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
Website: @unf

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NIST 1572

Classification: Reference Material -> NIST -> 1572 -> Citrus leaves

Citations 2

"On-line Preconcentration System For Lead Determination In Seafood Samples By Flame Atomic Absorption Spectrometry Using Polyurethane Foam Loaded With 2-(2-benzothiazolylazo)-2-p-cresol"
Anal. Chim. Acta 2001 Volume 441, Issue 2 Pages 281-289
Valfredo A. Lemos and Sérgio L. C. Ferreira

Abstract: In the present paper, an on-line system for enrichment and determination of lead is proposed. It is based on the chemical sorption of lead(II) ions on a minicolumn packed with polyurethane foam loaded with 2-(2-benzothiazolylazo)-2-p-cresol (BTAC) reagent. After pre-concentration, lead(II) ions are eluted by 0.10 mol L-1 hydrochloric acid solution and determined directly by flame atomic absorption spectrometry (FAAS). Chemical and flow variables as well as effect of other ions were studied. The results demonstrated that lead could be determinate with an enrichment factor of 26 for a sample volume of 7.0 mL and pre-concentration time of 1 min. The detection limit (3 s) was 1.0 µg L-1 and the precision (assessed as the relative standard deviation) reached values of 6.0-0.7% in lead solutions of 10^-500 µg L-1 concentration, respectively. The enrichment factor and the detection limit can be further improved by increasing pre-concentration time without degradation in the efficiency due to the favorable kinetics and low hydrodynamic impedance of the present system. Achieved sampling frequency was 48 samples per hour. The effect of another ions in concentrations agreeing with biological samples was studied. It was found that the proposed procedure has necessary selectivity for lead determination in seafood and other biological samples. The accuracy was confirmed by analysis of the followings certified reference materials: fish tissue IAEA, lobster hepatopancreas NRCC TORT-1 and citrus leaves NIST 1572. Recoveries of spike additions (0.2 or 1.0 µg g-1) to several seafood samples were quantitative (90-107%). These results proved also that the procedure is not affected by matrix interferences and can be applied satisfactorily for lead determination in samples of shrimp, oyster, crab, fish and mussel contaminated by it.
Lead Spectrophotometry Preconcentration Interferences Amberlite Polyurethane foam Solid phase extraction

"Liquid-liquid Extraction In Flow Injection Analysis Using An Open-phase Separator For The Spectrophotometric Determination Of Copper In Plant Digests"
Analyst 1998 Volume 123, Issue 2 Pages 191-193
Telma Blanco, Nelson Maniasso, Maria Fernanda Giné and Antonio O. Jacintho

Abstract: A flow injection system with an open-phase separation device is presented for the liquid-liquid extraction of the diethyldithiocarbamate-copper complex (DDTC-Cu) using carbon tetrachloride (CCl4). An open tube enclosed by computer-controlled solenoid valves was installed vertically to promote fast phase separation by differences in density. The solenoid valves were used to introduce the reacted sample zone into the tube, to select a precise volume of the extracted complex to be detected and to pass the remaining solution to waste. A pre-concentration factor of 10 was attained, corresponding to the aqueous to organic phase volume ratio. The solenoid valve control allowed the use of a small solvent volume (0.7 mL) per determination The DDTC-Cu complex was detected at 436 nm. A sample throughput of 30 determinations per h for Cu ranging from 50 to 400 µg/L in real samples was achieved. A limit of detection of 5 µg/L of Cu was calculated using 3sv. A precision characterized by an RSD of less than 3 was typical for a sample with a Cu concentration of 145 µg/L. The accuracy was assessed with NIST SRM 1572 and no difference at the 95 confidence level was found.
Copper Sample preparation Spectrophotometry Reference material Solvent extraction Phase separator Computer