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Related Concept Videos

Aldehydes and Ketones with HCN: Cyanohydrin Formation Overview01:32

Aldehydes and Ketones with HCN: Cyanohydrin Formation Overview

Cyanohydrins are compounds that contain –CN and –OH groups on the same carbon atom. They are formed by the nucleophilic addition of the cyanide ions to the carbonyl group. Cyanide ions are highly basic and nucleophilic and can be generated from HCN under aqueous conditions. However, since HCN is a weak acid, the number of cyanide ions generated is very small. Hence, a small amount of base or KCN/NaCN is added to HCN to increase the concentration of the cyanide ions in the reaction mixture.
Sample Handling01:02

Sample Handling

Transportation of samples from the collection point to the laboratory, as well as storage and preservation techniques, are crucial for maintaining sample integrity and ensuring accurate and reliable test results.
Samples should be transported carefully from collection points to the laboratory. They should be properly sealed and clearly labeled to prevent cross-contamination. To preserve the sample integrity, optimal temperature conditions during transport are essential. This could involve using...
Aldehydes and Ketones with HCN: Cyanohydrin Formation Mechanism01:10

Aldehydes and Ketones with HCN: Cyanohydrin Formation Mechanism

Cyanohydrins are formed when cyanide nucleophiles and carbonyl compounds like aldehydes and ketones react. A strong base, the cyanide ion, catalyzes cyanohydrin formation. The ions are generated from HCN under aqueous conditions. Once the cyanide ions are generated, the first step involves the nucleophilic attack of the cyanide ions on the electrophilic carbonyl carbon. This attack shifts the π electrons from the C=O to the oxygen atom forming the alkoxide ion intermediate. The alkoxide anion...
Precipitation and Co-precipitation01:17

Precipitation and Co-precipitation

Precipitation and coprecipitation methods can be used to separate a mixture of ions in a solution. In qualitative inorganic analysis, ions that form sparingly soluble precipitates with the same reagent are separated based on the differences in solubility products. For example, consider the separation of Cu(II) and Fe(II) ions by precipitation as insoluble sulfides. First, copper(II) sulfide is precipitated by the addition of acidic H2S, where the dissociation of H2S is suppressed. Adding H2S...
Determining the pH of Salt Solutions04:08

Determining the pH of Salt Solutions

The pH of a salt solution is determined by its component anions and cations. Salts that contain pH-neutral anions and the hydronium ion-producing cations form a solution with a pH less than 7. For example, in ammonium nitrate (NH4NO3) solution, NO3− ions do not react with water whereas NH4+ ions produce the hydronium ions resulting in the acidic solution. In contrast, salts that contain pH-neutral cations and the hydroxide ion-producing anions form a solution with a pH greater than 7. For...
Formation of Complex Ions03:45

Formation of Complex Ions

A type of Lewis acid-base chemistry involves the formation of a complex ion (or a coordination complex) comprising a central atom, typically a transition metal cation, surrounded by ions or molecules called ligands. These ligands can be neutral molecules like H2O or NH3, or ions such as CN− or OH−. Often, the ligands act as Lewis bases, donating a pair of electrons to the central atom. These types of Lewis acid-base reactions are examples of a broad subdiscipline called coordination...

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Early Detection of Cyanobacterial Blooms and Associated Cyanotoxins using Fast Detection Strategy
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Published on: February 25, 2021

False cyanide formation during drinking water sample preservation and storage.

Michael F Delaney1, Charles Blodget, Corinna E Hoey

  • 1Massachusetts Water Resources Authority (MWRA), 190 Tafts Avenue, Winthrop, Massachusetts 02152, USA. mike.delaney@mwra.state.ma.us

Environmental Science & Technology
|January 19, 2008
PubMed
Summary

Cyanide can form in drinking water samples during storage and preservation. Formaldehyde, an ozone disinfection byproduct, can contribute to cyanide formation in stored water samples.

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Area of Science:

  • Environmental Science
  • Analytical Chemistry
  • Water Quality

Background:

  • Disinfection byproducts can impact water quality.
  • Accurate cyanide testing in drinking water is crucial.

Purpose of the Study:

  • To investigate cyanide formation in treated drinking water during sample preservation and storage.
  • To identify factors contributing to cyanide generation in water samples.

Main Methods:

  • Bench-scale experiments with formaldehyde-spiked and unspiked treated tap water samples over six months.
  • On-site experiments at a water treatment plant using various sample handling procedures.
  • Analysis of cyanide concentrations after different preservation and storage durations.

Main Results:

  • Cyanide was detected in formaldehyde-spiked and unspiked samples after storage.
  • Samples preserved using the conventional method (pH > 12) showed detectable cyanide.
  • Cyanide formation was linked to sample container preservation and storage conditions.

Conclusions:

  • Cyanide can form in treated drinking water during conventional preservation and storage.
  • Formaldehyde, an ozone disinfection byproduct, plays a role in cyanide formation.
  • Standard sample handling procedures may lead to artifactual cyanide detection.