Sample Preparation LCW 909. Total Kjeldahl Nitrogen, TKN NB: NEW! LCW 909 GB

Transcription

1 Principle Organically bound nitrogen is digested by hot fuming sulphuric acid in the presence of catalysts and converted to ammonium, which, after steam distillation, can be determined as so-called Total Kjeldahl Nitrogen () together with the ammonium-nitrogen which was originally present; the cuvette test LCK 303 ammonium is used for this purpose. NB: NEW! The actual edition date is given with the procedure or evaluation. See also under Note (below). Sample Preparation Safety Advice On grounds of quality and reliability, the analysis should be carried out only with original HACH LANGE accessories. CADAS 100 (LPG 185 / LPG 210) If this test is not already stored in your instrument please ask your HACH LANGE Agency for programming instructions. GB Range of Application The method has been optimized for the analysis of surface water, ground water and waste water (especially for drawing up the total nitrogen balance). Note The change indicated by the new edition date and the new colour of the working procedure concerns a change of factor for the photometer type CADAS 30/50/50S and CADAS 100. Storage Information The test reagents are stable at +15 to +25 C up to the expiry date given on the package. The reagent bottles must be closed immediately after use and stored at room temperature in clean surroundings. Interferences Laboratory air contaminated with volatile nitrogen compounds (ammonia, amines, nicotine, etc.), and poor-quality laboratory water cause high-bias results. It is therefore recommended that the influence of the laboratory air and water quality on the analysis results is regularly checked by determining a blank-value (procedure and analysis without sample addition, see table in Procedure ). The blank-value should be subtracted from the analysis results obtained with the sample. If deionized water is used the conductivity should not exceed 5 10 µs/cm; distilled water should be distilled from water which has had dilute sulphuric acid added to it. Low-bias results are to be expected if the nitrate content (in mg/l NO 3 -N) and/or nitrite content (in mg/l NO 2 -N) exceed the total Kjeldahl nitrogen content (in mg/l N) by a factor of 3 or more. The measurement results must be subjected to plausibility checks (dilute and/or spike the water sample). AE 909 H / Druckfarbe schwarz / 1

2 Procedure Applies to all types of photometer Sample Preparation The operating instructions for the digestion and distillation apparatus EBG 023 must be followed with great care! Before carrying out the following steps the cooling water should be turned on until the mark is reached (see operating instruction for EBG 023). The references marked Fig. in the description of the procedure refer to the corresponding illustrations on page 18 of the operating instructions for the digestion and distillation apparatus. The letters in brackets refer to the corresponding parts of the digestion and distillation apparatus shown in illustrations 7 and 8 on page 18 of the operating instructions. If no data exist concerning the expected total Kjeldahl nitrogen content then it is recommended that measuring range II and a sample volume of 10 ml are selected. Measuring Measuring Measuring Blankrange I range II range III value**) 1 10 mg/l mg/l mg/l Into a 100 ml round-bottom flask (n) pipette [Fig. 9] Sample 50 ml*) 10 ml 1 ml Digestion reagent A ( A) 10 ml 10 ml 10 ml 10 ml Heating time 120 min 70 min 60 min 60 min *) Add 50 ml sample volume from a 50 ml volumetric flask (h). Prerinse with sample and rinse out afterwards with a little distilled water. **) The evaluation of the blank-value is carried out in the same measuring range as for the sample. 1. Place the beaker (k), without the volumetric flask stand (j), beneath the condenser downpipe (f) of the digestion and distillation apparatus. 2. Close stopcock III (b), turn stopcock II (s) to AUFSCHLUSS (digestion) (arrow pointing down), and open stopcock I (c). 3. Connect the round-bottom flask (n) containing the sample and the digestion reagent A ( A) to the distilling adapter (d) of the digestion and distillation apparatus and secure it with the forked clamp (o) [Fig.10]. 4. Fix the heating mantle (l) under the round-bottom flask (n), close the protective shield and set the timer (p) to the relevant heating time. When the heating time has elapsed: 5. Open the protective shield, lower the heating mantle (l) to its lowest position, and allow the sample to cool for about 15 min. 6. When the sample has cooled, close stopcock I (c). Cover the heating mantle (l) with the glass cover (g). 7. Pipette 5 ml of the sulphuric acid C ( C) into the 50 ml volumetric flask (h) and position this on volumetric flask stand (j) under the condenser of the digestion and distillation apparatus in such a manner that the end of the condenser downpipe (f) is immersed in the sulphuric acid [Fig.11]. If necessary adjust the height of the volumetric flask stand (j) with the setting screw. 8. Use the plastic measuring cylinder (i) to pour 10 ml sodium hydroxide solution B ( B) into the addition funnel (a) of the digestion and distillation apparatus. 9. Close the protective shield. 10. Carefully open stopcock III (b) so that the sodium hydroxide solution is added very slowly (3 5 min for adding 10 ml sodium hydroxide solution) [Fig.12]. There may be a vigorous reaction with the digestion mixture in the 100 ml round-bottom flask (n)! 11. Before the addition funnel (a) is completely empty, add sufficient distilled water (to avoid loss of nitrogen) so that the end of the steam pipe (e) is immersed in the digestion mixture in the 100 ml roundbottom flask (n). Close stopcock III (b) so that a small amount of the rinsing water remains in the addition funnel [Fig.13]. 12. Switch on the steam generator with the switch (q) and after about 1 2 min turn stopcock II (s) to DESTILLATION (distillation). 13. Watch the distillate flow into the volumetric flask (h): as soon as the liquid level in the volumetric flask reaches the lower edge of the volumetric flask neck [Fig.14]: open the protective shield, hold the volumetric flask (h), remove the volumetric flask stand (j), pull the volumetric flask down and away [Fig.15], and place the beaker (k) under the condenser downpipe (f). switch off the steam generator with the switch (q) and immediately turn stopcock II (s) to BELÜFTUNG (ventilation) (arrow pointing to the right). 14. Add distilled water up to the mark in the volumetric flask (h), close with a stopper, and mix contents. If the temperature of the distillate in the volumetric flask is appreciably warmer than room temperature then the distillate should be allowed to cool down to room temperature before adding distilled water up to the mark. 15. Hold the 100 ml round-bottom flask (n) with the heat protective glove (m) and loosen the forked clamp (o). Remove the round-bottom flask downwards [Fig.16] and throw away the contents. (Take care hot and very corrosive! Rinse off with lots of water!) Clean the round-bottom flask. The round-bottom flask (n) must be removed from the apparatus as soon as the distillation has finished, otherwise the effects of the hot sodium hydroxide solution can cause the round-bottom flask to become inseparably fused to the standard ground joint of the distilling adapter (see operating instructions for EBG 023). 16. Place the beaker (k) on the glass cover (g) and position it beneath the steam pipe (e) by lifting and fixing the heating mantle. Open stopcock III (b) and thoroughly rinse out the distilling adapter (d) internally by pouring distilled water through the addition funnel (a) and externally by rinsing the standard ground joint with distilled water [Fig.17]. Then close stopcock III (b). Turn stopcock II (s) so that the arrow is pointing upwards and rinse out the steam pipe (e) internally through the ventilation opening of stopcock II (s). Then turn stopcock II (s) again to the position BELÜFTUNG (ventilation) (arrow pointing to the right). 17. Lower heating mantle (l) to the lowest position. Remove beaker (k) and glass cover (g). When no more work is to be carried out with the digestion and distillation apparatus the cooling water should be turned off. The determination of the total Kjeldahl nitrogen in the distillate is carried out with Cuvette Test LCK 303 ammonium. For the procedure please refer to the working procedure for Cuvette Test LCK 303 ammonium; for evaluation please refer to the relevant evaluation card of the working procedure for total Kjeldahl nitrogen.

3 CADAS 30S/50S CADAS 100 (LPG 185) / ( LPG 210) 1. Check program control number: : Select»TEST«mode. 3. Select test number (see below). 4. Control number must be 4 ( I) or 2 ( II) or 3 ( III). 5. Insert zero-solution cuvette (not zero-solution cuvette LCK 303) and press key below»zero«. 6. Insert sample cuvette and press key below»meas.«. 1. Select»TEST«mode. 2. Select symbol (see below). 3. Check factors and measuring wavelength in memory»mem«(lpg 185) or control number must be 1 ( I) or 7 ( II) or 8 ( III) (LPG 210). 4. Insert zero-solution cuvette (not zero-solution cuvette LCK 303) and press NULL (zero) key. 5. Insert sample cuvette and press MESS (measure) key. 50 ml I mg/l 10 ml II mg/l 1 ml III mg/l Sample volume Meas. range Symbol 50 ml I 909 A 1 10 mg/l 10 ml II 909 B mg/l 1 ml III 909 C mg/l DR 2800/3800/3900/5000/ Select menu Stored Programs. 2. Select test number (see below) and touch Start. 3. Insert zero-solution cuvette (not zero-solution cuvette LCK 303) and touch Zero. 4. Insert sample cuvette and touch Read. 50 ml I mg/l 10 ml II mg/l 1 ml III mg/l AE 909 H / Druckfarbe schwarz / 2

4 Data table LASA LP2W 06/1997 I F 1 = 0 F 2 = K = 0 II F 1 = 0 F 2 = K = 0 III F 1 = 0 F 2 = 1125 K = 0 CADAS 30/30S/50/50S 06/1997 I λ: 690 nm Pro.: 1 F 1 = 0 F 2 = K = 0 II λ: 690 nm Pro.: 1 F 1 = 0 F 2 = K = 0 III λ: 690 nm Pro.: 1 F 1 = 0 F 2 = 1092 K = 0 ISIS 6000/ /1997 I λ: 695 nm Pro.: 1 F 1 = 0 F 2 = K = 0 II λ: 695 nm Pro.: 1 F 1 = 0 F 2 = K = 0 III λ: 695 nm Pro.: 1 F 1 = 0 F 2 = 1133 K = 0 CADAS 100 / LPG /1997 I λ: 694 nm F = II λ: 694 nm F = III λ: 694 nm F = 1075 CADAS 100 / LPG /1997 I λ: 694 nm F 1 = II λ: 694 nm F 1 = III λ: 694 nm F 1 = Insert program filter for test LCK 303 N. 2. Select test with relevant key. 3. Check program control number: : Insert zero-solution cuvette (not zero-solution cuvette LCK 303). Make a note of the display (1). 5. Insert sample cuvette. Make a note of the display (2). Analysis result = (display 2 - display 1) x factor (Factor see following data table) If the display after the zero-solution cuvette () has been inserted is»u«, then display 1 is to be set to 0. Sample volume Meas. range Factor 50 ml I 2 10 mg/l 1 10 ml II mg/l 5 1 ml III mg/l 50 LASA 1 / plus LASA 10 / Press Mode key and check program control number: : Insert program filter 690 nm. 3. Select test with Mode key. 4. Insert zero-solution cuvette (not zero-solution cuvette LCK 303). 5. Insert sample cuvette. Sample volume Display Meas. range 50 ml 1 LCK mg/l 10 ml 2 LCK mg/l 1 ml 3 LCK mg/l 1. Press any key. 2. Check program control number: : 30 (LASA 10) : 34 (LASA 20) 3. Select test with or key. 4. Insert zero-solution cuvette (not zero-solution cuvette LCK 303). 5. Insert sample cuvette. Sample volume Display Meas. range 50 ml 1 LCK mg/l 10 ml 2 LCK mg/l 1 ml 3 LCK mg/l AE 909 H / Druckfarbe schwarz / 2a

5 LASA 30 LP1W, LKT 1. Insert filter 695 nm. 2. Select»Dr. Lange«mode. 3. Select test number (see below). 4. Control number must be Insert zero-solution cuvette (not zero-solution cuvette LCK 303) and press blue key. 6. Insert sample cuvette and press green key. 50 ml I mg/l 10 ml II mg/l 1 ml III mg/l 1. Insert filter 695 nm. 2. Enter factor (see below) and store. 3. Insert zero-solution cuvette (not zero-solution cuvette LCK 303) and press Null (zero) key. 4. Insert sample cuvette and press Ergebnis mit Faktor (result with factor) key. Sample volume Meas. range Factor 50 ml I mg/l 10 ml II mg/l 1 ml III mg/l LP2W CADAS 30/50/200Basis, ISIS 6000/9000, LASA Insert program filter 695 nm. 2. Press Tests key until display (see below) appears. 3. Control number must be 2 ( I) or 1 ( II) or 9 ( III). 4. Insert zero-solution cuvette (not zero-solution cuvette LCK 303) and press Null (zero) key. 5. Insert sample cuvette and press Ergebnis (result) key. Sample volume Meas. range Display 50 ml I I 1 10 mg/l 10 ml II II mg/l 1 ml III III mg/l 1. Check program control number: Version 1.8 (CADAS 30) Select»TEST«mode. Version 1.9 (CADAS 50) Select»TEST«mode. : 38 (CADAS 200) : 32 (ISIS 6000/9000) Select»TEST«mode. LASA 100 Select»Dr. Lange«mode. 2. Select test number (see below). 3. Control number must be: CADAS 30/50: 4 ( I) or 2 ( II) or 3 ( III) CADAS 200: 2 ( I) or 4 ( II) or 5 ( III) ISIS 6000/9000: 9 ( I) or 3 ( II) or 4 ( III) LASA 100: 3 ( I, II, III) 4. Insert zero-solution cuvette (not zero-solution cuvette LCK 303) and press blue key. 5. Insert sample cuvette and press green key. 50 ml I mg/l 10 ml II mg/l 1 ml III mg/l AE 909 H / Druckfarbe schwarz / 2b