Jin-Ming Lin

Microheterogeneous systems of micelles and microemulsions as reaction media in chemiluminescent analysis

The development of new or enhanced analytical methodologies based on the use of microheterogeneous systems is a very active area of current research. The use of organized surfactant molecular assemblies, such as micelles, reversed micelles and microemulsions, in analytical solution chemiluminescence is steadily increasing because it can change luminescent characteristics and result in a greatly improved analytical performance, in terms of selectivity, sensitivity and experimental convenience. This review focuses on how micelles, reversed micelles and microemulsions may be used to improve the quality of chemiluminescent analytical procedures and gives some applications of these microheterogeneous chemiluminescent systems.

Development of analytical methods for polycyclic aromatic hydrocarbons (PAHs) in airborne particulates: A review

In the present work, the different sample collection, pretreatment and analytical methods for polycyclic aromatic hydrocarbons (PAHs) in airborne particulates is systematacially reviewed, and the applications of these pretreatment and analytical methods for PAHs are compared in detail. Some comments on the future expectation are also presented.

Determination of folic acid by chemiluminescence based on peroxomonosulfate-cobalt(II) system

Based on the chemiluminescence (CL) phenomena of folic acid in peroxomonosulfate-cobalt(II) system, a rapid and sensitive CL method was developed for determination of folic acid in pharmaceutical preparations and its urinary metabolism processes. Under the optimum conditions, the relative CL intensity was linear over the concentration ranging from 10(-9) to 8 x 10(-7)molL(-1) (R(2)=0.9991) with a detection limit as low as 6 x 10(-10)molL(-1) (S/N=3) and relative standard deviation was 2.63% for 2 x 10(-8)molL(-1) folic acid (n=11). This method has been successfully applied to the determination of folic acid in tablets and human urine. The blank CL emission was yielded owing to the formation of singlet oxygen molecular pair from the quenching experiment of 1,4-diazabicyclo[2.2.2]octane, and pterine-6-carboxylic acid might be the degradation intermediate in this system and it also acts an energy acceptor and sensitizes the chemiluminescence based on the studies of the CL and fluorescence spectra.

Development and optimization of a method for the analysis of low-molecular-mass organic acids in plants by capillary electrophoresis with indirect UV detection

Capillary zone electrophoresis was developed to analyze low-molecular-mass organic acids including oxalic, tartaric, formic, malic, citric, succinic, glutaric, acetic and lactic acid. The influences of some crucial parameters such as buffer concentration, pH value, surfactant concentration and separation temperature, on electrophoretic separation were investigated. Under the conditions of 15 mM phthalate containing 0.6 mM tetradecyltrimethylammonium bromide as the run buffer (pH 5.6); separation voltage -15 kV (-263.2 V/cm) and temperature 25 degrees C, a satisfactory separation of nine organic acids was accomplished within 7 min. The detection limits (S/N=3) ranged from 0.008 to 0.08 microg/ml and the quantification limits ranged from 0.01 to 0.1 microg/ml for electrokinetic injection. The method was successfully applied to analyze organic acids in different parts of Var splendens (an edible vegetable in China). The recoveries of organic acids in real samples ranged from 88 to 121%.

Flow-injection chemiluminescent determination of nitrite in water based on the formation of peroxynitrite from the reaction of nitrite and hydrogen peroxide

In the present work, a new flow-injection chemiluminescent (CL) method for the determination of nitrite has been proposed. In acidic medium, nitrite reacts with hydrogen peroxide to form peroxynitrous acid, which is an unstable compound in acidic solution and can be quenched into peroxynitrite in basic solution. During the decomposition of peroxynitrite a weak CL was observed. With the presence of ethyldimethylcetylammonium bromide (EDAB) and uranine, the CL intensity was enhanced significantly. This CL system was developed as a flow-injection method for the determination of nitrite. The CL intensity is proportional to the concentration of nitrite in the range from 1.0 x 10(-7) to 5.0 x 10(-5) M. The analytical frequency is 30 samples/h. The detection limit (S/N = 3) is 5.0 x 10(-8) M and the relative standard deviation for nine repeated measurements of 1.0 X 10(-6) M nitrite was 4.3%. The interferences of some cationic and anionic ions on the CL were studied. The anionic ions have almost no effect on the nitrite determination. After using a cation-exchange column as pre-treatment, the interferences of the cationic ions can be removed well. This method has been satisfactorily applied to determine nitrite in tap and well waters with recoveries of 94-106%

Determination of total bilirubin in human serum by chemiluminescence from the reaction of bilirubin and peroxynitrite

Peroxynitrous acid (ONOOH) was produced by the on-line reaction of acidified hydrogen peroxide with nitrite in a flow system, and peroxynitrite (ONOO(-)) was generated from ONOOH in NaOH solution. A weak chemiluminescent (CL) emission was observed due to the production of singlet oxygen ( O(2)1) during the decomposition of ONOO(-). Bilirubin and its conjugate were found to enhance the CL emission of O(2)1 in a suitable micellar medium. For the first time, the feasibility of employing the present CL system for the sensitive and selective determination of total bilirubin contents in human serum was demonstrated and the results were compared with certified values. The present method showed a great improvement on overcoming bis(2,4,6-trichlorophenyl)oxalate CL highly insolubility in aqueous solution and exhibiting higher tolerance towards interferences than redox reaction of bilirubin with various oxidizing agents such as sodium hypochlorite and iodine. The recoveries of bilirubin were found to fall in the range between 95 and 108%. The detection limits (S/N=3) for bilirubin and its conjugate were determined to be 10 and 8ngml(-1), respectively. The relative standard deviations (R.S.D.) for the consecutive CL detection of a series of bilirubin (30mugl(-1)) and bilirubin ditaurite (25mugl(-1)) were 3.2 and 2.9% (n=11), respectively.

Molecularly imprinted solid-phase extraction and flow-injection chemiluminescence for trace analysis of 2,4-dichlorophenol in water samples

AbstractHighly sensitive flow-injection chemiluminescence (CL) combined with molecularly imprinted solid-phase extraction (MISPE) has been used for determination of 2,4-dichlorophenol (2,4-DCP) in water samples. The molecularly imprinted polymer (MIP) for 2,4-DCP was prepared by non-covalent molecular imprinting methods, using 4-vinylpyridine (4-VP) and ethylene glycol dimethacrylate (EGDMA) as the monomer and cross-linker, respectively. 2,4-DCP could be selectively adsorbed by the MIP and the adsorbed 2,4-DCP was determined by its enhancing effect on the weak chemiluminescence reaction between potassium permanganate and luminol. The enhanced CL intensity was linear in the range from 1 × 10−7 to 2 × 10−5g mL−1. The LOD (S/N = 3) was 1.8 × 10−8g mL−1, and the relative standard deviation (RSD) was 3.0% (n = 11) for 1.4 × 10−6g mL−1. The proposed method had been successfully applied to the determination of 2,4-DCP in river water.n FigureEffect of 4-VP content on the ultraviolet spectrum of 2,4-DCP in chloroform

Development of a gel monolithic column polydimethylsiloxane microfluidic device for rapid electrophoresis separation

A beta-cyclodextrin (beta-CD)-bonded gel monolithic column polydimethylsiloxane (PDMS) microfluidic device was developed in a simple and feasible way. Before preparation of gel monolithic column in PDMS microchannel, PDMS surface was activated by UV light to create silanol groups, which is an active molecule to covalently bond 3-(trimethoxysilyl)-propyl methacrylate (Bind-Silane) and seal microfluidic device. By the way, Bind-Silane is a bifunctional molecule to link polyacrylamide (PAA) gel and inner wall of PDMS microchannel covalently. Allyl-beta-CD was used not only as a multifunctional crosslinker in PAA gel to control the size of the pores, but also as a chiral selector for the enantioseparation. The stability, transferring heat and optical characteristic of the microfluidic device were examined. The separation capability of the gel monolithic column was confirmed by the successful separation of fluorescein isothiocyanate (FITC)-labeled arginine (Arg), glutamine acid (Glu), tryptophan (Try), cysteine (Cysteine) and phenylalanine (Phe) in the PDMS microfluidic device less than 100 s at 36 mm effective separation length. A maximum of 2.06 x 10(5) theoretical plates was obtained by the potential strength of 490 V/cm. A pair of FITC-labeled dansyl-D,L-threonine (Dns-Thr) was separated absolutely.

Chiral separation of underivatized and dansyl amino acids by ligand-exchange micellar electrokinetic capillary chromatography using a copper(II)-L-valine complex as selector.

Ligand-exchange micellar electrokinetic capillary chromatography was used for the chiral resolution of underivatized and dansyl amino acid enantiomers simultaneously. The separation was achieved by chiral copper(II)-L-valine complexes incorporated in micelles of sodium dodecyl sulfate (SDS). The enantioresolution was strongly affected by SDS and a concentration of 20 mM SDS was shown to be necessary for the separation. Other impacting factors were investigated including pH, the molar ratio of copper(II) to L-valine and the total concentration of complex. Using the proposed method, 11 different dansyl amino acids and two underivatized amino acids were separated successfully with a running electrolyte of 20 mM NH4OAc, 4 mM CuSO4, 8 mM L-valine and 20 mM SDS at pH 9.0 in less than 25 min. Experiments were also performed with other amino acid ligands in order to vary the stability and the sterical arrangement of the copper(II) complexes and the possible chiral recognition mechanism was also discussed briefly.

Determination of Carbamate and Organophosphorus Pesticides in Fruits and Vegetables Using Liquid Chromatography-Mass Spectrometry with Dispersive Solid Phase Extraction

A liquid chromatography-mass spectrometry (LC-MS) method was established for the simultaneous determination of carbamate and organophosphorus pesticides (OPPs) in fruits and vegetables by dispersive solid phase extraction using acetonitrile as extraction solvent and primary secondary amine (PSA) as sorbent instead of octadecyl bonded silica (ODS). Four common representative samples (tomato, apple, carrot and cabbage) were selected from the supermarket in order to validate the method by recovery and precision. The obtained recoveries were, with a few exceptions, in the range of 80% - 110% with RSDs less than 8%; and limits of detection ranged from 0.5 to 35 mu g/kg in tomato. In addition, the method was applied to pesticides residue detection in vegetables and fruits obtained from local markets.