Kinetic spectrophotometric determination of thiocyanate based on its inhibitory effect on the oxidation of methyl red by bromate

Microextraction with smartphone detection of thiocyanate in saliva of tobacco smokers using paper-based analytical method

This study presents a novel, cost-effective approach involving spectrophotometric and smartphone paper-based (SPB) methods and a distinctive salting-out air-assisted dispersive microextraction procedure to quantify thiocyanate in saliva samples. The method relies on the inhibitory effect of thiocyanate on quinoneimine dye formation during the Emerson reaction with sodium hypochlorite. Spectrophotometry quantifies the extracted dye by monitoring quinoneimine color intensity reduction at 525 nm. In the SPB method, extracted dye is applied to a paper strip, a smartphone captures the colored paper, and an application analyzes red, green, and blue components. All analyte determination and extraction variables were explored. Both methods exhibit good linearity (10-100 μg/L) with a coefficient of determination of 0.9991 and a limit of detection of 7.5 μg/L for the spectrophotometric method, and a coefficient of determination of 0.9988 and a limit of detection of 8.8 μg/L for the SPB method. The calculated values for the enrichment factor and extraction recovery of the developed extraction methodology were 46% and 93%, respectively. The methods detect thiocyanate in saliva samples, producing results comparable to a validated method.

Kinetic spectrophotometric method for trace determination of thiocyanate based on its inhibitory effect

A kinetic spectrophotometric method for the determination of thiocyanate, based on its inhibitory effect on silver(I) catalyzed substitution of cyanide ion, by phenylhydrazine in hexacyanoferrate(II) is described. Thiocyanate ions form strong complexes with silver(I) catalyst which is used as the basis for its determination at trace level. The progress of reaction was monitored, spectrophotometrically, at 488 nm (lambda(max) of [Fe(CN)(5)PhNHNH(2)](3-), complex) under the optimum reaction conditions at: 2.5x10(-3)M [Fe(CN)(6)](4-), 1.0x10(-3)M [PhNHNH(2)], 8.0x10(-7)M [Ag(+)], pH 2.8+/-0.02, ionic strength (mu) 0.02 M (KNO(3)) and temperature 30+/-0.1 degrees C. A linear relationship obtained between absorbance (measured at 488 nm at different times) and inhibitor concentration, under specified conditions, has been used for the determination of [thiocyanate] in the range of 0.8-8.0x10(-8)M with a detection limit of 2x10(-9)M. The standard deviation and percentage error have been calculated and reported with each datum. A most plausible mechanistic scheme has been proposed for the reaction. The values of equilibrium constants for complex formation between catalyst-inhibitor (K(CI)), catalyst-substrate (K(s)) and Michaelis-Menten constant (K(m)) have been computed from the kinetic data. The influence of possible interference by major cations and anions on the determination of thiocyanate and their limits has been investigated.

Determination of trace amounts of thiocyanate by a new kinetic procedure based on an induction period

A new, simple and sensitive kinetic spectrophotometric method with no need for removing of interfering substances is proposed for the determination of thiocyanate ion in biological and water samples. The procedure is based on the inhibiting effect of thiocyanate on the sodium periodate-potassium bromide-meta cresol purple (MCP) system in acidic media. The induction period of the reaction is proportional to the SCN- concentration. The decolorization of meta cresol purple by the reaction products was used to monitor the reaction spectrophotometrically at 525 nm. Under optimum conditions, thiocyanate can be determined in the range of 0.02-0.8 microg ml(-1) with a 3sigma detection limit of 5 ng ml(-1). The relative standard deviations for 10 replicate determinations of 0.060, 0.10 and 0.50 microg ml(-1) thiocyanate are 3.7, 2.4 and 1.0%, respectively. This method has been successfully used to the determination of thiocyanate content in smokers and non-smokers saliva and spiked water sample.

Determination of trace thiocyanate with nano-silver coated multi-walled carbon nanotubes modified glassy carbon electrode

Novel nano-silver coated multi-walled carbon nanotube composites were prepared and used to fabricate a modified electrode. The application of the nano-silver coated multi-walled carbon nanotube composites modified electrode for determination of trace thiocyanate is demonstrated for the first time. The influence of substrate, pH and interference of coexisting substances was investigated for response properties of the electrode. There was a linear relationship at the range 2.5 x 10(-9) to 5 x 10(-8) mol L(-1) and 5 x 10(-8) to 1 x 10(-6) mol L(-1) of thiocyanate with the decrement of anodic DPV peak currents. The limit of detection was 1 x 10(-9) mol L(-1)(S/N=3). The constructed electrode showed excellent reproducibility and stability. Actual urine and saliva samples of smoker and non-smoker were analyzed and satisfactory results were obtained. This method provides a new way to construct any electrode for biological and environmental analysis.