Cross-contamination fields

For stone fmit, e.g., olive cherries, where the mature fruit is analyzed, the stone should be removed, and the weight of pulp and stone should be recorded. The residue is calculated on the basis of whole fruit. This step can be done either in the field prior to the fruit being frozen, which makes the procedure easier, or in the analytical laboratory. In either case, care needs to be taken to avoid cross-contamination. 

The field laboratory set up by the field research group is a key element to completing successful worker exposure/re-entry research. The field laboratory may be set up in close proximity to the treated field, but should be located at a reasonable distance from the treated area to avoid cross-contamination of field samples and field controls. 

Patches are removed from the test subject immediately after the study replicate is completed. The Field Scientist should wear disposable surgical gloves to remove the patches and change gloves often to reduce the chance of cross-contamination of samples. Individual patches are wrapped in aluminum foil prior to placing them in a pre-labeled sealable plastic bag. Combined patches are placed exposed face to face, wrapped in aluminum foil, and stored frozen in sealable plastic bags. Patch samples may be placed in dry-ice in a cooler or directly into a freezer for storage. 

Foot exposure of workers can be measured by using socks as dosimeters or anklet dosimeters worn under ordinary socks. Usually an ordinary sock or anklet bought at a retail store will suffice for the dosimeter. As with whole-body dosimeters, the sock material should be 100% cotton but may be other materials. Pre-washing the socks or anklets prior to use in the field may be necessary if analytical interferences are found in the sock material. The socks or anklets should be put on the volunteer using procedures similar to those already described in order to avoid cross-contamination of the sock dosimeter. 

Field fortification (commonly referred to as field spiking) is the procedure used to prepare study sample matrices to which have been added a known amount of the active ingredient of the test product. The purpose for having field fortification samples available in a worker exposure study is to provide some idea of what happens to the test chemical under the exact environmental field conditions which the worker experiences and to determine the field storage stability of the test substance on or in the field matrix materials. Field fortifications do not serve the purpose of making precise decisions about the chemical, which can better be tested in a controlled laboratory environment. The researcher should not assume that a field fortification sample by its nature provides 100% recovery of the active ingredient at all times. For example, a field fortification sample by its very nature may be prone to cross-contamination of the sample from environmental contaminants expected or not expected to be present at the field site. 

One alternative method for preparing field fortifications solutions/suspensions is to prepare each fortification sample of each matrix in a separate mini-vial in the analytical laboratory and ship the vials to the field for use. This procedure precludes the use of pipets in the field and may be useful when Field Scientists not experienced in the use of pipets are involved in the field fortification process. One disadvantage of this procedure is that the mini-vials, if not designed correctly, will be hard to handle in the field, and surface tension of the suspension or fortification solution will tend to leave unacceptable amounts of the solution/suspension in the vial or at the lip of the vial and not on the matrix in question. This procedure may lead to cross-contamination of samples as the field fortification liquid is forced from the top... 

The potential of flow of plant-made biopharmaceuticals into the human food chain remains. For example, plant-derived pharmaceuticals could cross-contaminate foodstuffs by spontaneous growth of transgenic crops in areas outside the intended field, or by pollen flow between some plants such as corn. It has been suggested that plant-derived biopharmaceuticals should be generated in nonfood crops, such as tobacco. However, food crops produce the greatest opportuitities for efficient production since they are among the most well-studied of crops. This continues to make them more feasible for edible vaccine production. 

The purpose of trip blanks is to assess the collected sample representativeness by determining whether contaminants have been introduced into the samples while they were handled in the field and in transit, i.e. in coolers with ice transported from the site to the analytical laboratory. A possible mechanism of such contamination is the ability of some volatile compounds, such as methylene chloride or chlorofluor-ocarbons (Freons), to penetrate the PTFE-lined septum and dissolve in water. Potential sources of this type of contamination are either ambient volatile contaminants or the VOCs that could be emanating from the samples themselves, causing sample cross-contamination. To eliminate ambient contamination, samples must not be exposed to atmospheres containing organic vapors. Cross-contamination is best controlled by such QA measures as sample segregation and proper packaging. 

Equipment blanks enable us to assess the collected sample representativeness. The purpose of collecting equipment blanks is to detect the presence of contamination from the sampling equipment itself or any cross-contamination with previously collected samples. For example, metal liners for core barrel or split spoon samplers are not always precleaned by the manufacturer or distributor. They must be cleaned in the field prior to sampling to eliminate the potential for sample contamination. 

The centrifugal method of separation employed by Van Lancker and Holtzer (V2) was among the earlier ones in the field, and there was probably considerable cross contamination of the fractions. Nonetheless, the distribution seems more disperse than that obtained by de Duve et al. (DIO) for rat liver with a comparable method. For example, in the case of the mouse pancreas the small mitochondrial fractions, c, d, and e, obtained by centrifugation between 17 X 10 and 263 X 10 gr-min contained 27% of the acid phosphatase and the succeeding microsomal fractions, f and g, obtained by centrifugations between 263 X 10 g-min and 3170 X 10 g-min, contained 24% of the acid phosphatase (V2). For rat liver, comparable fractions, obtained by centrifugation between 33 X 10 to 250 X 10 g-min and 250 X 10 to 3000 X 10 g-min contained 41 and 20%, respectively (DIO). 

Insects are usually held in groups of ten. Adams showed that cross-contamination occurs between individuals. A female cockroach could transfer a dose sufficient to kill a male. A case could be made for holding insects separately unless the material has such a slow action that return of the insects to their harbourage would occur in the field before immobilization. 

The sad experience with the conditions at IBT, where multiple studies were run simultaneously in the same room with the concomitant problems of mix-ups of animals and treatment cross-contamination by volatile test substances, have resulted in the requirement of sufficient space to assure the isolation of test systems . Through a sufficient number of rooms or at least sufficiently separable areas, it should become possible to avoid any crosscontaminations or mix-ups of projects, tests or treatments. Also the positioning of test systems used in field studies requires an appropriate degree of separation, as it is specified in the GLP Principles ( Test systems used in field studies should be located so as to avoid interference in the study from spray drift and from past usage of pesticides . In the same sense, isolation of individual projects in aquatic toxicity testing should be applied to the extent necessary, to prevent cross-contamination through spray, mist or overflow. 

With the ever-increasing need to improve quality and productivity in the analytical pharmaceutical laboratory, automation has become a key component. Automation for vibrational spectroscopy has been fairly limited. Although most software packages for vibrational spectrometers allow for the construction of macro routines for the grouping of repetitive software tasks, there is only a small number of automation routines in which sample introduction and subsequent spectral acquisition/data interpretation are available. For the routine analysis of alkali halide pellets, a number of commercially available sample wheels are used in which the wheel contains a selected number of pellets in specific locations. The wheel is then indexed to a sample disk, the IR spectrum obtained and archived, and then the wheel indexed to the next sample. This system requires that the pellets be manually pressed and placed into the wheel before automated spectral acquisition. A similar system is also available for automated liquid analysis in which samples in individual vials are pumped onto an ATR crystal and subsequently analyzed. Between samples, a cleaning solution is passed over the ATR crystal to reduce cross-contamination. Automated diffuse reflectance has also been introduced in which a tray of DR sample cups is indexed into the IR sample beam and subsequently scanned. In each of these cases, manual preparation of the sample is necessary (23). In the field of Raman spectroscopy, automation is being developed in conjunction with fiber-optic probes and accompanying... 

Sterility and cross contamination during dissection are a concern. Disposable absorbent pads and even paper towels can be laid out to create a field that is at least clean if not sterile. Sterile blades and sterile gloves come in packaging that can be opened and laid out to create a small cutting surface that is sterile. The use of disposable knives will prevent cross contamination between samples. Beakers of bleach and 95% ethanol can be used to sterilize forceps and other non-disposable dissection tools between samples. 

To increase throughput and eliminate sample cross contamination, which is common when analyzing cells sequentially, Munce et al. [22] developed a microfluidic device with four parallel CE channels. Calcein-labeled acute myeloid leukemia cells were selected and transported with optical tweezers to injector structures at the entrance of each channel, as shown in Fig. 3a. Once loaded, the cells were lysed by the combined action of an applied electric field and the reduction in channel cross section (Fig. 3b). The injector design also enabled stepwise lysis of the cell, shown in Fig. 3c, where only the cytoplasmic material (containing calcein AM in green) was injected into the capillary, while the nucleus (stained blue with Hoechst 33342) remained in the injector structure. This selective lysis is especially useful to separate the cytoplasm from the... 

Many patients who have field decontamination (especially those with only dry decontamination) will require further decontamination at the hospital. If the scene is close to the hospital, many victims may transport themselves directly to the hospital and amve having had no decontamination at all (as in the Tokyo sarin attacks). Hospitals usually have little in the way of decontamination equipment other than wading pools, water hoses, and soap. Most emergency departments have no PPE available and no training in the use of PPE. Thus, if contaminated victims arrived at the emergency department, the staff would become cross-contaminated while trying to perform decontamination of the patients. Most hospitals depend on the fire service, EMS, or EMA to provide a decon trailer in an emergency situation. The problem with this is the decon trailer may be in use at the scene of the incident and not be available. 

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