Columns suppressed conductivity

High-sensitivity detection of non-chromophoric organic ions can be achieved by combining the power of suppressed conductivity detection with these columns. Suppressed conductivity is usually a superior approach to using refractive index or low UV wavelength detection. 

Figure 3 Gradient separation of anions using suppressed conductivity detection. Column 0.4 x 15 cm AS5A, 5 p latex-coated resin (Dionex). Eluent 750 pM NaOH, 0-5 min., then to 85 mM NaOH in 30 min. Flow 1 ml/min. 1 fluoride, 2 a-hydrox-ybutyrate, 3 acetate, 4 glycolate, 5 butyrate, 6 gluconate, 7 a-hydroxyvalerate, 8 formate, 9 valerate, 10 pyruvate, 11 monochloroacetate, 12 bromate, 13 chloride, 14 galacturonate, 15 nitrite, 16 glucuronate, 17 dichloroacetate, 18 trifluoroacetate, 19 phosphite, 20 selenite, 21 bromide, 22 nitrate, 23 sulfate, 24 oxalate, 25 selenate, 26 a-ketoglutarate, 27 fumarate, 28 phthalate, 29 oxalacetate, 30 phosphate, 31 arsenate, 32 chromate, 33 citrate, 34 isocitrate, 35 ds-aconitate, 36 trans-aconitate. (Reproduced with permission of Elsevier Science from Rocklin, R. D., Pohl, C. A., and Schibler, J. A., /. Chromatogr., 411, 107, 1987.)...

Figure 10 Separation of monochloroacetate, dichloroacetate, and trichloroacetate on a sulfonated poly(styrene-divinyl benzene) column with suppressed conductivity detection. Column 2% cross-linked sulfonated poly(styrene-divinyl benzene) capacity 0.02 meq/g. Flow rate 64 ml/hr. Eluant 15 mM sodium phenate. Suppressor 0.28 x 25 cm Dowex 50W X8 column (200-400 mesh). Detector Chromatronix conductivity cell connected to a Dow conductivity meter. (Reprinted with permission from Small, H., Stevens, T. S., and Bauman, W. C., Anal. Chem., 47,1801,1975. 1975 Analytical Chemistry.)...

Many IC techniques are now available using single column or dual-column systems with various detection modes. Detection methods in IC are subdivided as follows [838] (i) electrochemical (conductometry, amper-ometry or potentiometry) (ii) spectroscopic (tJV/VIS, RI, AAS, AES, ICP) (iii) mass spectrometric and (iv) postcolumn reaction detection (AFS, CL). The mainstay of routine IC is still the nonspecific conductometric detector. A significant disadvantage of suppressed conductivity detection is the fact that weak to very weak acid anions (e.g. silicate, cyanide) yield poor sensitivity. IC combined with potentiometric detection techniques using ISEs allows quantification of selected analytes even in complex matrices. The main drawback... 

Although AS and AES can be detected at a low UV wavelength, sensitivity is lacking and a more suitable detection was achieved using indirect photometric detection, post-column colour formation reactions, or a pre-column derivatisation, suppressed conductivity detection and refractive index detection [1,42,43]. A comparison of detection limits for the determination of these anionic surfactants shows that photometric and conductivity detectors are better (picomole or nanogram range) than refractive index or fluorometry detectors by about a factor of 1000 [40],... 

Thiocyanate Human urine Dilution with water then passage through disposable Toyo pack ODS and IC-SP columns Suppressed ion chromatography with conductivity detection 200 nM No data Miura and Koh 1991... 

FIGURE 6 Effect of p-cyanophenol on the separation of perchlorate. Column 4x250mm lonPac ASII. Flow rate I.OmLmin. Injection volume 25pL. Detection suppressed conductivity utilizing the Anion Self Regenerating Suppressor (4mm), recycle mode. Ion I—perchlorate (20mgL" ). (a) Eluent lOOmM NaOH. (b) Eluent 50 mM NaOH and 5mM p-cyanophenol. 

FIGURE 19 Choline in infant formula. Columns 4x250mm lonPac CSI2A, and 4x50mm CGI2A. Flow rate I mLmin. Eluent l8mM MSA. Injection volume lOpL. Detection suppressed conductivity, CSRS (4 mm), recycle mode. Ions I— sodium 2—ammonium 3—choline 4—potassium 5—magnesium 6—calcium. Sample preparation add 30 mL of I M HCI to 5 g sample, mix well, place in 70°C water bath for 3 h, cool, filter and dilute to 100 mL. 

FIGURE 14.3 Isocratic separation of morpholine, alkali, and alkaline earth metals on lonPac CS12A column. Eluent lOmM sulfuric acid. Detection suppressed conductivity. Peaks 1, lithium (0.5mg/L) 2, sodium (2mg/L) 3, ammonium (2.5mg/L) 4, potassium (5mg/L) 5, morpholine (25mg/L) 6, magnesium (2.5mg/L) 7, calcium (5mg/L). (From Rey, M.A. and Pohl, C.A., J. Chromatogr. A, 739, 87, 1996. Copyright 1996. With permission from Elsevier.)... 

Non-suppressed conductivity detection furnishes a signal that is the sum of the conductance of the analyte ion, its co-ion, and the decrease in the eluent counterion that remains on the column... 

Avicel RC and CL are water-dispersible, colloidal, microcrystalline cellulose products made for use in liquid preparations. Avicel RC and CL are coprocessed mixtures of microcrystalline cellulose and sodium carboxymethylcellulose. The amount of NaCMC can be determined using the IC method. About 10 g of Nasonex and about 25 mg of NaCMC NF are separately refluxed with 30 mL of glacial acetic acid for 2 h. The refluxed mixture is transferred to a 100-mL volumetric flask and diluted to volume with purified water, and mixed. The ion chromatograph (IC) was equipped with a suppressed conductivity detector, a 4-mm CSRS suppressor, current at 50 mA, a 250 mm x 4-mm Ion CS 12A column and a 50 mm x 4 mm Ion CG 12A guard column. The mobile phase is 0.13% methanesulfonic acid in water with a flow rate of 1 mL/min. Equal... 

In Fig. 2, the columns were IonPac ICE-AS6 (250X9-mm i.d.), AG9-HC (concentrator, 50X4-mm i.d.) and AG9-HC/AS9-HC (analytical, 250X2-mm i.d.). The ion exclusion sample treatment eluent was deionized water and the flow rate was 0.55 ml/min. The sample volume was 750 pi. The ion exchange eluent was 8.0 mM sodium carbonate and 1.5 mAf sodium hydroxide. The flow rate on the 2-mm analytical column was 0.25 ml/ min. Detection was by suppressed conductivity using the ASRS -I electrolytically regenerated suppressor in the external water mode. 

Figure 10.1 Ion-exchange chromatographic separation of main anions found in water using a Dionex HPLC and AS-11 HC column. Conditions column Dionex AS-11 HC 250 X 4 mm solvent Milli-Q water and 3 mM NaOH for 6 mins then to 30 mM NaOH over 15 min flow rate 1.5 ml/min suppressed conductivity detection.

Figure 10.8 HPLC separation of organic acids and anions by ion-exchange chromatography and conductivity detection. Conditions column Dionex AS-11 250 X 4 mm suppressed conductivity...

Mobile phases useful for suppressed conductivity detection of anions include sodium hydroxide, potassium hydroxide, and the sodium and potassium salts of weak acids such as boric acid. In nonsuppressed conductivity detection, the ionic components of the mobile phase are chosen so that their conductivities are as different from the conductivity of the analyte as possible. Large ions with poor mobility are often chosen, and borate-gluconate is popular. For cations, dilute solutions of a strong acid are often used for nonsuppressed conductivity detection. For more information on the application of electrochemical detection to inorganic analysis, see Ion Chromatography Principles and Applications by Haddad and Jackson,17 which provides a comprehensive listing of the sample types, analytes, sample pretreatments, columns, and mobile phases that have been used with electrochemical detection. 

Anion Analysis (Figure 9.6b). For anion analysis the analogous principles apply, only now the eluant is, for example, the hydroxide or mixed carbonate/bicarbonate ion and the suppressor column a cation exchange resin in the hydrogen form, thereby suppressing conductivity by the formation of water and dissolved carbon dioxide respectively. 

Fig. 3-16. Elution profile of the IonPac AS4A separator column for simple inorganic anions depending on the ratio of the two eluent components. — Eluent (A) 0.0028 mol/L NaHC03 + 0.0022 mol/L Na2C03, (B) 0.0017 mol/L NaHC03 + 0.0018 mol/L Na2C03 flow rate 2 mL/min detection suppressed conductivity injection volume 50 pL solute concentrations see Fig. 3-13.

Fig. 3-20. Elution profile of a Fast-Sep anion exchange column. - Eluent 0.00015 mol/L NaHCOj + 0.002 mol/L Na2C03 flow rate 2 mL/min detection suppressed conductivity injection volume 20 pL solute concentrations 1.5 ppm fluoride, 2.5 ppm chloride, 7.5 ppm nitrite and bromide, 10 ppm nitrate and sulfate, 15 ppm orthophosphate.

Fig. 3-46. Separation of mineral acids and oxy non-metal anions. — Separator column Ion Pac AS4A eluent 0.00075 mol/L NaHC03 + 0.002 mol/L Na2C03 flow rate 2 mL/min detection suppressed conductivity injection 50 pL solute concentrations 3 ppm fluoride, 4 ppm chloride, 10 ppm nitrite, 10 ppm bromide, 20 ppm nitrate, 10 ppm selenite, 10 ppm orthophosphate, 25 ppm sulfate, 20 ppm sele-nate, and 25 ppm arsenate.

Fig. 3-56. Separation of fluoride, iodate, bromate, and chloride. - Separator column IonPac AS6 (CarboPac) eluent 0.0034 mol/L NaHCO, + 0.0036 mol/L Na2C03 flow rate 1 mL/min detection suppressed conductivity injection volume 50 pL solute concentrations 2 ppm fluoride, 10 ppm iodate, 20 ppm bromate, and 5 ppm chloride.

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