Storage blanks

Storage blanks (40 mL vials with analyte-free water) are placed in cold storage with samples for VOC analysis. Regular analysis of storage blanks enables laboratories to detect whether sample cross-contamination may have taken place in cold storage. 

The most important evaluation of an ANG storage systems performance is the measurement of the amount of usable gas which can be delivered from the system. This is frequently defined as the volume of gas obtained from the storage vessel when the pressure is reduced from the storage pressure of 3.5 MPa (35 bar) to one bar, usually at 298 K. This parameter is referred to as the delivered V/V and is easy to determine directly and free from ambiguity. Moreover, it is independent of the ratio of gas adsorbed to that which remains in the gaseous state. To determine the delivered V/V an adsorbent filled vessel of at least several hundred cubic centimeters is pressurized at 3.5 MPa and allowed to cool under that pressure to 298 K. The gas is then released over a time period sufficient to allow the bed temperature to return to 298 K. A blank, where the vessel is filled with a volume of non-porous material, such as copper shot. 

Prior to entry into large tanks containing inert medium, ensure that pipes to the tank from cryogen storage are blanked off or positively closed off purge with air and check oxygen levels. 

Keep blank field samples separate from treated samples, both when in transit from the field and when in refrigerated storage awaiting processing. 

Field spikes with laboratory standards as well as spraying solutions were taken at a wide range of concentrations to determine the stability of the samples during both sampling and storage and possible contamination during the sampling procedure. Field blanks were also taken. 

T. C. Lee, B. Malone, M. L. Blank, V. Fitzgerald, F. Snyder, Regulation of the Synthesis of Platelet-Activating Factor and Its Inactive Storage Precursor (l-Alkyl-2-acyl-sw-glycero-3-phosphocholine) from 1-Alky 1-2-acety 1-mi-glycerol by Rabbit Platelets , J. Biol. Chem. 1990, 265, 9181-9187. 

This type of QC blank consists of a batch or subset of individual SPMDs of the same size and material as those prepared for a specific project. After preparation, SPMD-fabrication blanks are maintained frozen in vapor-tight metal cans under argon at -10 to -20 °C in the laboratory until the analysis of the project SPMDs. Processing and analysis of these blanks is concurrent with and identical to that of environmentally exposed SPMDs. The primary purpose of this type of QC sample is to account for any background contribution due to interferences from SPMD components, and for contamination incurred during laboratory storage, processing, and analytical procedures. 

This type of QC blank consists of a subset of SPMDs, made just prior to initiation of the analysis of an SPMD sample set. Operationally, the only difference between SPMD-process blanks and SPMD-fabrication blanks is the time of preparation and that the SPMD-process blanks are not subjected to storage, but are immediately processed and analyzed along with the environmentally exposed... 

SPMDs. Use of this type of blank is generally limited to laboratories that assemble SPMDs. If the numbers of SPMD-fabrication blanks are inadequate, SPMD-process blanks can be used to determine analyte recovery and the precision of the overall analytical method. Also, this type of QC sample can be used for other purposes, such as determining potential effects of storage or changes in batches or lots of SPMD materials. 

Blank and spiked samples were created by pipeting standard amounts of TRIS and Decabrom onto 10 cm2 areas (2x5 cm) of glass fiber filter leaving blank (2x5 cm) blocks between each spiked area. The filter was then used to collect a 2038 m3 air sample in the Research Triangle Park, NC. This filter was shipped to the field and returned for analysis. The results of analysis of areas of the filter are shown in Table IV. These results indicate the overall recoveries for sampling, shipping and storage as well as extraction recovery from this filter. 

Simplified analytical procedures for determination of gas-phase organic acids would be very beneficial. Currently, the acids are collected by using impregnated filters, denuder tubes, or water absorption techniques and then an ion chromatographic analysis. Normally, the collection and analysis steps are decoupled in time (i.e, samples collected at a field site are returned to a home laboratory for IC analysis). Once again, blank samples must be utilized to compensate for contamination during transport and storage prior to analysis. 

Blank /t595 is normal, but standards Improper reagent storage show less color than expected... 

The concurrent method allowed aqueous beef slurries to be irradiated (in the presence of oxygen) and at almost the same time volatile components were removed at pressures of about 25 mm. of Hg and at a temperature around 32°-36°C. When irradiation was carried out before distillation, the cans of irradiated beef were opened immediately or after G-months storage at ambient temperature. The beef was then slurried, and distillation was carried out in the usual manner 15,16). Nonirradiated beef slurries were distilled in exactly the same way as were periodic blank distillations of distilled water, to allow detection of contaminants or artifacts contributed by the distillation apparatus. In all cases, one condensate was collected at 0°C. (distillate) and another at — 78°C. (traps). 

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