Surfactant Columns

Figure 19.7. Sketch of a foam fractionating column. Surfactants or other foaming agents may be introduced with the feed or separately at a lower feed point. Packing may be employed to minimize axial mixing.

As a further chemical tracer method enabling ppm-resolution we have employed gas chromatography (GC). In combination with mass spectrometry this allows for material selective quantification of chemical impurities. The GC technique is based on the retention time of a given speeies on a functionalised column and varies with the respective molecular affinity to the column surfactants. By subsequent cycles of solvation and rinsing it is possible to obtain a depth profile of the ehemical impurities contained in the crystalline host [10]. The main requirements imposed by gas chromatography arc a sufficient solubility and separability of the analysed molecular species. For example, for tet-racene to be solvable to an adequate amount, saturation in toluene is reached at 150 ng/1 pL [31]. 

Isolation from water of alkoxy-lated nonionics AE, NPE, PEG, acid ethoxylates, sorbi-tan ester ethoxylates, E/P copolymers, E/P adducts of alcohols, PPG Anion exchange resin in the cobal-tithiocyanate form, 15 x 200 mm 1 L or more of sample is passed through the column surfactant is eluted with 50 mL MeOH, EtOH, or 2-PrOH. 207... 

As another illustration, Eq. (22-48) becomes Eq. (22-50) for an enriching column which is concentrating a surfactant with a constant E ... 

A small amount of collector (surfactant) or other appropriate additive in the liquid may greatly increase adsorption (Shah and Lemlich, op. cit.). Column performance can also be improved by skimming the surface of the liquid pool or, when possible, by removing adsorbed solute in even a tenuous foam overflow. Alternatively, an immiscible liquid can be floated on top. Then the concentration gradient in the tall pool of main hquid, plus the trapping action of the immiscible layer above it, will yield a combination of bubble fractionation and solvent sublation. 

Many proteins and polymers have been analyzed on SynChropak GPC and CATSEC columns. Table 10.6 lists some of the published applications. The use of a surfactant to analyze the caseins in milk is illustrated in Eig. 10.12. Viruses have also been analyzed on SynChropak GPC columns, as seen in the chromatogram from Dr. Jerson Silva of the University of Illinois (Pig. 10.13). Dr. Nagy and Mr. Terwilliger analyzed cationic polymers on a series of CATSEC columns using differential viscometry as detection (Pig. 10.14) (9). 

Figure 13.22 shows the resolution of the surfactants Tween 80 and SPAN. The high resolution obtained will even allow the individual unreacted ethylene oxide oligomers to be monitored. Figure 13.23 details the resolution of many species in both new and aged cooking oil. Perhaps the most unique high resolution low molecular weight SEC separation we have been able to obtain is shown in Fig. 13.24. Using 1,2,4-trichlorobenzene as the mobile phase at 145°C with a six column 500-A set in series, we were able to resolve Cg, C, Cy, Cg, C9, Cio, and so on hydrocarbons, a separation by size of only a methylene group. Individual ethylene groups were at least partially resolved out to Cjg. This type of separation should be ideal for complex wax analysis.

Figure 12.18 LC-SFC analysis of mono- and di-laurates of poly (ethylene glycol) ( = 10) in a surfactant sample (a) normal phase HPLC trace (b) chromatogram obtained without prior fractionation (c) chromatogram of fraction 1 (FI) (d) chromatogram of fraction 2 (F2). LC conditions column (20 cm X 0.25 cm i.d.) packed with Shimpak diol mobile phase, w-hexane/methylene chloride/ethanol (75/25/1) flow rate, 4 p.L/min UV detection at 220 nm. SFC conditions fused-silica capillary column (15 m X 0.1 mm i.d.) with OV-17 (0.25 p.m film thickness) Pressure-programmed at a rate of 10 atm/min from 80 atm to 150 atm, and then at arate of 5 atm/min FID detection. Reprinted with permission from Ref. (23).

For stable foam drilling operations, much less volumetric rate of air flow is needed (i.e., usually less than 500 actual cfm). Also, the compressor should be capable of variable volumetric rate of flow and variable output pressure. The back pressure must be continuously adjusted to maintain a continuous column of stable foam in the annulus. This continuous adjustment of back pressure requires, therefore, continuous adjustment of input volumetric rate of airflow and output pressure (also, water and surfactant must be adjusted). 

Naphthalenedisulfonate-acetonitrile as the only mobile phase with a silica column coated with a crosslinked aminofluorocarbon polymer has proven to be an effective combination for the separation of aliphatic anionic surfactants. Indirect conductivity and photometric detection modes are used to monitor these analytes. The retention of these surfactants is found to depend on both the ionic strength and the organic solvent content of the mobile phase. The mechanism of retention is considered to be a combination of both reverse phase and ion exchange processes. Selective separation of both alkanesulfonates and... 

Alcohol ether sulfates with different number of moles of ethylene oxide are also used in emulsion polymerization and in the paint industry as dispersing agents. A particular use of alcohol ether sulfates is as foamers in low- and medium pressure drilling for water, oil, and gas. The foam produced by the surfactant reduces the pressure of the water column as water is replaced by air. 

Alcohol sulfates and alcohol ether sulfates separated by HPLC on a styrene-divinylbenzene copolymer column with 4 1 (v/v) methanol and 0.05 M ammonium acetate aqueous solution as the mobile phase were analyzed by simultaneous inductively coupled argon plasma vacuum emission spectroscopy (IPC), monitoring the 180.7-nm sulfur line as a sulfur-specific detector [294]. This method was applied to the analysis of these surfactants in untreated wastewaters. 

A very sensitive method for the determination of MCA in surfactants is a gas chromatographic one [249]. The method is based on the derivatization of the sample with ethanol and subsequent extraction of the derived ester with cyclohexane. The acids are identified and qualified gas chromatographically by the use of an electron capture detector and two capillary columns of varying polarities. The detection limit is 0.2 ppm. 

The amount of residual sulfonate ester remaining after hydrolysis can be determined by a procedure proposed by Martinsson and Nilsson [129], similar to that used to determine total residual saponifiables in neutral oils. Neutrals, including alkanes, alkenes, secondary alcohols, and sultones, as well as the sulfonate esters in the AOS, are isolated by extraction from an aqueous alcoholic solution with petroleum ether. The sulfonate esters are separated from the sultones by chromatography on a silica gel column. Each eluent fraction is subjected to saponification and measured as active matter by MBAS determination measuring the extinction of the trichloromethane solution at 642 nra. (a) Sultones. Connor et al. [130] first reported, in 1975, a very small amount of skin sensitizer, l-unsaturated-l,3-sultone, and 2-chloroalkane-l,3-sultone in the anionic surfactant produced by the sulfation of ethoxylated fatty alcohol. These compounds can also be found in some AOS products consequently, methods of detection are essential. 

MacMillan and Wright [133] identified and measured saturated and unsaturated 1,3- and saturated 1,4-sultones in anionic surfactants by a series of separation maneuvers. Ion exchange treatment separates sultones from the bulk of the ionic surfactant. TLC concentrates the sultones systems for HPLC analysis. They found that pentane-ether is preferable to the usual hexane-ether system and that the addition of a little methanol sharpens the separations. Finally, HPLC using a micro-Porasil column with 90 1 isooctane/ethanol provides quali-... 

The alkanephosphonic acid dichlorides obtained by these methods are converted with amines, with all reactions carried out in solvents such as acetone, benzene, or diethyl ether at 10°C with triethylamine as HC1 captor. The conversion runs quantitatively followed by a purification with the help of column chromatography with chloroform/methanol in a ratio of 9 1 as mobile phase. The alkanephosphonic acid bisdiethanolamides could be obtained as pure substances with alkane residues of C8, C10, C12, and Ci4. The N-(2-hydroxyethane) alkanephosphonic acid 0,0-diethanolamide esters were also prepared in high purity. The obtained surfactants are generally stable up to 100°C. Only the alkanephosphonic acid bismonomethylamides are decomposed beneath this temperature forming cyclic compounds. 

The neutral surfactant is measured after fixing of the ionic substances on a combined anionic/cationic ion exchange column. Volatile substances in the eluate are determined by gas chromatography and nonvolatile substances are measured gravimetrically. In the bulk of the neutral compounds phosphoric acid triesters may be present. This part is additionally determined by atom emission spectroscopy. 

Fig. 18. Comparison of results from various particle systems for stirred vessel with baffles and bubble columns Activity a/ao of Acylase resin after t = 300 h, equilibrium drop diameter dg of silicon oil-water-surfactant emulsion and reference floe diameter dpv of floe system in dependency on specific power P/V H/D = 1 D = 0.15 m 0.4 m...

This paper will be limited to a discussion of our packed column studies in which we have addressed attention to questions regarding, (a) the role of ionic strength and surfactant effects on both HDC and porous packed column behavior, (b) the effects of pore size and pore size distribution on resolution, and (c) the effects of the light scattering characteristics of polystyrene on signal resolution and particle size distribution determination. 

To reduce or eliminate polymer solute/glass packing interactions the following parameters were optimized a) pH, ionic strength and concentrations of additives such as nonionic surfactants, b) selection of pore sizes in a column combination. 

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