The sample is not preserved and analysed as soon as possible, at least within 24 hours after collection. Store the sample at 4 C till analysis.

Transcription

1 SKALAR METHODS ANALYSIS: NITRATE + NITRITE /TOTAL NITROGEN RANGE: mg N/liter / ( mg N/liter) SAMPLE: SURFACE, WASTE, RIVER, BOREHOLE & LAKE WATER / (WATER DIGEST) SAN ++ Catnr Xw/r(+P3) issue /MH/ PRINCIPLE The automated determination for the determination of Nitrate + Nitrite / Total Nitrogen is based on the hydrazine reduction method; nitrate is reduced to nitrite by hydrazinium sulfate and the nitrite (originally present plus reduced nitrate) is determined by diazotizing with sulfanilamide and coupling with N-(1- naphthyl)ethylenediamine dihydrochloride to form a highly coloured azo dye which is measured at 540 nm. LABORATORY FACILITIES 1. Maximum power consumption depending on the analyser configuration, 2000 VA. Check voltage at the back of the instrument before installation. 2. Facilities for chemical s. Check environmental regulations for proper disposal of. PROCEDURE SAMPLE PREPARATION Water no (nitrate+nitrite) Field of application Sample preparation for the determination of total alkalinity, aluminium, amino acids, ammonia, anionic surfactants (MBAS), bromide, calcium, C.O.D., chromium, conductivity, D.O.C., ethanol, hardness, magnesium, manganese, methanol, nitrate + nitrite, nitrite, nonionics, ortho-phosphate, potassium permanganate, potassium, total-n (UV digestion),total-p (UV digestion), protein, silicate, sodium, volatile acids and urea in water. Principle The sample is not preserved and analysed as soon as possible, at least within 24 hours after collection. Store the sample at 4 C till analysis. Persulfate microwave digestion (total nitrogen) 1. Ensure all digestion equipment is chromic acid washed and rinsed in double-distilled deionized water. Wear sterile gloves at all times to prevent phosphorus contamination. Use analytical reagent grade chemicals and only make up reagents using double-distilled deionized water. 2. Dissolve 75 g sodium hydroxide (e.g BDH Aristar ) in 500 ml double-distilled deionized water, dilute to 1000 ml to produce a 3.75M NaOH solution. catnr Xw/r(+P3) 1 of 9

2 3. Add 15 ml of the 3.75M NaOH solution to 500 ml double-distilled deionized water. Dissolve 50 g K2S2O8 in the solution using gentle eating to < 40 C if necessary. Dilute to 1000 ml. Prepare this oxidizing reagent fresh as required. 4. Add 4 ml of oxidizing reactant to 8 ml of sample in 120 ml capacity Teflon vessels. Cap immediately ensuring that the pressure disk is correctly positioned inside the cap. Tighten the pre-set pressure using the microwave digestion system capping station and place in carousel. Connect vent tube to the central receptacle. 5. Place the completed carousel in the microwave unit and run at 80% for 45 min with a fan setting of 5. When the digestion run is completed, allow samples to cool to room temperature before uncapping. If necessary, the sample vessels can be placed unopened in cold water. 6. Decant the digest samples into the sample cups of the auto analyser. Note 1 The actual concentration of total nitrogen and total phosphorus is determined by multiplying auto-analyser results by 1.6 since 8 ml of sample is initially diluted in this ration when 4 ml of oxidizing reagent is added. Note 2 Standards must be digested prior to sample digestion in order to ensure comparable conditions with respect to interferences and acidity. Sufficient volumes should be digested to provide for the number of scheduled analyses. Note 3 The oxidizing reagent will recrystallize when the temperature falls below 30 C. It can be re-dissolved by gentle heating to < 40 C as required. The sample preparation in this method is only meant to be an example procedure. It requires validation on its correct procedure for all types of samples to be analyzed, which is the responsibility of the user. REAGENTS A. Buffer solution (1 liter) Required chemicals: Potassium sodium tartrate g. C 4H 4O 6KNa.4 tri-sodium citrate g. C 6H 5O 7Na 3.2 Brij 35 (30%)... 3 ml. B. Sodium hydroxide solution (1 liter) Required chemicals: Sodium hydroxide... 6 g. NaOH. Brij 35 (30%)... 3 ml. Preparation: Dissolve the potassium sodium tartrate in ± 800 ml distilled water. Add the trisodium citrate and dissolve. Fill up to 1 liter with distilled water, add the Brij 35 and mix. Solution is stable for 1 week. Store at 4 C when the solution is not used. Preparation: Dissolve the sodium hydroxide in ± 800 ml distilled water. Fill up to 1 liter with distilled water, add the Brij 35 and mix. Solution is stable for 1 week. Store at 4 C when the solution is not used. catnr Xw/r(+P3) 2 of 9

3 C. Stock solution copper(ii) sulfate (1 liter) Required chemicals: Copper(II) sulfate g. CuSO 4.5 Preparation: Dissolve the copper(ii)sulfate in ± 800 ml distilled water. Fill up to 1 liter with distilled water and mix. Solution is stable for 1 week. D1. Hydrazinium sulfate solution (1 liter) ( mg N/liter) Required chemicals: Hydrazinium sulfate g. N 2H 6SO 4 Stock solution copper(ii) sulfate ml. Preparation: Dissolve the hydrazinium sulfate in ± 800 ml distilled water. Add the stock solution copper(ii) sulfate. Fill up to 1 liter with distilled water and mix. D2. Hydrazinium sulfate solution (1 liter) ( mg N/liter) Required chemicals: Hydrazinium sulfate g. N 2H 6SO 4 Stock solution copper(ii) sulfate ml. E. Colour reagent (1 liter) Required chemicals: o-phosphoric acid ml. H 3PO 4 (85%) Sulfanilamide g. C 6H 8N 2O 2S N-(1-Naphthyl)ethylene diamine dihydrochloride g. C 12H 16Cl 2N 2 F. Rinsing liquid sampler (nitrate+nitrite) Solution is stable for 1 week. Preparation: Dissolve the hydrazinium sulfate in ± 800 ml distilled water. Add the stock solution copper(ii) sulfate. Fill up to 1 liter with distilled water and mix. Solution is stable for 1 week. Preparation: Dilute the o-phosphoric acid in ± 700 ml distilled water. Add the sulfanilamide and the N-(1-naphthtyl)ethylene diamine dihydrochloride and dissolve. Fill up to 1 liter with distilled water and mix. Store in a dark coloured bottle. Solution is stable for 2 weeks. Store at 4 C when the solution is not used. Required chemicals: G. Rinsing liquid sampler (total nitrogen) Prepare fresh weekly. The rinsing liquid sampler has to be the same as the sample matrix after sampler pretreatment. catnr Xw/r(+P3) 3 of 9

4 P3. + Brij 35 (required for predilution step P3) (1 liter) Required chemicals: Brij 35 (30%)... 3 ml. Preparation: Dilute the Brij 35 in ± 800 ml distilled water. Fill up to 1 liter with distilled water and mix. Solution is stable for 1 week. STANDARDS Stock solution 1000 mg N/liter (1 liter) Required chemicals: Sodium nitrate g. NaNO 3 Preparation: Dissolve the sodium nitrate in ± 800 ml distilled water. Fill up to 1 liter with distilled water and mix. Solution is stable for 1 month. Store at 4 C when the solution is not used. Working standards (total nitrogen, dialyzer is connected, predilution step is connected) 50 mg N/liter: Dilute 5 ml stock solution 1000 mg N/liter to 100 ml with rinsing liquid sampler G. 40 mg N/liter: Dilute 4 ml stock solution 1000 mg N/liter to 100 ml with rinsing liquid sampler G. 30 mg N/liter: Dilute 3 ml stock solution 1000 mg N/liter to 100 ml with rinsing liquid sampler G 20 mg N/liter: Dilute 2 ml stock solution 1000 mg N/liter to 100 ml with rinsing liquid sampler G. 10 mg N/liter: Dilute 1 ml stock solution 1000 mg N/liter to 100 ml with rinsing liquid sampler G. Stock solution 100 mg N/liter Dilute 10 ml stock solution 1000 mg N/liter to 100 ml with distilled water. Working standards (nitrate+nitrite, dialyzer is disconnected) 1.0 mg N/liter: Dilute 1.0 ml stock solution 100 mg N/liter to 100 ml with rinsing liquid sampler F. 0.8 mg N/liter: Dilute 0.8 ml stock solution 100 mg N/liter to 100 ml with rinsing liquid sampler F. 0.6 mg N/liter: Dilute 0.6 ml stock solution 100 mg N/liter to 100 ml with rinsing liquid sampler F. 0.4 mg N/liter: Dilute 0.4 ml stock solution 100 mg N/liter to 100 ml with rinsing liquid sampler F. 0.2 mg N/liter: Dilute 0.2 ml stock solution 100 mg N/liter to 100 ml with rinsing liquid sampler F. 1. Prepare the working standards fresh daily. 2. The water used for the reagents and standards must be degassed properly before making up the reagents and standards. Especially water produced by reverse osmosis or ion exchange equipment contains a lot of gasses, which must be removed by degassing (degassing procedure see operational remarks and trouble shooting). CATALOGUE NUMBERS REQUIRED CHEMICALS Product Supplier and catnr. Danger classification Sodium hydroxide Merck corrosive Potassium peroxodisulfate Merck harmful, irritant, sensitizing catnr Xw/r(+P3) 4 of 9

5 Potassium sodium tartrate tetrahydrate Merck tri-sodium citrate dihydrate Merck Sodium hydroxide Merck corrosive Brij 35 (30%) Skalar Copper(II) sulfate pentahydrate Merck harmful, irritant, dangerous for the environment Hydrazinium sulfate Merck carcinogenic, toxic, sensitising, dangerous for the environment o-phosphoric acid (85%) Merck corrosive Sulfanilamide Merck N-(1-Naphthyl)ethylenediamine dihydrochloride Merck irritant Sodium nitrate Merck harmful, irritant Hydrochloric acid (32%) Merck corrosive RECOMMENDED OPERATIONAL SETTINGS 1. System sample time: 80 sec., wash time: 80 sec., air time: 0 sec. 2. Module sample time: 60 sec., wash time: 60 sec., air time: 0 sec. 3. Calibration type: 1 st order ISO OPERATIONAL REMARKS AND TROUBLE SHOOTING 1. The stabilising time of the system is approximately 30 minutes. 2. The sensitivity of the highest standard 1 mg N/liter is ± AU. (nitrate+nitrite) 3. The sensitivity of the highest standard 50 mg N/liter is ± AU. (total nitrogen) 4. Persons using this Skalar method should be familiar with normal laboratory practice. This Skalar method does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user to establish appropriate safety and health practices and to ensure compliance with any national regulatory conditions. 5. The connection between the sampler and the sample pump tube is made of 5175 tube. 6. If a digital matrix photometer , is in use, a correction interference filter of 620 nm ± 10 nm is advised. 7. If reaction coils with water heating are used, the water bath has to be cooled with tap water when the environment temperature is above 25 C. 8. The reagent bottles must be rinsed thoroughly with distilled water before refilling with fresh reagents. This is done to remove precipitation of micro organism and other interferences. 9. If solvents or high concentrated acids (> 2M) must be controlled by a rinsing valve, use the solvent/acid resistant type. 10. To check the complete reduction of nitrate + nitrite is performed by the comparison of a nitrate standard solution with a nitrite standard solution. These two solutions must be equal in nitrogen concentration and must be within the range of this method described. Due to the quality of the hydrazinium sulfate the reduction will not be complete, for every new batch of hydrazinium sulfate check the reduction. When no nitrite is present in the sample or is (in relation to the nitrate concentration) to be neglected, it is not necessary to check the reduction and use the amount of hydrazinium sulfate as described in this method. If the results of the nitrate standard and nitrite standard differs more then 10% the reduction is not complete, prepare 10 times the copperhydrazinium sulfate solution, 5 solutions lower than described in this method, each solution with decreased concentrations of 0.1 g./liter, and 5 solutions with increased concentration than described in this method, each solution 0.1 g./liter higher in concentration. 11. Avoid any turbidity in the reagents, filter if necessary. catnr Xw/r(+P3) 5 of 9

6 12. After 6 months the amount of Brij 35 can be reduced to 1 ml/liter. 13. Degassing procedures; a) Good: degas the water with a helium gas flow of approximately 20 liter/hour with aid of a sparger. Degas 5 liter water for 15 minutes. This procedure removes all dissolved air or, degas the water by boiling the water for 10 minutes. Cool down to room temperature before usage. b) Medium: degas the water with a nitrogen gas flow of approximately 20 liter/hour with aid of sparger. Degas 5 liter water for 15 minutes. This procedure will remove most of the dissolved gasses. c) Bad: degas the water by ultrasonic waves. This procedure will remove a small part of the dissolved gasses. GENERAL REMARKS 1. In most analyses, the first peak coming from the baseline is lower than it should be. The first peak coming from the baseline is rejected and will not be included in the calculation of the CV-value. 2. If the sample take up volume is less than 1.00 ml/min, a bypass is required to increase the sample stream to approximately 1.00 ml/min. For 5210 debubbler, when the sample is 1.00 ml/min and higher use 0.23 ml/min debubble tube. MAINTENANCE 1. Daily; when daily analysis is finished rinse all reagent lines with distilled water for 30 minutes. 2. Weekly; to decontaminate the system, rinse with 30 minutes with 1M hydrochloric acid solution and for another 30 minutes with distilled water. 3. Monthly; replace all pump tubing (or shift pump tube one colour-bridge on pump). DIALYSER MAINTENANCE Instructions to change catnr and 5282 ready mount dialyser membrane; 1. Unscrew the dialyser block and remove the old membrane. 2. Clean the dialyser block on both sides with a brush. 3. Open the package and carefully remove the new membrane. 4. Rinse the new membrane with plenty of distilled water to remove the preservation liquid. 5. Centre the membrane on the bottom dialyser plate. 6. Make a cross incision with a blade in the membrane on the 2 centre holes of the dialyzer bottom plate. 7. Make several small holes in the membrane through the holes for the mounting screw-bolts. 8. Position carefully the dialyser top plate on the bottom plate. 9. Push the screw-bolts carefully through the membrane and tighten the screw-bolts, finger tight. 10. Tighten screw-bolts with an Allan-key (starting with the inside), carefully tighten down in stages to hand tight. 11. Rinse the system several minutes with distilled water to remove any remaining preservation liquid from the membrane. Important: 1. When the analyser is not in operation the membrane should remain in contact with the rinsing liquid for the analyser. Never leave the membrane dry. If the membrane frequently breaks during rinsing, it is advisable to use 1 drop of detergent / liter in the rinsing liquid. catnr Xw/r(+P3) 6 of 9

7 MODULE CONSUMABLES silicone tube catnr membrane catnr polyethylene tube catnr pump tube 1.40 ml/min. catnr polyethylene tube catnr pump tube 0.16 ml/min. catnr sleeves catnr pump tube 0.80 ml/min. catnr sleeves catnr pump tube 1.00 ml/min. catnr acid flex sleeves catnr pump tube 0.42 ml/min. catnr MODULE COMPONENTS (for cartridge with electrical heating) manifold holder catnr connector catnr x module catnr dialyser catnr end block catnr valve catnr inlet connector catnr reactor catnr inlet connector catnr clamps small catnr x inlet connector catnr x sinkers catnr glass coil catnr flow cell 50 mm catnr glass coil catnr filter 540 nm catnr MODULE COMPONENTS (for predilution step P3) shared with total phosphate module inlet connector catnr clamps small catnr glass coil catnr sinkers catnr debubbler catnr pump tube 2.00 ml/min. catnr pump tube 0.23 ml/min. catnr REFERENCES Chemical method (no. 455) 1. ISO 13395:1996, Determination of nitrite nitrogen and nitrate nitrogen and the sum of both by flow analysis (CFA) and spectrometric detection. 2. Kamphake, L.J., Hannah, S.A., Cohen, J.M., "Automated analysis for nitrate by hydrazine reduction", Water Research, 1, 1967, page Kempers, A.J., Luft, A.G., "Re-examination of the determination of environmental Nitrate as Nitrite by reduction with hydrazine", Analyst, Vol. 113, July 1988, pp ISO 3696:1987, Water for analytical laboratory use. Specification and test methods. 5. ASTM, D1193, Standard Specification for Reagent Water. Sample preparation (water no ) 1. Environmental Protection Agency, methods for chemical analysis of water and s, Standard Methods for the determination of water and water, 17 th edition, ASTM, International Organisation for Standardisation, ISO catnr Xw/r(+P3) 7 of 9

8 FLOW DIAGRAM nitrate+nitrite mg N/liter ml/min 5323 Flow cell 50 mm Filter 540 nm Colour reagent / C Hydrazinium sulfate solution Sodium hydroxide solution * Sample Sampler * standard membrane catnr catnr Xw/r(+P3) 8 of 9

9 FLOW DIAGRAM total nitrogen mg N/liter ml/min 5323 Flow cell 50 mm Filter 540 nm Colour reagent / C Hydrazinium sulfate solution Sodium hydroxide solution Buffer solution * Resample To total phosphate module ml/min * standard membrane catnr B rij Sample 0.23 Predilution P3 Sampler catnr Xw/r(+P3) 9 of 9