Esterquat

Quaternized Esteramines. Esterquatemary ammonium compounds or esterquats can be formulated into products that have good shelf stabihty (209). Many examples of this type of molecule have been developed (see Fig. 1). 

The single largest market for quaternary ammonium compounds is as fabric softeners. In 1993 this market accounted for over 50,000 metric tons of quaternaries in the United States (235). Consumption of these products is increasing at an annual rate of about 2—3%. The hair care market consumed over 9000 metric tons of quaternary ammonium compounds in 1992 (236). The annual consumption for organoclays is estimated at 12,700 metric tons (237). Esterquats have begun to gain market share in Western Europe and growth is expected to continue. 

In 1991, the European fabric softener market took a sharp turn. Producers in Germany, the Netherlands, and later in Austria and Switzerland voluntarily gave up the use of DHTDMAC (238) because of pressure from local environmental authorities, who gave an environmentally hazardous classification to DHTDMAC. A number of esterquats were developed as candidates to become successors to DHTDMAC (see Fig. 1). The ester group facihtates biodegradation. 

Fig. 6 General structures of the most important surfactants and metabolites alkylphenol polyethoxylate (APE) alkylphenol (AP) alkyl ether (AE) alkylphenol ethoxy carboxylate (APEC) linear alkylbenzenesulfonates (LAS) alkyltrimethylammonium compounds (ATMAC) dialkyldimethylammonium compounds (DADMAC) alkyldimethylbenzylammonium compounds (ADMBAC) esterquat (EQ) diesterquats (DEQ). X is usually a chlorine or bromine atom. DDAC (didecyldimethylammonium chloride) and BDD12AC (benzyldimethyldode-cylammonium) are the two target analytes with a reported immunochemical technique developed for their analysis [153,154]...

The toxicity of these compounds [ 173,175] can be relatively high compared to other surfactants, but their poor solubility and their tendency to adsorb to solids or to complex with anionic substances considerably reduce the real risk and adverse effects for the aquatic environment. [30,31,176]. The use of alkylquats has been substituted by the more easily biodegradable and less toxic esterquats that are nowadays the cationic surfactants produced in higher volumes. 

R = Alkyl radical of partially hydrogenated palm grease ESTERQUAT AU35... 

However, since DTDMAC also shows a pronounced resistance to biodegradation (see Chapter 1.7), it has been almost completely replaced by the more environmentally acceptable esterquats. 

From the esterquats introduced onto the surfactant market in the early 1990s, DEEDMAC, LEQ and EQ (Table 1.3) have gained widespread use [24-26]. 

Taking into consideration its physico-chemical properties, removal efficiencies, low biodegradability, predicted environmental levels, toxicity, and the need to provide sufficient safety margins for aquatic organisms, the demand for alternative cationic surfactants arose. Since 1991, DTDMAC has been replaced in some European countries due to producer s voluntary initiatives with new quaternary ammonium compounds, the esterquats. These contain an ester function in the hydrophobic chain (Table 1.3) that can be easily cleaved, releasing intermediates that are susceptible to ultimate degradation [24-26]. The effects of the phasing-out and replacement of DTDMAC can be demonstrated by the results of a Swiss study, where the surfactant... 

The trend of discovering the analytical field of environmental analysis of surfactants by LC-MS is described in detail in Chapters 2.6-2.13 and also reflected by the method collection in Chapter 3.1 (Table 3.1.1), which gives an overview on analytical determinations of surfactants in aqueous matrices. Most methods have focused on high volume surfactants and their metabolites, such as the alkylphenol ethoxylates (APEO, Chapter 2.6), linear alkylbenzene sulfonates (LAS, Chapter 2.10) and alcohol ethoxylates (AE, Chapter 2.9). Surfactants with lower consumption rates such as the cationics (Chapter 2.12) and esterquats (Chapter 2.13) or the fluorinated surfactants perfluoro alkane sulfonates (PFAS) and perfluoro alkane carboxylates (PFAC) used in fire fighting foams (Chapter 2.11) are also covered in this book, but have received less attention. 

Fig. 2.12.1. Chemical structure of different classes of cationic surfactants (a) quaternary ammonium surfactants (quats) (b) dialkylcarboxyethyl hydroxyethyl methyl ammonium surfactants (esterquats) (c) alkyl polyglycol amine surfactants (d) quaternary perfluoro-alkyl ammonium surfactants (e) N, N, N1, JV -tetramethyl-iV, iV -didodecyle-l,3-propane-diyle-diammonium dibromide (cationic gemini surfactant). R = alkyl or benzyl group.

Esterquats, quaternary carboxyalkyl ammonium compounds, have been developed as substitutes for the quats, especially DTDMACs which are applied as softeners in household products because they are resistant to degradation [42] and toxic [43,44]. Today, the esterquats are preferentially used (see Fig. 2.12.1(b)). As previously noted, the detection of all types of esterquats in environmental samples is difficult because of their tendency to adsorb at surfaces. Even in the inflows of wastewater treatment plants (WWTP) it is extremely difficult to find these compounds, which are reduced in toxicity [45] compared with the DTDMACs. One reason is that these carboxyalkyl ammonium compounds are not very stable in the environment. A second reason is that these compounds are not stable during the ionisation process. 

The results of ion-pairing separation of this compound according to the method of Conboy et al. [36] with MS detection in the ESI—LC— MS(+) mode was not promising. Even at a concentration of 50 mg L 1 of this esterquat in the standard solution, the S/N ratio was poor [39]. The base peak was the ion at m/z 428, representative of the fragment ions (R(CO)OCH2CH2)-N (CH3)(CH2CH2OH)2 with R = C17H33. 

APCI- and FIA-ESI-MS-MS(+) were applied for the examination of esterquats used in the household as textile softener (R(CO)OCH2 CH2)2-N (CH3)CH2CH2OH X- where R = tallowyl or oleyl moieties. 

Fig. 2.12.6. Identification of esterquat compounds FIA-APCI-MS-MS(+) (CID) product ion mass spectrum of selected [M — RCO]+ base peak ion of cationic surfactant blend of di-hydrogenated tallowethyl hydroxyethyl ammonium methane sulfate type (mlz 692 general formula (R(C0)0CH2CH2)2-N (CH3)-CH2CH2(0H)CH30S03) fragmentation behaviour under CID...

Various classes of cationic surfactants, including quats, esterquats, alkyl ethoxy amines, quaternary perfluoroalkyl ammoniums and gemini surfactants have been analysed extensively with LC—MS and LC—MS—MS techniques, and their spectra have been fully characterised. Different ionisation methods have been applied for the detection of such surfactants, including API techniques (APCI and ESI) in negative and positive modes of operation. In addition, detailed examples regarding MS—MS fragmentation of these compounds have been reported and presented in this chapter. 

Determination of two esterquats used as substitution products of DTDMAC, such as diethylester dimethylammonium chloride (DEED-MAC) and diesterquaternary (DEQ) (Fig. 4.2.8) in sewage water samples was carried out by the same ion-pair extraction procedure for the analysis of DTDMAC reported elsewhere [103,111] followed by microbore HPLC-ESI-MS analysis [116] and quantification employing commercial blends. 

Simms et al. [119] employed an integrated approach to determine the mechanism and kinetics of surfactant biodegradation by FAB-MS and liquid scintillation counting. Two compounds, the esterquat A -octadecyl-A - [palmytoyloxyethyl]-A V-dimethyl ammonium chloride and AM2-hydroxyethyl)-AyV-dimethyloctadecyl ammonium chloride,... 

The anaerobic biodegradability and toxicity on anaerobic bacteria of cationic surfactants such as ditallow dimethylammonium chloride (DTDMAC) and two esterquats have been investigated in a recent study [52], For the esterquats studied, high biodegradation levels were obtained and no toxic effects on anaerobic bacteria were observed even... 

Choose esterquats over DHTDMAC for environmentally friendly products, since they biodegrade more rapidly and are less toxic to aquatic life. 

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