A Sensitive Chemiluminescence Flow Injection Procedure for Assay of Fluoride in Waters and Humane Urine by Use of Immobilized Reagents

A new simple, rapid, selective and sensitive analytical procedure based on chemiluminescence (CL) detection is described for the determination of free fluoride at sub‐nanogram levels by use of controlled‐reagent‐release technology in a flow injection system. The analytical reagents involved in the CL reaction, including luminol and periodate, were both immobilized on anion‐exchange resins in a flow injection system. Through water injection luminol and periodate were eluted from the anion exchange column to generate the chemiluminescence, which was enhanced in the presence of fluoride. The increased CL intensity was linear with fluoride concentration in the range from 0.1 to 10 ng·mL^? 1. The limit of detection was 20 pg·mL^? 1 (3σ) and the relative standard deviation (RSD) was 1.02% (n = 5) for a 1.0 ng·mL^? 1 fluoride. At a flow rate of 2.0 mL·min^? 1, including sampling and washing, a typical analytical procedure could be performed in 0.5 min with a RSD of less than 3.0%. The proposed method was successfully applied to determine the free fluoride in water and human urine, and the results were in good agreement with those obtained by ion chromatography.     

Flow‐Injection Chemiluminescence Study of Luminol–Hydrogen Peroxide–Carbendazim System

Abstract

A new flow‐injection chemiluminescence (CL) method is described for the determination of carbendazim. The method is based on the CL reaction of luminol and hydrogen peroxide (H₂O₂). Carbendazim can greatly enhance the chemiluminescence intensity in sodium hydroxide–sodium dihydrogen phosphate (NaOH–NaH₂PO₄) medium (pH=12.6). Under the optimum conditions, the linear range for the determination of carbendazim is 2.00×10^?8 to 2.00×10^?6 g mL^?1 with a detection limit (S/N=3) of 7.24×10^?9 g mL^?1. The relative standard deviation is 1.8% for 1.0×10^?7 g mL^?1 carbendazim (n=8). The proposed method has been applied to the determination of carbendazim in tap‐water samples. Furthermore, the possible enhanced CL mechanism is discussed by examining the CL spectra and fluorescence spectra.     

Multipumping Nitrite Determination in Exhaled Breath Condensate

Abstract

A flow system based on multicommutation is proposed for the rapid, clean, and inexpensive determination of nitrites in small volumes of breath condensates. The procedure exploits the colorimetric detection of nitrite with the Griess reagent [0.03% naphthylethylene diamine dihydrochloride (NED), 0.5% sulpfhanilamide, and 3.0% phosphoric acid] in acidic medium at 540 nm correcting the variations of the baseline with measurements at 424 nm. The flow system was designed with a set of solenoid micropumps to minimize sample and reagent consumption and waste generation. The detection limit was estimated as 3.8 ng mL^?1 (99.7% confidence level) with a linear response ranging up to 500 ng mL^?1. The coefficient of variation was estimated as 0.7% for a solution containing 300 ng mL^?1 nitrite (n=9). Approximately 144 determinations can be carried out per hour, consuming only 678.4 µg Griess reagent and generating 1.184 mL of effluent per determination, thus providing an environmentally friendly alternative and a nonexpensive method. The procedure was successfully applied to determine nitrite in breath condensates.     

Comparative Study on Three Different Systems of Chemiluminescence Flow‐Injection Determination of Leucogen

Abstract

The effects of three systems on the chemiluminescence (CL) intensity have been studied in this paper, such as leucogen–potassium permanganate–rhodamine B, leucogen–cerium (IV)–rhodamine B, and leucogen–luminol–hydrogen peroxide (called system 1, system 2, and system 3, respectively). The mechanism of these reactions is also discussed. Surfactant (CTMAB) has a remarkably sensitive effect on these systems mentioned above. Therefore, three new flow injection chemiluminescence methods for the determination of leucogen have been established. For system 1, the linear range is 8.0×10^?8 to 4.0×10^?5 g mL^?1, with limits of detection 2×10^?8 g mL^?1; the relative standard deviation is 2.5% (n=11, Cs=4.0×10^?6 g mL^?1). For system 2, the linear range is 1.0×10^?8 to 5.0×10^?6 g mL^?1, with limits of detection 3×10^?9 g mL^?1; the relative standard deviation is 5.1% (n=11, Cs=1.0×10^?6 g mL^?1). For system 3, the linear range is 4.0×10^?8 to 2.0×10^?6 g mL^?1, with limits of detection 1×10^?8 g mL^?1; the relative standard deviation is 1.3% (n=11, Cs=1.0×10^?7 g mL^?1). Compared with the three methods above, system 3 is confirmed as the best method. This method has been applied to the determination of leucogen with satisfactory results.     

Solid-Phase Extraction Using Polymer-Based Cartridge Modified with 2-(2-benzothiazolylazo)-3-hydroxyphenol for Preconcentration of Uranium(VI) Ions from Water and Real Samples

ABSTRACT

A highly sensitive, selective, and rapid method for the determination of ng mL^?1 level of U(VI) based on the rapid reaction of U(VI) with 2-(2-benzothiazolylazo)-3-hydroxyphenol (BTAHP) and the solid-phase extraction of the colored complex with a reversed-phase polymer-based C18 cartridge was developed. The BTAHP reacted with U(VI) to form a violet complex of molar ratio 2:1 [BTAHP to U(VI)] in the presence of 4.0 M of phosphoric acid solution and Triton X-114 medium. This complex was enriched by the solid-phase extraction with a polymer-based C18 cartridge. The enrichment factor of 200 was achieved. The molar absorptivity of the complex is 2.73 × 10⁶ L mol^?1 cm^?1 at 639 nm in the measured solution. The system obeys Beer's law in the range of 2.0–125 ng mL^?1, whereas the optimum concentration range obtained from Ringbom plot was 8.0–115 ng mL^?1. The relative standard deviation for 10-replicates sample of 100 ng mL^?1 level is 1.05%. The detection and quantification limits are 0.6 and 1.98 ng mL^?1 in the original sample. This method was applied to the determination of uranium(VI) in sea, tap, and waste waters, ore standard reference material, soil and sediment samples with good results comparing to the graphite furnace atomic absorption spectroscopy (GFAAS) method.     

Vortex-Assisted Liquid–Liquid Microextraction for the Determination of Residual Sulfonamides in Meat Samples with Spectrofluorophotometer

A simple and fast extraction termed vortex-assisted liquid–liquid microrextraction coupled with molecular fluorescence spectroscopy has been developed and used for the detection of three sulfonamides (sulfadiazine sodium, sulfamethoxazole, and sulfaguanidine) in the meat samples. In the vortex-assisted liquid–liquid microrextraction method, 400 µL of nonanoic acid was used as extractant and directly injected into 10 mL centrifuge tube containing a derivative, which sulfonamides derived with o-phthaladehyde. And the extraction solvent was dispersed into the water phase under mechanical force with the vortex-mix. The polar side was reduced and the strong fluorescence produced at λ_ex = 295 nm. Variable parameters affecting the derivatization and vortex-assisted liquid–liquid microrextraction procedure were evaluated and optimized. The vortex-mix substituted effect of disperser solvent in this procedure. The limits of detection were 2.0 ng mL^?1 for sulfadiazine sodium and sulfamethoxazole, 0.5 ng mL^?1 for sulfaguanidine with the relative standard deviations of the method ranging from 2.5% to 6.1%. And the calibration graph was linear from 5 to 5000 ng mL^?1 with coefficient of determinations more than 0.9995. Recoveries of the three sulfonamides on spiked meat samples at different levels were 92.2–102.5%. Finally, the method has been successfully applied to the determination of sulfonamides from meat samples.     

Silver Nanoparticle Based Analysis of Aminoglycosides

Colorimetric silver nanoparticle sensor was developed for determination of aminoglycosides in milk. Silver nanoparticles were synthesized by using sodium borohydride as reducing agent and sodium dodecyl sulfate as stabilizer. Yellow color of silver turned into orange and red in proportion to the concentrations of analytes. Quantitative analyses were performed by using decrease in absorbance of silver nanoparticles at 394 nm. Linear ranges were 20–60 ng mL^?1, 23–60 ng mL^?1, and 60–100 ng mL^?1 for gentamicin, tobramycin, and amikacin, respectively. The method was optimized in terms of pH, ionic strength, and time. This simple and validated method was applied to milk samples and pharmaceutical preparations.     

Binding Study of Phenformin with Bovine Serum Album Using a Combined Technique of Equilibrium Dialysis with Flow-Injection Chemiluminescence Detection

ABSTRACT

The interaction between phenformin hydrochloride and bovine serum albumin (BSA) was investigated by the methods of chemiluminescence combined with equilibrium dialysis technique. A novel N-bromosuccinimide (NBS)–eosin Y (EY) chemiluminescence (CL) method was established for the determination of phenformin. The mechanism of this chemiluminescence system was proposed. Optimization studies were performed to determine the phenformin. Under the optimal conditions, the CL intensity was linear for a phenformin concentration over the range of 4.6 × 10^?8 to 5.0 × 10^?5 g/mL. The detection limit was 1.5 × 10^?8 g/mL. The data obtained by the present equilibrium dialysis–CL system were analyzed using the Klotz plot and the Scatchard analysis. The results showed that the Klotz plot and the Scatchard plot are linear with good correlation coefficient, indicating that the phenformin has only one type of binding site on BSA. The binding parameters were the number of the binding sites n (1.02) and the estimated association constant K (2.66 × 10⁴ L/mol). The chemiluminescence system combined with equilibrium dialysis developed in this work demonstrated its use for determination of interaction between drug and protein by using relatively simple instrument.     

UV–Vis Spectrophotometric Determination of Mercury Based on Room Temperature Ionic Liquids Enhanced Hollow-Fiber Liquid-Phase Microextraction

A novel method based on the enhancement effect of room temperature ionic liquids for hollow-fiber liquid-phase microextraction trace amounts of mercury combined with UV–Vis spectrophotometry for the determination of Hg was developed. The addition of room temperature ionic liquids led to 6.0 times improvement in the determination of mercury. Under optimized conditions, an enrichment factor of 120 could be obtained, and the detection limit for Hg was 0.2 ng mL^?1. The relative standard deviations for five replicate determinations of 20 ng mL^?1 Hg(II) was 5.4%. The proposed method was successfully applied to certified reference materials and environmental water samples with satisfactory results for the determination of Hg.     

Sensitive Detection of Luteolin Using Thioglycolic Acid–Capped Cadmium Telluride/Cadmium Sulphide Quantum Dots as the Fluorescent Probe

ABSTRACT

A sensitive and simple method for the determination of luteolin (LTL) was developed based on the fluorescence quenching effect of LTL for thioglycolic acid–capped (TGA-capped) CdTe/CdS quantum dots (QDs). Under optimum conditions, a good linear relationship was obtained from 0.3 to 20.0 µg · mL^?1 with a correlation coefficient of 0.9972, and the detection limit was 7.2 ng · mL^?1. The fluorescence quenching mechanism has been proposed on the basis of electron transfer supported by ultraviolet-visible (UV-Vis) absorption, fluorescence (FL) spectroscopy. The proposed method was successfully applied to the determination of LTL in commercial capsules and human urine samples. It manifested several advantages such as high sensitivity, short analysis time, low cost, and ease of operation.     

Automated Flow Injection Method for Monitoring Total Cyanide Concentration in Petroleum Refinery Effluents Using Ninhydrin as Color Reagent

Abstract

An automated flow injection system was developed for monitoring cyanide concentration in effluents from petroleum refineries. The method takes advantage of the reaction of cyanide ions with ninhydrin in basic medium in a flow injection system. A linear range of 0.01 to 0.04 µg mL^?1 was obtained with a detection limit of 1.5 ng mL^?1 by using 500 µL sample injection, with an analytical throughput of 30 samples hr^?1, excluding sample pretreatment by distillation if required. Regarding interferences, cyanide can be determined in the presence of 100 mg L^?1 of thyocianate and sulfide, both species normally found in industrial effluents. For total cyanide determination, strong acid distillation is recommended due to the presence of cyano‐metallic complexes in the refinery effluents. The method was validated by analyte addition and results compared with the standard methodology proposed by the American Public Health Association (APHA). The more significant advantage of the proposed method is the lack of use of carcinogenic reagent such as pyridine and psychotropic compound such as barbituric acid, both used in the recommended method by APHA. Thus, the proposed method is really a friendly analytical procedure.     

Spectroscopic Study on the Interaction of Pyronine Y with Nucleic Acids and Its Analytical Application

ABSTRACT

The interaction of pyronine Y (PY) with nucleic acids was studied by resonance Rayleigh scattering (RRS) for nucleic acid detection. The enhanced RRS intensity of nucleic acids reacted with PY was proportional to the concentration of nucleic acids in the ranges of 27.0–625 ng ml^?1 for fish sperm DNA, 39.0–500 ng ml^?1 for calf thymus DNA, and 59.0–375 ng ml^?1 for yeast RNA. The limits of determination were 0.2 ng ml^?1 for fish sperm DNA, 0.6 ng ml^?1 for calf thymus DNA, and 0.7 ng ml^?1 for yeast RNA. The method had been successfully applied to the quick determination of nucleic acids in synthetic and natural samples.     

Determination of Nucleic Acids Sensitized by Emulsifier OP‐micelle Using Ethyl Rhodamine B as a Resonance Light‐Scattering Probe

Abstract

The resonance light scattering (RLS) spectra of ethyl rhodamine B with nucleic acid (calf thymus DNA and herring sperm DNA) have been studied. The effective factors and the optimum conditions have been studied, and the enhanced intensity of RLS is in proportion to the concentration of nucleic acids in the range 0～5.00 µg mL^?1 for calf thymus DNA (ctDNA) and 0～3.50 µg mL^?1 for herring sperm DNA (hsDNA). The limits of detection are 3.42 and 3.14 ng mL^?1, respectively. Based on this, a RLS method for the determination of nucleic acids sensitized by emulsifier OP‐micelle was accordingly established. The binding mode concerning the interactions of ethyl rhodamine B with nucleic acids was also studied, and this method has good selectivity and high sensitivity and it has been applied to the determination of DNA in synthetic samples and real samples with satisfactory results.     

Determination of Cd in Water Samples by Hollow-Fiber–Supported Liquid-Membrane Extraction Coupled with Thermospray-Flame–Furnace Atomic-Absorption Spectrometry

ABSTRACT

A new method of hollow-fiber–supported liquid-membrane extraction (HF-SLME) coupled with thermospray-flame–furnace atomic-absorption spectrometry (TS-FF-AAS) for the determination of cadmium in water samples was developed. 1-Octanol was immobilized in the pores of the polypropylene hollow fiber as liquid membrane and used as the acceptor solution. Cd was selectively extracted from water samples into 1-octanol that filled the inner part of hollow fiber as the acceptor solution. The authors evaluated in detail some parameters that influence extraction and determination, such as the concentration of sodium diethyldithiocarbamate (DDTC), pH of samples, stirring rate, extraction time, flow rate of the pump, and interferences. Under optimized conditions, an enrichment factor of 146 could be obtained. In combination with thermospray-flame–furnace atomic-absorption spectrometry, a very low limit of detection (LOD) (5 ng L^?1) was achieved. The relative standard deviation (RSD) was 4.3% for five determinations of 0.1 ng mL^?1 cadmium. The accuracy of this method was validated by determination of certified reference water samples (GBW(E) 08607 and GSBZ(E) 50009-88). The proposed method was also applied to the determination of cadmium in tap water and river water, with the recoveries in the range of 90–96% for spiked samples.     

Novel Method for Determination of Anthracene by Coupling Dispersive Liquid-Liquid Extraction to First-Derivative Synchronous Spectrofluorimetry

A novel method could be adopted successfully for determination of anthracene in environmental samples, utilizing dispersive liquid-liquid extraction followed by first-derivative synchronous fluorimetry at a constant wavelength difference Δλ?=?165 nm, where a linear calibration curve was obtained in a concentration range of 0.5–100 ng mL^?1 at 244 nm. The detection limit was 0.1 ng mL^?1. The method can be easily adopted for determination of anthracene in aqueous media including tap water and river water. The recoveries obtained were 85.40–108.02 %. The proposed method was validated according to International Conference of Harmonization (ICH) guide lines and successfully applied to determine anthracene in pure form and in water samples including real life water samples from different sources. All the results obtained were compared with those of published method, where no a significant difference was observed.     

Application of Gas Chromatography–Atomic Fluorescence Spectrometry Hyphenated System for Speciation of Butyltin Compounds in Water Samples

ABSTRACT

A laboratory-established capillary gas chromatography (GC)–atomic fluorescence spectrometry (AFS) hyphenated system was applied to butyltin speciation in water samples. Monobutyltin (MBT), dibutyltin (DBT), and tributyltin (TBT) were extracted and preconcentrated with headspace solid-phase microextraction (SPME) technique after derivatization using KBH₄, and then determined by GC-AFS directly. The experimental conditions—including the flow rates of carrier gas, argon and hydrogen–and the lamp current—were optimized in detail. Under the optimum conditions, the detection limits for MBT, DBT, and TBT, calculated as three times the baseline noise, were 10, 0.2, and 0.1 ng mL^?1 Sn, respectively. Good linear relationships were obtained when the concentrations of MBT, DBT, and TBT increased to 3000, 100, and 200 ng mL^?1 Sn. The relative standard deviations (RSDs) of five replicates were 5.2%, 7.4%, and 7.1% for MBT, DBT, and TBT, respectively. The recoveries of MBT, DBT, and TBT in three different types of water samples (seawater, tap water, and wastewater) were between 72.1% and 97.9%, indicating that the proposed method was accurate and feasible for speciation analysis of butyltin compounds in water samples.     

Determination of Montelukast in Plasma Using β − Cyclodextrins Coated on CoFe<Subscript>2</Subscript>O<Subscript>4</Subscript> Magnetic Nanoparticles in Luminol–H<Subscript>2</Subscript>O<Subscript>2</Subscript> Chemiluminescence System Optimized by Doehlert Design

A novel chemiluminescence method using β ? cyclodextrins coated on CoFe₂O₄ magnetic nanoparticles is proposed for the chemiluminometric determination of montelukast in plasma. The effect of coated β ? cyclodexterinon CoFe₂O₄ magnetic nanoparticles in the chemiluminescence of luminol–H₂O₂ system was investigated. It was found that β ? cyclodexterin coated on CoFe₂O₄ magnetic nanoparticles could greatly enhance the chemiluminescence of the luminol–H₂O₂ system. Doehlert design was applied in order to optimize the number of experiments to be carried out to ascertain the possible interactions between the parameters and their effects on the chemiluminescence emission intensity. This design was selected because the levels of each variable may vary in a very efficient way with few experiments. Doehlert design and response surface methodology have been employed for optimization pH and concentrations of the components. Results showed under the optimized experimental conditions, the relative CL intensity (ΔI) is increased linearly in the concentration range of 0.003–0.586 μgml^?1 of montelukast with limit of detection (LOD) 1.09 × 10^?4 μgml^?1 at S/N ratio of 3, limit of quantitative (LOQ) 3.59 × 10^?4 μgml^?1 and the relative standard deviation 2_.63 %. The method has been successfully applied to the determination of montelukast in plasma of human body. Results specified that relative chemiluminescence intensity (ΔI) has good proportional with the montelukast concentration with R² = 0.99979. The test of the recovery efficiency for known amounts of montelukast was also performed, the recoveries range obtained from 98.2 to 103.3 %, with RSDs of <4 % indicated that the proposed method was reliable.     

Determination of Silver by Chemical Vapor Generation with In Situ Trapping Flame Atomic Absorption Spectrometry

ABSTRACT

The hyphenation of chemical vapor generation with an integrated atom trap system for flame atomic absorption spectrometry (CVG-IAT-FAAS) was evaluated for determination of silver in real samples (coal fly ash, sediment, and nickel alloy). The volatile species of silver were formed by reaction with sodium tetrahydroborate(III) in the presence of nitric acid. A new CVG-IAT-FAAS design (versus a water-cooled single silica tube, double-slotted quartz tube) significantly improved the sensitivity and detection limits compared with conventional flame atomic absorption spectrometry (FAAS) for determination of silver. The concentration limit of detection was 0.7 ng mL^?1 for Ag. The overall efficiency of the vapor generation process was estimated to be ca. 12%. For a 2 min in situ preconcentration time, sensitivity was enhanced 143-fold for Ag using the vapor generation atom trapping technique, compared to conventional FAAS. Sensitivity can be further improved by increasing the collection time. The precision of measurement at 10 ng mL^?1 of Ag was 10% RSD. The accuracy of this method was validated by analyses of NRC GBW 07302 (Stream Sediment), BCS CRM No. 346 (Nickel Alloy), NIST SRM 2710 (Montana Soil), NRCC LUTS-1 (Lobster Hepatopancreas), and NIST SRM 1643e (Trace Element in Water) certified reference materials. The measured Ag contents in these five reference materials were in satisfactory agreement with the certified values (spanning the range of 0.066–35 µg g^?1).     

Flow Injection Kinetic Spectrophotometric Determination of Cerium Based on the Decolorization Reaction Between Arsenazo III and Cerium (IV)

ABSTRACT

Trace amounts of cerium were analyzed by flow injection kinetic spectrophotometry, based on the decolorization reaction between arsenazo III and Ce(IV) in sulfuric acid medium at room temperature. The absorbance difference (ΔA) of decolorization was linear with the concentration of Ce(IV). The flow injection technique was used to precisely control the timing. Under the optimum conditions, the determination of Ce(IV) in the range 0.0–8.0 µg mL^?1 with a correlation coefficient (r) of 0.9982, the regression equation was ΔA = 0.0014 + 0.0406c (µg mL^?1). The detection limit (3σ) of 0.2 µg mL^?1 was achieved at a sampling frequency of 60 h^?1. The proposed method was applied to the analyses of Ce in soil successfully.