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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Surekha Devi

Abbrev:
Devi, S.
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Department of Chemistry, Faculty of Science, M.S. University of Baroda, Baroda-390 002, India
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Citations 5

"Determination Of Nanogram Levels Of Zirconium By Chelating Ion Exchange And Online Preconcentration In Flow Injection UV-visible Spectrophotometry"
Talanta 1997 Volume 44, Issue 3 Pages 319-326
Rajesh Purohit and Surekha Devi*

Abstract: Sample was subjected to online pre-concentration (diagram of continuous-fold manifold given) at 2 ml/min on microcolumns (4 cm x 2 mm i.d.) containing resins based on 8-hydroxyquinoline, resorcinol or hydroquinone and formaldehyde, furfuraldehyde or benzaldehyde as cross-linking agents (cf., Ibid., 1991, 38, 753). Detection was at 535 nm using Xylenol Orange as reagent. The chelated Zr(IV) was eluted from the columns with 20 µL 2 M HCl followed by acetate buffer. The method was suitable for determination of Zr in the presence of Cu(II), Ni(II), Pb(II), Zn(II), Cd(II), Fe(II), Mn(II), Al(III), Cr(VI), Mo(VI), Th(IV), V(V), Ce(IV), VO22+ and Ti(IV). Calibration graphs were linear for 0.5-2.5 µg/ml Zr for a 5 mL sample and the detection limit was 10 ng/ml. RSD were 0.8-2.65%. Separations of Zr, Ti and Th were also carried out on columns (10-18 cm x 7 mm i.d.) packed with the resins with a flow rate of 1 ml/min. Recoveries were 99.2-102.8%.
Zirconium Ion exchange Spectrophotometry Preconcentration Resin Column 8-Hydroxyquinoline Interferences Chelation

"Determination Of Copper At Ng-levels By Inline Preconcentration And Flow Injection Analysis Coupled With Flame Atomic Absorption Spectrometry"
Talanta 1991 Volume 38, Issue 7 Pages 753-759
Rajesh Purohit and Surekha Devi*

Abstract: The synthesis and characterization of oxine (I) - formaldehyde (II) - resorcinol and I - II - hydroquinone chelating resins are described. Conditions were optimized for the pre-concentration. of Cu from binary and ternary mixtures also containing Co, Pb and/or Ni by batch extraction and by column chromatography, alone or in a flow injection system, with use of the resins. For batch pre-concentration, a pH of ~2.5 to 3 was optimal whereas in the flow injection method a broader pH range (~2 to 3.5) could be used. Separations of binary mixtures of Cu(II) with Ni(II) or Pb(II) at the µg mL-1 level did not show any cross contamination. A flow injection analytical procedure is described in which Cu was pre-concentrated by passage of the sample solution through a microcolumn (2 cm x 2 mm) containing the oxine resin. The carrier (2 mL min-1) was 0.2 M acetate or -phosphate buffer (pH 2 or 3, adjusted with HCl). The column was washed with buffer, and the chelated Cu was eluted by the injection of 50 µL of 0.5 M HCl, and was determined by flame AAS. The detection limit was 5 ng mL-1 with pre-concentration. from a 15 mL solution
Copper Chromatography Spectrophotometry Sample preparation Buffer Chelation Column Extraction Preconcentration Resin Synthesis 8-Hydroxyquinoline

"Determination Of Manganese In Vegetables And Medicinal Plants Using Flow Injection System"
Indian J. Technol. 1990 Volume 28, Issue 2 Pages 78-80
Devi, S.

Abstract: Sample solution (20 µL) was injected into a flowing stream (1 mL min-1) of methanolic 1 mM 2-acetylpyridine thiosemicarbazone (I) and buffer solution (pH 9.0), and the Mn(II) - I complex was extracted into CHCl3 by passage along a 50-cm coil. The phases were separated in a PTFE separator, and the absorbance of the organic phase was measured at 410 nm. The calibration graph was rectilinear for 50 to 150 µM-Mn, and the detection limit was 0.5 µM. The sampling rate was 60 h-1. The method was applied to plant material after dry ashing and acid dissolution. Results showed good agreement with those of AAS.
Manganese Vegetable Plant Sample preparation Spectrophotometry Sample preparation Buffer Calibration Extraction Method comparison Phase separator Organic phase detection

"Determination Of Trace Amounts Of Lead By Chelating Ion Exchange And Online Preconcentration In Flow Injection Atomic Absorption Spectrometry"
Anal. Chim. Acta 1992 Volume 259, Issue 1 Pages 53-60
Rajesh Purohit and Surekha Devi*

Abstract: Resins synthesized from quinolin-8-ol and resorcinol or quinol, with furfuraldehyde, formaldehyde or benzaldehyde as cross-linking agent, were evaluated for the pre-concentration. of traces of Pb. Characteristics of each column are tabulated. Columns (2 to 3 cm x 2 mm) of any of the resins could be used in a flow system for separation of Pb from Cu or Zn. The metals were adsorbed at pH ~3 on to the resin, which was washed with acetate buffer solution of pH 3 before elution of (a) Pb with 0.05 M HNO3 followed by Cu(II) with 1 M HNO3 or (b) Zn with 0.2 M acetic acid followed by Pb with 0.1 M HNO3. The eluted metals were determined by flame AAS. There was no cross-contamination, and the detection limit was 10 ng mL-1 of Pb with pre-concentration. from 5 mL of solution Resins synthesized from quinolin-8-ol and resorcinol or hydroquinone, with furfuraldehyde, formaldehyde, or benzaldehyde as crosslinking agent, were used for the pre-concentration. of nanogram amounts of lead. The rate of exchange and activation energy of lead exchange were calculated Column sepns. of lead-copper and lead-zinc did not show any cross-contamination. A continuous-flow manifold using resin microcolumns was developed for the pre-concentration. and determination of lead.
Lead Ion exchange Spectrophotometry 8-Hydroxyquinoline Preconcentration Resin Interferences Buffer Chelation

"Determination Of Chromium By Online Preconcentration On A Poly (hydroxamic Acid) Resin An Flow Injection Atomic Absorption Spectrometry"
Anal. Chim. Acta 1990 Volume 236, Issue 2 Pages 469-473
Ajay Shah and Surekha Devi

Abstract: Seven poly(hydroxamic acid) resins [Analyst (London), 1985, 110, 501] were evaluated for LC separation of Cr(III) from U(VI) and from multi-component mixtures. Columns (17 cm x 5 mm) containing the resins in H+ form were used, and the flow rate for sorption and elution was 1 mL min-1. At pH 5, U(VI), Fe(III), Zn and Cu(II) were retained on the resin, but ~80% of the Cr(III) passed through. Retained U(VI) was eluted by 1 M HCl, Zn and Cu(II) by 0.1 M HCl and Fe(III) by 3 M HCl. Cross-contamination was observed between Zn and Cu. Tervalent Cr could also be determined by flow injection flame AAS with use of a column (4 cm x 2.5 mm) of poly(hydroxamic acid) resin and a carrier stream of 0.2 M acetate buffer (pH 2) for pre-concentration.; the Cr(III) was then eluted with 1 M HCl for AAS at 357.9 nm. The calibration graph was rectilinear for 10 µL portions of solution containing 20 to 100 ng mL-1 of Cr(III). The flow injection method was used to determine Cr(III) in seawater at pM concentration.
Chromium Sea Spectrophotometry Preconcentration Resin Multicomponent Column pH Buffer Calibration