Tetrabutylammonium ions, analysis

To determine secondary alkanesulfonates in sewage wastewaters, solid phase extraction (SPE) and a single-step procedure which combines elution and injection port derivatization for analysis with GC-MS were developed [36]. Again a tetrabutylammonium ion pair reagent was employed both to elute the secondary alkanesulfonates as their ion pairs from CI8-bonded silica disks and to derivatize sulfonate ion pairs under GC injection port conditions. Secondary alkanesulfonates were effectively recovered from samples of raw sewage (>92%) and from primary (>98%) and secondary (>85%) effluents. No... 

Girault and Schiffrin [6] and Samec et al. [39] used the pendant drop video-image method to measure the surface tension of the ideally polarized water-1,2-dichloroethane interface in the presence of KCl [6] or LiCl [39] in water and tetrabutylammonium tetraphenylborate in 1,2-dichloroethane. Electrocapillary curves of a shape resembling that for the water-nitrobenzene interface were obtained, but a detailed analysis of the surface tension data was not undertaken. An independent measurement of the zero-charge potential difference by the streaming-jet electrode technique [40] in the same system provided the value identical with the potential of the electrocapillary maximum. On the basis of the standard potential difference of —0.225 V for the tetrabutylammonium ion transfer, the zero-charge potential difference was estimated as equal to 8 10 mV [41]. 

The effect of additives on the rates of the individual step rates is experimentally traceable in the case of Pd hydrogen electrode.As discussed above in Section 5.5, analysis of the overpotential decay transient on Pd, upon interruption of the current, directly gives information on the affinity values shared by the Volmer and the Tafel steps during steady polarization. Typical results are shown in Figure Tetrabutylammonium ion (Figure... 

In the as-synthesized MFI-crystals the tetrapropylammonium (TPA) ions are occupying the intersections between the straight (parallel) and the sinusoidal channels of the zeolite, thus providing an efficient pore filling. The detailed structure of as-synthesized MFI-TPA has been elucidated by X-ray single crystal analysis (ref. 3). Also the combination tetrabutyl-Ztetraethylammonium can be applied as template in MFI-synthesis. A 1 1 build-in is found then (Fig. 1). When only tetrabutylammonium is available as template, the MEL (ZSM-11) lattice is formed with another distance between the channel intersections. 

Apart from improving extractions, ion-pairing techniques can also improve liquid-liquid partition cleanup. Examples of effective ion-pairing cleanup procedures have been described in the analysis of tetracycline (60) and penicillin (68) residues in milk using tetrabutylammonium reagent, the resulting ion pairs turned out to be fairly lipophilic and readily extractable with organic solvents. 

Increased retention of the analytes can also be achieved by addition of various ion-pair reagents in the mobile phase Tetrabutylammonium cations have typically been used as counter ions, at around pH 6.5, to increase retention and improve the selectivity in the analysis of monobasic penicillins (105, 123). Alkyl-sulfonic acids have been also used to improve the separation of -lactams bearing an amine function in their side chain or having a neutral side chain. Heptanesul-fonic acid (80, 103), decanesulfonic acid (87, 93, 106), dodecanesulfonic acid (77, 107-110), or mixtures of octanesulfonic and dodecanesulfonic acids (73, 75, 78, 79) constitute the principal alkylsulfonic acids used in -lactam analysis. In some applications, heptafluorobutyric acid (74, 76) or sodium thiosulfate (90, 112, 115, 116, 121, 122) has also been used as an ion-pairing reagent. 

Herrmann et al. (24) used ion-pair chromatography for the determination of cyclamate. The efficiency of LiChrosorb RP-18 and Hypersil MOS 3 with a mobile phase of 5 mM tetrabutylammonium p-toluenesulfonate, pH 3.5, mixed with 12% methanol for the separation of cyclamate from other sweeteners was investigated. With the first column, cyclamate separated from saccharin, but the second was the recommended column for the analysis of cyclamate, saccharin, aspartame, and dulcin in a single run. 

The first successful attempt to use HPLC for the analysis of betalains was carried out by Vincent and Scholz (247). With the help of paired-ion chromatography (PIC) on an RP column (/zBon-dapak C, 8) they separated betacyanins and betaxanthins of red beets. The ion-pairing approach was adopted in order to exploit the highly ionic character of these pigments and the durability of the C18 columns. Using methanol-water at pH 7.5 and tetrabutylammonium as the PIC reagent,... 

Alternatively, ionic compounds can be recovered from solution on hydrophobic sorbents using ion-pair SPE (IP-SPE). Carson [121] notes that advantages of IP-SPE over ion-suppression RP-SPE or ion-exchange SPE include selectivity, compatibility with aqueous samples and rapid evaporative concentration of eluents, and potential application to multiclass multiresidue analysis. IP reagents (e.g., 1-dodecanesulfonic acid for pairing with basic analytes or tetrabutylammonium hydrogen sulfate for pairing with... 

An alternative approach for MOCA analysis by HPLC, also involving reverse phase chromatography on a yBondapak Cis column, utilizes the paired ion technique. Paired ion chromatographic (PIC) analysis is effective for the determination of compounds which may exist as ionic species in the polar mobile phase. A counter ion, such as an alkyl sulfonate for cations or tetrabutylammonium phosphate for anions, is added to the mobile phase at a concentration of approximately 0.005 M. This technique generally affords Improved efficiencies in comparison to ion exchange chromatography. For the analysis of MOCA by PIC, the following conditions apply ... 

For the analysis of atropine and its major acidic decomposition products, Kreilgard used 0.01 M tetrabutylammonium sulphate as pairing-ion in a mobile phase of acetonitrile - 0.05 M... 

The method of anion exchange chromatography for heavy metal analysis may also be applied to ion-pair chromatography. With oxalic acid as the complexing agent and tetrabutylammonium hydroxide as the ion-pair reagent, an elution order opposite to cation analysis is obtained. The separation of anionic metal complexes on MPIC phases... 

Parameters such as solvent, basic medium and reaction time, affecting the derivatization of alcohols and phenols with benzoyl chloride, were investigated. End analysis was by GC with UVD . a sensitive method proposed for trace determination of phenols in water consists of preconcentration by SPE with a commercial styrene-divinylbenzene copolymer, acylation with pentafluorobenzoyl chloride in the presence of tetrabutylammonium bromide and end analysis by GC with either ECD or ITD-MS. LOD was 3 to 20 ngL for ECD and 10 to 60 ngL for ITD-MS, with 500 mL samples . Acylation with the fluorinated glutaric acid derivative 43 was proposed for determination of urinary phenols, as indicative of exposure to benzene and other aromatic hydrocarbons. End analysis by GC-MS shows strong molecular ions of the derivatives by electron ionization. The proto-nated ions are the base peaks obtained by chemical ionization. LOD was 0.5 mgL and the linearity range 0-100 mg L for phenol . 

A method for direct Ag determination at ppb levels in blood plasma was developed, based on GF-AAS with Zeeman effect background correction55. Selective preconcentration of several metal ions can be accomplished with poly(chlorotrifluoroethylene). Thus, after SPE of the complexes of Ag(I), Cd(II) or Cu(II) with bismuthiol II (14) at pH 2 and elution with tetrabutylammonium chloride in acetone, the eluate was directly determined by AAS72. Sub ngL-1 concentrations of Ag(I) may be preconcentrated by sorption on finely ground dithizone (12), filtration, dissolution of the dithizone in CHCI3 and end analysis by ET-AAS LOD 1 ngL-1 with no interference by humic acids, fulvic acids or soluble silica73. Ag(I) in river bottom and sea floor was preconcentrated on activated carbon containing dithizone (12), at pH 1.5 a suspension of the carbon was injected into a metal furnace AAS LOD 0.05 pg AgL-1, for 100 mL samples at SNR 359. 

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