SmartChem测定水体中氰化物的方法

智能文字提取功能测试中

SmartChem Method #281N-0405C Cyanide， Total in Water， Waste Water， Soil Extracts and other aqueous samples 1.0 SCOPE AND APPLICATION 1.1 This method is applicable to the determination of cyanide in drinking， surface and saline waters， and domesticand industrial wastes. Each laboratory must verify the protocol is in compliance with current 40 CFR 136 and141 requirements. 1.2 The applicable range is 5 to 500ug/L. The method range can be extended either by manual or SmartChemsample predilution. 1.3 This method is based on USEPA 335.4， Revision 1， August 1993 tn2.0 SUMMARY OF METHOD e 2.1 Cyanide is defined as cyanide ion and complex cyanides converted to hydrocyanic acid (HCN) by reaction in amanual reflux distillation system of a mineral acid in the presence of magnesium ion. 2.2 Samples are prepared for analysis by first performing a distillation as described in Standard Methods 20"Edition 4500 CN-E or EPA 335.4. The same sample preparation process must treat samples， calibrators， blanksand controls. 2.3 The cyanide as hydrocyanic acid (HCN) is released from cyanide complexes by means of， a reflux-distillationoperation and absorbed in a scrubber containing sodium hydroxide solution. The cyanide ion in the absorbingsolution is then determined colorimetrically. The cyanide is converted to cyanogen chloride， CNCl， by reactionwith chloramine-T at a pH less than 8 and without hydrolyzing to the cyanate. After the reaction is complete， areddish color is formed with the addition of pyridine-barbituric acid reagent. The absorbance is read at 570nm. 3.0 DEFINITIONS 3.1 RBL-Reagent Base Line-Absorbance created when the Reagent water and certain reagents are addedto the cuvette. 3.2 WBL-Water Base Line- Absorbance created when Reagent water is added to the cuvette. The WBL isused to check the quality of the cuvette， condition of the filters， and lamp. If the value is too high or too low thecuvette will be rejected and will not be used for analysis. 4.0 INTERFERENCES 4.1 Several interferences are encountered with this method. Some of the known interferences are aldehydes，nitrate-nitrite， oxidizing agents， such as chlorine， thiocyanate， thiosulfate， and sulfide. Multiple interferencesmay require the analysis of a series of laboratory fortified sample matrices (LFM) to verify the suitability of thechosen treatment. Some interferences may be eliminated or reduced by the distillation. 4.2 Sulfides adversely affect the procedure by producing hydrogen sulfide during distillation. If a drop of thesample on lead acetate test paper indicates the presence of sulfide， treat 25 mL more of the stabilized sample(pH ≥12) than that required for the cyanide determination with powdered cadmium carbonate. Yellow cadmium 281N-0405C Cyanide， Midi Distillation 17.0 TABLES， DIAGRAMS， FLOWCHARTS， AND VALIDATION DATA R²=0.9998Y=0.0013x+0.0057 ug/L CN Absorbance 5.00 0.0096 10.00 0.0181 50.00 0.0712 100.00 0.1387 250.00 0.3395 500.00 0.6688 remAbs Conc ug/Lu http：//zeal-qu Page of - Cyanide， Midi DistillationPage of