Sodium phosphotungstate

TEM has been used to determine the shape and particle size of nanoparticles [27, 33]. Samples are prepared by placing a drop of preparation on copper grids, followed by negative staining with an aqueous solution of sodium phosphotungstate, phosphotungstic acid, or uranyl acetate [27, 163, 164]. Freeze fracturing with TEM has been... 

Phosphotungstic acid finds use in the precipitation of proteins, alkaloids, and certain amino acids. The solubility of sodium phosphotungstate, contrasted with the comparative insolubility of the potassium and ammonium salts, has suggested its use as a reagent in qualitative analysis. 

Fig. 2a-f. TEM images of PAMAM dendrimers positively stained with 2% aqueous sodium phosphotungstate a G10 b G9 c G8 d G7 e G6 f G5. Reprinted with permission from [14]. Copyright 2002 American Chemical Society... 

Wershaw and Vader (unpublished data) observed by TEM particles with a diameter of approximately 20 A in a humic acid fraction that had been negatively stained with sodium phosphotungstate. A similar size for these particles was measured by small-angle X-ray scattering. The particles measured in the other studies referenced before were substantially larger than these, and probably represent aggregates of smaller particles. 

Na402.P205.Wl2036.H360l8 Sodium phosphotungstate. 

Figure 36 TEM micrographs of PAMAM dendrimers. (Left) PAMAM dendrimers positively stained with 2% aqueous sodium phosphotungstate imaged by conventional TEM (a) GIO, (b) G9, (c) G8, (d) G7, (e) G6, and (f) G5. Scale=50nm. For G6 and G5, a small amount of G10 has been added as a focusing aid. (Right) GIO dendrimers imaged in vitrified water by ctyo-TEM. Scale=50nm. Reproduced with permission from Jackson, C. L. ...

Bromo-l-hydroxy-Nb-methoxycarbonyltryptamine (34) is obtained seven steps with a 17% overall yield from tryptamine (14) (Scheme 6) [17]. 1-Methoxy-JVb-methoxycarbonyltryptamine (35), available from 14 in four steps [5-7], is converted to 5-bromo-M>-methoxycarbonyltryptamine (36, 50%) employing our nucleophilic substitution reaction with 47% HBr [18]. Subsequent reduction (93%) with EtsSiH/CFaCOOH, followed by oxidation with 30% H202/sodium phosphotungstate, gives rise to 34 (66%) through a 2,3-dihydroindole (37). 

Toluene solutions of the styrene monomer are extracted with distilled water and to the extract are added sodium phosphotungstate and sodium carbonate solutions. The intensity of the blue colour produced is compared visually with that of standards comprising solutions of the inhibitor in toluene which have been similarly treated. 

Into seven further 5 cm separatory funnels pipette 0.1, 0.5, 1.0, 2.0, 5.0, 7.5 and 10.0 cm of a 10 ppm toluene solution of the inhibitor which is being determined in the monomer sample (ie. additions of between 5 and 100 u g of inhibitor. Extract the sample funnel and the seven standard funnels with 20 cm distilled water then two 10 cm portions of distilled water and collect the 40 cm aqueous extracts in 50 cm Nessler cylinders (filtering if necessary). Dilute to 50 cm with water. To the sample and standard solutions add 2 cm sodium phosphotungstate reagent and 4 cm of sodium carbonate (10%) in this order and mix well after the addition of each reagent. Leave the solutions for 15 min and compare the depth of the blue colour obtained for the sample with that obtained from the various standard solutions. If necessary, repeat the run this time more closely bracketing the sample solution with the standards to obtain a better colour match between sample and standards. 

Transmission electronic microscopy (TEM). TEM measurements were made on a Jeol JEM -2100 Transmission Electron Microscope operated at an accelerating voltage of 100 kV in the Institut Federatif d Exploration Fonctionnelle des Genomes (Toulouse, France). Samples were negatively stained by a solution of sodium phosphotungstate. 

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