Pyridine-barbituric Acid Research Articles

Spectrophotometric quantification of trace levels of cyanide in water-insoluble drug substances and confirmation of specificity through an orthogonal comparison approach

Some pharmaceutical ingredients use cyanide in their synthesis, and this impurity must be controlled as per ICH, FDA and EDQM regulatory compliance. Spectrophotometric approaches for measuring cyanide levels are confined to water or water-soluble compounds with poor solution stability and low sensitivity. No method is available for the cyanide in water-insoluble drug substances through spectrophotometry. To address this gap, our study proposed a spectrophotometric approach for measuring trace cyanide in water-insoluble drugs such as Primidone and Clobazam. This method utilizes chloramine-T, which reacts with cyanide to form cyanogen chloride (CNCl), consequently reacting with pyridine-barbituric acid to produce a coloured derivative (C13H10N4O6, MW: 318.06 g/mol). This protocol also involves the selection of a suitable solvent and optimizing the pH for sensitive/accurate quantification of cyanide impurity. Mass spectrometry confirms cyanide derivatization as part of the orthogonal procedure comparison of ICH Q2 (R2). Method validation follows ICH Q2 (R2) guidelines in determining specificity, LOD (0.396 ppm), LOQ (1.200 ppm), linearity (1.2-45 ppm), and recovery (91-99% with %RSD<10%) of the method. The stability of the pyridine-barbituric acid reagent and derivatized compound was also evaluated. This approach effectively measures cyanide in water-insoluble drugs, meeting essential regulatory standards.

Spectrophotometric Determination of Cyanide in Passaic River Paterson New Jersey by Distillation and Colorimetric Method with Pyridine: Barbituric Acid Reagent

Purpose: This work determines the concentration of total cyanide in the Passaic River in the New Jersey Area.&#x0D; Methodology: The concentration of cyanide and the subsequent reaction of the product with a mixed solution of pyridine-barbituric acid to form a stable complex. Therefore, before chlorination of cyanide, all cyanide compounds present in sample must be broken down by an acid reflux and distillation.&#x0D; Findings: The cyanide concentration in the Passaic River sediment solution and non-running wastewater was determined by measuring absorbance at max 578 nm, and cyanide amount has been found less than 0.005 ppm under the NEPA permit compliance. Industrial facilities who discharge wastewater to public waterways in the United States, stringent limits on cyanide, typically with monthly average effluent limits set around 0.005 ppm or less.&#x0D; Unique contributor to theory, policy and practice: This method is applicable to the determination of cyanide in drinking, saline, groundwater, surface water as well as domestic and industrial wastewater.

A simplified low volume colorimetric assay for rapid comparison of cyanogenic glycoside production between barley genotypes

Ethyl carbamate (EC), a genotoxic and carcinogenic compound, is an undesirable trace component in spirits and whisky. The precursor of EC produced from barley (Hordeum vulgare L.) malt is primarily a cyanogenic glycosidic nitrile (GN) known as epiheterodendrin (EPH). EPH production is genetically controlled in barley, low or non-GN varieties exist and EPH production can be controlled by using low or non-GN barley varieties for malt production. Here, we report on a rapid and inexpensive colorimetric assay modified from Cook and Oliver (in: European Brewery Convention (eds) Proceedings of the 23rd Congress, Lisbon. European Brewery Convention, Zoeterwoude, Netherlands, 1991). The new low-volume, high-throughput, semi-quantitative test method can be used for the selection of low or non-GN breeding lines through samples of acrospires. This method is based on the detection of cyanide by the reaction with chloramine-T followed by the addition of the reagent (pyridine-barbituric acid) to form a soluble violet-blue product measured at 590 nm. Absorbance measurements and the visual color are used to estimate the presence of EPH production in acrospires. In this report, the level of EPH production was compared among some commercial European non-GN lines, Canadian malt varieties and advanced barley breeding lines.

Assessment of Free and Total Cyanide Levels in the Water Environment of Shatt Al-Arab

The concentration of free and total cyanide in waters was measured by using the colorimetric method through complex formation with pyridine-barbituric acid at the wavelength of 578 nm. Ten stations were selected from water surfaces in the south of Iraq. The samples were distributed among two stations, one was on Euphrates River and the other was on Tigris River (before their confluence and formatting of Shatt Al-Arab) and selected seven stations along Shatt Al-Arab River. All the samples were collected from surface water at depth of 10–15 cm and their pH was adjusted to 12 by using sodium hydroxide. The results showed the highest concentration of free cyanide (0.254 mg/L) in station W7 and the lowest concentration in stations W2, W9 and W10, while the highest and lowest concentration of total cyanide (9.962, 0.207 mg/L) were recorded in station W7 and W1 respectively. The standard deviation of all sites (n = 3) of free and total cyanide was calculated and showed 0.007–0.048 and 0.001–0.042 ranges respectively. Furthermore, some of the physico-chemical properties of water were recorded in these stations.

Paper-based headspace extraction combined with digital image analysis for trace determination of cyanide in water samples

A simple, cost-effective, instrumental free and user-friendly analytical method based on the combination of paper-based headspace extraction and digital scanning image analysis was developed for the sensitive detection of cyanide in water and wastewater samples. The method relied on chloramine-T/pyridine-barbituric acid reaction, which is a well-known process for measuring cyanide in standard analytical methods. During the reaction, cyanide was converted to cyanogen chloride, which was extracted and collected on a paper impregnated with pyridine-barbituric acid. The color appeared on the paper was used to quantify the analyte using a scanning-assisted image processing software. Experimental parameters affecting the sensitivity of the method such as stirring rate, paper size, chloramine-T and barbituric acid concentration, equilibrium and extraction time were studied. Under optimal conditions, the calibration curve was linear in the range of 3.0–100 μg L−1 with the detection limit of 0.7 μg L−1. The intra- and inter- day relative standard deviations of the method at 10 and 70 μg L−1 concentration levels were less than 6%. Analyte recovery in real samples was in the range of 69–111%.

Optimization of the spectrophotometric determination of Aqueous Cyanide: Application on Samira (Niger) Gold Mine Groundwater Analysis

Cyanide is very toxic to humans, and its usage in gold mining potentially poses serious environmental threats. In this paper, by revising the well-known colorimetric method based on the chlorination of cyanide with chloramine-T and subsequent reactions with pyridine-barbituric acid reagent, we have developed a robust and sensitive UV-Visible spectrophotometric method for cyanide determination in aqueous media.

Pyridine-barbituric acid spectrophotometry for determination of urine thiocyanate

目的 建立一个用于正常人和接触无机氰化物、有机氰化物的工人尿中硫氰酸盐自动测定方法.方法 在Hitachi 7080上建立自动化测定尿硫氰酸盐浓度的参数,对该方法的重复性、线性进行评估,并与行业标准对照.结果 反应的最大吸收峰在580 nm,选择反应的第300 s作为空白测定点,取加入试剂巴比妥酸、吡啶后300 s作为反应测定点.低、中、高3个浓度硫氰酸盐的相对标准偏差分别为4.3%、3.2%、3.0%.测定的线性范围为1～200 mg/L. 结论 建立的硫氰酸盐浓度的自动化检测方法具有简便、可靠、快速、廉价的优点.能对正常人和接触无机氰化物、有机氰化物工人的尿中硫氰酸盐进行快速测定。

Indirect determination of free cyanide in water and industrial waste water by flow injection-atomic absorption spectrometry

A simple and rapid flow injection system is proposed for indirect determination of cyanide by flame atomic absorption spectrometry. It consists of a microcolumn of immobilized salen (N,N′-bis(salicylidene)ethylenediamine) on sodium dodecyl sulfate (SDS)-coated alumina saturated with silver ion and a carrier of dilute solution of sodium hydroxide (10−5 mol L−1). The micro-column was located between the injection valve and nebulizer of atomic absorption spectrometry. Injection of 250 µL of aqueous cyanide standard or sample solution at pH range of 9–11 cause elution of silver as silver cyanide complexes, which was then measured by flame atomic absorption spectrometry. The absorbance was proportional to the concentration of cyanide in the sample. The graph of absorbance (as peak height) vs. cyanide concentration was linear over the concentration range of 0.1–10 mg L−1 of cyanide, and the detection limit was 0.06 mg L−1. The relative standard deviation at 1 and 3 mg L−1 of cyanide concentration were 4.1 and 4.7%, respectively. The method was successfully applied to determination of cyanide in water and industrial waste waters, and the accuracy was examined through independent analysis by accepted method of pyridine-barbituric acid.

Spectrophotometric Determination of Cyanide Based on Berthelot Reaction

The proposed spectrophotometric method for the determination of cyanide involves conversion of cyanide to cyanate using sodium hypochlorite followed by acid hydrolysis to form ammonium sulphate. The formed ammonium sulphate is determined based on Berthelot reaction using salicylic acid, sodium hypochlorite, and sodium nitroprusside. The λmax for the formed dye is at 648 nm and the calculated molar absorptivity is 1.8 × 104 L mol−1 cm−1. Beer's law is obeyed in the concentration range 0–5 µg and the relative standard deviation is 2.2% for n = 10 at 0.3 ppm of CN−. The developed method was applied for the determination of cyanide in the hypochlorite/H2O2 treated electroplating effluents and sludges. The results obtained in the developed method compares well with the pyridine–barbituric acid method and by recovery studies of added cyanide.

Micellar enhanced cyanide ion determination in samples from synthetic organic processes

A method was developed for the recovery and determination of cyanide ion in organic sample matrices. To facilitate the solubilization of cyanide ions, cetyltrimethylammonium bromide (CTAB) was added at concentrations above the critical micelle concentration. Sample cyanation reaction products consisted of solvent mixtures of a hydroxynitrile in DMF-toluene or DMF-isopropylacetate (IPAC). Spectrophotometric determination of cyanide ion at 578 nm by the pyridine-barbituric acid method was automated by flow injection analysis. Recovery of cyanide ion from spiked samples was 93.2% in DMF-IPAC solvent matrix and 93.9% in DMF-toluene. Low alkali concentration was observed to favor solubilization of cyanide ion in the micellar solution.

Flow-injection determination of cyanide by detecting an intemediate of the pyridine-barbituric acid chromgonic reaction

A unstable intermediate product with peak absorbance at 494 nm was found in the reaction of cyanide with pyridine-barbituric acid reagent. The intermediate was applied to the determination of cyanide by reagent-injection flow-injection analysis. The calibration graph was linear over the range of0–4 μg ml −1 cyanide and the detection limit was 20 ng ml −1 cyanide; the relative standard deviation at 1.0 gmg ml −1 was 0.6% ( n=6) and the sampling rate was 60 h −1. Interface studies showed that the main inteferents are Co 2+, NI 2+, SCN -I - and formaldehyde. The proposed method was applied successfully to detemrine free cyanide in natural and waste water samples.

On-line monitoring of cyanide concentration via a gas membrane system in extractive metallurgical processes

The principle of molecular diffusion of gaseous HCN across a tubular microporous hydrophobic PTFE membrane directly immersed in an alkaline solution or in an aqueous mineral suspension has been applied to the design of an on-line sensing system for cyanide. It offers an efficient detection of “available” cyanide and does not require acidification and solution sampling in the reactor. Gaseous HCN diffused through the membrane is dissolved by a sodium hydroxide carder solution which is then submitted to a spectrophotometric analysis by the pyridine-barbituric acid method. The problems related to filtering of sludges are therefore overcome, and many chemical interferences can be eliminated. Complexation reactions of cyanide by metallic cations and the cyanide-consuming properties of sulphide minerals and ores were studied. This method allows the determination of concentrations down to ca. 6 × 10 −7 mol l −1 HCN + CN − in the reactor at Ph 10 with a 120-cm membrane tube and a carrier solution flow-rate of 8 cm 3 min −1.

Nitriles and isonitriles as interferents in cyanide determination in polluted waters

The interference of nitriles and isonitriles in cyanide determination was studied using the pyridine-barbituric acid direct spectrophotometric method or the same method after distillation of the sample, a microdiffusion-potentiometric (ion-selective electrode) also being used. Phenylacetonitrile, benzonitrile, acrylonitrile, iminodiacetonitrile and acetonitrile were tested as nitriles. Benzyl isocyanide butyl isocyanide and 1-[(isocyanomethyl)sulphonyl]-4-methylbenzene were assayed as isonitriles. It can be concluded that both nitriles and isonitriles should be considered as interferents in all the methods of cyanide determination studied. The level of interference generally increases with the ratio of interfering compound to cyanide and is greatest for low cyanide concentrations.

Interference Of Some Sulphur Compounds In The Analysis Of Aqueous Effluents For Cyanide

Abstract The unexpected and sporadic detection of cyanide in sour gas plant wastewaters and stack test scrubber solutions is investigated. It is shown that hydrogen sulphide and other reduced sulphur compounds are capable of producing a false positive in the standard method for cyanide analysis. The interference is unusual in that the response declines with increasing concentration of interferant. Introduction The pyridine-barbituric acid method for cyanide analysis in industrial wastewaters(1) is used widely, and is often a method recommended by statutory authorities where the wastewater is discharged to a natural watercourse. The limit of detection is commonly cited as 1 μg.dm−3. We have frequently seen reports of positive tests for cyanide by this method in sour gas plant wastewaters or stack test scrubber solutions. Such results are usually difficult to explain in terms of the processes involved, especially in the case of incinerator stack gases, where high temperatures (of the order of 500?C) prevail in the presence of excess oxygen. In the following, data are presented which suggest that the method may be limited to determining concentrations of CN-well above 40 μg.dm−3 in the presence of certain sulphur compounds, even when steps to remove interference from inorganic sulphides have been taken(1). A schematic of the reaction sequence is shown in Figure 1; accordingly, no positive interference is expected unless the interfering substance is capable of producing a compound analogous to the quaternized pyridine ring [A], which must also cleave to give the dye [C] with barbituric acid. In spite of this, the apparent detection of cyanidein sour gas plant incinerator stack gases led to the suspicion hat some sulphur compounds might give rise to an interference. Experimental In the present experiments, solutions of 5% and 10% w/v NaOH (ACS Reagent Grade, American Scientific &amp; Chemical Co.) were prepared in deionized water and were spiked in two or more replicates with COS, H2S, CS, and ethyl methyl sulphide. In the case of gases, the material was added slowly by means of a syringe, such that no visible gas bubbles escaped the solution. The liquids were added to the agitated aqueous solution by means of a microsyringe. No phase separation was to be expected at the concentrations used, and none was observed. The composition of CO2, H2S (Matheson Gas Products, 99.5%) CS2 (J.T. Baker Analyzed Reagent, 99+ %) and methyl ethyl sulphide (Canadian Western Natural Gas Co. Ltd., 98%) were known to be essentially free of HCN, such that a 1 μg.dm−3 concentration of CN− in solution could not be reached in this experiment. All solutions were stored in acid washed, deionized water rinsed amber glass bottles, and together with NaOH blanks, numbered at random. The numbering sequence was withheld from the analyst, who followed the "Standard Methods"(1) pyridine-barbituric acid procedure for cyanide; the method was amended in accordance with EPA method 335.3(2), to permit the use of a Technicon auto-analyzer. The V.V. lamp was shut off, and a distillation device described by Conetta et al. (3) was incorporated into the circuit.

An evaluation and modification of a microdiffusion method for the emergency determination of blood cyanide.

Data are presented to indicate the recovery one can expect with different diffusion times in the microdiffusion procedure for the determination of cyanide using Conway cells. Using a predetermined recovery factor, a diffusion time of 10 min is recommended for emergency situations. In the use of the pyridine-barbituric acid reagent for color development, it was found that the reagents could be added as rapidly as is manually possible and that while the color complex begins to fade as soon as developed, the error after 4 to 10 min ranges from 3 to 9%.

The effect of barbituric acid concentration in the spectrophotometric determination of cyanide and thiocyanate by the pyridine-barbituric acid method

The Konig reaction forms the basis of many analytical methods including those for the determination of chlorine, nicotinic acid, thiocyanate and cyanide. The colorimetric methods have, however, been plagued with various problems such as the use of hazardous, often carcinogenic compounds, and the instability of the final color formed as well as of the color reagent itself.

A Discussion of the Method for the Determination of Free Cyanide in Water and Wastewater by Microdiffusion

ASTM Committee D-19 on Water has recently published a method for the determination of free cyanide in water and wastewater by microdiffusion. This method (ASTM Method for the Determination of Free Cyanide in Water and Wastewater by Microdiffusion [ASTM D 4282-83]) is based on adjusting a sample in a microdiffusion cell to pH 6.0. All cyanides present that can form hydrogen cyanide (HCN) are defined as free cyanide by this method. The HCN is allowed to diffuse for 4 h into the center chamber of the microdiffusion cell, which contains sodium hydroxide. The cyanide ion thus formed is chlorinated and then reacted with pyridine-barbituric acid. A colorimetric measurement is made to determine the cyanide level. The round robin data obtained show percent biases of −1.9, −5.0, and −4.2% at concentrations of 32, 80, and 144 μg/L of CN−, respectively, in Reagent Type II water. Data are shown from the original investigation that established the method parameters. Additional pertinent work is documented.

Simultaneous reaction rate spectrophotometric determination of cyanide and thiocyanate by use of the pyridine-barbituric acid method

La methode est basee sur le fait que la vitesse de reaction entre thiocyanate et chloramine T varie fortement avec le pH tandis que la reaction entre cyanure et chloramine T est rapide et est independante du pH dans un grand domaine de pH

Spectrophotometric determination of cyanide with pyridine and 4,4′-diaminostilbene-2,2′-disulphonic acid

The use of 4,4′-diaminostilbene-2,2′-disulphonic acid (amsonic acid) as an alternative coupling agent to barbituric acid in the determination of cyanide is proposed. Amsonic acid possesses cost and availability advantages, and the stability of the pyridine-amsonic acid reagent is greater than that of pyridine-barbituric acid (17 d versus 24 h). The method can be applied at a wide range of cyanide concentrations, from 0.01 to 0.10 µg ml–1 at 490 nm and from 0.10 to 0.60 µg ml–1 at 545 nm. The detection limit is about the same order of magnitude as the standard method.

Preparation of pyridine pyrazolone reagent and pyridine-barbituric acid reagent for spectrophotometric determination of cyanide

A modification of the preparation of two reagents for the determination of cyanide is described. The reagents are easier to prepare and the colors developed fade less rapidly than with the usual reagents.