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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Jia Zhong Zhang

Abbrev:
Zhang, J.Z.
Other Names:
Jia-Zhong Zhang, Jiazhong Zhang
Address:
NOAA, Atlantic Oceanographic and Meteorological Laboratory, Oceanographic Chemistry Division, 4301 Rickenbacker Causeway, Miami, FL 33149 USA
Phone:
+1-305-361-4397
Fax:
+1-305-361-4392

Citations 7

"Optimization Of Performance And Minimization Of Silicate Interference In Continuous Flow Phosphate Analysis"
Talanta 1999 Volume 49, Issue 2 Pages 293-304
J. -Z. Zhang, Charles J. Fischer and Peter B. Ortner

Abstract: Specific reaction conditions for automated continuous flow analysis of phosphate are optimized in regard to minimizing coating and silicate interference, while maintaining high sensitivity. Use of Sb in the reagent increases sensitivity and yields absorbances with little temperature dependence. Coating can be minimized by using a final solution at a pH > 0.5. At final pH of 0.78 there is maximum interference from silicate in the sample. We recommend therefore as an optimal reaction condition with minimal silicate interference, the use of Sb, a final solution pH of 1.00, room temperature for the reaction and a [H+]/[Mo] ratio of 70. An equation is provided to correct silicate interference in high precision phosphate determination.

"Continuous Flow Analysis Of Phosphate In Natural Waters Using Hydrazine As A Reductant"
Int. J. Environ. Anal. Chem. 2001 Volume 80, Issue 1 Pages 61-73
Jia-Zhong Zhang; Charles J. Fischer; Peter B. Ortner

Abstract: The use of hydrazine to reduce 12-molybdophosphoric acid to phosphomolybdenum blue in continuous flow analysis of phosphate in natural water samples is characterized. Using hydrazine in gas-segmented continuous flow phosphate analysis minimizes coating and silicate interference in comparison with using ascorbic acid. The addition of Sb to the molybdate reagent increases sensitivity at temperatures greater than 50°C but causes severe additional coating. The degree of coating was found to be a function of pH. Minimal coatings were achieved at a final solution pH of 0.5. Silicate interference was found to increase dramatically with color development temperature. At room temperature no detectable silicate interference was found. We recommend hydrazine in preference to ascorbic acid for gas-segmented continuous flow phosphate analysis with optimal reaction conditions of room temperature color development and a final solution pH of 0.5.

"Comparison Of Open Tubular Cadmium Reactor And Packed Cadmium Column In Automated Gas-segmented Continuous Flow Nitrate Analysis"
Int. J. Environ. Anal. Chem. 2000 Volume 76, Issue 2 Pages 99-113
Zhang, J.Z.;Fischer, C.J.;Ortner, P.B.

Abstract: Detailed procedures are provided for preparing packed cadmium columns to reduce nitrate to nitrite. Experiments demonstrated the importance of conditioning both open tubular cadmium reactor (OTCR) and packed copper-coated cadmium columns to achieve 100% reduction efficiency. The effects of segmentation bubbles in the OTCR upon reduction efficiency and baseline noise in nitrate analysis are investigated using an auto-analyzer. Metal particles derived from segmentation bubbles in OTCR result in interference with continuous flow analyzes. Therefore packed columns are recommended for determination of low level nitrate in natural waters.

"Automated Analysis Of Nanomolar Concentrations Of Phosphate In Natural Waters With Liquid Waveguide"
Environ. Sci. Technol. 2002 Volume 36, Issue 5 Pages 1048-1053
Jia-Zhong Zhang and Jie Chi

Abstract: Concentrations of phosphate in natural waters are often below the detection limits of conventional nutrient autoanalyzers, by either gas-segmented continuous-flow analysis or flow injection analysis. A liquid waveguide capillary flow cell has been used to extend the sensitivity of a conventional autoanalyzer for the automated analysis of nanomolar concentrations of phosphate in natural waters. Total reflection of light can be achieved within the liquid core of the flow cell because the refractive index of a cell wall coated with Teflon 1600 is lower than that of water. This property allows the manufacturers to construct long liquid waveguide capillary flow cells in a helical, rather than a linear shape, with compact dimensions. A small sample volume is required because the internal volume of a 2-m long capillary flow cell is only approximately 0,5 cm(3). Adaptation of this long flow cell to autoanalyzers significantly enhances the sensitivity of automated colorimetric analysis of phosphate with a molybdenum blue method, allowing for the accurate and precise determination of nanomolar concentrations of phosphate in natural waters. The advantages of this technique are a low detection limit (0.5 nM), a small sample volume (2 mL), high precision (2% at 10 nM levels), and automation for the rapid analysis of a large number of samples.

"Shipboard Automated Determination Of Trace Concentrations Of Nitrite And Nitrate In Oligotrophic Water By Gas-segmented Continuous Flow Analysis With A Liquid Waveguide Capillary Flow Cell"
Deep Sea Res. I 2000 Volume 47, Issue 6 Pages 1157-1171
Jia-Zhong Zhang

Abstract: Incorporation of a liquid waveguide capillary flow cell in a gas-segmented continuous flow auto-analyzer significantly enhances the sensitivity of automated colorimetric analysis. Nanomolar concentrations of nitrite and nitrate in oligotrophic surface seawater can be accurately determined. The advantages of this technique are low detection limit, high precision, and automation for rapid analysis of a large number of samples. This technique was successfully used on shipboard measurements of about 1000 seawater samples during a one-month cruise in the North Atlantic.

"Enhanced Sensitivity In Flow Injection Analysis Using A Long Pathlength Liquid Waveguide Capillary Flow Cell For Spectrophotometric Detection"
Anal. Sci. 2006 Volume 22, Issue 1 Pages 57-60
Jia-zhong Zhang

Abstract: Incorporation of a liquid waveguide capillary flow cell into a flow injection instrument enhances the sensitivity of flow injection analysis with spectrophotometric detection by two orders of magnitude. Nitrite determination at nM levels has been used to demonstrate the feasibility of this novel technique for trace analysis. Combining the long pathlength spectrophotometry with flow injection analysis, this technique has advantages of low detection limit, good precision and high sample throughput.

"Gas-segmented Continuous Flow Analysis Of Iron In Water With A Long Liquid Waveguide Capillary Flow Cell"
Anal. Chim. Acta 2001 Volume 438, Issue 1-2 Pages 49-57
Jia-Zhong Zhang, Chris Kelble and Frank J. Millero

Abstract: A long liquid waveguide capillary flow cell has been successfully adapted to a gas-segmented continuous flow auto-analyzer for trace analysis of iron in water. The flow cell was made of new material, Teflon AF-2400, which has a refractive index (1.29) lower than water (1.33). Total reflection of light can be achieved, provided that the incident angle at each reflection on the water/Teflon interface is greater than the critical angle. Teflon AF-2400 is superior to currently used materials in both refractivity and mechanical stability. This allows for construction of a long liquid waveguide capillary flow cell in a helical rather than linear shape, with compact dimensions. Since the internal volume of a 2 m long, 550 mum i.d. liquid waveguide capillary Row cell is only approximately 0.5 cm(3), a small sample volume is required. Utilization of this long flow cell significantly enhances the sensitivity of automated colorimetric analysis of iron by the ferrozine method, allowing for accurate determination of nanomolar concentrations of iron in natural waters. The advantages of this technique are low detection limit (0.1 nM), small sample volume (2 ml), high precision (1%), and automation for rapid analysis of a large number of samples. This technique is applicable to any gas-segmented continuous flow analysis or flow injection analysis with spectrophotometric detection.