Eluents methanesulfonic acid

The system in Figure 26-6 can be adapted to produce the strong-acid eluent methanesulfonic acid (CH3S03H+). For this purpose, the polarity of the electrodes is reversed and the reservoir... 

Figure 4.23 Separation of alkali metals, alkaline-earth metals, ammonium, and alkanol-amines on lonPac CS17. Column temperature 30 °C eluent methanesulfonic acid (EG) gradient 0.5 mmol/L linearly to 0.8 mmol/L in 25 min and then step change to 9 mmol/L and isocratic for 10 min flow rate 1.4mL/min ...

Figure 4.25 Separation of biogenic amines together with common inorganic cations on lonPac CS17. Column dimensions 250 mm x 2 mm i.d. column temperature 40°C eluent methanesulfonic acid (EG) gradient 3 mmol/L isocratic for 33 min, then linearly to 6 mmol/L in 8.5 min, isocratic for 3 min, and then linearly to 40mmol/L in 5 min flow rate 0.4mL/min ...

Figure 4.81 Gradient elution of ethanolamines together with the six standard inorganic cations. Separator column lonPac CS15 column dimensions 250 mm x 2 mm i.d. column temperature 40 °C eluent methanesulfonic acid gradient 2 mmol/L isocratically for 14 min and then to 27 mmol/L in 16 min flow rate 0.3 ml7...

Fig. 3-84. Separation of various monocarboxylic acids at an anion exchanger IonPac AS6 (CarboPac). - Eluent 0.0017 mol/L NaHCOj + 0.0018 mol/L Na2C03 flow rate 1 mL/min detection suppressed conductivity injection 50 pL solute concentrations 3 ppm fluoride (1), 40 ppm acetic acid (2), 20 ppm glycolic acid (3), 10 ppm a-hydroxyisocaproic acid (4), 20 ppm formic acid (5), oxamic acid (6), methanesulfonic acid (7), amidosulfonic acid (8), and a-ketoisocaproic acid (9).

Figure 1.10. Schematic representation of EG40 electrolytic production of methanesulfonic acid (MSA) eluent (courtesy of Dionex Corp).

An analogous system can be used to generate methanesulfonic acid (MSA) eluent for the separation of cations (Fig. 1.10). In this case, the anode generates for eluent production. The cathode generates OH anion that combines with the H in the MSA electrolyte reservoir. MSA anion migrates across the anion exchange membrane to combine with the eluent cation (maintaining electric neutrality). 

The properties and performance of a commercial weak-acid resin column (Dionex CS12) have been described [41]. The substrate is a highly cross-linked, macroporous ethylvinylbenzene-divinylbenzene polymer with a bead diameter of 8 pm, a pore size of 6 nm, and a specific surface area of 3(X) m /g. In a second step, this substrate was grafted with another polymer containing carboxylate groups. The exchange capacity is listed as 2.8 mequiv/column for a 250 mm x 4 mm i.d. column. With this column, simple eluents such as hydrochloric or methanesulfonic acid can be used to separate mono- and divalent cations rapidly and efficiently under isocratic conditions. 

Considerable interest has been shown in a novel cation exchanger first developed by Schomburg et. al. [43]. The material consists of a silica substrate of very uniform particle size coated with a poly(butadiene-maleic acid) resin which serves as the cation-exchange moiety. This material, which is now conunercially available, gives good separations of both monovalent and divalent metal ions in a single run. Ordinary eluents such as hydrochloric or methanesulfonic acid, or complexing eluents may be used [44,45]. 

In this type of separation the analyte cations compete with the eluent cation for ion-exchange sites and move down the eolumn at different rates. The ionic eluent selected depends on the cations to be separated, the type of separation column and on the detector. In many cases an aqueous solution of a strong acid such as hydrochloric, sulfuric or methanesulfonic acid is a satisfactory eluent. Sample cations commonly separated include the following alkali metal ions (Li, Na+, K", Rb, Cs ), ammonium, magnesium, alkaline earths (Ca, Sr +, Ba ), and various organic amine and alkano-lamine cations. Most other metal cations are separated with a weakly complexing eluent. 

By using an ion exchanger with carboxyl groups or with both carboxyl and phos-phonate groups, it is possible to separate both monovalent alkali metal cations and certain divalent metal cations in a single nm. A dilute solution of a strong acid such as methanesulfonic acid is generally used as the eluent. Particular emphasis has been placed on separation of Li, Na, K, Mg + and because these ions are... 

The effect of solvent was studied by measuring the retention factor, k, for a series of protonated alkylamine cations with 25 mM methanesulfonic acid in the appropriate solvent as the eluent [11]. Ordinarily a plot of log k vs. the number of carbon atoms in such a homologous series would be linear. The slope of such a plot is at least in part an indication of the effect of the carbon chain on the retention factor. The retention factors were measured under identical conditions in each of four organic solvents. The k values of the alkylamines increased according to the solvent used in the following order methanol, ethanol, 2-propanol, acetonitrile. However, in any given solvent the k values of the individual amines were almost constant from Cl to CIO. Separation of the individual amines was not possible. 

Simultaneous analysis of alkali and alkaline earth metals can only be performed with weak acid cation exchangers, using carboxylic groups as ion-exchange functionality group and usually with methanesulfonic acid as the eluent. 

Dionex offers a just add water system for electrolyte generation and purification of commonly used eluents such as KOH and methanesulfonic acid. Eluents are generated from deionized water using an Eluent Generator (EG) cartridge and then polished of contaminants using a continuous-regeneration trap column. 

An acidic eluent such as methanesulfonic acid (MSA), which is used in cation chromatography, works on essentially the same principle. The of the eluent is... 

Later research has reafHrmed these early results [23]. A separation of alkali metal ions was first attempted in water alone using the lightly sulfonated macro-porous cation exchanger with aqueous 3 mM methanesulfonic acid as the eluent. Under these conditions the sample cations exhibited very similar retention times. The selectivity of the macroporous resin for alkali metal ions was improved con-... 

CS 12 Carboxylate High capacity, methanesulfonic acid eluent... 

The chemical type as well as the eluent concentration are important parameters in optimizing any given separation. Relatively minor differences in the separation of inorganic cations were observed when sulfuric acid and methanesulfonic acid (MSA) eluents of almost identical concentration were compared. Increasing the concentration of sulfuric acid eluent from 11 mM to 15.5 mM reduced the time for separation of common inorganic cations from about 11 min to 7 min (Figure 7.2). 

Figure 7.13 Separation of 12.5 ppm aniline (1), N-methyl-aniline and (2), N,N-dimethyl-aniline and (3), on a 5 cm sulfo-nated resin column (0.15 mmol L ). The eluent was methanesulfonic acid in methanol at a flow-rate of 1 ml min h (From Ref [13] with permission.)...

As discussed in the early part of this chapter, macro-cyclic complexes are generally more stable in nonaqueous solvents than in aqueous solution. Therefore, it is expected that adding 18-crown-6 to a nonaqueous mobile phase would increase the retention time of cations to be separated. Fritz s group added 18-crown-6 to a nonaqueous IC mobile phase to study the retention of alkali metal cations and ammonium ion on a sulfonic acid cation-exchange resin. The retention factors of all the ions increased with increasing concentration of 18-crown-6 in acetonitrile eluent containing 1 mM methanesulfonic acid. Most notably. 

Figure 4.4 Simultaneous analysis of alkali metals, alkaline-earth metals, and ammonium on lonPac CS12. Eluent 20mmol/L methanesulfonic acid flow rate 1 mL/min detection ...

Figure 4.5 Influence of acetonitrile on the retention of alkali and alkaline-earth metals employing lonPac CS12. Eluent lOmmol/L methanesulfonic acid/MeCN detection ...

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