Improper sample handling

The inherent lability of alkene- and hydroxyalkanesulfonates, variations in isomer composition, and the presence of the disulfonates are features which complicate AOS analyses. Improper sample handling, such as exposure to high temperatures, can also alter active matter composition. Consequently, analytical procedures have been developed that minimize potential sources of error. 

Similar to most Hg sampling methods, sampling sediments and soils require care in avoiding contamination artifacts due to improper sample handling. However, because Hg concentratiorrs are much higher in soUd matrices than in water, if corrrmonly accepted trace-metal protocols are used, substantial contamination artifacts should be exceedingly rare. Also, because sediment Hg concentration profiles... 

Trip blanks prepared in vials and containing aliquots of methanol or analyte-free water accompany soil samples collected in a similar manner for low concentration VOC analysis according to EPA Method 5035. In this case, field samples and trip blanks have the same contamination pathway when exposed to airborne contaminants and the same VOC transport mechanism. These trip blanks provide important information, which may enable us to recognize the artifacts of improper sample handling, storage, or shipping. 

Oxidation, abrasion, and evaporation are examples of improper sample handling because the sample integrity is not preserved. Getting a representative sample is useless if the value of the property of interest changes during transport. Then it is no longer representative. 

Gy refers to improper sample handling as preparation error. 

In addition to polymer degradation, surface contamination constitutes an issue for applications in which the surface state must be well controlled and, also, for polymer surface processing. Polymeric materials are almost never pure and, often, their surfaces are contaminated. The contamination can be caused by the migration of unstable components toward the surface (intrinsic) or by the improper sample handling and storage (extrinsic). SIMS analysis is especially appropriate for the monitoring of all these processes. 

It is well to remember at this point that there are errors of other kinds than those mentioned above. These other errors arise from insufficient knowledge of the sample, and from improper sampling or handling of the sample. As the following brief recapitulation shows, such errors have already been discussed. 

The four main phases involved in a field soil dissipation study are (I) planning and design phase, (II) field-conduct phase, (III) sample processing/analysis phase, and (IV) data handling/reporting phase. Each phase is vitally linked to the next and each is critical to study success. Results from an otherwise perfectly executed study may be made useless by uneven test substance application or improper sampling, sample handling, and/or analytical techniques. Each of these phases is discussed below. 

Methyl parathion may also be released to soils by improper handling of pesticide formulations during processing or handling. In a sampling of soils collected from processing facilities in Illinois, methyl parathion was detected in soil at 2 of the 49 sites tested (Krapac et al. 1995). 

However, some undetermined factor produces a negative bias, particularly in samples nos. 3, 6, 9, and 10 this points to either improper handling of the fixed-volume dispenser, or clogging. The reduction of the within-group variance from VVV to VWV is, to a major part, due to the elimination of... 

The sample subjected to factor changing its original content such as extended transportation time, incubated at high temperature, or improper handling... 

Communication between field personnel is especially important when samples need to be shipped or transported from the field to the laboratory (Eskenazi et al. 2003). A system of e-mail or telephone messages and confirmations should be established with backup contacts to avoid missed shipments or improper handling on arrival. 

The second point is to always run tests on representative samples. Table IV illustrates this point. Original thermal stability tests were run on an alpha-oximino ester intermediate product that had been isolated by adding water to the reaction mixture, extracting the oil layer that forms with methylene chloride, and removing the methylene chloride by vacuum distillation (labelled pure oil). Later in process development it was decided to eliminate the methylene chloride extraction and separate the oil from the water layer (labelled crude oil) If repeat safety tests had not been run, the thermal stability hazard of this compound might never have been realized, and the compound might have been improperly stored or handled at too high a temperature. 

Because of these findings, groundwater at the plant site was sampled and found to contain trichloroethylene. Apparently, improper handling and spill procedures led to the build-up of a pool of highly contaminated groundwater on-site. 

SAMPLE DEGRADATION (IMPROPER STORAGE AND HANDLING) - BIAS (POSITIVE OR NEGATIVE) - POSSIBLE FALSE NEGATIVE SERIOUS SUBCRITICAL... 

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