UNC-WRRI-92-265 DEVELOPMENT OF ANALYTICAL METHODS FOR THE IDENTIFICATION OF ORGANIC NITROGEN CHLORINATION BY-PRODUCTS IN NORTH CAROLINA SURFACE WATERS James k Jersey and J. Donald Johnson Department of Environmental Science and Engineering School of Public HeaIth University of North Carolina at Chapel Hill Chapel Hill, North Carolina 27514 The research on which this report is based was financed by the United States Department of the Interior, Geological Survey, through the North Carolina Water Resources Research Institute. Contents of this publication do not necessarily reflect the views and policies of the United States Department of Interior, nor does mention of trade names or commercial products constitute their endorsement by the United States Government. Agreement No. l4-O8-OOOl-GJ 580 UNC-WRRI Project No. 70104 USGS Project No. 10 (FY90) ACKNOWLEDGEMENT The authors wish to express their thanks to the U.S. Department of Interior and The University of North Carolina Water Resources Research Institute for funding the research summarized in this report. We also wish to acknowledge the Department of Environmental Science and Engineering, University of North Carolina at Chapel Hill for the use of their facilities. We wish to extend special thanks to Dr. Peter Kissinger of Bioanalytical Systems for providing the thin-layer flow through electrochemical cell used in this work. Dr. Jersey wishes to recognize Mr. Randall Goodman of the School of Public Health Machine Shop for his invaluable assistance in repairs and maintenance of HPLC instrumentation. ABSTRACT The goal of this research was to develop an analytical method for selectively and sensitively detecting N-chloramines in dilute aqueous systems. The organic N-chlor- amines comprise a class of chlorination by-products which is justifiably of concern since they interfere in measurements of free chlorine and monochloramine (NH,CI) and because of their potentially deleterious environmental and human health effects. The method developed exploited the mild conditions of high-performance liquid chro- matography (HPLC)and reductive amperometry for selective and sensitive detection of these relatively unstable oxidant compounds. Because large overpotentials were required for their direct amperometric detection, post-column reaction with iodide to produce iodine was employed. Using this technique, organic N-chloramines were measurable at concentrations down to lo-' M by direct injections. In addition, detector response was highly reproducible and could be calibrated over concentration ranges greater than three orders of magnitude with minimum error. This allowed quantitative measurement of oxidants separated by HPLC. By this technique, a number of organic N-chloramines were tentatively identified in a chlorinated primary wastewater. Analyses of chlorinated surface waters and wastewater final effluents demonstrated the clear dominance of inorganic N-chlorarnines among the combined residual chlorine pool in these much more dilute systems. A number of small and unidentified peaks were also detected in these systems. (Key words: chlorination; surface water; wastewater; N-chloramines; cyclic voltammetry; high-performance liquid chromatography; UV detection; electrochemical detection; post-column reaction; on-line enrichment) TABLE OF CONTENTS ACKNOWLEDGEMENTS ......................................... i ABSTRACT ..................................................... iii SUhlhlARY AND CONCLUSIONS ............................... xvii RECOMMENDATIONS .......................................... xxi INTRODUCTION ................................................ 1 OVERVIEW OF HEALTH CONCERNS AVD NEED FOR RESEARCH . 1 OVERVIEW OF REACnONS OF AQUEOUS CHLORINE ............ 2 LITERATURE REVIEW ........................................... 5 REACTIONS OF AQUEOUS CHLORINE .......................... 5 Inorganic Oxidations and Reactions with Organic Carbon .......... 5 Reactions with Nitrogenous Compounds ....................... 7 Kinetics of Formation of N-chloramino Compounds .......... 7 Hydrolysis ......................................... 8 Chlorine Transfers .................................. 9 Disproportionation .................................. 9 The Breakpoint Phenomenon ......................... 10 OCCURRENCE AND SIGNIFICANCE OF N-CHLORO ORGANIC COMPOUNDS .............................................. 11 Occurrence of Nitrogenous Compounds in Water ................ 12 Drinking Water .................................... 12 Surface Water ..................................... 13 Wastewater....................................... 13 N-chloro Compounds Identified in Chlorinated Waters and Model Compound Solutions .......................... 14 Sigmficance of Organic Nitrogen in Water Chlorination ........... 15 CURRENT ANALYTICAL METHODS FOR CHLORINE AND CKLORINEPRODUCEDOXIDANTS ........................... 16 Standard Methods ....................................... 16 Direct Chromatographic Methods Applied to the Analysis of N-Chloramines .................................. 19 Indirect Chromatographic Methods Applied to the Analysis of N-chlorarnines ................................... 20 ELECTROCHEMISTRY OF INORGANIC AND ORGANIC N-CKLORAMINES .......................................... 21 EXPERIMENTAL APPROACH ................................... 27 OVERVIEW OF DESIGN AND RATIONALE OF RESEARCH ........ 27 EXPERIMENTAL APPROACH AND OBJECTIVES ................. 27 RATIONALE AND SELECITON OF MODEL COMPOUNDS ......... 29 MATERIALS AND METHODS ................................... 33 REAGENTS ................................................ 33 MEASUREMENT OF OXIDANT CONCENTRATIONS .............. 33 PREPARATION OF CHLORINATED MODEL COMPOUND SOLUTIONS .......................................... 34 PROCEDURES FOR SPECI'ROPHOTOMETRIC MEASUREMENTS ... 34 CYCLICVOLTAMMETRY .................................... 35 HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY .............. 36 Pumps and Columns ................................. 36 Detection ........................................38 Injection ......................................... 40 COLLECTION AND CHLORINATION OF WASTEWATER AND SURFACE WATER SAMPLES .......................... 42 RESULTS Ah?) DISCUSSION .......................... ANALYSIS OF N-CHLORAMINES BY HPLC WITH UV DETECTION ..... 43 Preliminary Chromatographic Assessment .................... 43 Examination of N-Chloramine Mixtures ...................... 46 Application to Breakpoint Chlorination of a Tertiary Mixture ......... 51 Conclusions of N-Chloramine Analysis by HPLC-UV ............. 52 ELECTROCHEMICAL BEHAVIOR OF CHLORINE. IODINE AND INORGANIC AND ORGANIC N-CHLORAMINES IN AQUEOUS SOLUTION ...............................54 Electrode Materials and Background Currents ................. 55 Aqueous Free Chlorine ................................56 Aqueous Iodine ....................................56 Organic and Inorganic N-Chloramines ....................... 60 Conclusions of Electrochemical Reduction Studies ............... 65 ANALYSIS OF N-CHLORAMINES BY HPLC 'WITH POST-COLUMN REACTION ELECTROCHEMICAL DETECTION .............. 66 Optimization of Post-Column Reaction Detector Design ............ 67 Chromatography ............................... 67 Background Currents ............................. 67 Applied Potential ............................... 70 Kinetic Considerations ............................ 70 Detector Volume ............................... 72 Standard Post-Column Reaction Detector Conditions ......... 73 Post-Column Reaction Detector Evaluation Employing Model Compounds .............................. 74 Precision and Sensitivity ........................... 74 Calibration ................................... 75 Detector Durability ..............................79 vii Application to Analysis of an N-Chlorarnine Mixture Subjected to Breakpoint Chlorination ................... 79 Conclusions of HPLC with Electrochemical Detection Method Development ............................ 82 ANALYSIS OF N-CHLORAMINES IN CHLORINATED WASTEWATER AND SURFACE WATER BY ON-LINE ENRlCHMENT HPLC/EC ....................... 82 Analysis of N-Chlorarnines by On-Line Enrichment .............. 82 Applications to Model Compound Solutions ................... 86 Application to Chlorinated Primary Wastewater ................. 88 Application to Chlorinated Wastewater Final Effluent ............. 93 Application to Chlorinated Surface Waters .................... 95 Conclusions of Applications Studies ....................... 103 LIST OF REFERENCES ............................. 104 LIST OF PUBLICATIONS ........................... 121 GLOSSARY OF TERMS Ah?) ABBREVIATIONS ............ 122 APPEWIX A: GERMICIDAL PROPERTIES OF N-CHLORAMINES .......... 125 APPLImIX B: INTERFERENCES IN THE MEASUREMENT OF FREE AVAILABLE CHLORINE ........................ 129 APPLISIIX C: TOXICITY OF INORGANIC AND ORGANIC N-CHLORAMLNES . 135 APPENDIX D: HYPOCHLOROUS ACID AND N-CHLORAMINES AS MICROBIAL TOXINS IN ISOLATED NEUTROPHILS .......... 137 APPL1'DIX E: EFFECT OF POST-COLUMN REAGENT COMPOSITION UPON DETECTION OF N-CHLORAMINES ................. 139 APPENDIX F: ANALYSIS OF N-CHLOROGLYCYLGLYCINE BY HPLC WTTH POST-COLUMN REACT'9N DETECTION ............. 145 viii APPENDIX G: RETENTION TIME SUMMARY FOR MODEL N-CHLOR- AMINES ANALYZED BY POST-COLUMN REACTION ELECTRO- CHEMICAL DETECTION . 147 LIST OF FIGURES Figure 1. Reactions and by-products formed during disinfection by aqueous chlorine---- - ..........................................- - 6 Figure 2. Breakpoint cume