Lead determination limits

With some ISEs, measurement in flowing solutions leads to a substantial improvement in the value of the determination limit (down to 10" to 10" moir see section 5.1.2). 

The measurements on the control sample usually are made with each batch and finally marked on the control chart are done under between-batch conditions. Therefore the standard deviation for the calculation of the limits should also be determined under the same between-batch conditions. The most common way to estimate this standard deviation is to use the results from a pre-period of about 20 working days. The use of the repeatabihty standard deviation would result in too narrow limits whilst interlaboratory conditions would lead to limits that are too wide. 

Lead Determine as directed under Lead Limit Test, Appendix MB, using a solution of 2 g of sample in 20 mL of water, and 2 pig of lead (Pb) ion in the control. 

Lead Determine as directed for Method I in the Atomic Absorption Spectrophotometric Graphite Furnace Method under Lead Limit Test, Appendix IIIB. 

Lead Determine as directed for Method I in the Atomic Absorption Spectrophotometric Graphite Furnace Method under Lead Limit Test, Appendix IIIB, using a 10-g sample. Oxalate Neutralize 10 mL of a 1 10 aqueous solution with 6 N ammonium hydroxide, add 5 drops of 2.7 N hydrochloric acid, cool, and add 2 mL of calcium chloride TS. No turbidity develops. 

Lead Determine as directed under Lead Limit Test, Appendix IIIB, using a Sample Solution prepared as directed for organic compounds, and 5 p.g of lead (Pb) ion in the control. Loss on Drying Determine as directed under Loss on Drying, Appendix IIC, drying the sample at 105° for 3 h. Optical (Specific) Rotation Determine as directed under Optical (Specific) Rotation, Appendix IIB, using a solution containing 8 g of a previously dried sample in sufficient 6 N hydrochloric acid to make 100 mL. 

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