NR 252.035(4)(b)2.a.a. Calculate clean water precision and accuracy in accordance with standard statistical procedures. Clean water acceptance limits are presented in subd. 2. b. These criteria shall be met or exceeded before sample analyses can be initiated. A clean water standard shall be analyzed with each sample set and the established criteria met for the analysis to be considered under control.

NR 252.035(4)(b)2.b.b. Clean water precision and accuracy acceptance limits: for distilled water samples containing from 5 mg/l. to 50 mg/l. sulfide, the mean concentration from 4 replicate analyses shall be within the range of 50 to 110% of the true value.

NR 252.035(4)(c)(c) The method detection limits or MDL may be determined periodically by each participating laboratory in accordance with the procedures specified in ”Methods for Chemical Analysis of Municipal and Industrial Wastewater,” EPA- 660/4-82-057, July 1982, EMSL, Cincinnati, OH 45268. For the convenience of the user, these procedures are contained in s. NR 252.0365.

NR 252.035(4)(d)(d) A minimum of one spiked and one duplicate sample shall be performed for each analytical event, or 5% spikes and 5% duplicates when the number of samples per event exceeds 20. Spike levels are to be at the MDL and at x where x is the concentration found if in excess of the MDL. See par. (c) for MDL samples. Spike recovery shall be 40 to 120% for the analysis of a particular matrix type to be considered valid. If a sample or matrix type provides performance outside these acceptance limits, the analyses shall be repeated using the modified Monier-Williams procedures described in s. NR 252.036.

NR 252.035(4)(e)(e) Report results in mg/liter. When duplicate and spiked samples are analyzed, report all data with the sample results.

NR 252.036(1)(a)(a) Hydrogen sulfide is liberated from an acidified sample by distillation and purging with nitrogen gas (N2). Sulfur dioxide interference is removed by scrubbing the nitrogen gas stream in a pH 7 buffer solution. The sulfide gas is collected by passage through an alkaline hydrogen peroxide scrubbing solution in which it is oxidized to sulfate. Sulfate concentration in the scrubbing solution is determined by either EPA gravimetric test procedure 375.3 or EPA turbidimetric test procedure 375.4 (see 40 CFR 136.3, Table IB, parameter 65 (49 FR 43234, October 26, 1984, and correction notice at 50 FR 690, January 4, 1985)).

NR 252.036(1)(b)(b) (apparatus see figure 1.) Catalogue numbers are given only to provide a more complete description of the equipment necessary, and do not constitute a manufacturer or vendor endorsement.

NR 252.036(2)(a)(a) Potassium hydroxide, 6N: Dissolve 340 g. of analytical reagent grade KOH in one liter distilled water.

NR 252.036(2)(b)(b) Sodium hydroxide, 6N: Dissolve 240 g. of analytical reagent grade NaOH in one liter distilled water.

NR 252.036(2)(c)(c) Sodium hydroxide, 0.03N: Dilute 5.0 ml. of 6N NaOH to one liter with distilled water.

NR 252.036(2)(d)(d) Hydrochloric acid, 6N: Dilute 500 ml. of concentrated HCl to one liter with distilled water.

NR 252.036(2)(e)(e) Potassium phosphate stock buffer, 0.5M: Dissolve 70 g. of monobasic potassium phosphate in approximately 800 ml. distilled water. Adjust pH to 7.0 0.1 with 6N potassium hydroxide and dilute to 1 liter with distilled water. Stock solution in stable for several months at 4 degrees C.

NR 252.036(2)(f)(f) Potassium phosphate buffer, 0.05M: Dilute one volume of 0.5M potassium phosphate stock buffer with 9 volumes of distilled water. Solution is stable for one month at 4 degrees C.

NR 252.036(2)(g)(g) Alkaline 3% hydrogen peroxide: Dilute one volume of 30% hydrogen peroxide with 9 volumes of 0.03N NaOH. Prepare this solution fresh each day of use.

NR 252.036(2)(h)(h) Preparation of stock sulfide standard, 1000 ppm.: Dissolve 2.4 g. reagent grade sodium sulfide in one liter of distilled water. Store in a tightly stoppered container. Diluted working standards shall be prepared fresh daily and their concentrations determined by EPA test procedure 376.1 immediately prior to use (see 40 CFR 136.3, Table IB, parameter 66 (49 FR 43234, October 26, 1984, and correction notice at 50 FR 690, January 4, 1985)).