University of North Florida
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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

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Jose A. Gomes Neto

Abbrev:
Gomes Neto, J.A.
Other Names:
José A. Gomes Neto, José Anchieta Gomes Neto
Address:
Departamento de Quimica Analitica, Instituto de Quimica, Universidade Estadual Paulista-UNESP, P.O. Box 355, 14801-970, Araraquara, SP, Brazil
Phone:
+55-16-2322022
Fax:
+55-16-2227932

Citations 10

"Minimization Of Lead And Copper Interferences On Spectrophotometric Determination Of Cadmium Using Electrolytic Deposition And Ion-exchange In Multi-commutation Flow System"
Talanta 2000 Volume 53, Issue 3 Pages 497-503
José A. Gomes Neto, Adriana P. Oliveira, Gian P. G. Freshi, Carolina S. Dakuzaku and Mercedes de Moraes

Abstract: A new strategy for minimization of Cu2+ and Pb2+ interferences on the spectrophotometric determination of Cd2+ by the Malachite green (MG)-iodide reaction using electrolytic deposition of interfering species and solid phase extraction of Cd2+ in flow system is proposed. The electrolytic cell comprises two coiled Pt electrodes concentrically assembled. When the sample solution is electrolyzed in a mixed solution containing 5% (v/v) HNO3, 0.1% (v/v) H2SO4 and 0.5 M NaCl, Cu2+ is deposited as Cu on the cathode, Pb2+ is deposited as PbO2 on the anode while Cd2+ is kept in solution. After electrolysis, the remaining solution passes through an AG1-X8 resin (chloride form) packed minicolumn in which Cd2+ is extracted as CdCl42. Electrolyte compositions, flow rates, timing, applied current, and electrolysis time was investigated. With 60 s electrolysis time, 0.25 A applied current, Pb2+ and Cu2+ levels up to 50 and 250 mg L-1, respectively, can be tolerated without interference. For 90 s resin loading time, a linear relationship between absorbance and analyte concentration in the 5.00-50.0 µg Cd L-1 range(r2 = 0.9996) is obtained. A throughput of 20 samples per h is achieved, corresponding to about 0.7 mg MG and 500 mg KI and 5 mi sample consumed per determination. The detection limit is 0.23 mg Cd L-1. The accuracy was checked for cadmium determination in standard reference materials, vegetables and tap water. Results were in agreement with certified values of standard reference materials and with those Obtained by graphite furnace atomic absorption spectrometry at 95% confidence level. The RSD for plant digests and water containing 13.0 mg Cd L-1 was 3.85% (n = 12). The recoveries of analyte spikes added to the water and vegetable samples ranged from 94 to 104%.
Solid phase extraction Preconcentration

"Determination Of Mercury In Agroindustrial Samples By Flow Injection Cold Vapor Atomic Absorption Spectrometry Using Ion Exchange And Reductive Elution"
Talanta 2000 Volume 51, Issue 3 Pages 587-594
José A. Gomes Neto, Luís F. Zara, Julio C. Rocha, Ademir Santos, Carolina S. Dakuzaku and Joaquim A. Nóbrega

Abstract: A Bow-injection system with a Chelite-S(R) cationic resin packed minicolumn is proposed for the determination of trace levels of mercury in agroindustrial samples by cold vapor atomic absorption spectrometry. Improved sensitivity and selectivity are attained since mercuric ions are on-line concentrated whereas other potential interferents are discarded. With on-line reductive elution procedure, concentrated hydrochloric acid could be replaced by 10% w/v SnCl2, in 6 M HCl as eluent. The reversed-intermittent stream either carries the atomic mercury to the flow cell in the forward direction or removes the residue from reactor/gas-liquid separator to a discarding flask in the opposite direction. Concentration and volume of reagent, acidity, flow rates, commutation times and potential interfering species were investigated. For 120 s pre-concentration time, the proposed system handles about 25 samples h-1 (50.0-500 ng l-1), consuming about 10 mi sample and 5 mg SnCl2 per determination. The detection limit is 0.8 ng L-1 and the relative standard deviation (RSD) (n = 12) of a 76.7 ng L-1 sample is about 5%. Results are in agreement with certified value of standard materials at 95% confidence level and good recoveries (97-128%) of spiked samples were found.
Preconcentration Resin

"Spectrophotometric Detection Of Arsenic Using Flow Injection Hydride Generation Following Sorbent Extraction Preconcentration"
Talanta 1999 Volume 50, Issue 5 Pages 959-966
José Anchieta Gomes Neto, Ronaldo Montes and Arnaldo A. Cardoso

Abstract: An automated system with a C-18 bonded silica gel packed minicolumn is proposed for spectrophotometric detection of arsenic using flow injection hydride generation following sorbent extraction pre-concentration. Complexes formed between arsenic(III) and ammonium diethyl dithiophosphate (ADDP) are retained on a C-18 sorbent. The eluted As-DDP complexes are merged with a 1.5% (w/v) NaBH4 and the resulting solution is thereafter injected into the hydride generator/gas-liquid separator. The arsine generated is carried out by a stream of N-2 and trapped in an alkaline iodine solution in which the analyte is determined by the arsenomolybdenum blue method. With pre-concentration time of 120 s, calibration in the 5.00-50.0 µg As L-1 range and sampling rate of about 20 samples h-1 are achieved, corresponding to 36 mg ADDP plus 36 mg ammonium heptamolybdate plus 7 mg hydrazine sulfate plus 0.7 mg stannous chloride and about 7 mi sample consumed per determination. The detection limit is 0.06 µg L-1 and the relative standard deviation (n = 12) for a typical 17.0 µg As L-1 sample is ~6%. The accuracy was checked for arsenic determination in plant materials from the NIST (1572 citrus leaves; 1573 tomato leaves) and the results were in agreement with the certified values at 95% confidence level. Good recoveries (94-104%) of spiked tap waters, sugars and synthetic mixtures of trivalent and pentavalent arsenic were also found.
Speciation

"Pneumatic Nebulizer As A Dilution Chamber In A Flow Injection System For Multielement Analysis By ICP-MS"
Quim. Nova 1998 Volume 21, Issue 4 Pages 405-409
Gomes Neto, José Anchieta; Silva, José Bento B.; Rodrigues Neto, Renato; Curtius, Adilson José; Souza, Ivan G.

Abstract: An automatic dispenser based on a flow injection system used to introduce sample and anal. solution into an inductively coupled plasma mass spectrometer through a spray chamber is proposed. Anal. curves were constructed after the injection of 20 to 750 µL aliquots of a multielement standard solution (20.0 µg L-1 in Li, Be, Al, V, Cr, Mn, Ni, Co, Cu, Zn, As, Se, Sr, Ag, Cd, Ba, Tl, Pb) and the acquisition of the integrated transient signals. The linear concentration. range could be extended to ~five decades. The performance of the system was checked by analyzing a NiST 1643d reference material. Accuracy could be improved by the proper selection of the injected volume Besides good precision (relative standard deviation <2%), the results obtained with the proposed procedure were closer to the certified values of the reference material than those obtained by direct aspiration or by injecting 125 µL of several anal. solutions and samples.
Lithium Beryllium Aluminum Vanadium Chromium Manganese Nickel Cobalt Copper Zinc Arsenic Selenium Strontium Silver Cadmium Barium Thallium Lead NIST 1643 Mass spectrometry Dilution Nebulizer Reference material

"Spectrophotometric Determination Of Phosphite In Fertilizers In A Flow Injection System With Online Sample Preparation"
Lab. Rob. Autom. 2000 Volume 12, Issue 6 Pages 286-290
Jos&eacute; Anchieta Gomes Neto, Helenice Akemi Ito, Kelly das Gra&ccedil;as Fernandes, Mercedes de Moraes, Arnaldo Alves Cardoso

Abstract: A flow injection system with online sample preparation is proposed for the determination of phosphite in liquid fertilizers by spectrophotometry. After loop-based injection, phosphite is oxidized by an acidic permanganate solution (1.0 10^-2 mol L-1 KMnO4 + 1.0 mol L-1 H2SO4) in a heated reactor (50°C). The phosphate generated is then determined by the molybdenum blue method. Influence of flow rates, temperature, and concentration and order of addition of reagents, sample volume, and reactor configuration for the blue complex formation on recorded signals were investigated. The pow system was applied to phosphite determination in commercial samples of liquid fertilizers. The proposed system handles about 80 samples per hour [0.05-0.40% (w/v) H3PO3; R = 0,9998], consuming about 80 µL sample, 1 mg KMnO4, 25 mg (NH)(6)Mo7O24, and Ia mg ascorbic acid per determination. Results are precise [relative standard deviation less than or equal to 3.5% for 0.1% (w/v) H3PO3, n = 12] and in agreement with those obtained by gravimetry at 95% confidence level.
Microwave

"Linear Relationship Between Potential And Concentration In Flow Potentiometry"
Lab. Rob. Autom. 2000 Volume 12, Issue 1 Pages 41-45
Jos&eacute; Anchieta Gomes Neto*, Elias Ayres Guidetti Zagatto

Abstract: In potentiometric-flow systems, linear-potential responses for logarithmic concentrations can be attained for first-(or pseudo-first-) order reactions in which the monitored chemical species react with the analyte during a fixed time interval. To demonstrate this property, the determination of glycerol based on its oxidation by periodate and potentiometric monitoring of the remaining periodate was selected. Influence of reagent concentration and timing on the linearity of the analytical curve were investigated. A mathematical treatment was derived, and potentialities/limitations of the approach were outlined. The system was applied to analysis of soap and lixivia samples. The analytical curve within 200 and 2000 mg L-1 (r = 0.99975; n = 5) was described as E = 8.166 + 0.0478 [glycerol]. The sample throughput was 100 h-1, and a measurement repeatability within 0.5 mV was always observed. By applying a t-test, there was no statistical difference between the results obtained by the proposed procedure and by iodimetric titration at the 95% confidence level.

"Reversible Intermittent Flow Injection Determination Of Mercury In Sediments And Vinasses By Cold Vapor Atomic Absorption Spectrometry"
Lab. Rob. Autom. 1999 Volume 11, Issue 5 Pages 304-310
Jos&eacute; Anchieta Gomes Neto, Luis Fabr&iacute;cio Zara, Ademir Santos, Julio Cesar Rocha, Arnaldo Alves Cardoso

Abstract: A reversible intermittent pow-injection procedure is proposed for the automated determination of mercury in sediments and vinasses by cold vapor atomic absorption spectrometry, CVAAS. Solutions of sample and stannous chloride are carried by two air streams and sequentially injected into the generator/separator chamber in a segmented asynchronous merging zone configuration. The intermittent flow in the forward direction carries the mercury vapor through the flow cell, and in the backward direction, if aspirates the the remaining solution from the vessel to waste. We investigated composition and concentration of reagents, pow rates, commutation times, reactor configuration, and conditions for mercury release. The accuracy was checked by mercury determination in a certified sediment and spiked vinasses and river waters. The system handles about 100 samples per hour (0.50-5.00 µg L-1), consuming ~2.5 mL of sample and 50 mg of SnCl2 per determination; Good recoveries (92-103%) were obtained with spiked samples. Results are precise (RSD <3% for 2.5 µg Hg L-1, n = 12) and in agreement with values for certified reference material at 95% confidence level.

"Use Of FIA Systems For Online Dilution In Multielement Determination By ICP-MS"
Lab. Rob. Autom. 1999 Volume 11, Issue 4 Pages 240-247
Jos&eacute; Anchieta Gomes Neto, Jos&eacute; Bento Borba Silva, Ivan Gon&ccedil;alves Souza, Adilson Jos&eacute; Curtius

Abstract: A flow injection (FI) system to match concentrations was used as an auto-diluter in multielement determination by inductively coupled plasma-mass spectrometry (ICP-MS). The flow system comprised loop-based injection or a timed valve that introduced a variable sample volume info a spray chamber through a standard Meinhard nebulizer of an ICP-MS. Routinely analyzed samples such as water, plant, and steel were selected. The accuracy of multielement determination was checked against water standard reference material from the National Institute of Standards and Technology (1643d), plant standard reference material from the National Bureau of Standards (1572 citrus leaves), and steel standard reference material from the National Bureau of Standards (AISI 4340). The measuring system was calibrated with a multielement solution, yielding a linear plot with good precision [relative standard deviation (RSD) < 3%, n = 12]. The results were in agreement at a 95% confidence level with the certified values for the reference materials and also with those obtained by continuous aspiration and by (FI) with a discrete volume.
Interferences

"Evaluation Of Sample Treatment For Simultaneous Flow Injection Hydride Generation And Determination Of As, Bi, Sb And Se By GFAAS"
Atom. Spectrosc. 2004 Volume 25, Issue 3 Pages 133-139
Freschi, C. D.

Abstract: A new method was developed for the simultaneous determination of As, Bi, Sb, and Se by flow injection hydride generation graphite furnace atomic absorption spectrometry. An alternative two-step sample treatment procedure was used. The sample was heated (80?C) for 10 min in 6 M HCl to reduce Se(VI) to Se(IV), followed by the addition of 1% (m/v) thiourea solution to reduce arsenic and antimony from the pentavalent to the trivalent states. With this procedure, all analytes were converted to their most favorable and sensitive oxidation states to generate the corresponding hydrides. The pre-treated sample solution was then processed in the flow system for in situ trapping and atomization in a graphite tube coated with iridium. The Ir permanent modifier remained stable up to 300 firings and new coatings were possible without significant changes in the analytical performance. The accuracy was checked for As, Bi, Sb, and Se determination in water standard reference materials NIST 1640 and 1643d and the results were in agreement with the certified values at a 95% confidence level. Good recoveries (94-104%) of spiked mineral waters and synthetic mixtures of As(III), As(V), Sb(III), Sb(V), Se(VI), and Se(IV) were also found. Calculated characteristic masses were 32 pg As, 79 pg Bi, 35 pg Sb, and 130 pg Se, and the corresponding limits of detection were 0.06, 0.16, 0.19, and 0.59 ?g L-1, respectively. The repeatability for a typical solution containing 5 ?g L-1 As, Bi, Sb, and Se was in the 1-3% range.

"Flow Injection AAS Determination Of Cd, Cu, And Pb At Trace Levels In Wine Using Solid Phase Extraction"
Atom. Spectrosc. 2003 Volume 24, Issue 5 Pages 179-184
AP Fernandes, M De Moraes, J Neto

Abstract: A comparative study is reported between C18 bonded silica gel and powdered polyethylene (PE) as sorbent for Cd, Cu, and Pb determination using ammonium diethyldithiophosphate (ADTP) as the complexing agent in a flow injection system. The complexes were formed in 0.14 mol L-1 HNO 3 and processed in a simple flow system comprising a peristaltic pump, a manual injector-commutator, and a sorbent-packed mini-column. Ethanol was selected as the eluent and analytes in the eluate were determined by flame atomic absorption spectrometry. The optimum concentration of the complexing agent was 0.1% (m/v) ADTP for Cu and Pb determination using either C 18 or PE, and 0.25% (m/v) ADTP for Cd determination using PE. The sample loading flow rates were 5.0, 3.6, and 3.0 mL min-1 for Cu, Pb, and Cd, respectively. The best elution flow rate was 6.5 mL min-1 For a 60-sec pre-concentration time, the sampling rate was 40 h-1 and the enrichment factors of 33, 36, and 11 times (C18) or 18, 22, and 23 times (PE) were obtained for Cu, Pb, and Cd, respectively. The limits of detection (LOD) were 1.6 ?g L-1 Cu, 11 ?g L-1 Pb, and 2.0 ?g L-1 Cd using C18 or 2.9 ?g L -1 Cu, 19 ?g L-1 Pb, and 1.0 ?g L-1 Cd using PE, respectively. The relative standard deviations (n = 12) were typically <2%, <2%, and <6% for Cd, Cu, and Pb, respectively. The recoveries of Cd, Cu, and Pb added to wine samples varied from 96-99%, 97-102%, and 90-99%, respectively, using C18 or PE. Accuracy was checked for Cd, Cu, and Pb determination in six wine samples digested by block digestor and open-vessel microwave-assisted digestion systems. The results revealed that C18 was more efficient for Cu and Pb determination, while PE was the best sorbent for Cd.