Thiocyanate and nitrite analysis using miniaturised isotachophoresis on a planar polymer chip

3D Microfluidic Devices in a Single Piece of Paper for the Simultaneous Determination of Nitrite and Thiocyanate

The concentrations of nitrite and thiocyanate in saliva can be used as the biomarkers of the progression of periodontitis disease and environmental tobacco smoke exposure, respectively. Therefore, it is particularly necessary to detect these two indicators in saliva. Herein, the three-dimensional single-layered paper-based microfluidic analytical devices (3D sl-μPADs) were, for the first time, fabricated by the spraying technique for the colorimetric detection of nitrite and thiocyanate at the same time. The conditions for 3D sl-μPADs fabrication were optimized in order to well control the penetration depth of the lacquer in a paper substrate. Then, the developed 3D sl-μPADs were utilized to simultaneously detect nitrite and thiocyanate and the limits of detection are 0.0096 and 0.074 mM, respectively. What is more, the μPADs exhibited good specificity, good repeatability, and acceptable recoveries in artificial saliva. Therefore, the developed 3D sl-μPADs show a great potential to determine nitrite and thiocyanate for the assessment of the human health.

Colorimetric Sensor for Thiocyanate Based on Anti-aggregation of Gold Nanoparticles in the Presence of 2-Aminopyridine

Based on the anti-aggregation mechanism of citrate stabilized gold nanoparticle (AuNPs), a new specific and sensitive colorimetric sensor for thiocyanate (SCN^-) was developed. In this scheme, the AuNPs were aggregated in the presence of the aggregating agent 2-aminopyridine (2-AP) due to electrostatic attraction. The solution color changed from red to blue. When SCN^- was present, SCN^- formed a sulfur-gold bond with the AuNPs to protect the AuNPs from aggregation. Thiocyanate can be detected by the color change of the solution from blue to red. The results showed that the absorbance ratio A₆₇₅/A₅₂₀ was linear with the concentration of SCN^- in the range of 0.4 - 1.2 μmol L^-1 by UV-Vis spectroscopy. The limit of detection (LOD) of this assay was 0.37 μmol L^-1. The system also had excellent selectivity and anti-interference ability. In addition, this method was successfully used for the detection of SCN^- in actual water samples and achieved good results.

Nano-fluorescent probes based on DNA-templated copper nanoclusters for fast sensing of thiocyanate

A fast and label-free fluorescent sensor was developed to determine SCN⁻via inhibiting the formation of DNA-templated copper nanoclusters (CuNCs).

Detection of thiocyanate through limiting growth of AuNPs with C-dots acting as reductant

We have found that hydroxyl-rich carbon dots (C-dots) have the ability to reduce Au³⁺to form gold nanoparticles (AuNPs) which can be used as an optical sensor to detect SCN⁻in raw milk with satisfactory results.

Ultrasensitive turn-on fluorescent detection of trace thiocyanate based on fluorescence resonance energy transfer

Thiocyanate (SCN(-)) is a small anion byproduct of cyanide metabolism. Several methods have been reported to measure SCN(-) above the micromolar level. However, SCN(-) is derived from many sources such as cigarettes, waste water, food and even car exhaust and its effect is cumulative, which makes it necessary to develop methods for the detection of trace SCN(-). In this paper, a simple and ultrasensitive turn-on fluorescence assay of trace SCN(-) is established based on the fluorescence resonance energy transfer (FRET) between gold nanoparticles (AuNPs) and fluorescein. The detection limit is 0.09 nM, to the best of our knowledge, which has been the lowest detection LOD ever without the aid of costly instrumentation. The fluorescence of fluorescein is significantly quenched when it is attached to the surface of AuNPs. Upon the addition of SCN(-), the fluorescence is turned on due to the competition action between SCN(-) and fluorescein towards the surface of AuNPs. Under an optimum pH, AuNPs size and concentration, incubation time, the fluorescence enhancement efficiency [(IF-I0)/I0] displays a linear relationship with the concentration of SCN(-) in the range of 1.0 nM to 40.0 nM. The fluorescein-AuNP sensor shows absolutely high selectivity toward SCN(-) than other 16 anions. The common metal ions, amino acids and sugars have no obvious interference effects. The accuracy and precision were evaluated based on the recovery experiments. The cost effective sensing system is successfully applied for the determination of SCN(-) in milk products and saliva samples.