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FAQ
1   COD - Low-bias results in comparison with reference method
  Low-bias results in comparison with reference method DIN 38 409 – H41 can be caused by: • Turbidity in the cuvette after the digestion when COD tests LCK 414, LCK 314 and LCK 614 are used. • These Cuvette Tests determine the concentration of the residual potassium dichromate, i.e. the potassium dichromate that is not degraded by the organic components of the sample, by measuring the yellow color of the sample. If a sample is still turbid after the digestion, this reinforces the yellow color, so that it seems as though less potassium dichromate has been consumed. Careful inversion of the cuvette while its contents are hot but no longer boiling reduces the sedimentation time of any remaining solid particles, and suppresses the haze formation caused by density differences. Evaluate at room temperature. • A marked excess of COD-relevant substances may cause a result to be displayed within the measurement range. A plausibility check using sample dilutions reveals the faulty result. LCK414, LCK314, LCK614
  Date: 2005-08-02
2   COD- Can the digestion for the determination of COD also be carried out in a high-temperature thermostat (HT)?
  COD - High-bias results in comparison with reference method High-bias results in comparison with reference method DIN 38 409 – H41 may be obtained if: • the chloride interference limit is exceeded In order to avoid high-bias results in the Cuvette Test, chloride ions can be masked by mercury if they are present in quantities below the content shown in the table. Samples with a higher chloride content must be diluted. Cuvette Test Masking possible up to ..... chloride • Turbidity in the cuvette after digestion when COD tests LCK 514, LCK 114, LCK 014 and LCK 914 are used. • In the above Cuvette Tests, the green color of chromium(III) compounds is measured. Dichromate ions (Cr(VI) compounds) are reduced to chromium(III) compounds by the organic components of the sample. If a sample is still turbid after the digestion, this reinforces the green color, so that it seems as though there is a higher concentration of chromium(III) compounds. Careful inversion of the cuvette while its contents are hot but no longer boiling reduces the sedimentation time of any remaining solid particles, and suppresses the haze formation caused by density differences. Evaluate at room temperature. - LCK514, LCK114, LCK014 and LCK914
  Date: 2005-08-02
3   DOC - What is DOC and how is it determined?
  DOC stands for dissolved organic carbon. It is determined by the TOC Cuvette Test after the sample has been passed through a membrane filter (pore size 0.45 μm). - LCK385, LCK386, LCK387, LCK380, LCK381
  Date: 2005-08-02
4   PHOSPAHTE - Total or orthophosphate?
  In order to determine phosphate with the Cuvette Test, the phosphate must be present in the form of orthophosphate. Polyphosphates and organophosphates are determined after they have been converted to orthophosphates by digesting them with peroxodisulfate. After the oxidation, the phosphate is referred to as total phosphate. - LCK349, LCS349, LCK350, LCK049
  Date: 2005-08-02
5   PHOSPHATE - Can the digestion for total phosphate also be carried out in a high-temperature thermostat (HT)?
  Yes. Simply prepare the cuvette for the digestion and heat it for 15 minutes in the standard HT program. - LCK349, LCS349, LCK350
  Date: 2005-08-02
6   TOC - Can the digestion for the determination of TOC also be carried out in a high-temperature thermostat (HT)?
  Yes, provided the determination is carried out by the expulsion method, using LCK385, LCK386 and LCK387. Carry out the digestion under the digestion conditions of the standard thermostat, i.e. for two hours at 100°C. Preliminary heating is not necessary. A high-temperature thermostat cannot be used if the TOC determination is carried out by the difference method, using LCK 380 and LCK 381. Return - LCK384, LCK385, LCK386, LCK387, LCK380, LCK381
  Date: 2005-08-02
7   TOC - No powder dispenser available
  Include a dispenser (article number LCW 912) in your next order. Until it is delivered, add 120 mg digestion reagent per sample cuvette. Return - LCK380, LCK381
  Date: 2005-08-02
8   TOC - TOC by the difference method
  Carbon may be present in the form of either organic or inorganic compounds. Only the TOC, i.e. the organic carbon, is relevant. In the difference method, the total carbon (TC) and the total inorganic carbon (TIC = total inorganic carbon) are determined, and the TOC content is calculated as the difference between them: TOC = TC – TIC. - LCK380, LCK381
  Date: 2005-08-02
9   TOC - TOC by the expulsion method
  Carbon may be present in the form of either organic or inorganic compounds. Only the TOC, i.e. the organic carbon, is relevant. In the expulsion method, the sample is acidified, and then stirred to expel the inorganic carbon as carbon dioxide. Only organic carbon remains in the sample. - LCK385, LCK386, LCK387
  Date: 2005-08-02
10   TOC - What is TOC and how is it determined?
  TOC stands for total organic carbon. It is determined by oxidizing the organic carbon that is present in the sample. Under the conditions of the test, the carbon forms carbon dioxide, which diffuses through a membrane into an indicator solution. The change of color of the indicator solution is evaluated photometrically. The inorganic carbon is either purged from the sample before the analysis (see expulsion method), or it is determined and then the TOC content is calculated as the difference between the total carbon and the total inorganic carbon (see difference method). - LCK385, LCK386, LCK387, LCK380, LCK381
  Date: 2005-08-02
11   PHOSPHATE - What does –P stand for in the formula PO4–P?
  –P stands for phosphorus in the form of phosphate. PO4–P is the quantity of phosphorus that is present in the sample in the form of phosphate (PO4). - LCK349, LCS349, LCK350, LCK049
  Date: 2005-08-01
12   CADAS 100 - How do I program a new test on the CADAS 100?
  The programming instructions for the CADAS 100 are available on the Internet. They can be found under the corresponding test under the heading “Informationen für Kunden” / “Arbeitsvorschriften” [Customer Information / Working Procedures].
  Date: 2005-07-29
13   CADAS 200 - How can I program my own tests?
  Simply follow the detailed instructions in the User Manual. The programming procedure is extensive and must be carried out carefully if the desired result is to be obtained.
  Date: 2005-07-29
14   CADAS 50/30 50S/30S - How can I set the right evaluation?
  The results of a number of Dr. Lange Cuvette Tests can be expressed in different ways. If no specific option is set as the “permanent” form, all the different evaluation options are displayed. If one option is set to “permanent”, the result will automatically be expressed in this form. A “permanent” setting can be reversed as follows: Call the test under the function “Var” (Vary test). Change nothing and exit the “Var” menu. Next time the cuvette is inserted, all the available evaluation options are displayed.
  Date: 2005-07-29
15   LASA 1/2/plus - How can I program tests and modify (vary) them if necessary?
  In order to program and modify a test, insert the filter with the correct wavelength in the photometer (User Manual, pages 27/28). Call the first test under MODE. Then insert either the programming module (LZP300) or the variation module (LZP301) and press the MODE key to call the test that is to be programmed or modified.
  Date: 2005-07-29
16   LASA 100 - How can I switch between evaluation forms?
  The results of a number of Dr. Lange Cuvette Tests can be expressed in different ways. If no specific option is set as the “permanent” form, all the different evaluation options are displayed. If one option is set to “permanent”, the result will automatically be expressed in this form. A “permanent” setting can be reversed as follows: After the cuvette has been measured, press the “up” arrow. A dialogue window is displayed, in which the permanent form can be changed.
  Date: 2005-07-29
17   LASA 20 - My test has the wrong control number. What should I do?
  The EPROM has been updated and, with it, the test. In order to be able to use the old, still available, reagents, the old data must be called up (User Manual, page 15). To do this, call the program VAR by pressing both arrow keys simultaneously. Select the test. A prompt is displayed, asking whether the old or the new data should be used for the evaluation. Use the arrow keys to select the correct data.
  Date: 2005-07-29
18   XION 500 - Can I use the Xion 500 to carry out turbidity measurements?
  Turbidity measurements on the XION 500 are photometric measurements rather than turbidity measurements in the conventional sense. The photometer is calibrated using formazin and the result is expressed in Formazin Absorbance Units (FAU). The procedure is described in Application A24 (GA No.2 “Trübung” [Turbidity]). The evaluations are available on the XION 500 as Tests 746 - 10 mm and 746 - 50 mm.
  Date: 2005-07-29
19   XION 500 - How high is the beam path of the XION 500?
  The beam path of the XION 500 is 10 mm high.
  Date: 2005-07-29
20   CADAS 200 - How can I test my CADAS 200?
  The wavelength accuracy of the CADAS200 can be tested with a holmium perchlorate secondary standard (LZV086). The filter has maxima at defined wavelengths, which are checked by the test. The test filter set (LZP310) is used to check the scattered light and the photometric accuracy. The test solution set (LZP181) is also used to check the photometric accuracy of the photometer.
  Date: 2005-07-28
21   CADAS 200 - How can I update (vary) the CADAS 200 data?
  The data can be updated in 3 ways.
  1. If your photometers has a data handset, the barcode of barcode cuvette is automatically checked when the cuvette is inserted. If an update is necessary, it is requested via the data handset and the telephone.
  2. If a single test needs updating, select the menu options “Edit” and “Var” via the keyboard. The latest data are contained in the data table of the test.
  3. The free LZP900 diskette can be used to update all the tests.
  Date: 2005-07-28
22   PHOSPHATE - Can PO4–P be converted to PO4 3-?
  Yes. The determination is the same, but the result is expressed in a different form.
Conversion factors F:
PO4 -P * F = PO4 F = 3,066
PO4 * F = PO4-P F = 0,326
PO4 –P * F = P2O5 F = 2,291
P2O5 * F = PO4-P F = 0,436
P2O5 * F = PO4 F = 1,338
  Date: 2005-07-27