Sample storage freezers

Sample storage freezers located at the Research Farms and those of the Residue laboratories are considered to be limited access archives and are kept locked. Access is limited to the sample preparation laboratory employees. All movements of samples in and out of the freezers are recorded. One freezer in the Residue Laboratory... 

The field investigator s residue sample handling procedures and equipment are always inspected. It is policy that samples be held at the field locations for only short periods however, accurate records are kept on the storage and handling conditions from the time a sample is collected until it is shipped to the laboratory. The elapsed time from collection until a sample is placed in a freezer must be recorded as well as the location of the freezer and the temperature of the freezer during the storage. The sample storage freezer and the records kept on it are always inspected. 

To fortify a sample, the label from a fortification sampling vial was removed and secured to the pre-labeled sample jar. Spike vials were individually shaken before use. The cap was discarded, the contents of the vial were poured into the sample jar and then the vial was dropped into the sample. The sample jar was capped with a Tefion-lined lid, hand shaken to mix, placed in a Kapak bag and sealed. Jars were placed immediately in storage freezers. In all cases, quality control samples were transported and stored with their corresponding field plot samples throughout sample handling and shipment to the analytical facility. 

Field fortifications have also been used to measure the storage stability of the analyte in/on exposure matrices during freezer storage prior to analysis. Although use of field fortification samples for freezer storage stability is not the original purpose intended for field fortification samples, this has become an acceptable practice among scientists who work in this scientific discipline. 

The above findings suggest that if testing laboratories do not adjust their analytical and sample storage protocols according to the extent to which penicillin G decreases in tissues and biological fluids stored in conventional freezers, quantitative analyses conducted on such samples may not reflect concentrations at time of sample submission. 

Stability testing is performed to ensure that the analyte concentration does not change during sample storage, sample preparation, and sample analysis. The freeze and thaw stability of analyte in matrix as well as the short-term stability of analyte in matrix at room temperature should be examined. The long-term stability of analyte in matrix stored in freezer should also be tested, as should the stability of stock solution and working solutions ofthe analyte and internal standard. The stability of the analyte (and IS) is satisfactory when the determined concentration is within the limits of accuracy. 

SECTION A SECTION B SECTION C SECTION D SECTION E SECTION F Sample Records Field Handling and Cooling of Samples Freezer Maintenance and Freezer Logs Sample Storage Sample Shipping Calibration of Temperature Recording Instruments... 

Most >-xylene is available commercially at a purity less than 99.9 % and can be purified by recrystallization. To prepare 1.9 L of high purity p-xylene, begin with approximately 3.8 L of material and cool in a flammable storage freezer at -10 5 C until approximately A to V4 of the p-xylene has frozen. This should require about 5 h. Remove the sample and decant the liquid portion. The solid portion is the purified p-xylene. Allow the p-xylene to thaw and repeat the crystallization procedure on the remaining sample until the p-xylene is flee of contamination as indicated by gas chromatography. 

Samples collected from the field should ideally be placed in boxes in order to prevent damage to the crop sample and to aid storage, although this often depends on the freezing facilities of the organization concerned. Where samples are boxed, untreated samples should not be mixed with treated samples. When freezing, samples should be separated by space or by using separate freezers for treated and untreated samples. 

Sample transportation logistics Freezer storage sample processing j capabilities... 

A solution to this dilemma is to place soil samples immediately in a freezer located in the field, the temperature of which is continuously monitored, as described previously. Laboratory-prepared storage study samples can then be used to determine test substance stability under freezer storage conditions that match those used in the field and during transportation and final storage. If a valid laboratory storage stability... 

A second approach to determining freezer storage stability involves the reanalysis of incurred residues found in actual samples that are stored over time. Using this approach, soil from an actual field sample containing residues is periodically analyzed... 

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. 

Field fortification samples are stored under various conditions in the fleld. Generally, after the weathering period is complete, the fleld fortification samples such as dosimeter sections are wrapped in aluminum foil, placed in a pre-labeled zip-type bag, and immediately placed on dry-ice in a cooler or in a freezer. Field fortification samples such as hand washes or face wipes are prepared in labeled jars, the lids are immediately taped with electrical tape, and the jars are placed in a zip-type bag and wrapped in bubble-pack and immediately placed in frozen storage. Air tubes or air filters are collected after weathering and wrapped so as to prevent breakage. These samples are then placed in a pre-labeled zip-type bag and immediately placed in frozen storage. 

Field forms may also be used to document the movement of samples in and out of storage, whether in a freezer or held at ambient temperature. Field forms have also been used to document the environmental conditions for storage of the samples. 

No specific sample preparation or processing is needed for this method. In general, fruits and vegetables were macerated with dry-ice and placed into freezer storage prior to extraction. 

Where items are stored in close proximity to one another, such as in refrigerators, freezers and cupboards, there may be a significant risk of crosscontamination. Samples and concentrated solutions of chemical standards should certainly not be stored in the same storage area. 

Storage areas, such as refrigerators, freezers and cupboards, should be regularly checked to avoid build-up of unnecessary items. Reagents and standards, which have passed their expiry date, and samples which need no longer be retained, should be appropriately disposed of. The laboratory should ideally keep records of what it has disposed of and when (and possibly also how). 

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