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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Classification: Biological fluid -> saliva -> human

Citations 5

"Spectrophotometric Flow Injection Determination Of Trace Amounts Of Thiocyanate Based On Its Reaction With 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol And Dichromate: Assay Of The Thiocyanate Level In Saliva From Smokers And Non-smokers"
Analyst 1991 Volume 116, Issue 6 Pages 647-651
Anders Broe Bendtsen and Elo Harald Hansen

Abstract: A simple and very sensitive spectrophotometric flow injection (FI) procedure for the determination of trace amounts of thiocyanate is described. The proposed method is based on the reaction between thiocyanate and 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol, which, in 2 mol L-1 acidic media in the presence of a strong oxidizing agent, produces an intensely colored product. Several oxidants are potentially applicable, but it is shown that dichromate is preferable. As the reaction product formed is unstable and the signal inherently is recorded on a high background level, it is demonstrated that FI constitutes an ideal method in order to monitor reproducibly and repeatedly the kinetically transient signal that is obtained. Based on optimization by a factorial experimental design, the detection limit of the procedure was found to be 3.5 µmol L-1, and the standard deviation between samples was 0.16 µmol L-1. No significant interferences were observed; a 1000-fold excess of cyanide could readily be tolerated within the experimental error. With a sample volume of 50 µL being injected, the sampling frequency was 60 samples h-1. The system was tested with saliva samples from non-smokers and smokers, and the results show that it is possible to distinguish between these two categories of individuals. As an added benefit, the detection limit of the analytical procedure allows the samples to be diluted 100-fold, so that centrifugation for 5 min is the only preliminary sample preparation that is necessary. Sample (50 µL) was injected into a carrier stream of water and mixed with a stream of 1.7 mM 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol in aqueous ethanol - H2SO4 (both at 0.81 mL min-1) in a mixing coil (30 cm x 0.51 mm). The solution was reacted with a reagent stream of 0.2 mM Cr2O72- in 2 M H2SO4 (0.23 mL min-1) in a reaction coil (60 cm x 0.51 mm). Detection was at 570 nm. Conditions were optimized by factorial experimental design. The calibration graph was rectilinear for 5 to 100 µM-SCN-1, and the detection limit was 3.5 µM. There was no significant interference. The sampling rate was 60 h-1. The method was applied to saliva, after a 100-fold dilution of the sample and centrifugation.
Thiosulfate ion Spectrophotometry Interferences Kinetic Mixing coil Optimization

"Aqueous Nitrite Ion Determination By Selective Reduction And Gas Phase Nitric Oxide Chemiluminescence"
Anal. Chem. 1995 Volume 67, Issue 1 Pages 220-224
Andrew J. Dunham, Robert M. Barkley, and Robert E. Sievers

Abstract: An improved method of flow injection analysis for aqueous nitrite ion exploits the sensitivity and selectivity of the nitric oxide (NO) chemiluminescence detector. Trace analysis of nitrite ion in a small sample (5-160 ml) is accomplished by conversion of nitrite ion to NO by aqueous iodide in acid. The resulting NO is transported to the gas phase through a semipermeable membrane and subsequently detected by monitoring the photoemission of the reaction between NO and ozone (O3). Chemiluminescence detection is selective for measurement of NO, and, since the detection occurs in the gas-phase, neither sample coloration nor turbidity interfere. The detection limit for a 100 mL sample is 0.04 ppb of nitrite ion. The precision at the 10 ppb level is 2 relative standard deviation, and 60-180 samples can be analyzed per hour. Samples of human saliva and food extracts were analyzed; the results from a standard colorimetric measurement are compared with those from the new chemiluminescence method in order to further validate the latter method. A high degree of selectivity is obtained due to the three discriminating steps in the process: (1) the nitrite ion to NO conversion conditions are virtually specific for nitrite ion, (2) only volatile products of the conversion will be swept to the gas phase (avoiding turbidity or color in spectrophotometric methods), and (3) the NO chemiluminescence detector selectively detects the emission from the NO + O3 reaction. The method is free of interferences, offers detection limits of low parts per billion of nitrite ion, and allows the analysis of up to 180 mL-sized samples per hour, with little sample preparation and no chromatographic separation. Much smaller samples can be analyzed by this method than in previously reported batch analysis methods, which typically require 5 mL or more of sample and often need chromatographic separations as well. Copyright 1995, American Chemical Society.
Nitrite Chemiluminescence Sample preparation Method comparison Indirect Interferences PPB

"A Novel Flow Injection System For Simultaneous Determination Of Nitrate And Nitrite Based On The Use Of A Zinc Reductor And A Bulk Acoustic Wave Impedance Detector"
Microchem. J. 1998 Volume 59, Issue 3 Pages 341-350
Xiao-Li Su, Po Chen, Xiao-Ge Qu, Wan-Zhi Wei and Shou-Zhuo Yao

Abstract: A novel flow injection system was developed for the simultaneous determination of nitrate and nitrite present in water, foodstuffs, and human saliva. The system is based on the use of a Zn-filled reduction column and a bulk acoustic wave impedance sensor (BAWIS) as detector. With water as carrier stream, both nitrate and nitrite are converted online to NH3, whereas with sulfamic acid, only nitrate is converted to NH3. The NH3 formed diffuses across a PTFE membrane and is trapped in an acid stream causing a change in the solution conductance, which was monitored by a BAWIS detector. At a throughput of ~60 h-1, the proposed system exhibited a linear response to the concentration. of nitrate and nitrite from 2.5 µM to 1.00 mM, with detection limits of 1.7 and 1.8 µM, respectively, and the relative standard deviation of the peak heights (n = 6) ranged between 0.83 and 1.75% for the entire working range. In anal. of real samples, the simultaneous determination of nitrate and nitrite was achieved by the proposed method with a simple change of the carrier stream between water and sulfamic acid, and the results agreed well with those of conventional colorimetry. (c) 1998 Academic Press.
Nitrate Nitrite Conductometry Sensor Gas diffusion Reduction column Teflon membrane Simultaneous analysis

"High Performance Liquid Chromatographic Method For Determination Of Sulfapyridine In Human Saliva Using Post-column, Inline Derivatization With Fluorescamine"
J. Chromatogr. B 1983 Volume 273, Issue 2 Pages 464-468
H. S. Sista, D. M. Dye and J. Leonard

Abstract: A method for determination of sulfapyridine [144-83-2] in human saliva by the title methods is described. To an aliquot of saliva, MeCN, solid K2CO3 and the internal standard, sulfadiazine (148 ng/mL saliva) are added. After mixing and centrifuging the MeCN layer is separated and evaporated to dryness under N at 60°C. The residue is then dissolved in the mobile phase and an aliquot chromatographed. The mobile phase consists of 0.05 M NaHPO4, 0.1 M 1-hexanesulfonate sodium salt, 0.0072 M triethylamine, pH 3.0 (using phosphoric acid), and 15% MeOH. The column was packed with RP-18. The fluorescamine [38183-12-9] solution (stabilized by 2-mercaptoethanol [60-24-2]) was introduced into the mobile phase, post-column, and reacted in an in-line reactor at 60°C. Detection was with a spectrofluorometer with excitation at 395 nm and an emission wavelength of 470 nm. The detection limit for I in saliva is 5 ng/mL.
Sulfapyridine HPLC Fluorescence Post-column derivatization Heated reaction

"Flow Injection Spectrophotometric Determination Of Microamounts Of Thiocyanate"
Fenxi Huaxue 1998 Volume 26, Issue 7 Pages 836-839
Wang, K.;Chen, X.G.;Huang, J.;Hu, Z.

Abstract: Two flow injection methods have been developed for the spectrophotometric determination of µamounts of thiocyanate, based on the reaction of 2-(3,5-dibromo-2-pyridylazo)-5-diethylamino-phenol(3,5-Br2-PADAP)-thiocyanate-dichromate system in acidic medium (method A), and the reaction of 3,5-Br2-PADAP-thiocyanate-Cerium(IV) system in acidic medium (method B). Both reactions produce unstable violet products with max. absorption at 602 nm. In system A, the calibration curve is linear in the range from 0.80 to 7.20 mg/L of SCN- and the detection limit is 0.27 mg/L. In system B, the calibration curve is linear in the range from 0.80 to 6.40 mg/L of SCN- and the detection limit is 0.30 mg/L. With a sample solution of 100 µL being injected, the sampling frequency is 60/h for A or B method. Both methods have been applied to determine thiocyanate in waste water and saliva of non-smokers and smokers with satisfactory results.
Thiocyanate ion Spectrophotometry