Analysis of anionics

This chapter deals with the analysis of some individual anionic surfactants as raw materials and in some formulated products, or obtained as fractions separated by ion exchange or otherwise. It is assumed that materials obtained from unknowns will have been identified by spectroscopy or other means. 

Anionic raw materials do not usually contain more than one surfactant species, and the determination of total active matter is usually straightforward, provided that the molecular weight is known. Anionics in formulated products can be determined without separation provided that no other ingredient interferes. Determination of mixtures with other surfactants, including mixtures of anionics, is covered in chapter 8. 

Fractions obtained by anion exchange almost always contain other salts, as illustrated by the following examples. 

Fractions obtained by removing cationics and amphoterics on a strongly acidic cation-exchange resin and neutralising the effluent contain salts of the anions of the cationics, and possibly anions of non-surfactant salts that were not removed by the initial extraction from the sample. 

Fractions obtained by eluting from anion-exchange columns contain all the exchangeable anions from the resin. Hydroxide ions from a strongly basic resin eluted with hydrochloric acid emerge as water, and the excess acid is volatile, but if such an acidic eluate has been neutralised before evaporation it contains sodium or other metal chloride. Chloride ions from a weakly basic hydrochloride resin eluted with ammonia appear as ammonium chloride, which may be the chief constituent of the dried residue. 

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Selection and Standardization of Titrants EDTA is a versatile titrant that can be used for the analysis of virtually all metal ions. Although EDTA is the most commonly employed titrant for complexation titrations involving metal ions, it cannot be used for the direct analysis of anions or neutral ligands. In the latter case, standard solutions of Ag+ or Hg + are used as the titrant. 

Pretreatment of the collected particulate matter may be required for chemical analysis. Pretreatment generally involves extraction of the particulate matter into a liquid. The solution may be further treated to transform the material into a form suitable for analysis. Trace metals may be determined by atomic absorption spectroscopy (AA), emission spectroscopy, polarogra-phy, and anodic stripping voltammetry. Analysis of anions is possible by colorimetric techniques and ion chromatography. Sulfate (S04 ), sulfite (SO-, ), nitrate (NO3 ), chloride Cl ), and fluoride (F ) may be determined by ion chromatography (15). 

Faguy PW, Marinkovic NS, Adzic RR. 1996. Infrared spectroscopic analysis of anions adsorbed fi om bisulfate-containing solutions on Pt(l 11) electrodes. J Electroanal Chem 407 209-218. 

Saari-Nordhaus, R. and Anderson, Jr., J. M., Ion chromatographic analysis of anions using a solid-phase chemical suppressor, Am. Lab., 26 (January), 28C, 1994. 

CE has been used for the analysis of anionic surfactants [946,947] and can be considered as complementary to HPLC for the analysis of cationic surfactants with advantages of minimal solvent consumption, higher efficiency, easy cleaning and inexpensive replacement of columns and the ability of fast method development by changing the electrolyte composition. Also the separation of polystyrene sulfonates with polymeric additives by CE has been reported [948]. Moreover, CE has also been used for the analysis of polymeric water treatment additives, such as acrylic acid copolymer flocculants, phosphonates, low-MW acids and inorganic anions. The technique provides for analyst time-savings and has lower detection limits and improved quantification for determination of anionic polymers, compared to HPLC. 

In cases where 2D NMR experiments are insufficient for a complete analysis of anionic surfactant mixtures, LC-NMR may provide better information. Characterisation of fatty alcohol ethoxylate (FAE) based oligomeric surfactants by on-line 2D (GCOSY, TOCSY and Homo 2DJ) stopped-flow HPLC- H NMR has been described [655,656]. The analysis of a typical mixture comprising three components (PEG and PEOs with different end-groups) is shown in Figure 7.34. In this representation, the 111 NMR frequency domain is in the... 

ESI operating in the negative ion mode has been the interface most widely used for the analysis of anionic perfluorinated surfactants. In addition, ESI has also been optimized for the determination of neutral compounds such as the sulfonamides perfluorooctanesulfonamide (PFOSA), perfluorooctanesulfonami-doacetate (A-EtFOSAA), and t-Bu-PFOS. The use of APPI has been explored in few works [126-128], Takino et al. [126] found as the main advantage of this technology, the absence of matrix effects, but the LODs were considerably higher than those obtained by LC-ESI-MS-MS. 

Figure 4.18 Analysis of anions in water using ion-pair liquid chromatography. Column, octadecyl-bonded silica gel, 15 cm x 4.6 mm i.d. eluent, 2 mM tetrabutyl-ammonium hydroxide (pH 5.3) in 3% acetonitrile-water flow rate, 1 ml min- detection, UV200 nm. Peaks 1, Br 2, N03 and3,1. ...

Barco, M. Planas, C. Palacios, O. Ventura, F. Rivera, J. Caixach, J. Simultaneous Quantitative Analysis of Anionic, Cationic, and Nonionic Surfactants in Water by ESI-MS With Flow Injection Analysis. Anal. Chem. 2003, 75, 5179-5136. 

Prince Technologies CE-Sure Anion kit Analysis of Anions (CZE)... 

We have seen that a BGE for analysis of anions and organic acids needs to have (a) a pH above the p A 2 of the analyte, (b) a sufficient buffering effect, and (c) a co-ion as a probe for indirect UV detection, with mobility close to that of the analytes of interest. Furthermore, care should be taken to reverse the EOF of the capillary and to work in the anodic or reverse mode. 

Quantitative analysis of anions from a prenatal vitamin formulation chloride, sulfate, nitrate, citrate, fumarate, phosphate, carbonate, acetate (see also cations)... 

Kfivankova, L., Pantiickova, P., Gebauer, P., Bocek, P., Caslavska, J., and Thormann, W. (2003). Chloride present in biological samples as a tool for enhancement of sensitivity in capillary zone electrophoretic analysis of anionic trace analytes. Electrophoresis 24, 505—517. 

Because of its exceptional selectivity, sensitivity and speed, IC is particularly suited to applications involving analysis of anions and cations in wastewater, natural waters, source effluents, workplace environments, ambient air and rain water. The analysis of organic as well as inorganic ions can be performed by 1C. Table I is a growing list of ions which have been successfully separated and detected. The principles of IC and selected applications to environmental pollutants are described in this paper. 

Recent studies on the SEC analysis of anionic polyelectrolytes are given in references 68-78. and those for cationic polyelectrolytes are covered by references 55.58.61.62. 79-91. Papers dealing with adsorption of proteins during SEC are 9.30. 92-102. The reader should also refer to reviews 16 and 12 for older references on these topics. 

Analysis of anions and cations by mass spectrometry and mass spectrometry/mass spectrometry... 

Ilioudis, C. A., Georganopoulou, D. G., Steed, J. W., Insights into supramolecular design 2 Analysis of anion coordination geometry of oxoanions in a protonated polyamine matrix. CrystEngComm 2002, 4, 26. 

Figure 9. Analysis of anions and cations in river water using tartaric acid/18-crown-6/methanol-water eluent with a carboxylated polyacylate stationary phase in the protonated form. Ions 1) sulfate 2) chloride 3) nitrate 4) eluent dip 5) unknown 6) sodium 7) ammonium 8) potassium 9) magnesium 10) calcium (from ref. 80)...

Fig. 1.4 Separation unit in a column coupling configuration as used for the analysis of anions in river water...

Fig. 13.1 Separation unit in a column coupling configuration as used for the analysis of anions in river water 1, sampling block with a 30pL sampling valve 2, terminating electrolyte compartment with a cap (3) 4,...

The type of the oxidation product on galena is independent of the chemical environment during preparation. Rao152) measured the adsorption heat of K amyl xanthate (KAX) on unactivated and Cu2+-activated pyrrhotite (FeS) and compared his results with heats of the reaction between KAX and Fe2+ or Cu2+ salts. With the unactivated mineral, the interaction involves a chemical reaction of xanthate with Fe2+ salts present at the interface (i.e. not bound to the crystal surface). The adsorption enthalpy is identical with the formation of Fe2+ amyl xanthate FeS04 + 2 KAX —> FeX2 + K2S04, and -AH = 97.45 kJ/mol Fe2+). As revealed from the enthalpy values and the analysis of anions released into the solution, the interaction of xanthate with Cu2+-activated pyrrhotite consists of xanthate adsorption by exchange for sulfate ions (formed by an oxidation of sulfides) at isolated patches (active spots), and by further multilayer formation of xanthate. The adsorption heat of KAX on pyrrhotite at the initial pH 4.5 was - AH (FeS unactivated) = 93.55 kJ/mol Fe2+ and - AH (FeS activated) = 70.03 kJ/mol Cu2+. 

New methodologies for the laboratory analysis of cations and metals include the use of inductively coupled plasma emission spectrometry (ICP/ES) or the combinahon of ICP with mass spectrometry (ICP/MS) (e.g., Ivahnenko et al., 2001). The advantages of plasma techniques include (i) a wide and linear dynamic concen-trahon range (ii) multi-element capabihty and (iii) relatively free of matrix interferences. The use of ion chromatography (1C), gas chromatography (GC), and GC/MS has increased for the analysis of anions and dissolved organics (Barth, 1987 Kharaka and Thordsen, 1992 Ivahnenko et al., 2001). 

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