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

Rice

Classification: Agricultural -> grain -> rice

Citations 12

"Stopped-flow Injection Determination Of Copper(II) At The Ng/ml Level"
Anal. Chim. Acta 1984 Volume 165, Issue 1 Pages 177-185
F. Lázaro, M. D. Luque de Castro and M. Valcárcel

Abstract: The catalytic action of Cu(II) on the di-2-pyridyl ketone hydrazone - H2O2 system is quantitative. The oxidation product shows an intense blue fluorescence at 427 nm (excitation at 350 nm) in a strongly acidic medium. The sampling rate (72 h-1), coefficient of variation (1.4%) and freedom from interference from most foreign ions allow determination of 0.2 to 300 ng mL-1 of Cu in foods (e.g., fruits and rice) and blood serum.
Copper(II) Fluorescence Interferences Catalysis Stopped-flow PPB

"Determination Of Copper In Water And Rice Samples By Flame Atomic Absorption Spectrometry With Flow Injection Online Adsorption Preconcentration Using A Knotted Reactor"
Anal. Chim. Acta 1994 Volume 298, Issue 2 Pages 167-173
Hengwu Chen, Shukun Xu and Zhaolun Fang

Abstract: A flow-injection on-line adsorption pre-concentration flame atomic absorption spectrometric system for the determination of copper was developed. The copper diethyldithiocarbarmate ehelate was adsorbed on the walls of a PTFE knotted reactor. The sorbed species was eluted by isobutyl methyl ketone at a flow-rate of 4.1 mL min-1. Air segmentation between sample and eluent was employed to avoid mixing of the neighbouring phases under fast elution rates. An enhancement factor of 120 and a detection limit of 0.2 µg L-1 Cu were achieved for a 60 s loading period (sample throughput 46 h-1). The relative standard deviations were 1.7% and 3.6% at the 20 µg L-1 and 2 µg L-1 Cu levels, respectively. Interference from at least 50 µg L-1 Fe(III) was eliminated by adding ascorbic acid. The method has been applied successfully to determine µg L-1 amounts of copper in drinking water and sea water and Ju µg-1 amounts of copper in rice.
Copper Spectrophotometry Preconcentration Knotted reactor

"Complex Formation Of 2-(5-nitro-2-pyridylazo)-5-(N-propyl-N-sulfo-propy Lamino)phenol With Lead, Cadmium And Manganese For Their Sensitive Spectrophotometric Detection In Flow Injection And Ion Chromatography Systems"
Anal. Chim. Acta 1997 Volume 345, Issue 1-3 Pages 139-146
Takeshi Yamane* and Yuzuru Yamaguchi

Abstract: An ion-chromatographic method with post-column derivatization and spectrophotometric detection was developed for the simultaneous determination of Pb, Cd and Mn. Analysis was carried out on a strongly acidic cation-exchange column (7 cm x 4 mm i.d.). Elution (1 ml/min) was with 0.15 M malic acid of pH 5. The injection volume was 588 µL. The column effluent was merged with a reagent stream containing 60 µM-2-(5-nitro-2-pyridylazo)-5-(N-propyl-N-su lfo-propylamino)phenol/0.2 M 2-(cyclohexylamino)ethanesulfonic acid/0.16 M NaOH of pH 9.4 at a flow rate of 1 ml/min. Detection was at 574 nm. Calibration graphs were linear up to 150 ng/ml Cd and Mn, and 300 ng/ml Pb; detection limits were 1.9, 1.5 and 4.8 ng/ml, respectively. RSD were 2.1%, 2.5% and 3.2% for 50 ng/ml Cd, Mn and Pb, respectively. The method was verified by analyzing rice flour CRM following microwave assisted digestion and river water samples spiked with Cd, Mn and Pb.
Lead Cadmium Magnesium HPIC Spectrophotometry Sample preparation Post-column derivatization Reference material Interferences

"Catalytic Determination Of Manganese At Ultratrace Levels By Flow Injection Analysis"
Analyst 1986 Volume 111, Issue 1 Pages 69-72
S. Maspoch, M. Blanco and V. Cerdá

Abstract: The catalytic effect of Mn(II) on the oxidation of succinimide dioxime in alkaline medium was used for determination of Mn(II) by flow injection analysis with photometric detection at 695 nm. Variation of the reaction temperature between 25°C and 45°C allows the determination range to be extended from 0.2 to 1300 ng mL-1, with a sampling frequency of 45 h-1 and a coefficient of variation of 1.3 to 1.0%. Injection of the sample in a flow of EDTA solution overcomes most interference. Interference by Co(II), Fe(II) and Mg(II) was investigated. The method was used to determine Mn in reagent-grade ZnO and HClO4 and in powdered coffee and rice.
Manganese(II) Spectrophotometry Catalysis Heated reaction Interferences Optimization Ultratrace

"Ion-chromatographic Trace Analysis Of Mercury, Cadmium And Zinc By Post-column Derivatization With A Water-soluble Porphyrin"
Fresenius J. Anal. Chem. 1989 Volume 334, Issue 6 Pages 507-510
Daren Yan, Jingan Zhang and Georg Schwedt

Abstract: Sample solution was subjected to ion chromatography on a Nucleosil SA (10 µm) column (20 cm x 4 mm) with 0.5% NaCl solution in 1 mM tartrate (pH 4.3) as mobile phase (0.6 mL min-1). Post-column reaction with 10 µM-4,4',4'',4'''-(21H,23H-porphine-5,10,15,20-tetrayl)tetrabenzenesulfonic acid - 1 µM-4-(2-pyridylazo)resorcinol - 0.6% of NaCl - 32 mM borate buffer of pH 11.5 (0.3 mL min-1) was carried out in a T-shaped mixing cell, and detection was at 430 nm. Calibration graphs (injection volume 0.1 ml) were rectilinear for 0.002 to 0.8, 0.1 to 8 and 0.05 to 20 mg L-1 for Cd, Hg and Zn, respectively; corresponding detection limits were 0.5, 50 and 10 µg l-1. The method was successfully applied in the determination of these metals in waste water, a silicate sample and rice.
Mercury Cadmium Zinc HPIC Spectrophotometry Post-column derivatization Buffer Mixing chamber

"A Flow Injection System For Simultaneous Determination Of Starch And Glucose Concentrations"
J. Chem. Technol. Biotechnol. 1994 Volume 61, Issue 1 Pages 81-86
Enobong F. Umoh, Karl Schügerl

Abstract: A description of a flow injection analysis system that simultaneously determines the concentration of starch and glucose in samples. Conventional techniques cannot distinguish between glucose originally present in a system and that derived from the action of glucoamylase on the starch. Glucoamylase, glucose oxidase, and mutarotase were immobilized on macroporous polymer packed in reaction cartridges and operated at 30°C. Amperometric techniques were used to determine glucose resulting from the action of glucoamylase or originally present in the sample. Prehydrolysis with a-amylase was not required for starch analysis, and inclusion of mutarotase was necessary only when the original sample contained a-glucose. Linear detection ranges were as high as 1.5 g L-1 and 4.0 g L-1 for glucose and total sugar concentration measurements, respectively. The system was capable of analyzing 10 samples per hour.
Starch Glucose Amperometry Immobilized enzyme

"Rapid Determination Of Total Nitrogen, Phosphorus, Magnesium, Potassium And Amylose In Milled Rice By Flow Injection Analysis"
J. Flow Injection Anal. 1991 Volume 8, Issue 2 Pages 127-135
Hideharu NAKAJ MA and *Ryoichi YANAGIHARA

Abstract: Sample (0.5 g) was digested with 3 mL of concentrated H2SO4 and 1 mL of HCl and then diluted with water. To determine N, 30 µL of the solution was injected into a stream of 6% H2SO4 (0.8 mL min-1) and mixed with 2.5 M NaOH of pH 10 (2 mL min-1), with warming at 30°C, and with an indicator stream (0.1 g of Tecator 5000-0295 mixed indicator, 0.4 g of NaH2PO4 and water to 1 l) (2.8 mL min-1) before detection at 590 nm. When determining P, 100 µL of the solution was injected into a stream of 6% H2SO4 (2 mL min-1), followed by dilution with water (2.8 mL min-1), reaction with a reagent stream [prepared with 4 g of NH4VO3, 270 mL of HNO3, 80 g of (NH4)6Mo7O24 and water to 1 l] (0.8 mL min-1) and detection at 420 nm. Magnesium and K were determined with use of the same apparatus equipped with an atomic absorption spectrophotometer by using 6% H2SO4 as carrier solution and 1% LaCl3 solution as reagent stream. For determination of amylose, 20 mg of the sample was heated at 90°C with 0.5 mL of ethanol and 2 mL of 1 M NaOH for 60 min, cooled, and diluted with H2O; 30 µL of the supernatant solution was injected into a stream of ethanol - 0.1 M NaOH (2 mL min-1) and mixed with 0.1 M NaOH (2.8 mL min-1), ~2% citric acid - Na acetate (2 mL min-1) and iodine solution (1.5 mL min-1) before detection at 620 nm. The coefficient of variation were 4%. Satisfactory results were obtained.
Amylose Magnesium Nitrogen, total Phosphorus Potassium Spectrophotometry Dilution Heated reaction

"The Rapid Diagnosis Of Nutritional States Of Crops. 1. The Rapid Procedure For The Analysis Of Inorganic Nutrients Of Plants By Combining H2SO4 - H2O2 Digestion With Flow Analysis And Atomic Absorption"
Miyagiken Nogyo Senta Kenkyu Hokoku 1987 Volume 55, Issue 1 Pages 1-12
Saito, K.;Hasegawa, E.;Sasaki, J.

Abstract: A rapid and labor-saving method was established for determining N, P, K, Ca, and Mg in crop plants by H2SO4-H2O2 digestion, flow anal., and atomic absorption. Si in rice was determined also. For determination of N and P, the digested samples were diluted with water and were subjected to flow anal. SiO2 ppt. in digests was dissolved in diluted aqueous HF and analyzed with a flow-analyzer. For Ca, Mg, and K determination, the digested samples were diluted with water containing 1500 ppm La and were subjected to atomic absorption spectrophotometry in an air-acetylene flame under atomic absorption and flame emission mode, respectively. Contents of these elements in rice, wheat, and soybean plants were determined by this and conventional methods, and the data agreed excellently. (SFS)
Nitrogen Phosphorus Potassium Calcium Magnesium Silicon Sample preparation Spectrophotometry Method comparison

"Determination Of Amino-acids In The Rice Residue From A Gourmet Powder Factory By High Performance Liquid Chromatography"
Sepu 1991 Volume 9, Issue 3 Pages 207-208
Lin Quan

Abstract: Sample was dissolved in 6 M HCl,hydrolyzedat 110°C for 24 h and the pH was adjusted to 2.2. The amino-acids in the solution were analyzed by HPLC on a column (15 cm x 4 mm) of Shim-pack ISC-07/S1504 Li, operated at 38°C to 58°C with gradient elution (0.4 mL min-1) with Li citrate - 1,2-dimethoxyethane - HClO4 - H3BO3 - LiOH - water (details given) and post-column derivatization with reagent B (o-phthalaldehyde - ethanol - mercaptoethanol - Brij-35) in reagent A (NaOCl in Na2CO3 - H3BO3 - K2SO4 - water buffer of pH 10) at 55°C with detection at 450 nm (excitation at 350 nm). The coefficient of variation were 4.2%; the detection limit was 1 nM.
Amino Acids HPLC Buffer Heated reaction pH Post-column derivatization

"Rapid Determination Of Amylose In Rice By Flow Injection Analysis"
Tohoku J. Agric. Res. 1990 Volume 43, Issue NA Pages 95-96
Nakajima, H.;Takahashi, K.

Abstract: NA
Amylose

"Rapid Determination Of Total Magnesium And Potassium In Rice By HCIO4-H2SO4 Digestion"
Tohoku J. Agric. Res. 1990 Volume 43, Issue NA Pages 97-98
Nakajima, H.;Takahashi, K.

Abstract: NA
Magnesium Potassium Sample preparation

"Rapid Determination Of Total Nitrogen And Phosphorus In Rice By HCIO4-H2SO4 Digestion-flow Injection Analysis"
Tohoku J. Agric. Res. 1990 Volume 43, Issue NA Pages 99-100
Nakajima, H.;Takahashi, K.

Abstract: NA
Nitrogen Phosphorus Sample preparation