An HPLC Method with UV Detection, pH Control, and Reductive Ascorbic Acid for Cyanuric Acid Analysis in Water

Abstract

Every year over 250 million pounds of cyanuric acid (CA) and chlorinated isocyanurates are produced industrially. These compounds are standard ingredients in formulations for household bleaches, industrial cleansers, dishwasher compounds, general sanitizers, and chlorine stabilizers. The method developed for CA using high-performance liquid chromatography (HPLC) with UV detection simplifies and optimizes certain parameters of previous methodologies by effective pH control of the eluent (95% phosphate buffer: 5% methanol, v/v) to the narrow pH range of 7.2-7.4. UV detection was set at the optimum wavelength of 213 nm where the cyanuric ion absorbs strongly. Analysis at the lower pH range of 6.8-7.1 proved inadequate due to CA keto-enol tautomerism, while at pHs of <6.8 there were substantial losses in analytical sensitivity. In contrast, pHs of >7.4 proved more sensitive but their use was rejected because of CA elution at the chromatographic void volume and due to chemical interferences. The complex equilibria of chlorinated isocyanurates and associated species were suppressed by using reductive ascorbic acid to restrict the products to CA. UV, HPLC-UV, and electrospray ionization mass spectrometry techniques were combined to monitor the reactive chlorinated isocyanurates and to support the use of ascorbic acid. The resulting method is reproducible and measures CA in the 0.5-125 mg/L linear concentration range with a method detection limit of 0.05 mg/L in water.

Electrochemical Degradation of Atrazine in Aqueous Solution at a Platinum Electrode

“…Several degradation routes of atrazine and similar compounds have been proposed. These routes involve free radicals [12][13][14]. The following reactions have been proposed:…”

Determination of Cyanuric Acid in Milk Powder by Anion-exchange Chromatography

“…[1][2][3] CA and melamine have the same parent structure (Fig. 1), both belonging to the group of triazine nitrogen heterocylic organic compounds.…”

“…Several methods have been reported for the analysis of CA in swimming pool water, such as gas chromatography (GC), 6 gas chromatography-mass spectrometry (GC-MS), 7 liquid chromatography (LC), 1,3,8 liquid chromatography-mass spectrometry (LC-MS) [9][10][11][12][13] and ion-pair LC. 14 There has been no report about the determination of CA by ion chromatography (IC).…”

Applicability of Liquid Chromatography with Time-of-Flight Mass Spectrometric Detection for Determination of Cyanuric Acid in Soil

“…The HPLC-UV methods using the modified silica or porous graphitic carbon columns, phosphate buffer eluents, and UV detection at wavelengths of 200 nm to 220 nm have been developed for determining CA in water, 1,15,16 cereal flours, 17 pet food, 18 and animal feed samples. 19 The UV-detection has also been applied for the determination of free CA in nylon by ion-exclusion chromatography.…”

“…In solution, it occurs as a mixture of keto (isocyanuric acid) and enol tautomers, the latter form being stable under alkaline conditions (pH > 7.2) (Figure 1). 1 CA is an industrial chemical whose derivatives are widely used as disinfectants, sanitizers, and bleaches (chloroisocyanurates), cross-linking and curing agents (triallyl and tris(hydroxyethyl) isocyanurates), ingredients of weather resistant powder coatings (tris(epoxypropyl)isocyanurate), and fire retardants in plastics (melamine cyanurate). 2 CA is used to stabilize the chlorine disinfectant in swimming pools because it is able to form N-chlorinated isocyanurates and prevent the rapid photolytic degradation of residual chlorine.…”