Sampling – but correctly!

Sampling plan

The sampling plan serves as a guide for the sampling procedure. It is based on the research and strategies established during preparation. Also, the sampling plan defines the questions to be answered during sampling. These may look like the following:

• What are the reason for and the aim of sampling?
• Where does the sample come from?
• What spectrum of pollutants or substances can be expected?
• Are there temporal and/or local variations in the distribution of the substance inventory?
• Which parameters are to be determined by sampling?
• Do special occupational safety measures have to be observed in the process?

Correct sampling procedure

Already from the extensive preparation it can be deduced that sampling does not only mean the mere collection of material. Instead, several aspects must be considered that make sampling successful in the first place. The most important criteria for the correct procedure are the following:

• person and protective clothing: Especially if biological contamination is suspected, sampling should be carried out under the guidance of qualified personnel including the selection of suitable protective clothing.
• Exclusion of hazardous substances:An exclusion of explosive, radioactive and/or hazardous volatile chemical substances must also be performed at the sampling site.
• Determination of the state of aggregation:The state of aggregation of the sample is also determined directly at the sampling location.
• Representativeness: As already mentioned in the preparation, a representativeness of the sample must be ensured. This applies to both the material and the selected area.
• Container:The container for sample transport must be clean, resistant and approved. In the case of biological samples, it must also be sterile. In order to ensure safe specimen transport, the responsible laboratory should be informed at this point.
• Sample division:Since it can happen that a single sample is unsuitable, a differentiation is usually made into main sample and reserve sample. Therefore, one sample split must be made per specified sampling location.
• Baseline sample:The so-called baseline sample is taken outside the contaminated zone in order to be able to determine the actual baseline contamination of the area individually.
• Sampling along the line of dispersion:In addition, sampling should be carried out along the line of dispersion in order to be able to analyze the spread of contamination as accurately as possible.
• Sampling of the lead substance: In order to determine the source of release of the contamination, additional sampling is performed for substance identification of the lead substance.
• Sample collection point:The contamination should not be carried over, of course. Therefore, a central sample collection point is needed to plan and execute the decontamination of containers.
• Documentation:In addition, there is the documentation of the sampling, which should be both comprehensible and unambiguous.

The correct handling of specimens

Not all samples are the same – there are many different samples and substances for which different equipmentis ideal. The same applies to the equipment and procedures for picking up the substance. According to the Robert Koch Institute (RKI), for example, the ideal handling of recognizable sample material can be defined as follows:

Soil sample: While small objects are gripped with tweezers or crucible tongs, powder and loose samples should be picked up with a spoon spade. For pastes, on the other hand, ordinary stainless steel spatulas are useful.

Fouling sample: Fouling samples are taken with a side cutter and placed in a sampling bag or PE sampling container. The latter is the case when there is a risk of perforation by sharp plant parts. The bag should be turned inside out when the specimen is collected so that it can be easily slipped over the specimen afterwards.

Liquid specimen: For liquid specimens, several acquisition routes are possible. Small quantities are best taken up with an absorbent compress, all other quantities are suitable for pasteur pipettes, syringes and ladles, for example. The sample is then stored in a measuring cup or in a PE sampling bottle.

Wipe test:Swabs are used for wipe tests. Depending on the material properties, these are provided with NaCl, a bacterial medium or a viral medium. Alternatively, sponges and compresses moistened with NaCl are suitable.

Document sampling correctly

Extensive documentationis essential so that samples cannot be confused or significance lost due to missing circumstance information. While the exact aspects will depend in large part on the type of sample and the reason for sampling, the following documentation data should never be omitted:

• Date: The date indicates when the sample was taken. This is important because the nature and extent of contamination can change over time.
• Time:The same applies to the exact time. Often several samples are taken on one day – then the time also serves to document the course over time.
• Name of the sampler:The name of the sampler makes it easier to trace the responsible institution and the contact to the control center.
• Sampling Team: The sampling team should also be documented for the same reason. In addition, different tasks belong to different teams, for example.
• Sample number: The sample number not only enables precise identification of the individual samples, but also contributes significantly to sample management.
• Location of the sample: The exact location should be specified in order to be able to accurately assign the results of the sample analysis.
• Weather: The weather also has an influence on the sample. For example, volatile substances in the air may concentrate differently depending on whether it is raining or whether there is high/low humidity.
• Type of sample: If the type of sample is noted directly after sampling, the analysis in the laboratory can be accelerated. This way, the responsible persons know how best to proceed with the material or aggregate state – even before the sample is opened.
• Observations:For example, if discoloration, unusual features, or dead animals are seen at the sampling site, these observations should be documented in any case.
• Sketch: In some cases, it may also be useful to make a sketch of the sampling location. This can help identify areas, for example, or highlight significant changes to the site.

Sampler types

Since samples are needed in diverse areas of research, the types of samplers can also differ greatly. However, for sampling to work properly, the individual advantages and disadvantages of the samplers should be considered.

Sampler for liquids

Depending on the quantity and volume, different samplers can be used for liquids. These range from pasteurizer pipettes to syringes and ladles. The liquid is then stored in a measuring cup or a special PE sample bottle. For smaller quantities, compresses are also an option. In the meantime, for example, angle cups with telescopic rods have become established to hold liquids with more distance.