Recovery lead from water samples

Dialkyl and trialky Head salts Atomic absorption 90% recovery of di- and trialkyl lead salts from water 1.25mg PbL (500ml sample)... 

Tsunogai and Nozaki [6] analysed Pacific Oceans surface water by consecutive coprecipitations of polonium with calcium carbonate and bismuth oxychloride after addition of lead and bismuth carriers to acidified seawater samples. After concentration, polonium was spontaneously deposited onto silver planchets. Quantitative recoveries of polonium were assumed at the extraction steps and plating step. Shannon et al. [7], who analysed surface water from the Atlantic Ocean near the tip of South Africa, extracted polonium from acidified samples as the ammonium pyrrolidine dithiocarbamate complex into methyl isobutyl ketone. They also autoplated polonium onto silver counting disks. An average efficiency of 92% was assigned to their procedure after calibration with 210Po-210Pb tracer experiments. 

LLE has been used in the past for the extraction of pesticides from environmental water samples [17]. However, its application in the extraction of waste-water samples is scarce due to the low efficiency of extraction, especially for polar analytes. Because of the vast amount of surfactants and natural products present in wastewater samples, emulsions are formed which complicate the process of extraction and lead to low extraction recoveries. However, there have been some useful applications of LLE to wastewater analyses. For example, LLE was found to be effective for the isolation of herbicide and pesticide organic compounds from industrial wastewater samples and also from complex matrices [18]. 

These data indicate recoveries of 82-90, but lead is removed from water because of the initial precipitation of this element. This phenomenon might not occur in real field sampling because all lead compounds should be in dissolved forms. 

Direct titration of samples that are only partially dissolved in the reagent usually leads to incomplete recovery of the water. Satisfactory results with this type of sample are often obtained, however, by the addition of excess reagent and back-titration with a standard solution of water in methanol after a suitable reaction time. An effective alternative is to extract the water from the sample by refluxing with anhydrous methanol or other organic solvents. The resulting solution is then titrated directly with the Karl Fischer solution. 

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