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

Abstract

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...

Bis(trichloromethyl)carbonate (BTC, Triphosgene): A Safer Alternative to Phosgene?

“…Methods for analyzing BTC have been published using a Forster resonance energy transfer (FRET) method 35 and a reaction system consisting of pyridine and dimethylbarbituric acid for in situ detection and estimation, allowing selective detection in nanomolar quantities of analyte. 36 However, because of the instability of the analyte under the given circumstances, the GLP-compliant validation of this method failed. 4 OSHA derivatization method no.…”

Development of a Novel Spectrophotometric Method Based on Diazotization- Coupling Reaction for Determination of Bisphenol A

“…To develop such a test strip, we employed a simple method of making test strips. 39 A filter paper was first coated with a mixture solution of SMZ (19.2 μg mL -1 ), HCl (6.4 × 10 -2 mol L -1 ), and NaNO 2 (28.0 μg mL -1 ) in ice-water bath, which was then dried with freezer dryer. It should be immediately stored to the refrigerator when not used.…”

Acute nose-only inhalation exposure of rats to di- and triphosgene relative to phosgene

“…Therefore, a precise determination of the mass-loss during the exposure period was not possible. A sensitive detection method for di-and triphosgene by spectrophotometry has been described (Joy et al, 2009). Attempts were made to duplicate this method using bis(1,3-dimethyl barbituric acid) pentamethine oxonol as the recommended reference standard (analyte).…”