Control of relative migration of small inorganic and organic anions with cyclodextrins in capillary electrophoresis (CE)

Abstract

The capillary electrophoretic separation of iodide, nitrate, perchlorate, thiocyanate, bromate, iodate, and ethane-, butane-, pentane-, and octanesulphonate was examined in sodium chromate or potassium hydrogen phthalate electrolytes and in the presence of α -, γ -, (0-40 mmol/L) and β -cyclodextrin (0-10 mmol/L). Largest decreases in electrophoretic mobility were observed for iodide, perchlorate, and thiocyanate, probably due to inclusion of these anions in the cyclodextrin (CD) cavity. Changes in migration patterns and electroosmotic flow were observed, which depended on cyclodextrin type and concentration and on electrolyte-cyclodextrin interactions. Thus for larger cavity cyclodextrins ( β-or γ-cyclodextrin) or in the presence of chromate, relatively small decreases in electrophoretic mobilities for all the anions were observed, indicating that a good match between analyte and cavity size and minimal cyclodextrin affinity for electrolyte ions are essential for different migration patterns. Separation efficiencies were between 50 000 and 400 000 theoretical plates, and calibration plots for iodide and octanesulphonate were linear; R2 = 0.998 and 0.9999, respectively, in the concentration range (5 x 10-5)-(5 x 10-3) mol/L.Key words: capillary electrophoresis, inorganic and organic anions, cyclodextrins, inclusion complex, electroosmotic flow control.

Fast and simple method for determination of iodide in human urine, serum, sea water, and cooking salt by capillary zone electrophoresis

“…The ionic mobility of iodide is close to the ionic mobilities of other small ions such as chloride, bromide, or anions sulfate, and nitrate (Table 1), and the main task is usually to increase resolution of iodide from these anions. The most often used way is decreasing mobility of iodide by complexation with quaternary ammonium surfactants [14,20,23,[25][26][27]31] or quaternary ammonium salt (tetrabutylammonium, TBA) [17,29], host-guest interactions with cyclodextrins [19,24,28,30], calix [4]arene [32], 18-crown-6 [15,17], diazocrown ether [16], and ion-pairing with cationic polymers poly(diallyldimethylammonium chloride) (PDADMAC) [33], Polybrene [21], PVPyB [21], PVP [28], and PEI [18]. The effect of huge amounts of chloride present in the sample was eliminated also by adding NaCl into the BGE used for the separation [26,27] or by performing the separation directly in BGE composed of higher concentrations of KCl [15] or NaCl-HCl [50].…”

“…The effect of huge amounts of chloride present in the sample was eliminated also by adding NaCl into the BGE used for the separation [26,27] or by performing the separation directly in BGE composed of higher concentrations of KCl [15] or NaCl-HCl [50]. As iodide has an absorption maximum at 235 nm and its molar absorption coefficient increases also below 220 nm, optical detection in the low UV region can simply be used but also indirect detection with chromate BGE [21,24,25,46,48], phthalate [24,47], pyromellitate [22], or Tiron [19] being the absorbing BGE co-ion was reported. Amperometric [47], conductivity [13,[28][29][30] or potentiometric detectors [42,44,49,53] were used as well.…”

Determination of bromate in drinking water by zone electrophoresis-isotachophoresis on a column-coupling chip with conductivity detection

“…Here, a general guidance is known [53,54] and the use of the separation mechanism providing larger differences in the effective mobilities of bromate and anionic macroconstituents than those attained in this work offers a general way in reaching this goal. An experimental search for such a mechanism is, however, needed as the data relevant to the migration properties of bromate are very scarce [17,18,20,21]. …”

“…Although these methods are suitable to the resolutions of bromate from other anions that are currently present in water samples [17][18][19][20][21], they do not meet requirements relevant to the concentration sensitivity, especially in instances when this anion is accompanied in the loaded sample by anionic matrix constituents (chloride, sulfate, nitrate) in a larger excess. As some of the above sample pretreatment procedures developed for IC of bromate are very likely applicable also in CE [15,17], they may, at least partially, diminish these sensitivity limitations of CE.…”

Chiral ion‐exchange capillary electrochromatography of arylglycine amides with dextran sulfate as a pseudostationary phase

“…Stathakis and Cassidy [10,11] extended this technique to enable the separation of UVtransparent ions. Since then, numerous publications have appeared , focusing on the separation of small organic and inorganic ions [12] with different types of stationary phases, such as charged surfactants [13][14][15][16][17][18] or polymers [8][9][10][11][19][20][21] dissolved in background electrolyte (BGE), ion-exchange resins packed in capillaries [22][23][24], and charged polymers or nanoparticales attached to capillary wall to increase the exchange surface area [25][26][27][28][29][30].…”