ISO-10304-2-1995.pdf

INTERNATIONAL STANDARD IS0 10304-2 First edition 1995-04-01 Water quality - Determination of dissolved anions by liquid chromatography of ions - Part 2: Determination of bromide, chloride, nitrate, nitrite, orthophosphate and sulfate in waste water Qualit de I eau - Dosage des anions dissous par chromatographie des ions en phase liquide - Partie 2: Dosage des ions bromure, chlorure, nitrate, nitrite, orthophosphate et sulfate dans /es eaux u) 0.1 to 50 CD or UV (200 nm to 215 nm) Nitrite (NO,) 0,05 to 20 CD or UV (200 nm to 215 nm) Orthophosphate (PO:-) 0,l to 20 CD Sulfate CSO-) 0.1 to 100 CD NOTE - The working range is limited by the exchange capacity of the columns. 1.2 Interferences 1.2.1 Organic acids, such as monocarboxylic or dicarboxylic acids, can interfere with the determi- nation of inorganic anions. 1.2.2 In a buffered eluent (e.g. carbonate/hydrogen carbonate), the determination will not be influenced by the sample pH in the range of pH 2 to pH 9. 1.2.3 Large concentration differences between the anions Br-, Cl-, NO, NO, PO:- and SOi- may lead to typical cross-sensitivity interferences caused by an insufficient separation. The respective concentrations given in table2 were typical for conductivity detectors and UV-detectors; no interferences could be observed with a sample volume of 50 1. The data given are valid only when the quality requirements specified for the columns are met (see clause 6). The determi- nation of chloride may be subject to interference from high fluoride concentrations. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/19/2007 05:54:27 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 10304-2:1995(E) 0 IS0 Table 2 - Cross-sensitivity of anions Detection: conductivity (CD) and direct UVI Maximum Ratio of the mass tolerable absolute concentrations concentration of solute/interfering ion interfering ionsl) t-w/l Br-/Cl- I:500 Cl- 500 Br-/PO:- I:100 PO;- 100 Br-/NO; I:50 NO, 100 Br-/SO:- I:500 so:- 500 Br-/SO:- 1:502) Cl-/NO, I:50 NO, 5 Cl-/NO, 1:500 NO, 500 cl-/so:- I:500 so:- 500 NO;/Br- I:100 Br- 100 NO,/CI- I:500 (CD) Cl- 500 I:2 000 (UV) cl- 500 NO,/SO:- I:500 (CD) so:- 500 1 :I 000 (UV) so:- 500 NO,/SO:- 1:502) NO,/CI- I:250 (CD) Cl- (CD) 100 1 :lO 000 (UV) cl- (UV) 500 NO;/PO;- I:50 PO;- 20 NO;/NO, I:500 NO, 500 NO;/SO:- I:500 (CD) so:- 500 I:1 000 (UV) so;- 500 PO:-/Br- I:100 Br- 100 Po;-/cI- I:500 Cl- 500 PO;-/NO, I:500 NO, 400 PO;-/NO, I:100 NO, 100 PO;-/so;- 1:500 so:- 500 PO;-/so;- 1:502) so;-/cl- I:500 Cl- 500 SO:-/NO, I:500 NO, 400 so:-/so;- 1:502) so:-/s,o;- I:500 so;-/I- I:500 1) Dilute the sample if the interfering concentration is exceeded. 2) When it is present, SO:- will always interfere. 1.2.4 The determination of sulfate may be subject to interference by high iodide or thiosulfate concen- trations. Relations: SOi-/I- or SO:-/S,O:- or I-/S,Oz- = I:500 Cross-sensitivities to other anions, such as Br-, Cl-, NO, NO, PO:- and SO:-, may occur, especially in the presence of sulfite ions whose retention strongly depends on the selectivity of the separating column used. Inorganic anions such as fluoroborate or chlorite can interfere with the determination of the named in- organic anions. NOTE 1 The identification of some anions (e.g. nitrite) or the detection of interferences (e.g. fatty acids) can be fa- cilitated by using a conductivity detector and UV-detector placed in series. Anion combinations (e.g. Cl-/l-) which are not listed in table2 will not interfere in the specified range of application. Solid particles and organic compounds (such as min- eral oils, detergents and humic acids) shorten the lifetime of the separating column and are therefore eliminated before the analysis is started (see clause 7). Sulfide ions can cause errors during the determination of sulfate; they are eliminated according to clause 7. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this part of IS0 10304. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this part of IS0 10304 are encouraged to investi- gate the possibility of applying the most recent edi- tions of the standards indicated below. Members of IEC and IS0 maintain registers of currently valid International Standards. IS0 5667-l :1980, Water quality - Sampling - Part 1: Guidance on the design of sampling pro- gfammes. IS0 5667-2:1991, Water quality - Sampling - Part 2: Guidance on sampling techniques. IS0 5667-3:1994, Water quality - Sampling - Part 3: Guidance on the preservation and handling of samples. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/19/2007 05:54:27 MDTNo reproduction or networking permitted without license from IHS -,-,- Q IS0 IS0 10304-2: 1995(E) IS0 8466-1:1990, Water quality - Calibration and evaluation of analytical methods and estimation of performance characteristics - Part 1: Statistical evaluation of the linear calibration function. IS0 10304-l : 1992, Water quality - Determination of dissolved fluoride, chloride, nitrite, orthophosphate, bromide, nitrate and sulfate ions, using liquid chro- matography of ions - Part 1: Method for water with low contamination. 3 Principle Liquid chromatographic separation of ions by means of a separating column. Use of an anion exchanger as the stationary phase, and usually, aqueous solutions of salts of weak monobasic and dibasic acids as mo- bile phases (eluent, see 4.17). Conductivity and UV-detectors are used within this part of IS0 10304. When using conductivity detectors, it is essential that the eluents have a sufficiently low conductivity. For this reason, conductivity detectors are often com- bined with a suppressor device (e.g. a cation exchanger) which decreases the conductivity of the eluent and converts the separated anions into their corresponding acids. UV-detection either measures the absorption directly (see table 1) or, in the case of anions which are transparent in the UV-range, measures the decrease in the background absorption caused by a UV-absorbing eluent (indirect measurement). If in- direct UV-detection is used, the measuring wave- length depends on the composition of the eluent. The concentration of the respective anions is deter- mined by a calibration of the overall procedure. Par- ticular cases may require calibration by means of standard addition (spiking). If no suppressor device is used, it is essential that the conductivity of the eluent be as low as possible. NOTE 2 References covering this analytical technique are summarized in annex A of IS0 10304-I :I 992. 4 Reagents Use only reagents of recognized analytical grade. Weigh with an accuracy of 1 % of the nominal mass. The water shall have an electrical conductivity of 0,45 pm. The increase of the elec- trical conductivity due to an uptake of carbon dioxide does not interfere with the determination. 4.1 Sodium hydrogencarbonate (NaHCO,). 4.2 4.3 4.4 4.5 Sodium carbonate (Na,CO,). Potassium hydrogenphthalate (C,H,O,K). Sodium tetraborate (Na,B,O,.l OH,O). Gluconic acid, w(C,H,O) = 50 % (WV), aqueous solution. 4.6 Methanol (CH,OH). 4.7 Lithium hydroxide (LiOH). 4.8 Glycerol (CsHsO,). 4.9 Acetonitrile (CHsCN). 4.10 Potassium hydroxide (KOH). 4.11 Sodium bromide (NaBr). 4.12 Sodium chloride (NaCI). 4.13 Sodium nitrate (NaNO,). 4.14 Sodium nitrite (NaNO,). 4.15 Potassium dihydrogenphosphate (KH,PO,). 4.16 Sodium sulfate (Na,SO,). 4.17 Eluents Different eluents are used, their choice depending on the type of separating column and detector. There- fore, follow the column manufacturer s instructions for the exact composition of the eluent. The eluent compositions described in 4.17.1 and the last two paragraphs of 4.17.2.2 are examples only. A choice of reagents commonly used as eluents is given in 4.1 to 4.10. Degas all the eluents or prepare eluents using degassed water. Take steps to avoid any renewed gas pick-up during operation (e.g. by helium sparging). In order to avoid the growth of bacteria or algae, store the eluents in the dark and renew every 2 d to 3 d. 4.17.1 Examples of eluents for ion chromatography using the suppressor technique For the application of the suppressor technique, sodium hydroxide and salt solutions of weakly dissociated acids, such as sodium carbonate/sodium 3 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/19/2007 05:54:27 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 10304-2:1995(E) 6 IS0 hydrogencarbonate, sodium hydrogencarbonate and sodium tetraborate can be used. 4.17.2.1.1 Potassium hydrogenphthalate concentrate 4.17.1.1 Sodium carbonate/sodium hydrogencarbonate concentrate The addition of the following eluent concentrate to the sample has proved to be helpful for sample pretreat- ment and eluent preparation (4.17.2.1.2). The addition of the following eluent concentrate to the sample has proved to be successful for sample pre- treatment and eluent preparation (see 4.17.1.2). Place 20.5 g of potassium hydrogenphthalate (4.3) in a volumetric flask of nominal capacity 1 000 ml, dis- solve in water and dilute to volume. Place 25,4 g of sodium carbonate (4.2) and 25,5 g of sodium hydrogencarbonate (4.11, in a volumetric flask of nominal capacity 1 000 ml, dissolve in water (see first paragraph of this clause) and dilute to volume. The solution contains 0,l mol/l of potassium hydro- genphthalate and is stable for a longer period of time if stored at 4 “C to 6 “C. The solution contains 0,24 mol/l of sodium carbonate and 0,3 mol/l of sodium hydrogencarbonate and is stable for several months if stored at 4 “C to 6 “C. 4.17.2.1.2 Potassium hydrogenphthalate eluent For the determination of chloride, nitrate, nitrite, orthophosphate and sulfate in a single determination, the following eluent has proved to be successful. Place 100 ml of the concentrate (4.17.2.1 .l) in a volumetric flask of nominal capacity 5 000 ml. Add 4.17.1.2 Sodium carbonate/sodium hydrogencarbonate eluent The following eluent is applicable for the determi- 500 ml of methanol (4.61, dilute with water (see first nation of bromide, chloride, nitrite, orthophosphate, paragraph of this clause), adjust to pH 5 with potass- and sulfate in a single determination. ium hydroxide (4.10) and dilute to volume. Place 50 ml of the concentrate (4.17.1.1) in a volumetric flask of nominal capacity 5 000 ml, and di- lute to volume with water (see first paragraph of this clause). The solution contains 0,002 4 mol/l of sodium car- bonate and 0,003 mol/l of sodium hydrogencarbonate. 4.17.2 Examples of eluents for ion chromatography without using the suppressor technique For ion chromatography techniques which do not util- ize suppressor devices, salt solutions (e.g. potassium hydrogenphthalate, p-hydroxybenzoic acid, sodium borate/sodium gluconate and sodium benzoate) are used. The solutions may contain various additions, e.g. alcohols. The concentration of the salts is usually in the range of 0,000 5 mol/l to 0,Ol mol/l. Concen- trate and eluent solutions are prepared as described in 4.17.2.1 .l and 4.17.2.1.2. Note that some alkaline concentrate solutions of the cited salts are not stable. Adjust the pH of the eluent after the dilution of the concentrate. 4.17.2.1 Mobile phases for anion exchanger on a silica gel base The solution contains 0,002 mol/l of potassium hy- drogenphthalate and 10 % (V/VI of methanol. 4.17.2.2 Eluents for an anion exchanger on a polymer base Acidic as well as basic eluents may be used for ion chromatography with an anion exchanger on a poly- mer base. Examples of typical acidic eluents are solutions con- taining potassium hydrogenphthalate. Examples of typical basic eluents are solutions containing p-hydroxybenzoate or sodium borate/sodium glucon- ate. For the determination of chloride, nitrate, orthophos- phate and sulfate in a single determination, the sodium borate/sodium gluconate eluent has proved to be successful. It is prepared in the following way. Place 0,85 g of sodium tetraborate (4.41, and 0,22 g of lithium hydroxide (4.7) in a volumetric flask of nominal capacity 5 000 ml. Add 0,6 ml of gluconic acid (4.51, 3,l ml of glycerol (4.81, and 600 ml of acetonitrile (4.9). Dilute to volume with water. 4.18 Stock solutions For ion chromatography using anion exchanger col- umns on a silica gel base, use only eluents in the pH range of I,5 to 6,5. Prepare stock solutions with mass concentration p of 1 000 mg/l for each of the anions: bromide, chloride, nitrate, nitrite, orthophosphate and sulfate. 4 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/19/2007 05:54:27 MDTNo reproduction or networking permitted without license from IHS -,-,- 8 IS0 Dissolve the appropriate mass of each of the sub- stances, prepared as stated in table3, in a small quantity of water in volumetric flasks of nominal ca- pacity 1 000 ml. Dilute to volume with water. The solutions are stable for several months if stored at 4 “C to 6 “C. Alternatively, use commercially available solutions of the required concentration. NOTE 3 Nitrite is easily oxidized to nitrate and therefore nitrite standard solutions should be prepared on the day of use. Table 3 - Mass of portion and pretreatment for stock solutions Pretreatment by drying ) Anion Salt Mass of portion Duration Temperature 9 h “C Bromide NaBr 1,287 7 6 105 Chlonde NaCl 1,648 4 2 105 Nltrate NaNO, 1,370 7 24 105 NItrIte NaNO, 1,499 8 1 105 Ortho- phosphate KH,PO, 1,433 0 1 105 Sulfate Na,SO, 1,479 0 1 105 1) Let the substance cool rn a desiccator after drying. 4.19 Mixed standard solutions 4.19.1 Mixed standard solution I The mass concentrations of this solution are as fol- lows: p(Br-, NO;, PO:-) = 10 mg/l p(CI-, NO, SO:-) = 100 mg/l Pipette the volumes given in table4 into a volumetric flask of nominal capacity 100 ml, and dilute to volume with water. Store these solutions in polyethylene bottles. If stored at 4 “C to 6 “C, the solutions are stable for one week. Table 4 - Volumes of stock solutions for the preparation of the mixed standard solution I Stock solution Anion concentration Anion ml w/l Br- 1 10 cl- 10 100 NO, 10 100 NO, 1 10 PO;- 1 10 so:- 10 100 4.19.2 Mixed standard solution II The mass concentrations of this solution are as fol- lows: p( Br-, NO;, PO:-) = 1 mg/l pp. NO, SO:-) = 10 mg/l