Filtration of water samples

Arce et al. [39] developed a flow injection analysis (F1A) system (Fig. 5.3) for online filtration of water samples prior to CE analysis. They also constructed a pump-driven unit for extraction and filtration of soil samples combined with CE in an online mode (automated sample transfer between pre-CE sample preparation step and the CE) [40]. The method was precise and four times faster than conventional methods of sample preparation with an off-line unit. Blood samples are centrifuged immediately to remove red blood cells and the serum is stored as discussed above. Sometimes, urine samples also contain precipitates which are removed by centrifuge. 

For soil/sediment samples the results of these analyses are reported based on the wet weight of the sample. However, use of the SDS apparatus allows the water content of a sample to be determined from the same aliquot of sample that is also extracted for analysis. The amount of water evolved from the sample during extraction is used to approximate the percent solids content of the sample. The percent solids data may be employed by the data user to approximate the dry weight concentrations. The percent solids determination does not apply to the extraction of particulates from the filtration of water samples or to the extraction of fly ash samples which are treated with an HC1 solution prior to extraction. 

Extracts of the aqueous filtrate of water samples are in methylene chloride which is concentrated to approximately 10 mL by K-D or rotary evaporator prior to combining with the toluene extract of the particulates. If using K-D, the methylene chloride can be concentrated in a water bath instead of a heating mantle. 

Filtration of water samples at collection removes from the water the suspended and colloidal fractions (for separate analysis, if desired) but some dissolved... 

The role of filtration of water samples at the time of collection and in relation to storage and preservation of the sample is often an important consideration. Many substances of interest may be present in a water sample in particulate as well as soluble form. Filtration removes particulate matter, so that a decision on whether to filter at the point of collection will depend on the objectives of the study. Another consideration relevant to filtration and the possible presence of particulate matter are the effects on such matter of adding a sample preservative such as acid. Generally, it is sound practice to filter before adding a preservative that may solubilize particulate matter or leach contaminants from it. 

Normann B. 1993. Filtration of water samples for DOC studies. Mar. Chem. 41 239-242. Cauwet G. 1999. Determination of organic carbon and nitrogen by high-temperature combustion. In Grasshoff K., Kremling K., and Ehrhardt M. (Eds.), Methods of Seawater Analysis, 3rd edn. Wiley VCH, Weinheim, pp. 407-420. 

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. 

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... 

In the analysis of seawater, the only significant interference arises from turbidity caused by particles in the sample. Prior filtration of the sample is therefore necessary. For anoxic waters, however, sulfide concentrations over 2 pm were found to decrease the absorbance. This was overcome by adding an excess of either Cd2+ or Hg2+ to the sample [171,172],... 

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. 

Experimental Technique. The solid material (1-3 g) with known particle size and standard water (30-50 ml) containing the radionuclide of interest were shaken in glass bottles for 8-12 hours at constant temperature (25°C or 65 C). The phases were separated by centrifugation (50 min, 7000 rpm) and the distribution coefficient of the radionuclide was determined from measurements of the remaining activity of the water. Filtration of the samples through 0.2 pm membrane filter did not change the values. 

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. 

The use of three 250-mm X 8-mm columns in series (Shodex S-801/S S-802/S S-802/S) controlled by thermostat at 75°C, using water as mobile phase at 1 ml/min and a refractive index as detector, allowed Sanchez Munoz et al. (30) to quantify, with a single injection, the glycerol in wines after a simple filtration of the sample through a 0.2-/am membrane. Furthermore, the authors were also able to quantify the ethanol and sucrose and conduct, for glycerol, a comparison between the method suggested and an enzymatic one see Fig. 3. 

Traditionally, in order to prevent oxidation of unstable Fe(II) species, the water sample has to be filtered immediately after sampling (filtration of the sample in the field needs to be carried out under completely oxygen-free conditions) and stabilized stabilization depends on the subsequent analytical method.51 Even when all sample treatment protocols are rigorously applied, Fe(II) is so easily oxidized that the initial speciation can be distorted simply by contact of the sample with air. Mn(II) oxidizes much more slowly than Fe(II) this reaction is about 107 times slower than that of Fe(II) at pH 8 and 25°C,52 reducing the risk of error during the speciation procedure. After filtration, only Mn(II) and Mn(IV) colloids remain in the sample. Filtered samples, mostly acidified, are commonly stored in precleaned Teflon bottles at 4°C. 

Step 1. Measure 1 to 4 L (or 25 mL, as specified by instructor) of water sample (which has been previously acidified) with a graduated cylinder and record the volume to the nearest 1 (or 0.1) mL. Filter the sample through a fluted filter paper and collect the filtrate in a clean beaker of appropriate size. 

The manifold filtering device allows for simultaneous filtration of six samples simultaneously. Glass vials are placed under each filter support to collect the eluate. A vacuum pump applies a negative pressure to the water sample. 

The Empore Rad disk method allows to save time since it is no more necessary to proceed to a tedious preconcentration in routine. An acidification of water is sufficient before filtration of the sample through the membrane. The strontium fixed on the membrane is recovered by elution using a solution of 0.025 M EDTA in a basic medium. 

The filtration experiments were conducted in cross-flow mode at pressure 0.25-0.5 MPa in the system. In that pressure range for filtration of water, permeate flux was 26-85 L/m. AU process parameters were recorded with data acquisition system periodically the samples of permeate and retentate were collected for chemical analysis. 

Clarification of surface water samples is achieved by using a laminar flow filtration chamber (Fig. 3.17C). The concentrated particles and clarified water are removed through separate outlets. The filter operates vertically, with a continuous flow of water sample being fed upward from the base of the system into the ultrasonic field. Particles concentrate along the central axis of the chamber and allow the clarified material to be drawn out of the filter at the edges. 

Figure 3. Dissolved organic carbon (DOC) size distribution of water samples taken at Volo Bog filtered immediately after sampling and after storage for three weeks before filtration.

The reversal of this trend, or the decrease in Kads when one progresses from 25Z seawater to distilled water can be explained if one considers the solubility behavior of the adsorbent, humic acid. Humic acid was found to be fairly insoluble in solutions varying from 25Z to lOOZ seawater. These solutions are characterized by a faint coloration even after the humic acid has been centrifuged out. As mentioned earlier, filtration of these samples resulted in retention of DPM by the filter paper, probably due to adsorption. The coloration of the centrifugate was considerably darker for the distilled water experiments, suggesting that the humic acid was more soluble in this medium. Thus the increased concentration of dissolved humic acid in distilled water led to greater solubilization of DPM and its sorptive behavior was thus modified by the greater concentration of dissolved humic acid. 

There are two different approaches available for taking samples of suspended matter from waterways. These are filtration or centrifugation of water samples and collecting settled particulate matter in a sediment trap. Filtration or centrifugation can be conducted on grab samples or on water which is pump-extracted from instream. It is necessary to measure volumes filtered or centrifuged to calculated concentrations or loads in water samples. 

Using pure ( ) water, an appropriate equilibrium step and - if neeessary - filtration of the sample are adequate measures for gradient elution to avoid dirt and ghost peaks. With isocratie elution, aet only when necessary (see above), however some precautions such as filtration are right on target (see Tip No. 19). 

Sea, river and industrial water samples collected in Nalgene plastics were acidified by adding 1 mL of hydrochloric acid (0.1 M) per 100 mL of sample solution behind filtration over 0.45 pm Millipore Filter (Millford, MA). After filtration, 20 pL of water samples were injected directly into the FIA system for the determination of iron (II). Total iron was determined by reducing of all forms of iron to iron (II) in the procedure described (van Staden J.F. and Kluever L.G. 1998 Asan A., et al. 2003). 

Several authors have used ion-exchange methods to preconcentrate trace metals for further analysis from geothermal water 410) for x-ray determination 411, 412) for y-spectroscopy (475) and for atomic absorption spectroscopy (474, 475). For x-ray analysis, an attractive method for preconcentration is the use of ion-exchange resin-loaded paper (476-422). Although these methods often need slow filtration of the sample or several passes to obtain quantitative extraction of the metals, the sorbed material is presented in a convenient form for X ray, and low-concentration solutions and large sample volumes can be used. 

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