Sampling continuous-flow centrifugation

Bates et al. [35] collected suspended particulate matter from river water and wastewater effluents using high speed continuous flow centrifugation, and analysed the isolated solids for hydrocarbons. The results were compared with those obtained on samples obtained by glass filter filtration. It was concluded that the use of a continuance flow centrifuge allows the concentration of organic associated with suspended particulate matter to be estimated more accurately. 

Water/SPM Collect water samples on disposable octyl-bonded silica solid-phase extraction columns dry elute with hexane/ether SPM collected by continuous flow centrifugation extract with acetone/water/benzene GC/ECD GC/MS O.lpg/L (water) 0.1 mg/kg (suspended particulate) 83 (water) 82 (suspended particulate) Ritsema et al. 1989... 

Standing-Crop Particles. Standing-crop, noncolloidal, particulate matter was sampled by using two techniques 1, niskin casts followed by filtration onto track-etched filters and 2, serial sieve fractionation in-line with continuous-flow centrifugation, which enabled the collection of gram quantities of suspended particles. 

Fractionation of Particulate Matter. Duplicate samples of river particulates collected by continuous-flow centrifugation were leached sequentially according to the following schema ... 

A total of 25 samples were collected from the upper and lower St. Clair and Detroit Rivers, and from the lower Niagara River and the river plume in Lake Ontario in the summers of 1984 and 1985. Water was pumped from a 1 m depth using a submersible pump which fed directly into a Westphalia continuous-flow centrifuge (9500 rpm). The centrifuged water was then collected in a 200 L stainless-steel aqueous phase liquid-liquid extractor (APLE)..A surrogate spike containing 1,3-dibromobenzene 1,3,5-tribromobenzene 1,2,4,5-tetra-... 

Flow injection analysis (FIA) was developed in the mid-1970s as a highly efficient technique for the automated analyses of samples. °> Unlike the centrifugal analyzer described earlier in this chapter, in which samples are simultaneously analyzed in batches of limited size, FIA allows for the rapid, sequential analysis of an unlimited number of samples. FIA is one member of a class of techniques called continuous-flow analyzers, in which samples are introduced sequentially at regular intervals into a liquid carrier stream that transports the samples to the detector. ... 

Fig. 4. 33 The AKUFVE solvent extraction apparatus Efficient mixing is achieved in the separate mixing vessel, from which the mixture flows down into the continuous liquid flow centrifugal separator (the H-centrifuge, hold-up time <1 s). (From Refs. 83a,b.) The outflow from the centrifuge consists of two pure phases, which pass on-line detectors, AMXs, for on-line detectors or continuous sampling. (From Refs. 80a-80d, 81.)...

Check the sample solution for particulate material. If insoluble silicate (white, gelatinous materials) or other particles are noted, centrifuge or filter the solution through a glass fibre filter before loading the sample onto the preconditioned column. This step is important in order to maintain a continuous flow of the sample solution through the column. 

Total suspended solids (TSS) were collected from 15 liters of each sample with a Sorvall SS-3 centrifuge, equipped with a "Szent-Gyorgyi and Blum" KSB continuous flow system. Titanium tubes were used to minimize contamination. The system was operated at 10,000 rpm with a flow rate of 125 mL/min. The solids were quantitatively transferred to 50 mL, polycarbonate centrifuge tubes and excess water was removed by centrifugation. Solids were frozen and later extracted in these centrifuge tubes. Additional material to determine total suspended solids (TSS) was collected from 8 liters of water by use of the continuous flow system. Finally the solids were transferred to porcelain crucibles and dried at 110° C to a constant weight. 

The discrete systems of automatic analysis developed so far have not, in general, solved the problem of deproteinization in a way as satisfactory as the dialysis step adopted in the continuous-flow system. An earlier version of the Robot Chemist included a module in which precipitation of proteins followed by filtration was carried out, and the Mecolab system can incorporate a centrifugation step, following which a sample of supernatant can be automatically aspirated, but both these approaches are relatively cumbersome. Consequently attention has been directed to the development of analytical methods for blood serum or plasma that do not involve a deproteinization stage, but although alternative methods not involving the removal of protein may be feasible for many estimations, the responsibility for confirming the validity of such alternative procedures remains with the analyst. 

FFF is a one-phase chromatographic system in which an external field or gradient replaces the stationary phase. The applied field can be of any type that interacts with the sample components and causes them to move perpendicular to the flow direction in the open channel. The most highly developed of the various FFF subtechniques is sedimentation FFF (SdFFF), in which the separations of suspended particles are performed with a single, continuously flowing mobile phase in a very thin, open channel under the influence of an external centrifugal force field. 

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