Hand sampling methods

The importance of effective antimicrobial handwashing has been known throughout the healthcare field for many years. Accurate and reliable determinations of the microbial populations residing on the hands are critical in evaluating the effectiveness of both handwash products and methods. Only when one is sure of reliable hand sampling methods can he or she attempt to assess the benefits of a personnel handwash product in terms of microbial reductions [1]. 

A randomly collected sample makes no assumptions about the target population, making it the least biased approach to sampling. On the other hand, random sampling requires more time and expense than other sampling methods since a greater number of samples are needed to characterize the target population. 

For each group, one representative sample matrix has to be used for method validation. If the intended use is restricted to one of the crop groups, the method must be validated only for this group. On the other hand, the method has to be validated for all groups if the use is intended for a variety of crops that belong to two or more different groups. In addition, specific crops which are difficult to analyze due to matrix interference require individual method validation (e.g., hops, brassica varieties, bulb vegetables, herbs, tea). 

On the other hand, samples can be irradiated at constant microwave power over a certain fixed period, for example at 100 W for 10 min. As there is no control over the resulting temperature or pressure, care has to be taken not to exceed the operational limits of the system and this type of program should only be used for well-known reactions with non-critical limits, or under open-vessel (reflux) conditions. Since in this method only the applied energy and not the resulting temperature is controlled, the quality of reaction control is often superior employing a temperature-controlled program. 

When adsorption and condensation can be avoided, both dynamic and static sampling methods can be used. Often rinsing the sampling apparatus or even the whole olfactometer with odorous air is necessary to reduce adsorption. Before using the static method a comparative study should be carried out if possible. On the other hand extreme fluctuating emissions can only be sampled statically. 

The analysis involves gas chromatographic methods such as purge and trap, vacuum distillation, and headspace (Askari et al., 1996). On the other hand, samples for the determination of semi- and nonvolatile hydrocarbons need not be collected in such a rigorous manner. On arrival at the laboratory, they require extraction by techniques such as solvent or supercritical fiuid. Some cleanup of... 

Upon use of structurally modified variants as internal standards for the particular analytes, the relative quantificahon of oligonucleotides, peptides, and small proteins was demonstrated [44]. The potential of the ILM to allow quantitative analyses of peptides without the use of internal standards was presented recently [43]. Linear correlahons between peptide amount and signal intensities could be found upon applicahon of increased matrix-to-analyte ratios between 25,000 and 250,000 (mokmol). The dynamic range of linearity thus spanned one order of magnitude. Unfortunately, the importance of the M/A ratio prevents the use of this method in samples with unknown orders of concentration, for example, in a proteomics environment. On the other hand, the method is applicable for the screening of enzyme-catalyzed reactions because the starting concentrahons of the peptides are generally known in such assays. 

Calculation of paleopressure and thus the success of this approach to determining paleoelevation depend upon our ability to accurately measure the size distribution of vesicles in hand samples of basalt (Fig. 4). In the course of our research, we have developed three techniques for measurement. The first involved injecting hand samples with plastic monomer which subsequently polymerized, and then dissolving away the basalt to leave a large number of plastic casts of vesicles for measurement and counting. The plastic casts were resistant to the effects of HF acid, so they reliably represented the actual vesicle sizes and shapes but were difficult to measure accurately and very tedious to work with (Sahagian et al. 1989). This was a laborious and inefficient technique that should be abandoned in favor of faster and more accurate methods. 

Organic substances that are not volatile are grouped under semivolatiles. The latter class also includes substances of very low volatility such as chlorinated biphenyls and polynuclear aromatics. As far as the GC/MS technique goes, the principle of analysis of the semivolatile organics is not so distinctly different from that of the volatile organics. On the other hand, the method of extraction of analytes from the sample matrices and the sample concentration steps for these semivolatile organic compounds vastly differ from the volatile organics. Such extraction techniques and the sample cleanup methods are discussed more extensively in Chapter 1.5. 

Sample collection varies from hand sampling procedures at a single point to more sophisticated multipoint sampling techniques, such as the equal discharge increment (EDI) method or equal transit rate (ETR) method. Different types of water samplers can be used to collect water samples from bodies such as rivers, seas, lakes, etc. The Blumer sampler [30], Deutsche Hydrographisches Institute sampler (DHI) [31], and a high volume water sampler, designed to pump water from a defined depth below the water body surface outside the wake of the survey vessel, are suitable as samplers [32], The Kemmerer and van Dorn samplers may also be used for water sample collection. For rivers, up- and downstream samples are usually required, as well as the points where tributaries or waste drains join the main stream under study. 

As shown in Table 3.4, acceptance criteria for stabilization parameters may have a range of recommended values. Because some are more stringent than others, they should be used with caution and be adjusted as necessary based on the knowledge of site-specific conditions. For example, the criterion for turbidity of + 10 percent may be too stringent for some hydrogeological conditions or for the conventional sampling method. On the other hand, this criterion may be easily achieved for wells with dedicated submersible pumps and non-turbid, clear groundwater. 

The use of retain samples to routinely examine a statistically sound number of units is a valuable investigative tool. If the retain samples do not reveal any degradation, but other quality markers, such as consumer complaints, manufacturing deviations, and QC profiles, indicate shifts in quality, a problem with the retain sampling method should be considered. On the other hand, if the retain samples... 

The spectroscopic measurement of 02 is more expensive and more complicated than the previously described methods. On the other hand, those methods allow the monitoring of multiple components simultaneously. As was discussed in some detail in Section 3.2.12, mass spectroscopy can be used to monitor Oz by ionizing the sample and separating the ions according to their mass. As was covered in Section 3.2.11, NIR spectroscopy is widely used for stack monitoring, which includes 02 measurement. 

Using the traditional methods of polymer analysis, such as infrared or nuclear magnetic resonance spectroscopy, one can determine the type of monomers or functional groups present in the sample. However, the determination of functional end groups is complicated for long-chain molecules because of low concentration. On the other hand, these methods do not yield information on how different monomer units or functional groups are distributed in the polymer molecule. Finally, these methods do not in general provide molar mass information. 

I would like to distinguish between methods that are performed with undiluted and diluted samples and further on between methods that are performed with the initial or freshly prepared samples on the one hand, and methods or protocols performed with stressed samples on the other hand. Stress for an SB can come fi om various sources. Most important are temperature, time and shear stress. 

The instrument is calibrated for a given element for each series of samples. Direct calibration requires detailed knowledge of the milieu to be analysed. Precise results depend on the composition of the calibration solutions being as close as possible to that of the solutions to be analysed. The standard addition method can be u.sed in cases where it is not possible to produce external reference solutions similar to the solutions to be analysed. This method should be used with considerable caution because it assumes that the absorption is due solely to the element under analysis and, in particular, that the non specific absorption is fully corrected for. If this is not the case, any interfering absorption leads to an overestimate of the values observed. On the other hand, this method does have the advantage of eliminating the matrix effect. 

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