Eluant sodium carbonate

R)-(-)-5 -Methoxylaudanosine (7.2 g), 3-chloropropanol (3.5 g), sodium iodide (5.6 g) and sodium carbonate (0.5 g) were refluxed in 2-butanone (125 mL) for 16 h. The white suspension was filtered hot and solvent removed from the filtrate under vacuum. The residual gum was trituated with hot ethyl acetate to remove excess 3-iodopropanol, dissolved in 200 mL methanol and passed through a column packed with Dowex RTM.1-X8 ion exchange resin (60 g chloride form). The eluant was stripped of solvent under vacuum to give N-3-hydroxypropyl-l-(R)-5 -methoxylaudanosinium chloride (8.4 g) as an amophous solid. The material was assayed by HPLC as a 2.3/1 mixture of the... 

Ion chromatography has been applied to the determination of cobalt, nickel, copper, zinc and cadmium as their EDTA complexes using anion separation and suppressor columns and 0.03pm sodium bicarbonate0.03gm sodium carbonate [28] eluant and a conductiometric detector. 

When using conventional ion chromatographic separation techniques, it is possible that other matrix anions also common to non saline waters may coelute with bromide. For example, bromide and nitrate elute simultaneously using a standard anion separator column (Dionex No. 30065), standard anion suppressor (Dionex No. 30366) and standard eluant (0.003M sodium bicarbonate/0.0024M sodium carbonate). 

A remarkable property of the AS9 column with its acrylate-based latex beads is the relatively short retention times of polarizable anions such as iodide, thiocyanate and thiosulfate, for which the lonPac ASS has been used in the past (see Fig. 3-29). On lonPac AS9 (-SC), these anions, together with mineral adds, can be separated within 20 minutes using a sodium carbonate eluant (Fig. 3-32). Although retention times are very different for non-polarizable and polarizable anions, the latter ones do not exhibit tailing. Therefore, the ASS column is currently only used for analyzing polarizable anions if short retention times are required. 

The versatile mixture of sodium carbonate and sodium bicarbonate, on the other hand, finds widespread application, because the elution power and the selectivity resulting there from are determined solely by the concentration ratio of these two compounds. A great variety of inorganic and organic anions can be separated with this eluant combination. As the product of the suppressor reaction, the carbonic acid is only weakly dissociated, so that the background conductivity is very low. 

Pure sodium carbonate eluants were used in the past for the separation of several phosphorus species such as hypophosphite, orthophosphite, and orthophosphate they were separated in one run on lonPac AS3 and detected via electrical conductivity. Today, an lonPac AS12A is used for this application, and the three phosphorus species are separated with a carbonate/bicarbonate eluant (Fig. 3-84). 

Environmentally important anions such as sulfide and cyanide can be determined very sensitively via amperometric detection. For their separation on a conventional lonPac AS3 anion exchanger (Fig. 3-85), a mixture of sodium carbonate and sodium dihydrogen borate is used as an eluant. A small amount of ethylenediamine is added to the mobile phase to complex traces of transition metal ions, which could be present in the eluant [88, 89]. While the detection of these two anions is very easy, the interpretation of experimental results for the investigation of real-world samples is very difficult. These samples normally contain transition metal ions in their presence, sulfide and cyanide do not exist or only partly exist as free ions. However, only free ions are detected under the chromatographic conditions listed in Fig. 3-85. 

When polarizable anions are to be analyzed together with non-polarizable ones, the most suitable stationary phase available today is an acrylate-based anion exchanger such as lonPac AS9-SC. Pure sodium carbonate (c = 3 mmol/L) is used as an eluant. As can be seen from the chromatogram in Fig. 3-32 (see Section 3.4.2), the analysis time for such a separation is not much longer than that of polarizable anions on lonPac ASS. Thiosulfate and chromate cannot be separated under these chromatographic conditions, but they do not co-exist anyway for chemical reasons. 

The addition of even minute amounts of sodium carbonate has a particularly strong effect on the retenhon behavior of mulhvalent anions. The two iron cyanide complexes, Fe(CN)6 and Fe(CN)e, are a good example their separation is obtained with an eluant containing only 3 10 mol/L sodium carbonate (see Fig. 6-9), in addihon to tetrabutylammonium hydroxide and acetonitrile. Lowering the acetonitrile content in favor of sodium carbonate, the resoluhon between both signals will decrease drashcally, although the peak shape of the iron(II) complex will be significantly improved. 

Fig. 6 -8. Illustration of the sodium carbonate influence on retention exemplified with an inorganic anion separation. — Separator column lonPac NSl (lO-pm) eluant ...

A number of different ion chromatographic techniques exist for bromate analysis. In method 300.0 (Part B) [20], the U.S. EPA describes the separation of oxyhalides - chlorite, chlorate, and bromate in the presence of mineral acids on lonPac AS9-SC with suppressed conductivity detection. On this stationary phase, adequate separation between bromate and chloride is achieved with the standard eluant mixture of sodium carbonate and sodium bicarbonate if the chloride excess is less than 100-fold. Because in real-world samples the chloride content can easily be 50-100 mg/L, bromate quantification in the concentration range between 1 pg/L and 10 pg/L is impossible under standard conditions. Kuo et al. [21] improved the separation by treating the sample with a cation exchanger in the silver form, through which the chloride content is decreased to a value determined by the solubility of silver chloride in solution ( 0.4 mg/L chloride). 

The chromatogram of an acetone sample obtained under these chromatographic conditions is shown in Fig. 9-79. Even after prechloride concentration is below the detection limit. In comparison. Fig. 9-80 illustrates anion analysis in dimethylformamide, which is significantly more contaminated. In this case, a Metrosep Anion SUPP 1 column was used as a stationary phase, with a sodium carbonate eluant. 

A solution of 1-trimethylsilyloxycyclohex-l-ene (5.12 mmol) and benzaldehyde dimethyl acetal (5.47 mmol) in dichloromethane (15 ml) was cooled to —78°C, and to this was added TMSOTf (0.05 mmol) in dichloromethane (0.5 ml). The mixture was stirred at -78°C for 8h, and then quenched by the addition of water at —78 °C. Dichloromethane (50 ml) was added, and the mixture was washed with saturated sodium hydrogen carbonate solution and brine, and dried. Concentration provided a crude oil consisting of a 93 7 mixture of erythro- and r/jreo-2-(methoxyphenyl-methyl)cyclohexanone. Chromatography on silica gel (20g, eluant petroleum ether ether 10 1) gave the pure erythro (82%) and threo (6.7%) isomers as oils. 

Chlorotrimethylsilane (2.7 g, 25 mmol) (1) (CAUTION) is added to a solution of lithium bromide (1.74g, 20 mmol) in dry acetonitrile (20 ml) (2) with good stirring under a nitrogen atmosphere. Cinnamyl alcohol (1.34 g, 10 mmol) is then added and the reaction mixture heated under reflux for 12 hours. The progress of the reaction is monitored by t.l.c. on silica gel plates with hexane as the eluant. On completion of the reaction (12 hours), the reaction mixture is taken up in ether (50 ml), washed successively with water (2 x 25 ml), sodium hydrogen carbonate solution (10%, 50 ml) and finally brine, and dried over anhydrous sodium sulphate. Evaporation of the ether affords the pure bromide in 93 per cent yield. The product may be recrystallised from ethanol and has m.p. 31-32 °C CAUTION this compound is lachrymatory. 

Eluants other than carbonate/bicarbonate have also found wide application in many environmental and nonenvironmental analyses. Some common eluants are listed in Table 1.11.2. Sodium hydroxide solution has now become an eluant of choice for many ion chromatography analyses using suppressed conductivity detection. The schematic representation of the method is outlined in Figure 1.11.2. 

Jones and Tarter [11] have applied this technique to the simultaneous determination of metals (sodium, potassium, calcium, magnesium) and anions (chloride, sulphate, nitrate, bromide) in potable waters. The technique uses a cation separator column, a conductivity detector, an anion separator column and an anion suppressor column. Two different eluants were used lithium carbonate-lithium acetate dihydrate, and copper phthalate. 

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