauret (pp. 232-238).

Keywords: Plastic scintillation; Radionuclide mixtures; Mixed waste; Mixture quantification; Scintillator beads diameter

Speciation analysis of arsenic and selenium compounds in environmental and biological samples by ion chromatography–inductively coupled plasma dynamic reaction cell mass spectrometer by Ruoh-Yun Wang; Ying-Ling Hsu; Lan-Fang Chang; Shiuh-Jen Jiang (pp. 239-244).

An inductively coupled plasma mass spectrometer (ICP-MS) was used as an ion chromatographic (IC) detector for the speciation analysis of arsenic and selenium. The arsenic and selenium species studied included arsenite [As(III)], arsenate [As(V)], monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsenobetaine (AsB), selenite [Se(IV)] and selenate [Se(VI)]. Gradient elution using (NH₄)₂CO₃ and methanol at pH 9 allowed the chromatographic separation of all species in less than 12min. Effluents from the IC column were delivered to the nebulization system of ICP-DRC-MS for the determination of arsenic and selenium. The potentially interfering³⁸Ar⁴⁰Ar⁺ and⁴⁰Ar⁴⁰Ar⁺ at the selenium masses m/ z 78 and 80 were reduced in intensity by approximately 3 orders of magnitude by using 0.6mLmin⁻¹ CH₄ as reactive cell gas in the DRC while an Rpq value of 0.3 was used. Meanwhile, arsenic was determined as the adduct ion⁷⁵As¹²CHH⁺ at m/ z 89, which is more sensitive than⁷⁵As. The limits of detection for arsenic and selenium were in the range of 0.002–0.01ngmL⁻¹ and 0.01–0.02ngmL⁻¹, respectively, based on peak height. The relative standard deviation of the peak areas for five injections of 5ngmL⁻¹ As and Se mixture was in the range of 2–4%. The concentrations of arsenic and selenium species have been determined in urine samples collected locally. The major As and Se species in urines were AsB, DMA and probably selenosugar at concentration of 20–40, 15–19 and 17–31ngmL⁻¹, respectively. The recoveries were in the range of 94–105% for all the determinations. This method has also been applied to determine various arsenic compounds in two fish samples. In this study, a simple and rapid microwave-assisted extraction method was used for the extraction of arsenic compounds from fish. The arsenic species were quantitatively leached with an 80% v/v methanol solution in a focused microwave field during a period of 5min.

Keywords: Ion chromatography; Inductively coupled plasma dynamic reaction cell mass spectrometer; Speciation analysis; Arsenic; Selenium

Time measurement-visual analysis of nickel(II) using autocatalytic reaction with sodium sulfite/hydrogen peroxide system and its application to the length detection-flow analysis by Jun Kato; Tetsuo Higuchi; Toshio Kubota; Shukuro Igarashi (pp. 245-252).

Trace amounts of nickel(II) can function as a trigger (=reaction initiator) in an autocatalytic reaction with the sodium sulfite/hydrogen peroxide system. Based on this finding, sub-μgL⁻¹ levels of nickel(II) were determined by a time measurement using the autocatalytic reaction. The detection range using the above method was 10⁻⁹–10⁻⁵M, the detection limit (3 σ) was 8.1×10⁻¹⁰M (0.047μgL⁻¹), and the relative standard deviation was 2.66% at nickel(II) concentration of 10⁻⁷M ( n=7). This method was applied to length detection-flow injection analysis. The detection range for the flow injection analysis was 2×10⁻⁹–2×10⁻³M. The detection limit (3 σ) was 1.4×10⁻⁹M (0.082μgL⁻¹), and the relative standard deviation was 1.86 at initial nickel(II) concentration of 10⁻⁶M ( n=7).

Keywords: Autocatalytic reaction; Nickel; Time measurement; Flow injection analysis; Length detection; Visual analysis

Kinetic spectrophotometric method for rapid determination of trace formaldehyde in foods by Xiaojun Cui; Guozhen Fang; Liqin Jiang; Shuo Wang (pp. 253-259).

A simple and sensitive kinetic-spectrophotometric method was developed for the determination of ultra trace amount of formaldehyde in food samples. The method was based on the oxidation of rhodamine B (RhB) by potassium bromate in sulfuric acid medium (formaldehyde as catalyst). The reaction was monitored by measuring the decrease in absorbance of the dye at 515nm after 6min. The developed method allowed the determination of formaldehyde in the range of 10–100μgL⁻¹ with good precision, accuracy and the detection limit was down to 2.90μgL⁻¹. The relative standard deviations for the determination of 10 and 60μgL⁻¹ of formaldehyde were 3.0% and 1.9% ( n=10), respectively. The method was found to be sensitive, selective and was applied to the determination of formaldehyde in foods with satisfactory results.

Keywords: Formaldehyde; Spectrophotometric method; Kinetic determination; Rhodamine B

Kinetic spectrophotometric method for rapid determination of trace formaldehyde in foods by Xiaojun Cui; Guozhen Fang; Liqin Jiang; Shuo Wang (pp. 253-259).

Keywords: Formaldehyde; Spectrophotometric method; Kinetic determination; Rhodamine B

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Analytica Chimica Acta (v.590, #2)