Identification and colorimetric determination of organic cyanates in nanomolar quantities

Kohn, Joachim; Albert, Elizabeth C.; Wilchek, Meir; Langer, Robert

doi:10.1021/ac00127a058

Cited by 8 publications

(5 citation statements)

References 34 publications

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“…At pH 9, the standard pH for activation, greater than 95% of the CDAP had hydrolyzed within 3 min. We confirmed these results by directly assaying for CDAP using the dimethylbarbituric acid assay [19] (data not shown). In a separate experiment, we assayed for CDAP at 310 nm after 30 s at each pH (Figure 3b).…”

Section: Cdap Stability As a Function Of Phsupporting

confidence: 63%

Activation of Soluble Polysaccharides with 1-Cyano-4-Dimethylaminopyridine Tetrafluoroborate (CDAP) for Use in Protein–Polysaccharide Conjugate Vaccines and Immunological Reagents. III Optimization of CDAP Activation

2020

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CDAP (1-cyano-4-dimethylaminopyridine tetrafluoroborate) is employed in the synthesis of conjugate vaccines as a cyanylating reagent. In the published method, which used pH 9 activation at 20 °C (Vaccine, 14:190, 1996), the rapid reaction made the process difficult to control. Here, we describe optimizing CDAP activation using dextran as a model polysaccharide. CDAP stability and reactivity were determined as a function of time, pH and temperature. While the rate of dextran activation was slower at lower pH and temperature, it was balanced by the increased stability of CDAP, which left more reagent available for reaction. Whereas maximal activation took less than 2.5 min at pH 9 and 20 °C, it took 10–15 min at 0 °C. At pH 7 and 0 °C, the optimal time increased to >3 h to achieve a high level of activation. Many buffers interfered with CDAP activation, but DMAP could be used to preadjust the pH of polysaccharide solutions so that the pH only needed to be maintained. We found that the stability of the activated dextran was relatively independent of pH over the range of pH 1–9, with the level of activation decreased by 40–60% over 2 h. The use of low temperature and a less basic pH, with an optimum reaction time, requires less CDAP, improving activation levels while making the process more reliable and easier to scale up.

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Section: Cdap Stability As a Function Of Phsupporting

confidence: 63%

Activation of Soluble Polysaccharides with 1-Cyano-4-Dimethylaminopyridine Tetrafluoroborate (CDAP) for Use in Protein–Polysaccharide Conjugate Vaccines and Immunological Reagents. III Optimization of CDAP Activation

2020

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“…As shown earlier by Kohn et al ,[17] for organic cyanates and carbodiimides, the species at 598 nm is the pentamethine oxonol dye that is formed by the reaction with DBA in pyridine-H 2 O. From the proposed mechanism, phosgene precursors should react with DBA similarly to the cyanates and carbodiimides to produce the same oxonol dye.…”

Section: Resultsmentioning

confidence: 61%

“…Kohn and coworkers developed a spectrophotometric method for the detection of organic cyanates[17] and carbodiimides[18] based on work by König [19] on colored oxonol dyes. They have shown that organic cyanates react with dimethylbarbituric acid in pyridine-water to produce an intensely colored purple oxonol dye.…”

mentioning

confidence: 99%

Simple, rapid, and highly sensitive detection of diphosgene and triphosgene by spectrophotometric methods

Joy

Anim-Danso

Kohn

2009

Talanta

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Methods for the detection and estimation of diphosgene and triphosgene are described. These compounds are widely used phosgene precursors which produce an intensely colored purple pentamethine oxonol dye when reacted with 1,3-dimethylbarbituric acid (DBA) and pyridine (or a pyridine derivative). Two quantitative methods are described, based on either UV absorbance or fluorescence of the oxonol dye. Detection limits are ~ 4 µmol/L by UV and <0.4 µmol/L by fluorescence. The third method is a test strip for the simple and rapid detection and semi-quantitative estimation of diphosgene and triphosgene, using a filter paper embedded with dimethylbarbituric acid and poly(4-vinylpyridine). Addition of a test solution to the paper causes a color change from white to light blue at low concentrations and to pink at higher concentrations of triphosgene. The test strip is useful for quick on-site detection of triphosgene and diphosgene in reaction mixtures. The test strip is easy to perform and provides clear signal readouts indicative of the presence of phosgene precursors. The utility of this method was demonstrated by the qualitative determination of residual triphosgene during the production of poly(Bisphenol A carbonate). Keywordstriphosgene; phosgene; spectrophotometry; spectrofluorimetry; test strip; poly(Bisphenol A carbonate)Phosgene and its safer derivatives -diphosgene and triphosgene -are industrially important chemicals used in the manufacture of polyurethanes [1] and polycarbonates [2] and in the synthesis of various active pharmaceutical ingredients. [3] This market sector generates approximately 8 million tons of products and the global demand for phosgene is about 5 million tons per year.[4] Phosgene is very corrosive and has a high acute toxicity if inhaled. The danger of inhalation poisoning is particularly grave, since phosgene can be lethal before its odor is recognizable. [5] Current methods for the detection of phosgene are predominantly electrochemical and spectrophotometric. [6,7] A cellulose tape impregnated with 4-nitrobenzylpyridine and benzylaniline has been developed for monitoring phosgene in air. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. They have shown that organic cyanates react with dimethylbarbituric acid in pyridine-water to produce an intensely colored purple oxonol dye. The mechanism of color formation is based on the nucleophilic reaction of pyridine with an activated electrophilic species. This reaction is also used for the detection and determination of HCN. NIH Public Access Author Manuscript[20] A similar reaction between phosg...

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“…The purple dye which results when aryl cyanates react with pyridine and 1,3-dimethylbarbituric acid is used to determine the cyanates by a colorimetric method with a standard deviation of 2%. Isocyanates and inorganic isocyanates do not interfere (191). A flow injection system utilizing infrared spectrophotometric detection has been developed for the determination of phenyl isocyanate in solution.…”

Section: Cyanates and Isocyanatesmentioning

confidence: 99%

Functional group analysis

Smith¹,

Patterson²

1988

Anal. Chem.

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Identification and colorimetric determination of organic cyanates in nanomolar quantities

Cited by 8 publications

References 34 publications

Activation of Soluble Polysaccharides with 1-Cyano-4-Dimethylaminopyridine Tetrafluoroborate (CDAP) for Use in Protein–Polysaccharide Conjugate Vaccines and Immunological Reagents. III Optimization of CDAP Activation

Activation of Soluble Polysaccharides with 1-Cyano-4-Dimethylaminopyridine Tetrafluoroborate (CDAP) for Use in Protein–Polysaccharide Conjugate Vaccines and Immunological Reagents. III Optimization of CDAP Activation

Simple, rapid, and highly sensitive detection of diphosgene and triphosgene by spectrophotometric methods

Functional group analysis

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