Comparison of Sampling Procedures in the Field

Pre-treatment of the sample is especially important if lead particles are present in the sample. To obtain representative results, prescription of representative, reproducible, precise and accurate sampling, pre-treatment and methods of analysis are essential in the sampling procedure. 

For the determination of lead concentrations in drinking water, the analytical methods are atomic absorption spectrometry - electro-thermal atomization (AAS-ETA or AAS-fiimace), inductively coupled plasma with detection by atomic emission spectrometry (ICP-AES) or detection by mass spectrometry (ICP-MS). Laboratories are free to use their own chosen analytical techniques. More attention will be required to achieve the necessary analytical accuracy at the lower limit for lead. 

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Table 1 summarizes the results of the field sample analyses standardized for polymer concentration. The quality of the field injection sampled collected both at the well and bottom compared closely to that of a laboratory weighed and dried polymer standard prepared in the field using normal laboratory procedures. This 300 mg/l polymer solution had a measured screen factor of 12. 9 and a viscosity, measured at 115 seconds" shear rate, of 3. 93 cp. Laboratory derived correlations showed that this standard corresponded to a mobility reduction effect, expressed in terms of a resistance factor, of 32. The close comparison between this unsheared standard and field injection samples implied that neither the surface nor bottom hole sampling induced any shear degradation. 

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