NPECs

Breakthrough Behavior for Axial Dispersion Breakthrough behavior for adsorption with axial dispersion in a deep bed is not adequately described by the constant pattern profile for this mechanism. Equation (16-128), the partial differential equation of the second order Fickian model, requires two boundary conditions for its solution. The constant pattern pertains to a bed of infinite depth—in obtaining the solution we apply the downstream boundary condition cf — 0 as NPeC, —> < >. Breakthrough behavior presumes the existence of a bed outlet, and a boundary condition must be applied there. 

NP NPEC OC OP OPEC PCB PCDBT PCDD PCDF PCP PFB RA TCA TCDD TCF TCMTB TOC VSC VOC Nonylphenol Nonylphenol ethoxycarboxylate Organo chlorine Octylphenol Octylphenol ethoxycarboxylate Polychloroinated biphenyls Polychlorinated dibenzothiophene Polychlorin ated dib enzo-p - dioxins Polychlorinated dibenzo-p-furans Pentachlorophenol Pentafluorobenzyl Resin acids 2,4,6-Trichloroanisole Tetrachloro dibenzo dioxin Totally chlorine- free 2-(Thiocyanomethylthio)-benzothiazole Total organic carbon Volatile sulphur compounds Volatile organic compounds... 

Marcomini et al. [25] performed the protonation of the carboxylic groups of the SPC. This technique termed ion suppression effect chromatography enabled the individual elution of the SPC contained in a primary sludge from a wastewater treatment plant. The quantification of the SPC was performed under the assumption that the signals detected by fluorescence before the elution of the LAS (with the exception of NPEC) correspond solely to SPC. 

Methods applying LC—MS—MS for the quantitative determination of APEO were seldom reported. Houde et al. [29] recently described a LC(ESI)—MS—MS method for the determination of NPEO and nonylphenoxy carboxylates (NPEC) in surface and drinking water using a reversed-phase column (Cg) with isocratic elution. Transitions from the [M + NH4]+ ions to different product ions (m/z 127, 183, 227, 271, 315, 359 for NPEO reEO = 1-6 and m/z 291 for reEO = 7-17) were monitored, yielding detection limits from 10 to 50 ng L-1. 

Fig. 2.6.10. APCI-FIA-MS-MS(+) (CID) daughter ion mass spectrum of selected [M + NH4]+ parent ion (mjz 340) of potential carboxylated non-ionic surfactant metabolite of precursor NPEO prepared by chemical synthesis structure of short-chain NPEC CgHi9-C6H4-0-(CH2-CH2-0)-CH2-C00H fragmentation behaviour under CID presented in the inset [28],... 

ESI-MS-MS permitted unambiguous identification and structure elucidation of compounds detected under NI conditions (halogenated NPECs and NPs), while for NPEOs, detected under positive ionisation conditions no fragmentation was obtained and these compounds were analysed using a single stage MS as [M + Na]+ in selected ion... 

Fig. 2.11.15. General structural formulae of (I) di-nonylphenolethoxy carboxylates (di-NPEC CnIIl9)2-C6H3-0-(CIl2-CH2-())I-CIl2-C02), (II) nonylphenoldiethoxysulfo-nates (NP(EO)2-S03 C9H19-C6H4-0-(CH2-CH2-0)2-CH2-S03), (III) nonylphenol-ethoxy sulfates (NPEO-SO4 C -Ce -O-fCHa-CHa-O -SOgH), and (IV) nonylphenolethoxy phosphate (NPEO-PO4 O9II19—CBII/ —G—(CH2-CH2-0)x-...

A mixture of an industrial blend of di-nonylphenolethoxy carboxylates (di-NPECs (CnH2n+1)2-C6H3-0-(CH2-CH2-0)x-CH2-C00 (Fig. 2.11.15(1) R = (C9H19)2), which contained nonylphenolethoxylates (NPEO) as impurities from synthesis, was first analysed by APCI-FIA-MS(+/—) followed by a separation on a RP-Cig column in the presence of ammonium ions for ion-pairing purposes and for ionisation support. 

The FIA-MS(—) overview spectrum is presented in Fig. 2.11.16. It shows the di-NPEC homologue ions all equally spaced by Am/z 44. The ion starting at m/z 535 contains three ethoxylate units while the homologue at m/z 1019 represents a molecule with 14 EO units. In the APCI-LC-MS(+/—) mode, RICs and the selected mass traces at m/z 760 or 799 represent the di-NPEC homologue with nine EO units in the form of [M — CH2 — C02 + NH4]+ or [M — H] ions as shown in Fig. 2.11.17. Under positive ionisation conditions, the detection of the NPEO homologues ionised as [M + NH4]+ ions are favoured in the reconstructed ion mass trace (b) [22,61]. 

While APEO cannot be ionised successfully under negative conditions and consequently for identification MS-MS(—) is not informative, the identification of all anionic APEO derivatives is possible in the negative ionisation mode. For some derivatives, negative as well as positive ionisation can be applied. The loss of the anionic moiety, however, must be taken into account if ionisation is performed in the positive mode. Di-NPEC surfactant homologues submitted to negative CID resulted in the prominent di-alkyl-phenolate ion at m/z 345 (Fig. 2.11.18(a) as shown with the homologue m/z 799 under CID conditions). Therefore, the application of the parent ion scan of m/z 345 in the negative ESI and APCI-FIA-MS-MS mode is very specific for the detection of all anionic derivatives of di-NPEO comparable in... 

Fig. 2.11.16. APCI-FIA-MS(-) overview spectra of di-NPEC (C9Hi9)2-C6H3-0-(CH2-CII2-0)x-CH2-C02 H+) blend [22,61],...

Fig. 2.11.17. APCI-LC-MS(+/-) reconstructed ion current chromatograms (RIC) and selected mass traces (di-NPEC homologue with nine EO units) of di-NPEC separation of compound as in Fig. 2.11.16 [22,61].

The product ion spectra generated from the aromatic di-NPEC homologues ionised in the positive mode, however, suffered from the destructive ionisation of anionics, as also observed in the ionisation process of the aliphatic alkylether sulfates [22]. 

Fig. 3.1.4. Temperature profiles for in-sample derivatisation HS-SPME of NPEOs-NPECs using the CW-DVB fibre. Conditions as in Fig. 3.1.3. Compound identification ( ) NP ( ) NPEOi (A) NPEiC (X) NPE02 and (O) NPE2C compounds the relative area response is magnified by a factor of three (Figure taken from Ref. [80]).

The most commonly used solvent for the extraction of both alkylphenols and APEO is methanol [15-19]. If sodium hydroxide (20%, w/w) is added to the methanol, recoveries may increase by 25% [16,20]. Nonylphenoxy carboxylates (NPECs) can also be extracted using Soxhlet with methanol, but recoveries are often below 50% [19]. Only one method similar to Soxhlet has been reported for the extraction of AEOs, in which a Soxtec system with methanol is used [18]. 

A second SFE-based method for the extraction of NPEC from solid matrices is called subcritical (hot) water extraction [9], The method was applied for NPEi 4C in 0.25 g sludge samples. Subcritical water is used as the extraction solvent, with 30% ethanol as the modifier, yielding quantitative recoveries. Other tested extraction solvent compositions were C02, hot water, methanol-modified hot water, none of which were judged satisfactory. 

For several other non-ionic surfactant metabolites, standards are either commercially available, such as for dicarboxylated polyethylene glycols (DCPEGs) [20], or can be synthesised relatively easily, such as for nonylphenoxy acetic acids (NPECs) [21]. For quantification of metabolites for which standards are absent, the most similar available... 

In 40 WWTP all over Japan, primary effluents were found to contain mainly NPEOs with longer ethoxy units (ueo = 4-8), while NPECs accounted for <5% (mol mol-1) of total nonylphenolic compounds [18]. The average removal of nonylphenolic compounds was approximately 60% after biological treatment and 70% after full treatment (almost all studied WWTPs have a final disinfection process). 

Fujita et al. [18] studied formation of halogenated (chlorinated and brominated) NPEOs and NPECs during wastewater treatment. Halogenated derivatives were found to be produced during the disinfection processes by chlorination accounting for up to 10% of total nonylphenolic compounds. They were found in 25 of 40 WWTPs with concentrations up to 6.5 xgL 1 in secondary effluent and 52.4 jig L-1 in final effluent. Of all halogenated compounds, BrNPECs (nEo = 1-2) were found to be the most abundant. 

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