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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Modified simplex

Classification: Signal processing -> Modified simplex

Citations 9

"Study Of The Molybdenum(VI) Catalytic Response In The Oxidation Of Iodide By Hydrogen Peroxide Using A Mono-segmented Continuous-flow System"
Anal. Chim. Acta 1991 Volume 255, Issue 1 Pages 149-155
João Carlos de Andrade*, Sebastião P. Eiras and Roy E. Bruns

Abstract: Fractional factorial, modified simplex and response surface studies of the Mo(VI)-catalyzed and non-catalyzed oxidation of iodine by H2O2 in acidic media were executed using a monosegmented continuous-flow system (MCFS). As this reaction is commonly used for the spectrophotometric catalytic determination of Mo(VI), the behavior of the analytically useful response and the difference of the average absorbance values of the Mo(VI)-catalyzed and non-catalyzed reactions, was studied over a large range of experimental conditions. The effects of simultaneous changes in the sample flow-rate, the H2SO4, KI and H2O2 concentration. and the reaction time on the signals were measured. Rigorous control of the acid concentration. is essential to maintain the sensitivity of the analytical signal for operating conditions close to the optimum values recommended. Increasing the KI concentration. can improve the sensitivity but can also cause baseline instability. The response surface is convenient for visualizing the overall behavior of the system for the experimental control values investigated.
Molybdenum(VI)

"Flow Injection Spectrophotometric Determination Of Tetracycline Antibiotics"
Anal. Chim. Acta 1994 Volume 285, Issue 1 Pages 9-12
R. Karlicek and P. Solich

Abstract: Tablets were dissolved in water, sedimented and filtered. Portions of the filtrate were injected into a water carrier stream (0.67 ml/min) which mixed with a reagent comprising aqueous 4-aminophenazone, di-sodium EDTA buffer of pH 10 and 1% Brij 35 at 0.54 ml/min in a coil prior to reaction with potassium hexacyanoferrate(III) (0.54 ml/min) in a second coil at ambient temperature The absorbance of the dye formed was measured at 520 nm. A modified simplex method was employed to optimize several mutually affected variables and individual variables (tabulated), including the lengths of the coils used and the concentrations of reagents. Calibration graphs (peak height) were linear (r 0.995) for 1-20 and 20-250 mg/l of doxycycline, oxytetracycline, rolitetracycline and tetracycline with RSD of 1% for 10 and 100 mg/l and an output of 60-70 samples/h.
Doxycycline Oxytetracycline Rolitetracycline Tetracycline Pharmaceutical Spectrophotometry

"Reflections On The Modified Simplex - 2"
Talanta 1985 Volume 32, Issue 1 Pages 73-77
A. Izquierdo J. Guasch and F. X. Rius

Abstract: The protonation constants of 2-methyldithiocarbazate, 3,3-dimethyldithiocarbazate and 3-methyl-3-phenyldithiocarbazate, have been determined potentiometrically (I = 1.00 M) and spectrophotometrically (I = 0.01 M) at 25°C in aqueous solution. The analytical properties of the reagents have been studied, and also the compositions of some of their insoluble metallic chelates.

"Reflections On The Modified Simplex - 1"
Talanta 1985 Volume 32, Issue 8 Pages 709-722
D. Betteridge* and A. P. Wade, A. G. Howard

Abstract: The modified simplex method is a well-known method of optimization. In this study several changes have been made to it. These include an adaptive weighted centroid and a Lagrange interpolation procedure. The latter is used to get a better value of the reflected point when a contraction succeeds or an expansion fails. The new method, called the composite modified simplex method (CMS) has been rigorously evaluated by means of mathematical functions, maps and chemical experimentation. The effect of the starting point and the size of the simplex have been investigated in detail. For flow-injection analysis it has proved possible to optimize 2-12 variables. The method has proved most suitable for rapid and effective optimization of polarography, flow-injection analysis and chemical synthesis. This paper describes the evaluation procedures and reviews the results obtained.

"Computer-assisted Optimization For Flow Injection Analysis Of Isoprenaline"
Anal. Chem. 1983 Volume 55, Issue 8 Pages 1292-1299
D. Betteridge, Timothy J. Sly, Adrian P. Wade, and John E. W. Tillman

Abstract: The spectrophotometric determination of isoprenaline with K3Fe(CN)6 has been adapted to flow the variables were flow rate, length of the reaction coil, reagent concentration, pH and, sometimes, sample size. The software was written in BASIC. When the first four and all five variables were considered, the proposed simplex method required 34 and 37 experiments and the univariate procedure 88 and 168 experiments, respectively. The optimized flow injection determination of isoprenaline at the ppm level is simpler than the manual spectrometric method; the best sensitivity is maintained at a throughput of 45 samples h-1.
Isoprenaline Spectrophotometry

"Application Of Super Modified Simplex Optimization To The Flow Injection Spectrophotometric Determination Of Promethazine Hydrochloride In Drug Formulations"
Anal. Sci. 1992 Volume 8, Issue 6 Pages 841-843
S. M. SULTAN and F.-E. O. SULIMAN

Abstract: The flow injection system described earlier [Analyst (London), 1991, 116, 177) was applied to the determination of promethazine hydrochloride by using Ce(IV) in H2SO4 medium to oxidize promethazine hydrochloride to a reddish product having maximum absorption at 515 nm. Reaction coil length, Ce(IV) and H2SO4 concentration and flow rate were optimized by the super modified simplex procedure. The max. sampling frequency was 200 h-1 and the calibration graph was rectilinear for 60 to 200 ppm of promethazine hydrochloride. The coefficient of variation for standard solution was 0.8%. The results on tablet and syrup formulations were as accurate as those obtained by the BP method. An accurate, reproducible, flow injection spectrophotometric method for the assay of promethazine was developed using cerium(IV) as an oxidant. The super modified simplex program was utilized for the optimization of dependant parameters. In the method, a 110 µL drug sample was injected into a flowing stream of 6.19 x 10^-4 M cerium(IV) dissolved in 0.512 M H2SO4. The reaction takes place in a reaction coil 62 cm long. Finally, the colored oxidized form of the drug was monitored at 515 nm. Promethazine in the range 60-200 ppm with a 200-sample/h throughout was determined, 0.80% relative standard deviation being attained. The method was successfully applied to the determination of promethazine in proprietary drugs, its accuracy was statistically compared with the British Pharmacopeia official method.
Promethazine hydrochloride Pharmaceutical Pharmaceutical Spectrophotometry

"Optimization Of Flow Injection Analysis And Polarography By The Modified Simplex Method"
Anal. Proc. 1983 Volume 20, Issue 10 Pages 523-527
A. P. Wade

Abstract: The modified Simplex method is outlined, and its application to the optimization of single-, two- and multiple-factor responses in flow injection and polarographic analyzes and in ninhydrin amino-acid analysis, respectively, is reviewed. The method allows efficient optimization of several variables simultaneously, and is usually faster and more reliable than univariate methods. (13 references)
Amino Acids Polarography

"Modified Simplex Optimization For Operating An Enzyme Electrode"
Anal. Proc. 1989 Volume 26, Issue 8 Pages 290-292
S. K. Beh, G. J. Moody and J. D. R. Thomas

Abstract: The sample volume and flow rate for an enzyme electrode in a flow injection system were simplex-optimized on the basis of peak height and response time.
Electrode

"Development Of An Additonal Modified Simplex Approach For Optimization Illustrated By An Enzyme Electrode Set Up For Flow Injection Analysis"
Anal. Proc. 1990 Volume 27, Issue 4 Pages 82-87
G. J. Moody, J. D. R. Thomas

Abstract: After a brief introduction to the basic simplex, modified simplex and super modified simplex techniques of optimization, the additional modified simplex approach is described. This involves combining the modified simplex with a curve fitting technique to determine a new vertex. The method is illustrated for a glucose sensor in a flow injection analysis set-up. The optimum conditions reached by the new method show good agreement with those of the more laborious earlier methods.
Electrode