Other Eluent Salts

Alkali metal salts of benzenesulfonic acid are similar to benzoate in their eluting power although benzenesulfonate retains its 1- charge at a lower pH. 

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Between 20 and 200 L air at a flow rate of 1 to 3 L/min is passed through a glass fiber filter. The herbicides and their salts, deposited on the filter, are desorbed with methanol, and the chlorophenoxy acid anions are determined by HPLC using UV detector at 284 to 289 nm. The LC eluent is a mixture of NaC104-Na2B407 at 0.001 M concentration. Other eluent composition and UV detector wavelength may be used. A stainless steel column 50 cm x 2 mm ID, packed with Zipax Sax or equivalent may be used at ambient temperature and 1000 psi. 

On the other hand, the elution of sodium fluoride with sodium chloride solution yields a pair of positive and negative peaks the elution volumes of the positive and negative peaks correspond to those for the eluent salt and the sample salt, respectively [ref. 23]. The former and the latter chromatograms obtained by argentometry represent the elutions of the eluent counterion and coion, respectively. Concentration profiles of eluent counterion, x ", and coion, resulting from the injection of salt, are schematically illustrated in... 

Excessive baseline noise Grade of reagents employed Use HPLC grade reagents use better source of water re-cycle eluent investigate use of other buffer salts add 1-2 mmol L EDTA to eluent... 

An important publication by Kost et al. (63JGU525) on thin-layer chromatography (TLC) of pyrazoles contains a large collection of Rf values for 1 1 mixtures of petroleum ether-chloroform or benzene-chloroform as eluents and alumina as stationary phase. 1,3- and 1,5-disubstituted pyrazoles can be separated and identified by TLC (Rf l,3>i y 1,5). For another publication by the same authors on the chromatographic separation of the aminopyrazoles, see (63JGU2519). A-Unsubstituted pyrazoles move with difficulty and it is necessary to add acetone or methanol to the eluent mixture. Other convenient conditions for AH pyrazoles utilize silica gel and ethyl acetate saturated with water (a pentacyanoamine ferroate ammonium disodium salt solution can be used to visualize the pyrazoles). 

Deionized water can be used as an eluent for the analysis of nonionic polymers such as pullulan and polyethylene glycol. However, in most cases, salt solutions or buffer solutions are used to decrease ionic or other interactions between samples and the stationary phase or to prevent sample association (Eigs. 6.22 and 6.23, pages 196 and 197). 

One disadvantage of using salt solution as eluent is that the lignin sulfonates tend to adsorb onto the gel matrix, resulting in a resolution inferior to that obtained by elution with water. On the other hand, elution behavior with water is adversely affected by the polyelectrolyte properties of the lignin sulfonates. Adsorption, which is caused by the phenolic hydroxyl... 

Two resins were tested for the removal of succinic acid from simulated medium on a packed column of sorbent to simulate an actual process on a small scale. It is important to test the sorption with medium, because salts and other nutrients can interfere with the sorption. Table 4 presents the results for XUS 40285 MWA-1 was comparable. This indicates that either sorbent can remove succinic acid efficiently from the fermentation broth without direct loss of product. Both columns were then stripped or regenerated with hot water. Stripping with hot water recovered 70-80% of the succinic acid from the XUS 40285 resin whereas less (50-60%) was recovered from the MWA-1. The XUS 40285 column was stripped with 2 column volumes of hot water with eluent concentrations up to 49 g / L. Succinic acid was concentrated on average to 40 g/L in the XUS resin by this operation and to 30 g/L by the MWA-1. The 10-fold concentration factor bodes well for the use of sorbents to purify the fermentation broth. 

Due to its ability to withstand high pressure, its relative low cost, and inertness, stainless steel has become the standard material of columns and other chromatographic components. However, under certain circumstances, stainless steel has been shown to interact with the sample and the mobile phase [39]. The best known example is chloride salt corrosion of stainless steel. Data indicate that nearly all common eluents dissolve iron from stainless steel [39]. It appears that proteins also adsorb to stainless steel [39], The adsorption process is fast, whereas desorption is slow, a result which leads to variable protein recoveries. A number of manufacturers are offering alternatives to stainless components with Teflon -lined columns and Teflon frits. Titanium is being explored as an alternative to stainless steel. A cheaper and simpler procedure is to oxidize the surface of the stainless steel with 6N nitric acid. This procedure should be repeated about every 6 months. 

Because of the cobalt(II) contamination, the perchlorate salt is synthesized and then converted to other salts. Cobalt(II) chloride 6-hydrate (1.0 g, 4 mmole) and free [15]aneN4 (05 g, 4.2 mmole) are warmed in 100 mL of methanol for 15 minutes. Concentrated hydrochloric add is added dropwise (1 mL) and air is bubbled through the solution for at least 2 hours. Several drops of perchloric acid are added to precipitate the products as the perchlorates. The yield is 72%. The product is brown and is about 90% pure isomer I. The brown perchlorate salt is dissolved in acetonitrile and passed through a Dowex 1X8,200-400 mesh anion exchange column (Cl form) at a rate of 10 sec/drop. The eluent is concentrated by rotary evaporation. Some green solid (isomer II) precipitates. This is filtered and the volume of the filtrate is further reduced to precipitate the tan isomer (I) as the chloride salt. Yield 60% Anal. Calcd. for CoC2r H26N4a3 C, 34.80 H, 650 N, 14.76. Found C, 34.35 H, 7.09 N, 14.50. 

Currently, eluent composition, column temperature, and eluent pH are the only continuous parameters used as the arguments in functional optimization of HPLC retention. However, other parameters such as ionic strength, buffer concentration and concentration of salts and/or ion-pairing reagents can be taken into account, and mathematical functions for these can be constructed and employed. 

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