Storage, samples

Ammonia.. The most rehable results for ammonia are obtained from fresh samples. Storage of acidified samples at 4°C is the best way to minimi2e losses if prompt analysis is impossible. The sample acidity is neutrali2ed prior to analysis. Ammonia concentrations of 10 -0.5 M can be determined potentiometricaHy with the gas-sensing, ion-selective electrode. Volatile amines are the only known interferents. 

SAMPLE STORAGE AND ARSENIC DETERMINATION IN NATURAL WATERS... 

Although widely employed, the use of external standardization takes no account of matrix effects, i.e. the effect on the analytical signal caused by the interaction of analyte with the matrix in which it is found, or losses of analyte from the unknowns during sampling, storage and work-up. 

A manufacturer usually stores samples of both raw materials and finished products for extended periods of time. He may even be required to do so by law. Sample storage may present hazards often overlooked. A single bottle of perfume, for instance, is too small to be considered a fire hazard, even though the material is quite flammable. Hundreds of these bottles, however, stored away as retain samples by a cosmetics manufacturer will become a fire hazard. 

W. Yu, W. K. Dodds, M. K. Banks, J. Skalsky, and E. A. Strauss, Optimal staining and sample storage time for direet micro.scopic enumeration of total and active bacteria in soil with 2 fluore.scent dyes, Appl. Environ. Microbial. 61 3367 (1995). 

Storage stability studies for carfentrazone-ethyl compounds on crop matrices have shown a pattern of stability for at least 7-24 months, depending on the study program or the maximum sample storage interval for the study. Carfentrazone-ethyl was not stable in field corn starch, potato tuber and bovine kidney. The residue results indicated that a significant portion of carfentrazone-ethyl was converted to C-Cl-PAc in these matrices however, the total amount of carfentrazone-ethyl and C-Cl-PAc accounted for the original spiking level. Since both carfentrazone-ethyl and C-Cl-PAc were determined in these stability studies, the instability of carfentrazone-ethyl was not of any concern. 

Sample storage stability Prohexadione-calcium in strawberry, rice grain, rice straw, wheat grain and barley grain is stable at -20 °C for 40, 140, 60, 80 and 100 days, respectively. Approximately 88% of the applied prohexadione-calcium remained in soil when stored at —20 °C after 80 days. 

Storage stability studies for sulfentrazone compounds on crop matrices showed a pattern of stability for at least 3-38 months, depending on the study program or the maximum sample storage interval for the study. 

Anticipated persistence and mobility of agrochemical and degradates Anticipated variability in soil residues and cost constraints Depends upon specific analytical procedures (and associated LOQ) and available sample storage and processing capabilities Necessary for most dryland and irrigated cropping scenarios... 

Each of the five main steps in field conduct (site selection, test plot layout, test substance application, sample collection, and sample storage/handling) is addressed below. 

Crop samples, 0.5-2 kg, are chopped into small pieces and homogenized thoroughly in a food processor. A typical analytical sample size is <50 g. To prevent the potential degradation of the analytes during sample storage, samples should be frozen immediately after collection and maintained frozen until analyzed. 

Ammonium acetate, HPLC grade (Fisher Scientific, Fair Lawn, NJ) or equivalent Bags, sample storage, plastic... 

Vials autosampler, clear glass with Teflon-lined septum caps, 1.8-mL sample storage, clear glass with Teflon-lined caps, 12-mL... 

Sample storage stability. The level of fenothiocarb (0.4 mg kg ) in soils stored in the dark at 3 °C decreased to 94-97% after 40 days and to 68-82% after 120 days. 

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