Phosphate—continued solvents

The solvent properties of triethyl phosphate continue to be of interest. Tin(iv) chloride dissolves to give mono- and di-solvates, but with SnCl4,2py heterolysis of an Sn—Cl bond occurs and the reaction can be followed conductometrically. I.r. and Raman data indicate that similar mono- and disolvates can be obtained from tributyl phosphate and both tin(iv) chloride and bromide. 

The simplest and most thoroughly studied solutions are those based on phosphoric acid at low temperatures (<35°C) which alone can fulfil all three requirements of acid solvent, film former (as metal phosphate) and diffusion agent by virtue of its viscosity. Thus copper and its main alloys of brasses and bronzes can be very effectively electropolished in 60-70% orthophos-phoric acid with the temperature maintained below 35°C under other conditions copper passivates or dissolves freely under mass transfer controlled conditions, but by varying the conditions appropriately polishing can be continued under mild agitation. An annotated polarisation curve is given in Fig. 11.7 readers are referred to recent studies for more detailed 2ispects " . 

FAB ionization has been used in combination with LC/MS in a technique called continuous-flow FAB LC/MS (Schmitz et al., 1992 van Breemen et al., 1993). Although any standard HPLC solvent can be used, including methyl-ferf-butyl ether and methanol, the mobile phase should not contain nonvolatile additives such as phosphate or Tris buffers. Volatile buffers such as ammonium acetate are compatible at low concentrations (i.e., <10 mM). Continuous-flow FAB has also been used in combination with MS/MS (van Breemen et al., 1993). The main limitationsof continuous-flow FAB compared to other LC/MS techniques for carotenoids, such as ESI and APCI, are the low flow rates and the high maintenance requirements. During use, the 3-nitrobenzyl alcohol matrix polymerizes on the continuous-flow probe tip causing loss of sample signal. As a result, the continuous-flow probe must be removed and cleaned approximately every 3 hr. 

FAB ionization has been used in combination with LC/MS in a technique called continuous-flow FAB LC/MS (van Breemen et al., 1991b). Although any standard HPLC solvents may be used, including ethyl acetate, methanol, and water, the mobile phase should not contain nonvolatile additives such as phosphate or Tris buffers. Volatile buffers such as ammonium acetate are compatible. The low flow rate of... 

A polyvinyl acetate latex prepared by semi-continuous polymerization at 55° using a polymethacrylic acid-nonylphenol-poly-ethoxylate phosphate ester emulsifier and sodium persulfate-sodium formaldehyde sulfoxylate initiator (23). The latex was cleaned by ion exchange and serum replacement using both Nuclepore and Pellicon membranes, and the cleaned latex and serum fractions were analyzed by conductometric titration. In addition, the dried films were extracted with water and organic solvents, and the extracts were analyzed by infrared spectroscopy and thermo-gravimetric analysis. 

The use of trimellitates is expected to regain ground lost due to TMA shortages in the late seventies. Polymeries will continue to be used in those areas where high solvent extraction resistance and migration are major concerns. Phosphates are expected to continue their growth in flame retardant applications. Also, new capacity for dioctyl terephthalate (DOTP) has been announced(25). 

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