DEVELOPMENT AND APPLICATION OF COLORIMETRlC MICROASSAY FOR DETERMINING BORON- CONTAINING COMPOUNDS

azomethine-H methods are based on ABSTRACT photometry (1,9,33). AWPA A2-98 (1) This paper describes the development of a microsssay for boron and the application macroassay method has been used in of this microassay for evaluating leachability of boron by post-treatment of southern several studies to measure boron conpine with the calcium precipitating agent NHA (N'N-napthaloylhydroxylamine). The tent in wood and leachates (8,13,30,32). microsssay method for quantitative estimation of boron content in treated wood and In the microassay method we have leachates is a microadaptation of the colorimetric azomethine-H method. The primary adapted, each well is read by advantages of this microassay method are that it uses fewer reagents, uses smaller samabsorbance, avoiding the time-consum­ ple volumes, and conserves time for analysis when a large number of tests are required. ing reading step necessary in AWPA Wood blocks were treated with boric acid, disodium octaborate tetrahydrate (DOT), A2-98 standard method (1), which uses and NHA solutions at several concentrations. Boron leaching performance was evalua spectophotmeter with cuvettes. ated on the blocks using AWPA E11-97 standard method. Blocks treated sequentially The use of broad-spectrum biocides with DOT and then with 0.5 or 1.0 percent NHA solutions showed -30% less boron for wood preservation is being limited leaching, whereas similar treatment with boric acid and 0.1% NHA solutions did not because they include components that enhance boron retention compared with the blocks treated with only boric acid. We conare toxic to mammals and other non­ clude that precipitation of NHA at higher concentrations decreases or limits boron target organisms in the environment. leaching. These concerns have provided incentive to look for new wood preservatives. Ideally, new preservative systems might incorporate a simple, water-soluble Assay systems modified for simple the environment. In addition, boronchemical moiety, which binds to or pretesting in 96-well microtiter plates allow based preservatives arc colorless, odorcipitates into wood and protects the rapid screening of a large number of test less, noncorosive, and nonflamable wood against wood decay fungi and ter­ samples and substantially conserve time (25,29), Several methods have been demite attack (26,27). Hydrolyses of wood and reagents, especially when a large veloped for estimating boron content in pectin from ray parenchyma cells and number of tests are needed (4,11,18,40). wood and leachates based on photometori of pit membranes has been hypotheMost commercial microplate readers diftry and titration. Curcumin, carminsized as a necessary step in the coloniza­ ferentiate colorimetric reactions by transsäure, crystal violet, carminic acid, and tion of wood by brown-rot and white-rot mitted light (absorbance) at a specific wavelength. Either insoluble substrates, used in many assys (2), or the precipi­ tates formed during an assay prevent The authors are, respectively, Former Post-Doctoral Scientists (presently Assistant Profes­ penetration of light and render measuresor, Forestry Faculty, Istanbul Univ., Bahcekoy 80-895, Istanbul, Turkey); and Research Mi­ crobiologist, USDA Forest Serv., Forest Prod. Lab.m, One Gifford Pinchot Dr., Madison, WI ment by transmitted light inaccurate (18). 53705-2398. The use of trade or firm names in this publication is for reader information and does not imply endorsement by the U.S. Dept. of Agriculture of any product or service. This Boron wood preservatives are relapaper was received for publication in April 2001. Reprint no. 9304. tively cost-effective chemicals and have ©Forest Producgts Society 2002. minimal toxicity against mammals and Forest Prod. J. 52(6):75-79