Anion nitrate column

Example. A mixture of ca 0.05 mmole each of chloride and bromide ions is to be separated on an anion exchange column of length 10 cm and 1cm2 cross-section, using 0.035M potassium nitrate as the eluant. The distribution coefficients (Kd) for the chloride and bromide ions respectively are 29 and 65. 

Procedure. Prepare an anion exchange column (Section 7.8) using about 40g of Duolite A113 (chloride form). The ion exchange tube may be 16 cm long and about 12 mm internal diameter. Wash the column with 0.6M sodium nitrate until the effluent contains no chloride ion (silver nitrate test) and then wash with 50 mL of 0.3 M sodium nitrate. 

To date, a few methods have been proposed for direct determination of trace iodide in seawater. The first involved the use of neutron activation analysis (NAA) [86], where iodide in seawater was concentrated by strongly basic anion-exchange column, eluted by sodium nitrate, and precipitated as palladium iodide. The second involved the use of automated electrochemical procedures [90] iodide was electrochemically oxidised to iodine and was concentrated on a carbon wool electrode. After removal of interference ions, the iodine was eluted with ascorbic acid and was determined by a polished Ag3SI electrode. The third method involved the use of cathodic stripping square wave voltammetry [92] (See Sect. 2.16.3). Iodine reacts with mercury in a one-electron process, and the sensitivity is increased remarkably by the addition of Triton X. The three methods have detection limits of 0.7 (250 ml seawater), 0.1 (50 ml), and 0.02 pg/l (10 ml), respectively, and could be applied to almost all the samples. However, NAA is not generally employed. The second electrochemical method uses an automated system but is a special apparatus just for determination of iodide. The first and third methods are time-consuming. 

Figure 5 Chromatogram of a synthetic mixture of chloride (a), bromide (b), nitrate (c), and sulfate (d) separated on an anion-exchange column. (From Ref. 93, with permission.)...

Radioactivity of uranium can be measured by alpha counters. The metal is digested in nitric acid. Alpha activity is measured by a counting instrument, such as an alpha scintillation counter or gas-flow proportional counter. Uranium may be separated from the other radioactive substances by radiochemical methods. The metal or its compound(s) is first dissolved. Uranium is coprecipitated with ferric hydroxide. Precipitate is dissolved in an acid and the solution passed through an anion exchange column. Uranium is eluted with dilute hydrochloric acid. The solution is evaporated to near dryness. Uranium is converted to its nitrate and alpha activity is counted. Alternatively, uranium is separated and electrodeposited onto a stainless steel disk and alpha particles counted by alpha pulse height analysis using a silicon surface barrier detector, a semiconductor particle-type detector. 

Nitrite and nitrate may also be determined by HPLC using anion-exchange columns with either UV absorption or electrochemical detection. These methods are generally used for environmental samples and urine where fewer interfering compounds exist. The more extensive sample preparation and analysis time have limited its use for biological samples. 

A simpler and technologically superior approach is the measurement of the direct electrical conductance. The background conductivity of the mobile phase is electronically subtracted, not requiring a suppressor device. One example of direct conductivity detection is the simultaneous determination of potassium nitrate and sodium monofluorophosphate in dentrifices [76]. Alendronate, a bisphonate, can be directly detected in intravenous solutions and tablets using an anion-exchange column and conductivity detection [77]. Another example, from one of the author s (JA) laboratory is shown in Figure 5.3. Direct conductivity detection makes it possible to selectively detect choline in the presence of an equal molar amount of an antibiotic which is not detected. 

Yamamoto et al. [7] and Matsuchita [92] have described a method for the determination of chloride, phosphate, nitrate, nitrite, sulphate, calcium and magnesium in rainwater. They used lm mol L 1 EDTA as an eluent and a silica based anion exchange column. 

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). 

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. 

Step 9. Add 1 mL of 50% NaNOz solution to the dissolved sample in the flask [or to the small sample from Step 2] to adjust the Pu oxidation state to +4 and form the anionic nitrate complex of plutonium. Swirl to mix and let sample stand overnight, or at least two hours if the sample must be rushed. The sample is now approximately 50 mL of 8 M HN03, and ready for the plutonium column. 

Dissolution of the calcium fluoride in aluminum nitrate-nitric acid oxidizes the plutonium to the tetravalent hexanitrate complex (3), while the transplutonium nuclides remain in the trivalent state. The only actinides retained by a nitrate-form anion-exchange column are thorium, neptunium, and plutonium. The uranium distribution coeflBcient under these conditions is about ten, but uranium should not be present at this point since hexavalent uranium does not carry on calcium fluoride (4). 

Plutonium in this feed solution is removed by an anion exchange column process. The anion exchange resin is Dowex 1-X4, 50 to 80 mesh nitrate form, obtained from Bio-Rad Laboratories. Ferrous sulfamate is added to the solution to eliminate hexavalent plutonium, and the feed is passed through the column. The ion column effluent (ICE) contains the americium and impurities. Residual americium and impurities are washed from the column with 7M HNO3 anc t 1e was s combined with the ICE this is the feed to the bidentate process. A typical composition in g/1 is Am, 0.15 Pu, 8.2 x 10 3, Al,... 

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. 6-16. Indirect photometric detection of various inorganic anions. - Separator column 250 mm x 4 mm I.D. SAR-40-0.6 eluent 0.001 mol/L sodium phthalate (pH 7 to 8) flow rate 2 mL/min detection UV (285 nm, indirect) injection volume 20 pL solute concentrations 106 ppm chloride, 138 ppm nitrite, 400 ppm bromide, 310 ppm nitrate, and 480 ppm sulfate (taken from [29]).

Nitrate. In this case, the method of choice would be IC, with conductivity detection. The use of a dedicated ion chromatograph with an anion-exchange column allows the separation of nitrate (plus fluoride, chloride, bromide, nitrite, sulfate, etc.). 

Recently, Karmarkar reported an impressive dual IC-flow injection analysis (FIA) method for the sequential determination of anionic (nitrate and phosphate) and cationic (ammonium) nutrients in wastewater samples. The dual system was based upon the use of an anion exchange column (Lachat QS-A5) and two detectors, one suppressed conductivity detector using a Lachat Instruments QE-Al small suppressor cartridge, which is regenerated between samples, and a second visible absorbance detector. Upon injection of the sample the conductivity detector was switched off line and the nonretained ammonium was passed through the analytical column and detected by the visible absorbance detector, following an on hne colorimetric reaction. The conductivity detector was then immediately switched on hne to detect the retained nutrient anions. The method reported detection limits for phosphate of 0.006 mg/1 phosphate. 

A NF/IX water treatment system is very effective in removing virtually aU nitrates from drinking water [6]. In the NF/IX hybrid system, pre-filtered water flows through a NF membrane system, which removes all the multivalent ions and some of the monovalent nitrate ions. The NF permeate is then polished in an anion IX column where the nitrates are exchanged with chloride ions. NF pre-treatment increases the efficiency of the IX process since it removes dissolved organic carbon and divalent ions such as sulphate ions. 

Nitrate may also be determined by LC with an anion-exchange column. A comparison has been made between the traditional method of nitrate determination using a reducing cadmium column and spectrophotometric determination with a reversed-phase LC method with orthophosphoric acid adjusted to pH 3.5 with sodium hydroxide as the mobile phase. A high correlation was observed between the nitrate content determined by the two methods. However, LC was found to be more precise, reproducible, and appropriate for routine work. 

Dowex anion exchange resin AG1-X8 (Bio-Rad Laboratories, Richmond, Calif.). Lanthanum carrier solution. Lanthanum nitrate was dissolved in water and purified from interfering a activity be passage through the anion exchange column after adjusting the HCl content to ION. Excess HCl was removed by evaporation and... 

In 1987, the U.S. EPA presented a draft of Method 300.0, which was recommended for the determination of common anions (fluoride, chloride, nitrate, and sulfate) at milligram-per-liter levels using standard, low-capacity anion-exchange columns and conductivity detection. 

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