Cyanide quantification in post-mortem biological matrices by headspace GC–MS

Detection of Cyanide in a Decomposed Exhumed Body: A Case Report

Cyanide is a lethal poison that induces immediate fatality. Infrequently employed as a homicidal poison, it is not an ideal choice for homicide as it causes a 'dramatic' death causing suspicion among others. Cyanide is a rapidly metabolized poison that also rapidly disintegrates after death, posing challenges for chemical analysis, particularly when dealing with decomposed bodies. Detection of cyanide from a decomposed body is infrequent. A suspected case of intentional poisoning resulting in death was interred without conducting a postmortem examination. The exhumation process revealed the presence of hydrogen cyanide in the postmortem fluids collected from the body cavities three years after interment.

The stability of cyanide in human biological samples. A systematic review, meta-analysis and determination of cyanide (GC-QqQ-MS/MS) in an authentic casework 7 years after fatal intoxication

A 30 year old man was found with no signs of life in front of the house. The cyanide concentration in blood and urine was determined five years after the man's death. What is more, a stability study was conducted for 730 days in an authentic casework blood sample. Sample preparation procedure included precipitation with methanol:water mixture, solid phase extraction (SPE) and derivatization with the use of PFB-Br (pentafluorobenzyl bromide). The sample was analyzed using GC-QqQ-MS/MS (gas chromatopraphy coupled with tandem mass spectrometry) isotope dilution method. Separation was done using a SH-RXI-5MS column (30 m x 0.25 mm, 0.25 µm). Detection of PFB-CN and PFB-13CN was achieved using a triple-quadrupole mass spectrometer with an electron ionization (EI) ion source in multiple reaction monitoring (MRM) mode. After 5 years from the man's death, cyanide concentration was: 1900 ng/mL in blood and 500 ng/mL in urine. Stability study performed in an authentic blood sample 6 and 7 years after the man's death revealed cyanide concentrations of 1898.2 ng/mL and 1618.7 ng/mL, respectively. While spectrophotometric and colorimetric methods recorded both decrease and increase in cyanide concentration over time, newer chromatographic methods mainly indicate a decrease. The studies presented in this paper seem to confirm this trend. However, in order to interpretate the results of cyanide concentration in biological material reliably, more research is still necessary.

Fluorescent Carbon Dots: Aggregation-Induced Emission Enhancement, Application as Probe for CN- and Cr2O7-2, Sensing Strips and Bio-imaging Agent

Fluorescent carbon dots (Trp-CDs) were prepared using tryptophan as precursor and were characterized on the basis of elemental analysis, powder-XRD, IR, Raman spectroscopy, 13C-NMR, UV-Vis, fluorescence and TEM. Trp-CDs exhibit poor fluorescence in 100% water but showed strong Aggregation Induced Emission (AIE) in ethanol and higher alcohols. The anion sensing study of Trp-CD revealed that it selectively detects CN- and Cr2O7-2 and from fluorescence quenching titration study, quenching constant, LOD and range of detection were evaluated. The emission life-time of Trp-CD before and after addition of CN- and Cr2O7-2 were measured, the decay curve before addition of anion was best fitted with a bi-exponential function with life-time of τ1 2.79 ns (10.74%) and τ2 18.93 ns (89.26%). The mechanistic study revealed that for CN-, the fluorescence quenching is due to its interaction with protons attached to surface functional groups and for Cr2O7-2, it is due to inner filter effect (IFE). Sensing strips were prepared by coating Trp-CDs onto various solid surfaces including agarose films and were used for detection of CN- and Cr2O7-. Trp-CD was found to be nontoxic and biocompatible and used as staining agent for Artemia and Bacteria (Bacillus Subtilis, Pseudomonas) and detection of CN- and Cr2O7-.

Combination of headspace single-drop microextraction (HS-SDME) with a nickel-embedded paper-based analytical device for cyanide quantification

BACKGROUND

Cyanide anion can be found in foodstuffs, tobacco smoke and a variety of types of waters, mainly originating from anthropogenic activities. Due to its highly toxic nature, several agencies have established limits for cyanide levels in water. Additionally, monitoring cyanide levels in biological samples, such as blood and urine, is crucial for obtaining clinical information about the health condition of patients. Therefore, there is a pressing need for the development of simple, cost-effective, and reliable analytical methods capable of quantifying cyanide at low concentrations.

RESULTS

This study presents a novel analytical method for the selective and sensitive determination of cyanide based on analyte volatilization, pre-concentration via single-drop microextraction (SDME) using a selective reagent, and colorimetric quantification using a paper-based analytical device. For this, 10 mL of a liquid sample was acidified with phosphoric acid and the generated HCN was collected using a single drop of 3 μL of a palladium dimethylglyoximate solution (Pd (DMG)22-) positioned in the flask headspace using a syringe. The reaction of Pd (DMG)22- leads to the formation of Pd(CN)42- and the demasking of the organic ligand. After 15 min of extraction time, the reagent drop was added to a paper-based analytical device that has been previously impregnated with 3 μL of nickel chloride, resulting in the formation of a red precipitate of nickel (II) dimethylglyoximate. Digital images of the paper-based device were captured and the red channel (R) was used for quantification purposes. Under optimized conditions, the method demonstrates a suitable linear relation (r2 > 0.99) ranging from 26 to 286 μg L-1 and a limit of detection of 5 μg L-1.

SIGNIFICANCE

As a proof of concept, cyanide levels were quantified in water and urine samples using this method. The proposed approach offers high sensitivity and selectivity while requiring only a small volume of reagents. Furthermore, it exhibits a high degree of portability for in-situ applications.

Concurrent determination of cyanide and thiocyanate in human and swine antemortem and postmortem blood by high-performance liquid chromatography-tandem mass spectrometry

Cyanide (in the form of cyanide anion (CN-) or hydrogen cyanide (HCN), inclusively represented as CN) can be a rapidly acting and deadly poison, but it is also a common chemical component of a variety of natural and anthropogenic substances. The main mechanism of acute CN toxicity is based on blocking terminal electron transfer by inhibiting cytochrome c oxidase, resulting in cellular hypoxia, cytotoxic anoxia, and potential death. Due to the well-established link between blood CN concentrations and the manifestation of symptoms, the determination of blood concentration of CN, along with the major metabolite, thiocyanate (SCN-), is critical. Because currently there is no method of analysis available for the simultaneous detection of CN and SCN- from blood, a sensitive method for the simultaneous analysis of CN and SCN- from human ante- and postmortem blood via liquid chromatography-tandem MS analysis was developed. For this method, sample preparation for CN involved active microdiffusion with subsequent chemical modification using naphthalene-2,3-dicarboxaldehyde (NDA) and taurine (i.e., the capture solution). Preparation for SCN- was accomplished via protein precipitation and monobromobimane (MBB) modification. The method produced good sensitivity for CN with antemortem limit of detection (LODs) of 219 nM and 605 nM for CN and SCN-, respectively, and postmortem LODs of 352 nM and 509 nM. The dynamic ranges of the method were 5-500 µM and 10-500 µM in ante- and postmortem blood, respectively. In addition, the method produced good accuracy (100 ± 15%) and precision (≤ 15.2% relative standard deviation). The method was able to detect elevated levels of CN and SCN- in both antemortem (N = 5) and postmortem (N = 4) blood samples from CN-exposed swine compared to nonexposed swine.

Efficient fluorescence-enhanced probe for cyanide ions based on a tetraphenylethene pyridine coordinated copper-iodide complex

An efficient fluorescence-enhanced probe was developed for detecting cyanide ions (CN-) based on a tetraphenylethene coordinated copper-iodide complex (named CIT-Z). The coordination polymers (CPs) prepared were (Z)-1,2-diphenyl-1,2-bis[4-(pyridin-3-ylmethoxy)phenyl]ethene (1Z) and a CuI cluster, where the tetraphenylethylene (TPE) pyridine derivatives acted as organic ligands and the CuI cluster acted as a metal center. The higher-dimensional CIT-Z exhibited a 3-fold-interpenetrating network structure with excellent optical properties and chemical stability. This study also provides insights into the mechanism behind the fluorescence enhancement, which is attributed to the competitive coordination between CN- and the ligands. The probe showed high selectivity and sensitivity towards CN-, with a detection limit of 0.1 μM and good recovery in the real water samples.

Cysteamine-decorated gold nanoparticles for plasmon-based colorimetric on-site sensors for detecting cyanide ions using the smart-phone color ratio and for catalytic reduction of 4-nitrophenol

In this paper, we have reported the cyanide ions (CN^-) sensing in environmental water samples using cysteamine-capped gold nanoparticles (Cyst-AuNPs) by spectrophotometric, colorimetric, and smartphone-based RGB color detection. The surface plasmon resonance shift at around 525 nm for the Cyst-AuNPs could be used to detect quantitatively the amounts of CN^- with concomitant alteration of their color from wine red to purple visualized by the naked eye. For the first time, the Cyst-AuNPs-based visual sensing of CN^- was performed using smartphone-based detection with its detection limit of 159 × 10^-9 M, ten times lower than that of the highest tolerance level (2 × 10^-6 M) permitted by the world health organization. The Cyst-AuNPs displayed excellent specificity for detecting the concentration of 30 × 10^-6 M even amid the presence of other interfering inorganic anions with their concentrations about five times higher than it. Environmental real water samples were used to arrange the three different CN^- concentrations for plasmon-based colorimetric detection and smartphone-based method. Additionally, the catalytic performance of Cyst-AuNPs was demonstrated for the fast catalytic conversion of hazardous 4-nitrophenol (selected environmental contaminant) to the analogous amino aromatic compounds. A chemical kinetic study showed the conversion rate to be estimated as 1.65 × 10^-2 s^-1. Cyst-AuNPs can find an application in colorimetric sensing of CN^- while being able to be utilized as a catalytic nanomaterial for ecological remedies associated with health care.

Quantitation of free cyanide using ion exchange chromatography in Neisseria meningitidis serogroups A, C, W, Y and X conjugates used in vaccine manufacture

Polysaccharide vaccines essentially used in the prevention of bacterial infections are known to be good immunogens when conjugated to an immunogenic protein using various cyanylating agents. Analysis of residual cyanide in polysaccharide conjugate vaccines is an ardent task due to the complexity of the sample matrices and the lack of suitable methods. We report a selective ion chromatography method with electrochemical detection using IonPac AS7 column for estimation of residual cyanide in meningococcal serogroups A, C, W, Y and X bulk conjugates in presence of other interfering ions. Gold electrode and Ag/AgCl reference electrode ensures sensitivity and reproducibility of cyanide quantitation. The calibration curve of the method is linear having r² ≥0.990 over the concentration range 1.45 ng/mL to 93.10 ng/mL. The recovery of cyanide in bulk conjugates ranged between 96.0% and 108.9%. The limits of detection and quantitation were 0.50 ng/mL and 1.45 ng/mL which corresponds to 0.31 ng/μg and 0.91 ng/μg of polysaccharide respectively. The method validation and feasibility study were performed using Men W and Men X bulk conjugates respectively with in house residual cyanide specification due to unavailability of pharmacopeia guidelines. The method is reproducible and can accurately quantify residual cyanide in purified meningococcal bulk conjugates.

Diagnosis of lethal cyanide poisoning. Analysis by Anion-Exchange Chromatography with Pulsed Amperometric Detection

Cyanide is a poison widely used in cases of suicide or homicide. Although various methods to identify and quantify this substance are reported in the literature, they are mainly validated on biological fluids (e.g., blood and urine). In the present study, the Anion‐Exchange Liquid Chromatography with Pulsed Amperometric Detection (IC‐PAD) method was validated on blood and, for the first time, on gastric content, and organs (brain, lung, and liver). For each matrix, linearity, accuracy, precision, limit of detection (LOD), lower limit of quantification (LLOQ), matrix interferences, and carryover were assessed. The samples were extracted by steam distillation in acid environment for the following analysis by IC‐PAD. Furthermore, cyanide values found in two real poisoning cases are reported. For each investigated matrix, the analytical method satisfied all acceptance criteria for validation: it showed a good precision and accuracy, selectivity, and sensitivity with no carryover and matrix interference. The extraction by steam distillation in acid environment REDUCED the interference of the matrices and ALLOWED to perform the analysis with good precision and accuracy. In case #1, analysis showed a blood cyanide concentration of 0.99 μg/ml. In case #2, cyanide concentrations were 1.3 μg/g in brain, 0.8 μg/g in lung, 1.6 μg/g in liver, and 1.2 μg/g in gastric content. The cyanide concentrations found in the two reported cases have been suitable to cause death by poisoning.

Determination of cyanide based on a dual-emission ratiometric nanoprobe using silver sulfide quantum dots and silicon nanoparticles

A novel ratiometric fluorescent nanoprobe was designed for the sensitive determination of cyanide anion (CN^-) by the electrostatic attraction between positively charged silicon nanoparticles (Si NPs) and negatively charged silver sulfide quantum dots (Ag₂S QDs). The nanoprobe exhibited two well-resolved emission peaks at 446 nm and 540 nm under a single excitation wavelength (360 nm). In the presence of CN^-, the fluorescence of Ag₂S QDs at 540 nm was remarkably quenched, while the fluorescence of the Si NPs at 446 nm remained constant, establishing the desired conditions for ratiometric fluorescence detection. Under optimal conditions, the ratiometric fluorescence assay showed good linearity (R² = 0.9921) within the range 0.05-15 μM, and the limit of detection was calculated to be 56 nM (at an S/N ratio of 3). The proposed Ag₂S QD/Si NP nanoprobe has been successfully used to determine CN^- in water and sprouting potato samples with satisfactory recoveries in the range 97-110.5%.

Simple and simultaneous quantification of cyanide, ethanol, and 1-propanol in blood by headspace GC–MS/NPD with Deans switch dual detector system

Cyanide is a powerful and rapidly acting poison. In Japan, cyanide poisoning is rare, and regular cyanide testing can be costly and time consuming. In contrast, alcohol analysis is routinely performed in most forensic laboratories. In this study, we attempted to develop a method for the simultaneous quantification of cyanide and alcohols in blood using headspace gas chromatography (HS-GC). As nitrogen-phosphorus detection (NPD) is more sensitive to hydrogen cyanide than mass spectrometry (MS), a Deans switch was used to switch the detectors during a single run. The separation provided by three analytical columns, PoraBOND Q, CP-Sil 5 CB, and HP-INNOWax, was investigated, and PoraBOND Q was selected. The use of HS-GC-MS/NPD with a Deans switch enabled the simple and simultaneous quantification of cyanide, ethanol, and 1-propanol. Eighteen other volatile compounds were detected in the SIM/scan mode of the MS.

A novel method for cyanide quantification in human whole blood using ion chromatography with amperometric detection and its application to cyanide intoxication cases

Cyanide is a highly toxic agent that has been frequently used for suicide in South Korea. It is also used in various industrial fields, such as metal plating, in which many accidental cyanide intoxications have occurred. To overcome the disadvantages of conventional cyanide analysis methods, a simple and fast method for the analysis of cyanide in whole blood using ion chromatography (IC) with amperometric detection was developed in this study. Whole blood samples were deproteinized, diluted, and analyzed using an IC-amperometric detection system. The limits of detection and quantitation were 0.1 and 0.2 mg/L, respectively. The method showed good linearity in the range of 0.2 to 50 mg/L with R²  > 0.99. The intra- and inter-assay precision and accuracy values were <10%. The established method was successfully applied to analyze whole blood samples from three cyanide intoxication cases.

Determination of Cyanide in Blood for Forensic Toxicology Purposes-A Novel Nci Gc-Ms/Ms Technique

One of the recently evolving methods for cyanide determination in body fluids is GC-MS, following extractive alkylation with pentafluorobenzyl bromide or pentafluorobenzyl p-toluenesulfonate. The aim of this study was to improve previous GC methods by utilizing a triple quadrupole mass spectrometer, which could enhance selectivity and sensitivity allowing for the reliable confirmation of cyanide exposure in toxicological studies. Another purpose of this study was to facilitate a case investigation including a determination of cyanide in blood and to use the obtained data to confirm the ingestion of a substance, found together with a human corpse at the forensic scene. The blood samples were prepared following extractive alkylation with a phase transfer catalyst tetrabutylammonium sulfate and the PFB-Br derivatization agent. Optimal parameters for detection, including ionization type and multiple reaction monitoring (MRM) transitions had been investigated and then selected. The validation parameters for the above method were as follows-linear regression R2 = 0.9997 in the range of 0.1 µg/mL to 10 µg/mL; LOD = 24 ng/mL; LOQ = 80 ng/mL and an average recovery of extraction of 98%. Our study demonstrates the first attempt of cyanide determination in blood with gas chromatography-tandem mass spectrometry. The established method could be applied in forensic studies due to MS/MS confirmation of organic cyanide derivative and low matrix interferences owning to utilizing negative chemical ionization.

A new chemosensor for cyanide in blood based on the Pd complex of 2-(5-bromo-2-pyridylazo)-5-[N-n-propyl-N-(3-sulfopropyl)amino]phenol

A new indirect chemosensor for the detection of cyanide in blood is developed. 2-(5-Bromo-2-pyridylazo)-5-[N-n-propyl-N-(3-sulfopropyl)amino]phenol, a yellow dye, forms a blue-coloured complex with palladium ions. The yellow colour of this complex is regained upon reaction with cyanide ions. The complex shows high selectivity for the detection of cyanide over 16 other anions. The system was applied to two different methods for the detection of cyanide in human whole blood. As a quantitative absorbance method, blood samples were mixed with acid, and the resulting vaporised hydrogen cyanide was absorbed in an alkaline solution containing the complex in a Conway cell. The resulting absorbance response of the solution at 450 nm is linear over the range 4-40 μM (R2 = 1.000), and the limit of detection is 0.6 μM. Furthermore, the complex-soaked paper is applicable as a test strip for cyanide detection. When a test strip is used with 0.5 mL of blood, the limit of detection is 15 μM. The detection limits of these two methods are below the toxic blood cyanide concentration (19 μM). Therefore, both methods allow the quantification and screening of cyanide in blood samples. Furthermore, the test strip is low cost and enables on-site analysis.

Old Poison, New Problem: Cyanide Fatal Intoxications Associated with Internet Shopping

Widespread access to the Internet has an increasing influence on how suicides are committed. On websites such as eBay® or Amazon.com® highly toxic substances including cyanides are available for purchase. In the last 5 years, a few fatal intoxications associated with Internet shopping and buying "suicide kits" have been reported. Epidemiology of intoxications reported by American Association of Poison Control Centers between 2000-2018 shows that about 10% of all exposures to cyanide were related to suicide attempts and intentional ingestion of this substance. In order to determine the cyanide concentration in four fatal intoxication cases associated with Internet shopping, a headspace gas chromatography with dual column/dual flame ionization detector (HS-GC-FID/FID) method was validated and applied to casework. The method was linear in range, from 1 to 50 µg/mL, with a coefficient of determination of 0.999 (R2). The limit of quantification was 1.0 µg/mL; the detection limit was 0.5 µg/mL. Intra- and inter-day validation precision and accuracy did not exceed 10% and 15%, respectively. Recovery and matrix effect values ranged from 94.8- 103.8% and -5.2─3.8%, respectively. The cyanide concentrations were determined in biological fluids (blood, urine, bile, vitreous humor, gastric content) and postmortem tissue samples (spleen, kidney, liver, brain). The headspace gas chromatographic method, which is routinely used in clinical and forensic toxicology to quantify ethanol with its congeners (methanol, acetone, isopropanol, n-propanol and n-butanol), can be also applied to determine cyanide in intoxication cases. The global problem of a high number of suicides each year, requires increasing and more restrictive control of highly toxic substances available online as well as caution monitoring of human exposure to cyanide. This old and well known poison is being increasingly used nowadays for suicidal purposes, therefore determination of cyanide in biological samples is still important in terms of clinical and forensic toxicology.

Fluorous and Fluorogenic Derivatization for Selective Liquid Chromatographic Analysis of Cyanide in Human Plasma

A liquid chromatographic (LC) method with fluorous derivatization for the determination of cyanide in human plasma is described. In this method, the cyanide was transformed to a fluorous and fluorogenic compound by derivatizing with 2,3-naphthalenedialdehyde and perfluoroalkylamine reagent under mild reaction conditions (a reaction time of 5 min at room temperature). The obtained derivative was successfully retained on the perfluoroalkyl-modified LC column with the use of a high concentration of organic solvent in the mobile phase, whereas non-fluorous derivative was hardly retained, followed by fluorometric detection at excitation and emission wavelengths of 420 and 490 nm, respectively. Under the optimized conditions, the limit of detection and the limit of quantification for cyanide in a 5-μL injection volume were 1.3 μg/L (S/N = 3) and 4.4 μg/L (S/N = 10), respectively. The recovery from spiked human plasma was achieved in the range of 54 - 90% within a relative standard deviation of 3.5%. The feasibility of this method was further evaluated by applying it to the analysis of human plasma samples.

RECiQ: A Rapid and Easy Method for Determining Cyanide Intoxication by Cyanide and 2-Aminothiazoline-4-carboxylic Acid Quantification in the Human Blood Using Probe Electrospray Ionization Tandem Mass Spectrometry

In this study, we developed a rapid and easy method to determine cyanide (CN) intoxication by quantification of CN and 2-aminothiazoline-4-carboxylic acid (ATCA), which is a new and reliable indicator of CN exposure, in the human blood using probe electrospray ionization tandem mass spectrometry (PESI/MS/MS) named RECiQ. For CN, we applied the previously reported one-pot derivatization method using 2,3-naphthalenedialdehyde and taurine, which can directly derivatize CN in the blood. The analytical conditions of the CN derivatization were optimized as a 10 min reaction time at room temperature. In contrast, ATCA could be directly detected in the blood by PESI/MS/MS. We developed quantitative methods for the derivatized CN and ATCA using an internal standard method and validated them using quality control samples, demonstrating that the linearities of each calibration curve were greater than 0.995, and intra- and interday precisions and accuracies were 5.1-15 and 1.1-14%, respectively. Moreover, the lower limit of detections for CN and ATCA were 42 and 43 ng/mL, respectively. Finally, we applied RECiQ to three postmortem blood specimens obtained from victims of fire incidents, which resulted in the successful quantification of CN and ATCA in all samples. As PESI/MS/MS can be completed within 0.5 min, and the sample volume requirement of RECiQ is only 2 μL of blood, these methods are useful not only for the rapid determination of CN exposure but also for the estimation of the CN intoxication levels during an autopsy.

Highly sensitive turn-off fluorescent detection of cyanide in aqueous medium using dicyanovinyl-substituted phenanthridine fluorophore

Herein, the turn-off fluorescence sensor of 2-((4'-(7,8,13,14-tetrahydrodibenzo[a,i]phenanthridin-5-yl)-[1,1'-biphenyl]-4-yl)methylene)malanonitrile (7) was developed for the recognition of CN- ions and studied using different spectroscopic techniques. The selective recognition of CN- ions by 7 was investigated via UV-vis spectroscopy and fluorescence studies in acetonitrile solvent, which exhibited an obvious color change from orange to colorless under 365 UV light. The sensor compound 7 possesses a high binding constant (K a) for CN- ions in the order of 5.22 × 106 M-1. The results from the interference studies revealed that probe 7 shows high sensing selectivity and sensitivity for CN- ions over other competitive anions. Probe 7 interacts with cyanide to form a 1 : 1 adduct, and this mechanism was further verified by 1H NMR titration, Job's plot analyses and DFT studies. The sensor probe 7 exhibits advantages such as low limit of detection (LOD) of 39.3 nM, fast response and sensing in a wide pH range of 3 to 11. The practical application of 7 was successfully demonstrated for the determination of CN- ions in test paper strips and various water samples.

Lethal Hydrogen Sulfide poisoning in open space: An atypical case of asphyxiation of two workers

Hydrogen sulfide is one of the most dangerous toxic gases that has led to the deaths in confined spaces of many workers. We report an atypical case of a fatal accident of H₂S poisoning in an open space when two workers died during the opening of a hatch on a tanker truck filled with leachate water. Despite being outdoors, the two workers, were suddenly and quickly overwhelmed by a lethal cloud of H₂S, which escaped like a geyser from the hatch and hovered over the top of the tanker making it impossible for them to survive. The first operator was engulfed by the sudden flow of lethal gas near the hatch while the second worker, who came to his aid, immediately lost consciousness and fell off the tanker onto the ground. Environmental toxicological analyses were carried out on the air near the hatch and inside the tanker 2h, 20 days and 70 days after the accident. Toxicological analyses on the blood were also carried out but unfortunately, no urine sample was available. The thiosulfate, detected by GC/MS analysis after derivatization of PFBBr, was found to be 0.01 and 0.04mM/L. These values are included in the medium-low lethal values of occupational fatalities involving H₂S reported in the literature.

Colorimetric and visual detection of cyanide ions based on the morphological transformation of gold nanobipyramids into gold nanoparticles

In this study, we developed a facile, rapid, selective and sensitive colorimetric method for the detection of cyanide ions (CN⁻) by using gold nanobipyramids (Au NBPs).

Theoretical study on the sensing mechanism of a fluorescence chemosensor for the cyanide anion

The sensing mechanism of the ratiometric fluorescence chemosensor 2-((6-(diethylamino)quinolin-2-yl)methylene)malononitrile (3A) for the cyanide anion (CN^-) has been investigated theoretically. The calculated results show that the small reaction barrier (8.58 kcal/mol) of 3A implies a rapid response speed to CN^-, and that the large interaction energy (25.75 kcal/mol) between 3A and CN^- indicates a high selectivity to CN^-. The results of condensed dual descriptor calculation confirm that CN^- attacks the C₂ site of 3A rather than other sites. The nucleophilic addition reaction of CN^- breaks the original conjugation structure of 3A and results in the redistribution of the charge. The frontier molecular orbitals (MOs) and the Hirshfeld population analysis demonstrate that the long-rang electronic transition between the diethylamino moiety and the dicyanovinyl group in 3A is cut off after the addition of CN^- and a local electronic transition between the quinoline and diethylamino moiety is formed. These changes lead to a blue shift (63 nm) of the fluorescence emission in the nucleophilic addition product (P) compare to 3A.

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.

CdSe quantum dots-sensitized chemiluminescence system and quenching effect of gold nanoclusters for cyanide detection

An efficient chemiluminescence resonance energy transfer (CRET) induced chemiluminescence (CL) system was developed for the sensitive determination of cyanide ion (CN^-) in environmental and biological samples. The selected CL reaction was hydrogen peroxide (H₂O₂)-bicarbonate (HCO₃^-) system with an ultra-weak emission at about 470 nm. It was found that glutathione-stabilized CdSe quantum dots (CdSe QDs) superbly increase the obtained CL intensity. The high performance CRET between the CL emitters and CdSe QDs with a broad absorption was mainly responsible for the observed improving effect. The absorption spectrum of QDs completely overlaps with the CL emission wavelength of H₂O₂-HCO₃^- system. Besides, CdSe QDs could also catalyze the CL reaction of H₂O₂-HCO₃^-, efficiently. On the other hand, it was observed that the gold nanoclusters (Au NCs) could prohibit the CRET system and turn off the CL emission. This diminishing effect can be useful for the analytical application. Herein, it was successfully exploited for the selective recognition of CN^-, using its leaching effect on Au NCs. After efficient dissolution of NCs, the CRET to CdSe QDs restored and the CL emission was again turned on. This strategy resulted in a high sensitive and reliable measurement of CN^- in the concentration range of 2-225 nM, with a detection limit of 0.46 nM.

Application of ion chromatography with pulsed amperometric detection for the determination of trace cyanide in biological samples, including breast milk

Cyanide (CN) is the biomarker of exposure to the components of tobacco smoke, although its presence in biological samples is also due to the consumption of products containing cyanogenic glycosides. In this work, we determine the concentration of the free cyanide in urine, saliva and breast milk matrices, using ion chromatography with pulsed amperometric detection (IC-PAD). IC-PAD is an emerging method, with only few documented applications in urine and saliva, and the presented determination in breast milk is its first published report for any method. The biological samples, which were obtained from women staying in a maternity ward, showed cyanide concentrations spanning 1.82-98.47 μg L^-1. Under the optimized chromatographic conditions, the IC-PAD system exhibited satisfactory repeatability (R < 3%, n = 3) and good linearity in the range of 1-100 μg L^-1. Thus, it proved to be an effective tool for monitoring trace cyanide concentration in a series of human body fluid matrices, including breast milk. This last matrix is especially important due to the possible effect on infant health related to the mothers' smoking habits.

A tripodal supramolecular sensor to successively detect picric acid and CN− through guest competitive controlled AIE

Herein, we report a simple and efficient method for the selective and sensitive detection of picric acid (PA) and CN⁻via a novel guest competitive controlled aggregation-induced emission (AIE) mechanism based on a tris-naphthalimide derivative TG.

Development of an Analytical Protocol for Determination of Cyanide in Human Biological Samples Based on Application of Ion Chromatography with Pulsed Amperometric Detection

A simple and accurate ion chromatography (IC) method with pulsed amperometric detection (PAD) was proposed for the determination of cyanide ion in urine, sweat, and saliva samples. The sample pretreatment relies on alkaline digestion and application of Dionex OnGuard II H cartridge. Under the optimized conditions, the method showed good linearity in the range of 1-100 μg/L for urine, 5-100 μg/L for saliva, and 3-100 μg/L for sweat samples with determination coefficients (R) > 0.992. Low detection limits (LODs) in the range of 1.8 μg/L, 5.1 μg/L, and 5.8 μg/L for urine, saliva, and sweat samples, respectively, and good repeatability (CV < 3%, n = 3) were obtained. The proposed method has been successfully applied to the analysis of human biological samples.

Efficient On-Off Ratiometric Fluorescence Probe for Cyanide Ion Based on Perturbation of the Interaction between Gold Nanoclusters and a Copper(II)-Phthalocyanine Complex

A new ratiometric fluorescent sensor was developed for the sensitive and selective detection of cyanide ion (CN(-)) in aqueous media. The ratiometric sensing system is based on CN(-) modulated recovery of copper(II) phthalocyanine (Cu(PcTs)) fluorescence signal at the expense of diminished fluorescence intensity of gold nanoclusters (AuNCs). Preliminary experiments revealed that the AuNCs and Cu(PcTs) possess a turn-off effect on each other, the interaction of which being verified through studying their interactions by principle component analysis (PCA) and multivariate cure resolution-alternating least-squares (MCR-ALS) methods. In the presence of CN(-) anion, the AuNCs and Cu(PcTs) interaction was perturbed, so that the fluorescence of Cu (PcTs), already quenched by AuNCs, was found to be efficiently recovered, while the fluorescence intensity of AuNCs was quenched via the formation of a stable [Au(CN)2](-) species. The ratiometric variation of AuNCs and Cu(PcTs) fluorescence intensities leads to designing a highly sensitive probe for CN(-) ion detection. Under the optimal conditions, CN(-) anion was detected without needing any etching time, over the concentration range of 100 nM-220 μM, with a detection limit of 75 nM, which is much lower than the allowable level of CN(-) in water permitted by the World Health Organization (WHO). Moreover, the detection of CN(-) was developed based on the CN(-) effects on the blue and red florescent colors of Cu(PcTs) and AuNCs, respectively. The designed probe displays a continuous color change from red to blue by addition of CN(-), which can be clearly observed by the naked eye in the range of 7-350 μM, under UV lamp. The prepared AuNCs/Cu(PcTs) probe was successfully utilized for the selective and sensitive determination of CN(-) anion in two different types of natural water (Rodbal dam and rainwater) and also in blood serum as a biological sample.

Determination of formaldehyde and cyanide ion in human nasal discharge by using simple spectrophotometric methods

Environmental tobacco smoke (ETS) contains many toxic compounds which include substances classified as aldehydes (e.g. formaldehyde) and inorganic substances such as cyanide ions. The information on the determination of these compounds in water is available, but the monitoring data on the level of these substances in human body fluids are still lacking. In this work the procedure for determining cyanide ions and formaldehyde in samples of human nasal discharge by simple spectrophotometric technique is presented.