Phthalic Acid

High Performance Liquid Chromatography (HPLC) Method for Analysis of Phthalic Acid on Primesep B by SIELC Technologies

Separation type: Liquid Chromatography Mixed-mode SIELC Technologies

 High Performance Liquid Chromatography (HPLC) Method for Analysis of Phthalic Acid

Phthalic acid is an aromatic dicarboxylic acid with the chemical formula C₆H₄(CO₂H)₂. It consists of a benzene ring with two carboxylic acid groups (-COOH) attached to adjacent carbon atoms (in the ortho position). It is mainly produced by the oxidation of naphthalene or o-xylene.

Uses
Phthalic acid is primarily used as a precursor to other chemicals, including:

Phthalic anhydride: Used in the production of plasticizers for PVC (polyvinyl chloride).
Alkyd resins: Important in the manufacture of paints and coatings.
Dyes and pigments: Phthalic acid derivatives are often used in the production of dyes.

Phthalic Acid can be retained, separated and analyzed using a Primesep B mixed-mode stationary phase column. The analysis employs a gradient method with a simple mobile phase comprising water, acetonitrile (MeCN), and phosphoric acid as a buffer. This method allows for detection using UV 200 nm.

You can find detailed UV spectra of Phthalic Acid and information about its various lambda maxima by visiting the following link.

For optimal results in HPLC analysis, it is recommended to measure absorbance at a wavelength that matches the absorption maximum of the compound(s) being analyzed. The UV spectrum shown can assist in selecting an appropriate wavelength for your analysis. Please note that certain mobile phases and buffers may block wavelengths below 230 nm, rendering absorbance measurement at these wavelengths ineffective. If detection below 230 nm is required, it is recommended to use acetonitrile and water as low UV-transparent mobile phases, with phosphoric acid and its salts, sulfuric acid, and TFA as buffers.
For some compounds, the UV-Vis Spectrum is affected by the pH of the mobile phase. The spectra presented here are measured with an acidic mobile phase that has a pH of 3 or lower.

Phthalic acid, phthalic acid isomers, and related products present in the production of phthalic acid were separated on the Primesep D column, based on reversed-phase and in-exchange mechanisms. Neutral, hydrophobic compounds of the phthalic acid production are retained by a reversed-phase mechanism, and phthalic acid and other acidic compounds are retained by a combination of reversed-phase and anion-exchange mechanisms. Resolution and selectivity of this separation can be modified by varying the amount of acetonitrile, buffer concentrations, and buffer pH. This method can be used for monitoring the production cycle of phthalic acid and related impurities.

Phthalic acid, isophthalic acid and terephthalic acid are all isomers of each other. Being structurally similar, they can present difficulties to reverse-phase HPLC separation. Methods that require high organic concentrations in the mobile phase can cause dewetting in many reverse-phase columns. SHARC 1 column can be operated in anhydrous conditions and uses hydrogen bonding as the mechanism of separation. Here, phthalic acids were separated in pure acetonitrile (ACN), with the ability to adjust retention times by adding methanol (MeOH) to the mobile phase with formic acid and ammonium formate as buffer, making the method MS-compatible. Can also be UV detected at 270nm.

Primesep D separates organic acids such as fumaric, benzoic, phthalic, naphthoic, and maleic acids by a mixture of anion exchange and reversed phase. Retention times and elution order can be changed by adjusting the percentage of acetonitrile in the mobile. This can not be done by traditional ion-exchange and ion-exclusion chromatography. The HPLC separation uses a mobile phase of water, acetonitrile (MeCN, ACN) and trifluoroacetic acid (TFA) and UV detection at 250 nm.

Primesep B combines a hydrophobic, reversed-phase mechanism with ion exchange to separate the diacids, fumaric, benzoic, phthalic, naphthoic, and maleic acids. Changing the acetonitrile content of the mobile phase reverses the peak order for naphthoic and maleic acids. Primesep B combines reversed-phase and anion-exchange mechanism with a mobile phase of water, acetonitrile (MeCN, ACN) and trifluoracetic acid (TFA) and UV detection at 250 nm.