Sampling procedure design

Definition of the reference material, i.e. the matrix, the properties to be certified, and their desired levels Design of a sampling procedure Design of a sample preparation procedure... 

Before starting field activities, it is essential to define a sampling procedure designed to minimise human errors. This protocol should also respect international scientific community sampling guidance in order to encourage comparison with environmental research carried out in other urban areas. 

The need for skill and experience on the part of sample designers and persoimel cannot be overemphasized in chemical plant sampling. Safety precautions are of the utmost importance. Necessary steps must be taken to document the hazards involved in an operation and to ensure that the staff are weU-trained, informed, protected, and capable. Except for bulk powder sampling, most chemical plant sampling is hazardous and difficult and must be designed with care. The following discussions are based on the assumptions that most of these decisions have been made and a satisfactory sampling procedure has been planned. 

Estimations based on statistics can be made for total accuracy, precision, and reproducibility of results related to the sampling procedure being applied. Statistical error is expressed in terms of variance. Total samphng error is the sum of error variance from each step of the process. However, discussions herein will take into consideration only step (I)—mechanical extraction of samples. Mechanical-extracdion accuracy is dependent on design reflecding mechanical and statistical factors in carrying out efficient and practical collection of representative samples S from a bulk quantity B,... 

Sampling spills. Wear proper personal protective equipment (PPE) Follow proper sampling procedures Use safe sampling design CCPS G-22 CCPS G-23 CCPS G-29 Lovelace 1979... 

Overall, it is not possible to evaluate whether any of these factors have compromised the data included in published studies. More research is required to determine how U-and Th-series nuclides are affected by various well construction methods and sampling procedures, how reliable are data from wells not designed fro trace element monitoring, and if there are any factors that have affected the data collected from past studies. Most importantly, radionuclide studies must incorporate greater awareness of the potential problems, summarize whatever details are available regarding the wells used, and consider potential problems where the relevant information is not available. 

Modern-day chemical analysis can involve very complicated material samples—complicated in the sense that there can be many substances present in the sample, creating a myriad of problems with interferences when the lab worker attempts the analysis. These interferences can manifest themselves in a number of ways. The kind of interference that is most famihar is one in which substances other than the analyte generate an instrumental readout similar to the analyte, such that the interference adds to the readout of the analyte, creating an error. However, an interference can also suppress the readout for the analyte (e.g., by reacting with the analyte). An interference present in a chemical to be used as a standard (such as a primary standard) would cause an error, unless its presence and concentration were known (determinant error, or bias). Analytical chemists must deal with these problems, and chemical procedures designed to effect separations or purification are now commonplace. 

Sample pretreatment and varied experimental procedures designed to control or eliminate the effects of one or more of the aforementioned characteristics do not result in more than one order of magnitude change in the experimental dissolution rates. 

In terms of confidence limits the two Grand Means can be written as 38.5 + 6.4 mg/m2 for the EC plot and 49.9 + 32.7 mg/m for the GF plot at the 90 level. This statement emphasizes the extent to which sampling variability can affect the confidence with which an analytical result is known. Unless the sampling program is designed to measure and identify the source of the variability much effort towards improvement of the quality of the chemical analyses can be wasted (4). The difficulty of improving the sampling procedures to reduce the variability is illustrated by calculation of the number of samples that would have to be analyzed to obtain estimates known to have an uncertainty less than 10 at the 90 confidence level (4). This would require 106 analyses from the EC plot and 2140 from the GF. Both sample sizes... 

By the design of the sampling procedure, the LGC, and the laboratories within the British tobacco industry, have reduced to an aceptable level the random variations associated with the raw material and manufacturing process. The variables associated with machine smoking and analysis have been largely eliminated by testing the samples in a... 

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