Environmental Sampling & Analysis Quiz #1

Sampling is a process used to collect a representative portion of a larger population or material. The objective of sampling is to ensure that the collected sample accurately reflects the composition of the entire population. By collecting a portion of material that is representative of the whole, it is possible to make accurate inferences and generalizations about the population as a whole. Therefore, the statement that the objective of sampling is to collect a portion of material that represents the actual sample composition is true.

Analyte-free water is used for rinsing water and blanks preparation because it does not contain any substances that could interfere with the analysis or introduce contaminants. Using analyte-free water ensures that the rinsing process is effective in removing any residual analytes from equipment or samples. It also helps in preparing accurate blanks, which are used as a baseline reference in analytical testing. Therefore, it is important to use analyte-free water for these purposes to maintain the integrity and accuracy of the analysis.

Narrow neck glass bottles are recommended for extractable organics because they provide a better seal and minimize the risk of contamination. Plastic containers may allow the organic compounds to leach into the container, affecting the accuracy of the results. Rubber lined caps may also introduce contaminants. Therefore, narrow neck glass bottles are the best choice for preserving the integrity of the extractable organics.

This statement is false because not all materials listed can be used for microbiological samples. Some materials, such as plastic and glass, are commonly used for handling and storing microbiological samples due to their non-reactive nature and ease of sterilization. However, materials like aluminum and brass can react with certain chemicals or samples, potentially contaminating the sample and affecting the results. Therefore, it is important to choose the appropriate material based on the specific requirements of the microbiological sample.

Duplicate samples are taken to check the preciseness of the sampling process. By taking duplicate samples, the aim is to ensure that the results obtained are consistent and reproducible. This helps in assessing the precision of the sampling process, which refers to the degree of agreement or consistency between repeated measurements or samples. By comparing the results of the duplicate samples, any discrepancies or variations can be identified, indicating the level of preciseness in the sampling process.

The chain of custody is used to track samples from collection through analysis, ensuring that they are handled and stored properly to avoid any tampering. It also serves as a record of all actions taken with the sample, allowing for correction actions when needed. Therefore, the correct answer is "All of the above!" as it encompasses all the mentioned purposes of the chain of custody.

Microbiological samples do not need to be composited within 6 hours of sampling when time is a factor. Compositing refers to the process of combining multiple samples into a single representative sample, which is typically done to save time and resources. However, there is no specific time requirement for when this compositing should be done. It can be done immediately after sampling or at a later time, depending on the specific circumstances and requirements of the analysis. Therefore, the statement that microbiological samples must be composited within 6 hours of sampling is false.

Split samples are taken to check analytical performance. Split samples are created by dividing a larger sample into two or more smaller, representative portions. These split samples are then analyzed separately to ensure that the results are consistent and accurate. Split samples are commonly used in quality control and laboratory testing to verify the precision and reliability of analytical methods. By comparing the results of the split samples, any discrepancies or errors in the analysis can be identified and corrected.

The correct answer is VOCs, TRPH, total metals, dissolved metals, microbiological samples, inorganic nonmetals. This order is preferred because it follows a logical sequence for sample collection. VOCs and TRPH are collected first as they are volatile and can easily evaporate if not collected immediately. Total metals and dissolved metals are collected next as they are stable and require less immediate attention. Microbiological samples are collected after metals as they can be affected by metal contamination. Inorganic nonmetals are collected last as they are less likely to be affected by contamination from other samples.