Identifying Acids Through Novel Plastic Containers

Acid throwing is a historical method for retribution against women but has become a modern threat of another nature. Concentrated acids and other corrosive substances have appeared as modern tools of social violence. Offenders use common plastic containers such as lemon juice squeeze bottles which have openings that create a powerful directional spray.

Phosphoric and sulfuric acids have been chosen for analysis here as a result of their highly corrosive nature and because phosphoric, sulfuric and nitric acids are the most commonly used in acid attacks in London.

In 2017, the reported incidences of acid attacks in the UK averaged out at twice a day which is a remarkable number. Regulation and detection of acids may help to prevent this social scourge.

Sample

The Raman spectra of eight strongly corrosive acids and bases were collected through the material of a plastic squeeze lemon and in a vial.

Sample Preparation

For initial analysis, all of the acids and bases were sampled in glass vials. The sensitivity of Raman to protonation state is shown by polyprotic acid dilution. Phosphoric acid was then introduced into a plastic squeeze lemon and then analyzed through the plastic. Sulfuric acid underwent the same treatment.

The majority of the acids and bases were sampled in their concentrated state. Sodium hydroxide, however, was prepared as a saturated aqueous solution. Water was used in order to prepare acid dilutions.

Analysis

The Vial Holder attachment on Mira DS was used to analyze samples in glass vials. In order to collect spectra through the side of the plastic squeeze lemon, the Long Working Distance (LWD) attachment (focal length = 8mm) was used.

Parameters

Results

For each acid/base, a distinct spectrum was acquired. Peak presence from both acid and container (High Density Polyethylene, PET) was confirmed by comparison of standard and experimental spectra. These results are supported by MiraCal DS Mixture Matching analysis, below, which identifies both acid and PET.

This information has been sourced, reviewed and adapted from materials provided by Metrohm AG.

For more information on this source, please visit Metrohm AG.