Filtration, water samples

Ultra- filtration Water sample la filtered under pressure through a membrane that will pass molecular constituents below a certain size and retain those above that size. Large molecules Porosity of membrane daterminaa the size of molecules concentrated. Usually used for compounds > 1000 molecular weight. Can concentrate large sample volumes at low temperatures. 

Sea and river water samples collected in Nalgene plastics were acidified by adding 1 mL of nitric acid (0.1 mol L"i) per 100 mL of sample solution after filtration over a 0.45 pm Millipore Filter (Millford, MA). After the filtration, water samples were injected directly into the FIA system for the determination of iron(lll). 

A powerful tool now employed is that of diode array detection (DAD). This function allows peaks detected by UV to be scanned, and provides a spectral profile for each suspected microcystin. Microcystins have characteristic absorption profiles in the wavelength range 200-300 nm, and these can be used as an indication of identity without the concomitant use of purified microcystin standards for all variants. A HPLC-DAD analytical method has also been devised for measurement of intracellular and extracellular microcystins in water samples containing cyanobacteria. This method involves filtration of the cyanobacteria from the water sample. The cyanobacterial cells present on the filter are extracted with methanol and analysed by HPLC. The filtered water is subjected to solid-phase clean-up using C g cartridges, before elution with methanol and then HPLC analysis. 

Samples are generally prepared and analyzed in sets of 30 that include at least one control and one fortified control water sample. Optima-grade bottled water may be used as the matrix for the controls and the laboratory-fortified samples for all water types. Depending on the appearance of the samples, filtration may be required. 

A water sample is usually analyzed as it is, but is filtered through a glass-fiber filter to remove SS or to analyze both water and SS separately when chemicals adsorbed on SS used to be determined for a special purpose of a study. All filtration apparatus should be washed with the sample water in order to avoid contamination. 

Filter IL of water sample through a filter paper. Place an Empore extraction disk in a Millipore extraction funnel. Rinse the disk with 10 mL of ethyl acetate, dichloromethane, and acetonitrile, successively. Dry the disk under vacuum and then rinse the disk with 10 mL of methanol and 20 mL of deionized water by vacuum filtration. Pass the prefiltered sample through the disk and elute alanycarb with two portions of 10 mL of acetonitrile. Transfer the eluates through anhydrous sodium sulfate into a 50-mL flask. Remove acetonitrile by rotary evaporation. Dissolve the residue in 1 mL of acetonitrile. 

Presently, the precise determination of the true dissolved Th fraction in water samples remains a challenge. Results from ultrafiltration experiments on organic-rich water samples from the Mengong river tend to demonstrate that Th concentration is less than 15 ng/L in absence of DOC (Table 2 and Viers et al. 1997), and that Th is still controlled by organic carbon in the final filtrate of the ultrafiltration experiments. The latter conclusion is also supported by the results obtained for the Kalix river (Porcelli et al. 2001). These results therefore not only raised the question of the determination of the amount of dissolved Th in water but also of the nature of Th chemical speciation. 

SFE-GC-MS is particularly useful for (semi)volatile analysis of thermo-labile compounds, which degrade at the higher temperatures used for HS-GC-MS. Vreuls et al. [303] have reported in-vial liquid-liquid extraction with subsequent large-volume on-column injection into GC-MS for the determination of organics in water samples. Automated in-vial LLE-GC-MS requires no sample preparation steps such as filtration or solvent evaporation. On-line SPE-GC-MS has been reported [304], Smart et al. [305] used thermal extraction-gas chromatography-ion trap mass spectrometry (TE-GC-MS) for direct analysis of TLC spots. Scraped-off material was gradually heated, and the analytes were thermally extracted. This thermal desorption method is milder than laser desorption, and allows analysis without extensive decomposition. 

Serum blood, and urine Filtration of sample if needed blood requires digestion in a Parr bomb dilution of serum or urine with acid or water ICP/AES 10-50 pg/L 85 (serum) >80 (urine, blood) Que Hee and Boyle 1988... 

Water (dissolved or total) Digestion of water sample followed by filtration, acidification, addition of ammoniacal citrate-cyanide reducing solution extraction with chloroform containing dithizone. Measure absorbance at 510 nm (Standard Method 3500-PbD) 0.5 pg/L 98.6% at 10.4 pg/L (6.8% RSD) Eaton et al. 1995a... 

Shipboard analysis for the sampling of trace metals in seawater has been discussed by Schuessler and Kremling [2] and Dunn et al. [3]. Teasdale et al. have reviewed methods for collection of sediment pore-waters using in situ dialysis samples [4]. Bufflap and Allen [5] compared centrifugation, squeezing, vacuum filtration, and dialysis methods for sediment pore-water sampling. 

As a consequence of the previous considerations Kieber et al. [75] have developed an enzymic method to quantify formic acid in non-saline water samples at sub-micromolar concentrations. The method is based on the oxidation of formate by formate dehydrogenase with corresponding reduction of /3-nicotinamide adenine dinucleotide (j6-NAD+) to reduced -NAD+(/3-NADH) jS-NADH is quantified by reversed-phase high performance liquid chromatography with fluorimetric detection. An important feature of this method is that the enzymic reaction occurs directly in aqueous media, even seawater, and does not require sample pre-treatment other than simple filtration. The reaction proceeds at room temperature at a slightly alkaline pH (7.5-8.5), and is specific for formate with a detection limit of 0.5 im (SIN = 4) for a 200 xl injection. The precision of the method was 4.6% relative standard deviation (n = 6) for a 0.6 xM standard addition of formate to Sargasso seawater. Average re-... 

Gel filtration with Sephadex was used by Ghassemi and Christman [426] to make separations by molecular size on water samples concentrated by vacuum evaporation. Fluorescence was also used as one method for following the fractionation. Molecular size was also used by Gjessing [427] but with pressure dialysis as the method of separation. A similar method of concentration and separation was used by Brown [428] to follow the dispersion of these materials as fresh and salt water mixed in the Baltic Sea. 

Cores were collected from the NATA and adjacent wetland. Solid material was obtained from the aquifer beneath the NATA by filtering water samples from MW17. Pore water was squeezed from cores in a hydraulic press. Groundwater, surface and lake water samples were filtered (0.2 pm) in the field. Sub-samples were acidified to preserve cations. Arsenic species were separated on site by passing filtrate through SAX cartridges (Le et al. 2000). 

These results should be taken into account in the laboratory and field routines for characterizing AMD samples for instance they demonstrate the need to filtrate samples in the field, since refrigeration does not necessarily preserve this kind of water samples during transport to the lab. 

Water and waste water (APHA Method 4500-CN M) Filtration of sample optional treatment with resin treatment with ferric nitrate solution Colorimetric detection (thiocyanate) No data 71-99, 0.07-1.42 mg/L APHA 1992... 

Two reported identifications Of-1,2-diphenylhydrazine in water samples were located in the literature. Melton et al. (1981) reported that 1,2-diphenylhydrazine was present in Cincinnati, OH, drinking water (river water treated by coagulation, sand filtration, and chlorination). 

Water samples deserve some special attention despite of the apparent simplicity of their analysis. One reason is that, depending upon the source, water samples will have varying degrees of particulates. Most pollution surveys require filtration through a 0.45 M Millipore filter. In the event that filtration is omitted deliberately or unknowin gly, such particulates are entrained into the plasma, dissociated, and excited in the intense heat of the source. The efficiency of entrainment and nebulization depends on the specific nebulizer used, as well as the particle-size distribution. These in turn effect the degree of dissociation in the plasma. Thus, it is important to ensure that water samples are properly prepared. 

The purpose of this chapter is to discuss the use of Amberlite XAD-8 and Duolite A-7 in the field to process large volumes of water for the extraction of organic acids. Schemes involving filtration, concentration, and isolation steps for extracting organic acids from water by using XAD-8 and Duolite A-7 have been devised (9, 10). Some of the logistical problems of filtration and sample preservation are also discussed. 

Procedure. The procedure followed with XAD-8 was that of Thurman and Malcolm (8). The Suwannee River (GA) sample was filtered through 0.45-/zm Ag filters in Millipore, stainless steel, 142-mm, plate filter holders. The Laramie-Foxhills ground-water sample did not require filtration. Samples were processed on site within 24 h after collection to prevent alteration. All column eluates were adjusted to pH 2 upon collection and immediately refrigerated. 

The source of water samples was a 4-m3/h pilot plant on the Seine River located upstream from Paris, France. The background organic concentration ranged from 2 to 3 mg/L. The process, shown in Figure 1, included an upflow solids contact clarifier (Pulsator, Degremont, Rueil Malmaison, France) followed by rapid sand filtration (RSF). The effluent of the RSF was then split into four lines, which received various levels of ozonation followed by granular activated carbon (GAC) adsorption. Postchlorination (0.2 mg/L residual after 1 h) was used for bacterial control. 

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