Precipitation sample collection method

Cranston and Murray [35,36] took samples in polyethylene bottles that had been pre-cleaned at 20 °C for four days with 1% distilled hydrochloric acid. Total chromium Cr(VI) + Cr(III) + Crp (Crp particulate chromium) was coprecipitated with iron (II) hydroxide, and reduced chromium Cr(III) + Crp was co-precipitated with iron (III) hydroxide. These co-precipitation steps were completed within minutes of the sample collection to minimise storage problems. The iron hydroxide precipitates were filtered through 0.4 pm Nu-cleopore filters and stored in polyethylene vials for later analysis in the laboratory. Particulate chromium was also obtained by filtering unaltered samples through 0.4 pm filters. In the laboratory the iron hydroxide co-precipitates were dissolved in 6 N distilled hydrochloric acid and analysed by flameless atomic absorption. The limit of detection of this method is about 0.1 to 0.2 nM. Precision is about 5%. 

Cloud Water and Precipitation Collectors. Several methods have been developed for collecting cloud water samples (24-26). Probably the device most commonly used in warm clouds is the slotted rod collector developed by the Atmospheric Science Research Center at the State University of New York (SUNY) at Albany. Commonly known as the ASRC collector (25), this collector consists of an array of rods constructed from Delrin (a form of nylon). Each rod is hollow and has a slot located at its forward stagnation line. The rod radius determines the collection efficiency as a function of particle size, the rods are sized to collect cloud droplets but not submicrometer aerosol particles, and the 50% cutoff is calculated to be at about 3 xm. 

The collection of small amounts of very fine precipitates is the basis for many chemical and biochemical analytical procedures. Membrane filtration is an ideal method for sample collection. This is of great advantage in the... 

Several studies have examined the presence of PFCs in precipitation. Loewen et al. [172] examined a rainfall event sample collected from Winnipeg, Manitoba, and observed PFOS at a concentration of 0.59 ng/L, but PFCAs were not observed above method detection limits (1.1 to 7.2 ng/L). FTCAs and FTUCA were also observed concentrations of 8 2 and 10 2... 

Method B (Vacuum-sol method) A 0.96M aluminum nitrate solution was added to 50ml water glass solution until the Si/Al molar ratio was attained. The precipitate was collected by centrifugation and washed 7 times to remove the sodium ions. After washing, the precipitate was put into 200ml of water and then added a certain quantity of 0.94M nitric acid to peptize the precipitate to obtain the sol sample. The prepared sol was dried at room temperature in a vacuum box until it began to form the gel sample. The gels were also calcined at 550 C in air for 10 hours. The sol and solid samples produced by method B were defined as VSG samples [5]. 

Collection of sample vapors in the carrier gas effluent is performed automatically or manually, initiated by the detector signal. In purpose-designed instruments, injection and sample collection are automated for unattended operation. The exit from the detector splitter is usually led out through a side wall of the oven and thermostatted to avoid condensation of the sample. Several methods are used to trap samples, ineluding packed and unpacked cold traps, solution and entrainment traps, total effluent and adsorption traps, Volman traps, and electrostatie precipitators. Figure 11.12 [219-223]. 

Hg co-precipitation was demonstrated to be a considerably more effective method to pre-concentrate and isolate Pd from the matrix of airborne PM prior to analysis using ID-Q-ICP-MS, compared to Te co-precipitation. For all relevant elements, Hg co-precipitation reduced the concentrations of interfering matrix constituents by at least one order of magnitude more compared to Te co-precipitation (Table 3). The use of He as a collision gas was demonstrated to further increase the reliability of the measurements by minimizing molecular interferences. Pd concentrations measured for airborne PM samples collected in Frankfurt am Main demonstrate that they are significantly higher relative to those collected in more rural areas with a lower traffic density. Future levels of Pd in urban airborne PM need to be monitored to ensure they will not pose a human health risk, especially to vulnerable populations such as children. 

Extraction of botanical polysaccharides has traditionally been successfully carried out using the popular method of hot water extraction [1,2,5,71-77,85] and it is applicable in a variety of plant cell wall structures and water solubility of polysaccharide constitutes [65]. Briefly, the procedure involves large quantity of medicinal plant material/mushroom to be powdered, and then homogenized to maintain uniformity within and between the samples collected at different times. The powdered sample is then subjected to hot water extraction by autoclaving for approximately 2 h at 121 °C [5]. Autoclaved sample is filtered after allowing it to cool to room temperature, and the supernatant is then precipitated using 95% aqueous ethanol (supema-tant EtOH=l 4, v/v) for about 15 h at 2.5 °C to remove nonpolar... 

The specifics of sampling and storage for water are dependent upon the sample. Clearly, different procedures are required for groundwater, seawater, waste water, and atmospheric precipitation. Samples should be collected at a reproducible location and depth below the surface. In general, the contamination control procedures discussed above should be followed. Although it may be necessary to remove bacteria and other suspended solids from samples using membrane filters, it is necessary to investigate these methods for possible contamination or influence upon the types of species present. Acidification of water samples may also induce chemical transformations of some elements. 

Phosphate and polyphosphates are determined as total phosphorus in the ISO method (ISO 2294 1974). The sample is digested with nitric and sulfuric acids and the orthophosphate is precipitated as quinoline 12-molybdophosphate. The precipitate is collected on a glass filter, dried, and weighed and expressed as phosphorus pentoxide. A similar procedure described by the AOAC is ashing of the sample at 550°C, boiling of the ash in dilute nitric acid and filtration before precipitation of quinoline 12-molybdophosphate. 

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