University of North Florida
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Stuart Chalk, Ph.D.
Department of Chemistry
University of North Florida
Phone: 1-904-620-1938
Fax: 1-904-620-3535
Email: schalk@unf.edu
Website: @unf

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Hua Li

Abbrev:
Li, H.
Other Names:
Address:
Institute of Analytical Science, Northwest University, Xian, Shaanxi Province 710069, China
Phone:
+86-298302942
Fax:
+86-298303448

Citations 14

"Flow-injection Chemiluminescence Determination Of Dihydralazine Sulfate Based On Hexacyanoferrate(III) Oxidation Sensitized By Eosin Y"
Talanta 2004 Volume 64, Issue 2 Pages 478-483
Xiao-Feng Yang and Hua Li

Abstract: A novel flow-injection chemiluminescence (CL) method for the determination of dihydralazine sulfate (DHZS) is described. The method is based on the reaction between DHZS and hexacyanoferrate(III) in alkaline solution to give weak CL signal, which is dramatically enhanced by eosin Y. The CL emission allows quantitation of DHZS concentration in the range 0.02-2.8 µg mL-1 with a detection limit (3s) of 0.012 µg mL-1. The experimental conditions for the CL reaction are optimized and the possible reaction mechanism is discussed. The method has been applied to the determination of DHZS in pharmaceutical preparations and compared well with the high performance liquid chromatography (HPLC) method.

"Chemiluminescence Of Cobalt(II)-hydrogen Peroxide-hydrogencarbonate In The Absence Of Luminescent Reagents"
Talanta 2000 Volume 53, Issue 3 Pages 609-616
Sichun Zhang, Yayan Wu and Hua Li

Abstract: A novel chemiluminescence (CL) system, cobalt(II)-hydrogen peroxide-hydrogencarbonate without luminescent reagents, was described. When cobalt(II) was injected into mixed solution of 0.4 mol 1-1 hydrogencarbonate and 0.01 mol 1-1 hydrogen peroxide in a flow injection system, CL occurred, which was significantly enhanced when rhodamine B coexisted. The CL emission intensity was found correlation with the concentration of cobalt(II) in the range of 2.0 x 10^-9-1.0 x 10^-5 mol 1-1 with a detection limit of 1.2 x 10^-9 mol 1-1 cobalt(II). The relative standard derivative (RSD) for 5.0 x 10^-7 mol 1-1 cobalt(II) was 1.6% based on nine repetitive measurements. In addition to cobalt(II), other metal ions were also investigated, and only chromium(III) gave out measurable CL emission. The possible mechanism was discussed based on the CL emission spectrum. (C) 2000 Elsevier Science B.V. A novel chemiluminescence (CL) system, cobalt(II)-hydrogen peroxide-hydrogencarbonate without luminescent reagents, was described. When cobalt(II) was injected into mixed solution of 0.4 mol L-1 hydrogencarbonate and 0.01 mol L-1 hydrogen peroxide in a flow injection system, CL occurred, which was significantly enhanced when rhodamine B coexisted. The CL emission intensity was found correlation with the concentration of cobalt(II) in the range of 2.0 x 10^-9-1.0 x 10^-5 mol L-1 with a detection limit of 1.2 x 10^-9 mol L-1 cobalt(II). The relative standard derivative (RSD) for 5.0 x 10^-7 mol L-1 cobalt(II) was 1.6% based on nine repetitive measurements. In addition to cobalt(II), other metal ions were also investigated, and only chromium(III) gave out measurable CL emission. The possible mechanism was discussed based on the CL emission spectrum.

"Chemiluminescence Of Peracetic Acid In Alkaline Medium And Its Application To Dihydralazine Sulfate Determination"
Microchim. Acta 2006 Volume 153, Issue 3-4 Pages 171-178
Hanchun Yao, Xiaofeng Yang and Hua Li

Abstract: The chemiluminescence (CL) of peracetic acid (PAA) in alkaline medium is very weak but is strongly enhanced after the addition of dihydralazine sulfate (DHZS). Based on this phenomenon, a simple, rapid and highly sensitive flow-injection CL method for the determination of DHZS was developed. The CL emission was linearly related to the DHZS concentration in the range of 20-4000 ng mL-1 with a detection limit (3?) of 1.2 ng mL-1. As a preliminary application, the proposed method was successfully applied to the determination of DHZS in pharmaceutical preparations; the recovery of DHZS in human urine was between 96.5% and 102.2%. A detailed CL mechanism was proposed and singlet molecular oxygen (1O2) was suggested to be produced in the CL reaction process. © Springer-Verlag 2005.

"Flow Injection Chemiluminescence Determination Of Hemin Using The Rhodamine B-H2O2-NaOH System"
Microchim. Acta 2005 Volume 149, Issue 3-4 Pages 281-286
Suqin Han, Erbao Liu and Hua Li

Abstract: A flow injection chemiluminescence method has been developed and applied to the determination of hemin in tablets and animal blood. The proposed method is based on the luminescent properties of the Rhodamine B-H2O2-NaOH system and the addition of sodium dodecyl sulfonate (SDS) as emission-sensitizer. Hemin was determined over the concentration range of 8.6 x 10^-10-8.6 x 10^-7 M with a detection limit of 8.6 x 10^-11 M (3?). The relative standard deviation (RSD) for seven independent detections of 1.72 x 10^-8 M hemin was 3.0%. The proposed method was successfully applied to the analysis of hemin in pharmaceutical preparations and animal blood with a recovery of 96-108%. A possible CL mechanism of the present system was discussed, and free radicals were suggested to be involved in this reaction.

"Sensitive Determination Of Cobalt(II) Using A Spiro Fluorescein Hydrazide As A Chemiluminogenic Reagent"
Microchim. Acta 2005 Volume 149, Issue 1-2 Pages 123-129
Xiao-Feng Yang, Dong-Bing Wu and Hua Li

Abstract: A novel chemiluminogenic reagent, refered to as spiro form fluorescein hydrazide, was synthesized, and its application to chemiluminescence (CL) determination of Co2+ is described. The method is based on the catalytic effect of Co2+ on the autoxidation of sulfite in basic solution to generate a series of powerful oxidative intermediates, which then oxidize colorless, nonfluoresent fluorescein hydrazide to generate strong CL emission. The CL signal is linearly related to the concentration of Co2+ in the range of 0.1-200 nM with a detection limit of 0.04 nM. The optimal conditions for the detection of Co2+ were evaluated, and the possible CL mechanism is discussed. The proposed method has been applied to the determination of Co2+ in pharmaceutical preparations and in soil samples.

"Determination Of Tetracycline, Chlortetracycline And Oxytetracycline By Flow Injection With Inhibitory Chemiluminescence Detection Using Copper(II) As A Probe Ion"
Luminescence 2006 Volume 21, Issue 2 Pages 106-111
Suqin Han, Erbao Liu, Hua Li

Abstract: This paper reports an indirect flow-injection (FI) method for the determination of the tetracycline drugs (TCs), tetracycline (TC), chlortetracycline (CTC) and oxytetracycline (OTC), using copper(II) as a probe ion. The method was based on the inhibition caused by these TCs to the copper(II)-catalyzed chemiluminescence (CL) reaction between luminol and H2O2. The CL reaction was induced on-line and injection of the sample produced negative peaks as a result of the copper(II) complexation or displacement by the analytes. The height of the peaks was proportional to the drug concentration in the sample. The choice of the catalyst ion, the concentration of luminol, H2O2 and copper(II) are discussed. The linear range was 3.6 x 10^-8 - 1.0 x 10^-5, 1.1 x 10^-7 - 1.0 x 10^-5 and 1.9 x 10^-7 - 1.0 x 10^-5 mol/L for TC, CTC and OTC, respectively. The detection limit was 5.0 x 10^-9 mol/L for TC, 1.0 x 10^-8 mol/L for CTC and 2.0 x 10^-8 mol/L for OTC (3), respectively. The method was applied to the determination of TCs in pharmaceutical preparations and human urine with recoveries in the range 95-105%.

"Flow Injection Chemiluminescence Determination Of Dihydralazine Sulphate Based On Permanganate Oxidation Sensitized By Rhodamine B"
Luminescence 2004 Volume 19, Issue 6 Pages 322-327
Xiao-Feng Yang, Dong-Bing Wu, Hua Li*

Abstract: A novel flow injection chemiluminescence (CL) method for the determination of dihydralazine sulphate (DHZS) is described. The method is based on the CL produced during the oxidation of DHZS by acidic permanganate solution in the presence of rhodamine B. Rhodamine B is suggested as a fluorescing compound for the energy-transferred excitation. The CL emission allows quantitation of DHZS concentration in the range 5-800 ng/mL, with a detection limit of 1.9 ng/mL (3). The experimental conditions for the CL reaction are optimized and the possible reaction mechanism is discussed. The method has been applied to the determination of DHZS in pharmaceutical preparations and compares well with the high performance liquid chromatography (HPLC) method.

"Chemiluminescence Of Cobalt(II)-catalysed Auto-oxidation Of Sulphite And Its Application To Cobalt Analysis"
Luminescence 2004 Volume 19, Issue 5 Pages 253-258
Xiao-Feng Yang, Hua Li*

Abstract: The oxidation of sulphite by dissolved oxygen in aqueous solution catalyzed by cobalt(II) was investigated. A weak chemiluminescence (CL) emission was observed when the reaction took place in a strong alkaline solution without any special CL reagent. Further studies showed that in the presence of fluorescein sodium the CL signal was enhanced significantly. The CL emission is linear with Co(II) concentration in the range 0.6-80 nmol/L and the detection limit is 0.3 nmol/L. In addition to Co(II), other transition metal ions were also tested, and the results showed that the proposed system was highly selective for Co(II). The method was successfully applied to the determination of Co(II) in pharmaceutical preparations. The possible CL mechanism was also discussed.
Cobalt(II) Pharmaceutical Chemiluminescence Selectivity Interferences

"Investigation Of The Photodecomposition Of Hemin And Trace Amount Determination Of Hemin With Flow Injection Chemiluminescence Method"
J. Chin. Chem. Soc. 2005 Volume 52, Issue 3 Pages 399-404
Su-Qin Han, Er-Bao Liu and Hua Li

Abstract: Using the hemin-H2O2-Na2CO3-NaOH chemiluminescence (CL) system, the study on the photo decomposition behavior of hemin under ultraviolet light and solar light were carried out and the determination of hemin was developed coupled with simple flow injection technique. There suits showed that the decomposition reaction of hemin in different light irradiations corresponded with a first-order reaction. And then the determination of hemin was completed by the CL emission from the reaction of hemin with H2O2 in aqueous carbonate. The linear range was 2.2 x 10^-10 to 6.88 x 10^-7 M and the detection limit was 2.2 x 10^-11 M (S/N = 3). The relative standard deviation (RSD) was 2.82% for ten independent detections of 1.72 x 10-8 M hemin. As a preliminary application, the proposed method was successfully applied for the analysis of hemin in pharmaceutical formulations and animal blood with a recovery of 96-108%. A possible CL mechanism of the present system was discussed, and free radicals were suggested to be involved in this reaction.

"Indirect Flow Injection Chemiluminescence Method For The Determination Of Tetracyclines Using Cu(II) As A Probe Ion"
Chin. Chem. Lett. 2005 Volume 16, Issue 8 Pages 1067-1070
Han Suqin, Liu Erbao, Li Hua

Abstract: This paper reported an indirect flow injection chemiluminescence (FI-CL) method for the determination of the drugs tetracycline (TC), chlortetracycline (CTC) and oxytetracycline (OTC) using Cu(II) as a probe ion. The CL reaction was induced on-line and after injection of the sample the negative peaks appeared as a result of complexation. The method was applied to the determination of TCs in pharmaceuticals and human urine with recoveries in the range 95-105%.

"Cetyltrimethylammonium Bromide-Enhanced Chemiluminescence Determination Of Uric Acid Using A Luminol-Hexacyanoferrate(III)-Hexacyanoferrate(II) System"
Anal. Sci. 2005 Volume 21, Issue 2 Pages 111-114
Suqin Han, Erbao Liu And Hua Li

Abstract: A chemiluminescence (CL) method using flow injection (FI) was developed for the determination of uric acid based on the enhancement chemiluminescence intensity of luminol-hexacyanoferrate(III)-hexacyanoferrate(II) in the presence of cetyltrimethylammonium bromide and the uric acid species. The linear range was 7.0 x 10^-10 - 9.0 x 10^-7 M with a detection limit (3s) of 2.58 x 10^-10 M, which was about two orders of magnitude lower than those reported. The proposed method was used for the determination of uric acid in real samples.

"Investigation Of Chemiluminescence Behavior Of Flavonoids With Cerium (IV)-rhodamine B System"
Anal. Lett. 2006 Volume 39, Issue 9 Pages 2007-2024
Hanchun Yao; Xiaofeng Yang; Hua Li

Abstract: The chemiluminescence (CL) behavior of five major flavonoid types in cerium (IV)-rhodamine B system was investigated by flow-injection. Strong CL was observed when cerium (IV) reacted with rhodamine B in sulfuric acid medium in the presence of flavonoids. This reaction system has been established as a simple, rapid, and highly sensitive flow injection CL analysis for quercetin and kaempferol, and their detection limit (3?) was 2.7 and 0.22 nmol/L, respectively. The relative standard deviation (n=8) was 1.2% for 1.0 ?mol/L quercetin and 1.9% for 0.5 ?mol/L kaempferol. This method was successfully applied to the determination of quercetin in the hydrolysate of rutin and compared well with the high performance liquid chromatography (HPLC) method. From a comparison of several related flavonoids, it was concluded that only flavonoids that contain a free 3-hydroxyl and 2, 3-double bond in conjugation with 4-oxo function could produce a relatively strong CL emission. Copyright © Taylor & Francis Group, LLC.

"Flow Injection Chemiluminescence Sensor For The Determination Of Isoniazid"
Anal. Chim. Acta 2001 Volume 444, Issue 2 Pages 287-294
Sichun Zhang and Hua Li

Abstract: By electrostatically immobilizing the chemiluminescence (CL) reagent luminol and periodate on anion exchange resin separately, a novel CL sensor for isoniazid combined with flow injection analysis was developed. Isoniazid was sensed by its enhancing effect on the weak CL reaction between luminol and periodate, which were eluted from the ion exchange column. The calibration graph is linear in the range 8.0 x 10^-9 to 1.0 x 10^-6 mol L-1 and the detection limit is 4.2 x 10^-9 mol L-1 isoniazid (3s). A complete analysis could be performed in 1 min with a relative standard deviation 2.0% (n=9). The sensor could be reused for over 400 times and has been applied successfully to the determination of isoniazid in pharmaceutical preparations.

"Flow Injection Chemiluminescence Determination Of N-tetrahydrobenzothiazolyl Imines"
Analyst 2000 Volume 125, Issue 4 Pages 753-757
Sichun Zhang, Yayan Wu and Hua Li

Abstract: A flow injection chemiluminescence (CL) method is described for the determination of five newly synthesized N-tetrahydrobenzothiazolyl imines (N-THBTIs) based on their sensitizing effect on the CL reaction of cerium(IV) and sulfite. The fluorescence, CL and absorption spectra are studied. The CL is deduced to originate from the excited sulfur dioxide, which is formed in a free radical reaction initiated by the free radical of N-THBTI. The relationship between the CL intensity and the concentration of N-THBTI is linear in the range of 2.0 x 10^-7 to 8.0 x 10^-5 mol L-1 with a detection limit of 8.0 x 10^-8 mol 1-1. The relative standard deviation (RSD) for seven independent determinations of N-THBTI (1.0 x 10^-6 mol 1-1) is 1.2%. Most metal ions and some organic compounds do not interfere with the determination, except for Fe(III), Fe(II), Mn(II), Tl(I) and Bi(III). The method has been successfully applied to the determination of N-THBTI in synthetic samples.