University of North Florida
Browse the Citations
-OR-

Contact Info

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

View Stuart Chalk's profile on LinkedIn

Vegetable

Classification: Vegetable -> garlic

Citations 5

"Determination Of Trace And Ultratrace Amounts Of Germanium In Environmental Samples By Preconcentration In A Graphite Furnace Using A Flow Injection Hydride-generation Technique"
J. Anal. At. Spectrom. 1993 Volume 8, Issue 4 Pages 577-584
Guanhong Tao and Zhaolun Fang

Abstract: Trace and ultratrace levels of Ge were determined using flow injection (FI) hydride-generation followed by trapping and electrothermal atomization. Samples of garlic, tap water, ginseng and geochemical reference materials were pre-treated (details given) and diluted with 0.15 M or 3 M HCl then propelled into the FI system and merged with a tetrahydroborate reductant. This generated hydrides together with some H, which were separated in a gas - liquid separator, transferred to a Pd-coated graphite furnace pre-heated to 400°C and atomized by heating to 2500°C. Sensitivities and interference effects using different concentration. of HCl were compared. The use of high acidities and FI rather than batch collection led to reduced interference. Interference studies of 13 metals were performed (results given). Calibration graphs were rectilinear up to 0.5 µg L-1 of Ge for use of 0.15 M HCl and up to 2.5 µg L-1 for use of 3 M HCl with detection limits of 0.004 and 0.03 µg l-1, respectively, using 4.5 mL of sample. Coefficients of variation (n = 11) were 2.0% at 0.3 µg L-1 of Ge in 0.15 M HCl and 2.5% at 1.5 µg L-1 in 3 M HCl.
Germanium Spectrophotometry Phase separator Interferences Reference material Preconcentration Ultratrace

"Garlic Analysis. New Possibilities For Qualitative And Quantitative Determination Of Genuine Constituents"
Dtsch. Apoth. Ztg. 1989 Volume 129, Issue 7 Pages 318-322
Ziegler, S.J.;Meier, B.;Sticher, O.

Abstract: Cysteine derivatives were extracted from fresh garlic or dried garlic extract with aqueous 50% methanol and the extract was cleaned up on a column of Bond-Elut C18 or SCX. The primary amines in the extract were subjected to either pre- or post-column derivatization with phthalaldehyde - 1,1-dimethylethanethiol and subsequent analysis by reversed-phase HPLC. Optimization of the mobile phase was effected by using the PRISMA model. Electrochemical fluorimetric and UV detectors were used. A method is described for determination of alliin in garlic extracts by pre-column derivatization and HPLC with fluorimetric and electrochemical detectors in series.
Cysteine HPLC Fluorescence Spectrophotometry Electrochemical analysis Reverse Optimization Pre-column derivatization Dual detection

"A High-throughput Method For The Quantitative Determination Of Alliin"
Planta Med. 1998 Volume 64, Issue 8 Pages 736-740
Michael Keusgen

Abstract: The quality of most garlic (Allium sativum) preparations made from garlic powder or garlic dry extract is determined by their content of alliin. Therefore, a comprehensive documentation of alliin concentration. beginning with the crude material up to the final remedy is required. The newly developed anal. method described in this paper was designed in order to fulfill these demands. In contrast to conventional HPLC methods, neither a pre-column derivatization nor a chromatography separation are involved in this anal. procedure allowing a high throughput of samples. The currently investigated technique is based on immobilized alliinase (EC 4.4.1.4) which was combined with a two-channel flow injection analyzer (FIA) coupled to an ammonia detecting device. A high specificity for alliin could be demonstrated and a variety of garlic samples including garlic powders, dry extracts, and garlic preparations was analyzed. The results were in good correlation with those obtained by conventional HPLC methods.
Alliin Sensor Immobilized enzyme Method comparison

"Study And Application Of Flow Injection Spectrofluorimetry With A Fluorescent Probe Of 2-(2-pyridil)-benzothiazoline For Superoxide Anion Radicals"
Anal. Biochem. 2004 Volume 326, Issue 2 Pages 176-182
Bo Tang, Li Zhang and Li-li Zhang

Abstract: This paper presents an automatic spectrofluorimetric method (flow injection spectrofluorimetry) using a novel fluorescent probe named H. Py. Bzt (2-(2-pyridil)-benzothiazoline) for determining superoxide dismutase (SOD) activity. The fluorescent probe was synthesized in house and fully characterized by elemental analysis and by infrared and 1H nuclear magnetic resonance spectra. It could specially identify and trap O2-. and was oxidized by O2-. to form a strong fluorescence product. Based on this reaction, the flow injection spectrofluorimetric method was proposed and successfully used to determine SOD activity. The proposed method has a better selectivity in the determination of reactive oxygen species because the probe can be oxidized only by O2-. excluding H2O2. As a kind of simple, rapid, precise, sensitive and automatic technique, it was applied to measurement of SOD activity in scallion, garlic, and onion with satisfactory results.
Enzyme, superoxide dismutase Fluorescence Optimization

"Electrochemical Vapor Generation Of Selenium Species After Online Photolysis And Reduction By UV-irradiation Under Nano TiO 2 Photocatalysis And Its Application To Selenium Speciation By HPLC Coupled With Atomic Fluorescence Spectrometry"
Anal. Bioanal. Chem. 2005 Volume 381, Issue 2 Pages 366-372
Jing Liang, Qiuquan Wang and Benli Huang

Abstract: An online UV photolysis and UV/TiO2 photocatalysis reduction device (UV-UV/TiO2 PCRD) and an electrochemical vapor generation (ECVG) cell have been used for the first time as an interface between high-performance liquid chromatography (HPLC) and atomic fluorescence spectrometry (AFS) for selenium speciation. The newly designed ECVG cell of approximately 115 mgrL dead volume consists of a carbon fiber cathode and a platinum loop anode; the atomic hydrogen generated on the cathode was used to reduce selenium to vapor species for AFS determination. The noise was greatly reduced compared with that obtained by use of the UV-UV/TiO2 PCRD-KBH4-acid interface. The detection limits obtained for seleno-DL-cystine (SeCys), selenite (Se(IV)), seleno-DL-methionine (SeMet), and selenate (Se(VI)) were 2.1, 2.9, 4.3, and 3.5 ng mL-1, respectively. The proposed method was successfully applied to the speciation of selenium in water-soluble extracts of garlic shoots cultured with different selenium species. The results obtained suggested that UV-UV/TiO2 PCRD-ECVG should be an effective interface between HPLC and AFS for the speciation of elements amenable to vapor generation, and is superior to methods involving KBH4.
Selenomethionine Selenate Selenite Selenocysteine Fluorescence HPLC UV reactor Speciation