Potentiometric determination of cyanide with an ion selective electrode. Application to cyanogenic glycosides in Sudan grasses

Ratiometric detection and monitoring of cyanide in biological, environmental and food samples by a novel triphenylamine-xhantane based fluorescent probe

BACKGROUND

As cyanide (CN-) is a significant hazard to the environment and human health, it is essential to monitor cyanide levels in water and food samples. Moreover, real-time visualization of CN-could provide an additional understanding of its critical physiological and toxicological roles in living cells. The fluorescence approach based on small organic probes is an effective way for the detection of CN-. In this approach, a triphenylamine-xhantane conjugate was applied to detect in many samples such as sewage water, soil, sprouted potato, apricot seed, and living cells.

RESULTS

We report a new ratiometric near-infrared fluorescent probe based on a triphenylamine-xhantane derivative for CN-sensing in many samples. The probe displays high selectivity for only CN- ions among a series of analytes. The addition of cyanide to the dicyanovinyl moiety of the probe disrupts π-conjugation followed by the interruption of internal charge transfer. Consequently, the emission peak of the probe shifts hypsochromically from 655 to 495 nm. There is a linear correlation between the emission intensity (I495) and cyanide level, with a detection limit of 0.036 μM. The probe has many advantages over many probes, such as NIR fluorescence, ratiometric response, low cytotoxicity (85.0 % cell viability up to 50.0 μM of the probe), good membrane permeability, fast response time (4.0 min), high selectivity, good photostability, and anti-interference capability.

SIGNIFICANCE

Although various probes have been reported in the literature, the use of triphenylamine-xhantane unit as CN- probe has yet to be explored. The probe can detect trace levels of cyanide in many samples such as sewage water, soil, sprouted potatoes, and apricot seeds. Furthermore, it is successfully utilized for the ratiometric fluorescent bioimaging of cyanide in living cells.

Synthesis of gold nanoclusters-loaded lysozyme nanoparticles for ratiometric fluorescent detection of cyanide in tap water, cyanogenic glycoside-containing plants, and soils

The modification of protein-stabilized gold nanoclusters with fluorophores has been intensively applied for the ratiometric detection of biomolecules, metal ions, and anions. This study developed a straightforward strategy to prepare lysozyme nanoparticle-encapsulated gold nanoclusters (LysNP-AuNCs) as a dual-emission probe for the ratiometric sensing of cyanide through fluorescence resonance energy transfer (FRET) without the conjugation of additional fluorophores. The reduction of gold ion precursors with lysozyme generated lysozyme-stabilized AuNCs under an alkaline pH, which were demonstrated to self-assemble into nanoaggregates during the formation of AuNCs. The aggregated lysozyme molecules on the AuNCs were treated with glutaraldehyde, triggering the conversion of the aggregated lysozymes into blue-emitting lysozyme nanoparticles. As a result, the AuNCs were well distributed inside a single lysozyme nanoparticle, as demonstrated by transmission electron microscopy. The presence of cyanide triggered the etching of the AuNCs in the LysNP-AuNCs, leading to the suppression of FRET from lysozyme nanoparticle to AuNCs. The LysNP-AuNC probe was implemented for FRET detection of cyanide with a linear range of 3-100 μM. Additionally, the selectivity of the LysNP-AuNC probe for cyanide toward other anions was remarkably high. The practicality of the proposed probe was evaluated by quantifying cyanide in tap water and soils and monitoring the liberation of hydrogen cyanide from cyanogenic glycoside-containing foods.

Visual and quantitative detection of CN- ion in aqueous media by an HBT-Br and thiazolium conjugated fluorometric and colorimetric probe: Real samples and useful applications

Cyanide released from mostly industrial production is a highly toxic chemical. Its heavy industrial use and transportation increase the danger of human exposure. Since it can often lead to rapid death, selective, sensitive and on-site and rapid monitoring techniques for the detection of cyanide are essential. Therefore, we report an efficient cyanide probe based on thiazolium conjugated HBT-Br derivative. It has striking color change toward cyanide blue to yellow under daylight or colorless to cyan under UV-light. Interaction modes of the probe are based on ESIPT and ICT processes. It is selectively able to react free aqueous cyanide with detection limit of 1.79 μM, lower than physiologically lethal blood levels, >20 μM. Smartphone assisted and test kit applications are able to detect cyanide, qualitatively. Moreover, real samples such as tap or lake water and apricot seeds including cyanide are successfully determined through the present probe. Therefore, the designed probe displays excellent practical potential toward cyanide.

Distance-Based Paper Device Combined with Headspace Extraction for Determination of Cyanide

We report for the first time a distance-based paper device based on gold/silver core shell nanoparticles (Au@Ag NPs) for a simple, inexpensive, instrument-free, and portable determination of cyanide by the naked eye. Au@Ag NPs immobilized on a paper channel were etched by cyanide ions so that a yellow color band length of Au@Ag NPs is proportional to a decrease in the cyanide concentration. Quantification is achieved by measuring color length, thus eliminating the need to differentiate hues and intensities by the user, and the processing data of each imaging device. Moreover, the paper-based headspace extraction was combined with the distance-based paper device to improve the sensitivity. The enrichment factor was found to be 30-fold and the linearity was found in the range 0.05–1 mg L⁻¹. The naked eye detection limit was 10 μg L⁻¹ where the World Health Organization (WHO) have regulated the maximum level of cyanide in drinking water as 70 μg L⁻¹. Our proposed device also showed no interference from common cations and anions presenting in seawater and waste water including thiocyanate, chloride. Finally, our device has been successfully applied to determine cyanide ions in seawater, drinking water, tap water and wastewater providing satisfactory precision and accuracy.

A new biological assay for measuring cyanide in blood

Clinical diagnosis of cyanide poisoning is complicated by the lack of an easy, convenient assay for cyanide concentration in blood. Therapy may be delayed with unconfirmed diagnosis because the conventional antidote to cyanide poisoning exposes patients to substantial risks. We developed a new spectrophotometric assay to measure cyanide by extraction into a sodium hydroxide trap, followed by the addition of exogenous methemoglobin as a colormetric indicator. Samples of blood from 15 healthy subjects and 5 patients who had received prolonged nitroprusside infusions were assayed. To optimize assay characteristics, methemoglobin concentrations, pH, temperature, incubation time, and buffer strengths were varied. Duplicate samples were assayed by using the polarographic method for assay validation. Over a range from 300 ng/mL to 7 microg/mL, the correlation between methods was r = 0.983. Interassay and intraassay variability were 5% and 2%, respectively. Samples drawn from the five patients and tested by using both methods yielded a correlation of r = 0.978. This new assay for cyanide in blood may greatly facilitate the diagnosis and treatment of cyanide ingestion. The use of methemoglobin as the colorimetric indicator in the assay contributes to its low cost and ease of use.

IMPLICATIONS

Cyanide, an important factor in death from burn-related inhalation injury, is difficult and time-consuming to measure. We developed a new, rapid blood test for cyanide using methemoglobin as a colormetric indicator. A rapid, accessible test for cyanide may speed the diagnosis and treatment of cyanide poisoning.

Potentiometric measurements of hydrogen and cyanide ions in buffered media

Potentiometric measurements of hydrogen and cyanide levels were studied in different buffered media that are used in biological experiments. The addition of 1-10mM NaCN increased the pH (from 7.2-7.5 up to 9.5) of either bicarbonate/phosphate-buffered (artificial cerebrospinal fluid (ACSF), sera, and whole blood) or Hepes-buffered solutions in a concentration-dependent manner. While in aerated ACSF this increase was transient (half-relaxation time less than 4 min), the increase in pH was sustained in Hepes buffer. A mathematical model that predicts the maximum cyanide-induced increases in pH was derived. When NaCN was added to either ACSF or Hepes-buffered solutions, a Nernst relation was obtained, but deviations from Nernstian responses resulted when NaCN was added to sera or whole blood. These responses, however, differed substantially from the theoretical results that were based on the relative amounts of ionized cyanide present in the various pH environments. In addition, attempts were made to indirectly examine the formation and escape of HCN by calculating the time constants of decay (tau d) of the cyanide-induced potentiometric responses. With progressively higher NaCN concentrations in ACSF, the values of tau d did not decrease, but were constant. As predicted, however, the values of tau d were larger when solutions were covered or had higher initial pH values. These results suggest that in the solutions tested, the cyanide electrode used in the present study measured the total amount rather than the ionized portion of dissolved cyanide and that the values of tau d do not correspond to formation/escape rates of HCN.

Effects of thiosulfate on cyanide pharmacokinetics in dogs

One method to treat cyanide poisoning involves the administration of a combination of sodium thiosulfate and sodium nitrite. Sodium thiosulfate is believed to exert its antidotal effect by serving as a sulfur donor, thereby increasing the rate of rhodanese catalyzed biotransformation of cyanide to thiocyanate. To gain insight into the mechanism of action of thiosulfate on cyanide toxicity, a pharmacokinetic analysis of cyanide distribution and metabolism with and without sodium thiosulfate was conducted in mongrel dogs. A compartmental model for thiocyanate, the major metabolite of cyanide, was developed from plasma concentrations determined at various times after iv administration of thiocyanate; sodium thiosulfate did not alter thiocyanate-model parameters. The model for thiocyanate was coupled to a model for cyanide, and model based equations were fitted to the blood levels of both cyanide and thiocyanate that were measured after iv administration of cyanide. This kinetic analysis showed that thiosulfate increased the rate of conversion of cyanide to thiocyanate over 30-fold. The mechanism of thiosulfate protection appeared to be due to extremely rapid formation of thiocyanate in the central compartment, which thereby limited the amount of cyanide distribution to sites of toxicity.