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..a <br /> GT ENVIRONMENTAL LABORATORY (GTEL) <br /> STANDARD OPERATING PROCEDURE <br /> CONCERNING FIELD PRESERVATION OF BTX SAMPLES <br /> BY ACIDIFICATION <br /> SOP 12 <br /> If specially prepared acidified vials are not available, apply <br /> the following Field Procedures, using the field acidification <br /> kit. The kit contains: <br /> a) 500 cc glass measuring cup or breaker <br /> T b) dropping bottle of 50% hydrocloric acid or nitric <br /> acid. <br /> c) narrow range pH paper, 1.0-2.5 pH range. <br /> d) glass stirring rod. <br /> 1. Collect approximately 300cc of water in beaker. Try to <br /> minimize turbulence, bubbling, and time of exposure to the <br /> air. <br /> 2. For inorganic analysis: use 50% nitric acid <br /> _ For volatile organic analysis: use 50% hydrocloric acid <br /> Add 30 drops of 50% acid to measuring cup. Hold dropper <br /> - completely vertically. <br /> 3. Gently mix with glass bar. <br /> 4. Remove bar and touch wetted tip to the pH paper and check <br /> color code to assure it is below pH 2. As more acid is <br /> added the pH goes lower. Discard used pH strip. <br /> 5. Add mare acid if necessary. Too much acid is not a problem, <br /> i just record how much was added (this will be helpful next <br /> time) . Don't waste time trying to get it right - just add <br /> plenty of acid to get it below pH 2. Ideally, once you know <br /> how much acid needs to be added at one well, that amount i <br /> will be sufficient for the rest. However, test the pH each <br /> time. <br /> 6. Pour the water i:ito the vials prepared far that well and cap f <br /> -- off with no bubbles inside. Again turbulence and bubbling <br /> are to be minimized. Also note that it is important that <br /> all of the vials for a given well be poured and sealed one <br /> -- right after another. Make sure the 300cc collected is <br /> enough to fill all of the vials with some to spare at the <br /> end. The volume collected can be increased but remember to <br /> proportionally increase the amount of acid added. <br /> /. Acidification does not replace chilling. Always chill <br /> samples and ship via air for next day delivery. <br /> I , <br /> V _ ._ r GNrrl�IrtltrF:k <br />