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AN HPLC METHOD WITH UV DETECTION, PH CONTROL, AND REDUCTIVE ASCORBIC ACID FOR CYANURIC ACID ANALYSIS IN WATER
Citation:
Cantu, R, O M. Evans, J A. Shoemaker, A P. Dufour, AND A. Dufour. AN HPLC METHOD WITH UV DETECTION, PH CONTROL, AND REDUCTIVE ASCORBIC ACID FOR CYANURIC ACID ANALYSIS IN WATER. Analytical Chemistry 72(23):5820-5828, (2000).
Impact/Purpose:
Develop a method to determine the volume of recreational water ingested by relating the quantity imbibed to the level of a chemical biomarker measured in urine.
Description:
Every year over 250 million pounds of cyanuric acid (CA) and chloroisocyanurates 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 control of pH 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 213 nm wavelength intercept 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 < 6.8 there were substantial losses in analytical sensitivity. In contrast, pHs > 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 was suppressed using reductive ascorbic acid to restrict the products to CA. UV, HPLC-UV, and electrospray ionization/mass spectrometry were combined to monitor reactive chlorinated isocyanurates and to support the use of reductive ascorbic acid. The resulting method measures CA in the 0.5-125 mg/L linear concentration range with a method detection limit of 0.05 mg/L in water.