1、July 2005DEUTSCHE NORM English price group 7No part of this translation may be reproduced without prior permission ofDIN Deutsches Institut fr Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany,has the exclusive right of sale for German Standards (DIN-Normen).ICS 13.060.60!,x1X“9851453w
2、ww.din.deDDIN 38404-3German standard methods for the examination of water, waste waterand sludge Part 3: Determination of spectral absorption in the UV range, spectralabsorption coefficient (C 3)Deutsche Einheitsverfahren zur Wasser-, Abwasser- und Schlammuntersuchung Physikalische und physikalisch-
3、chemische Kenngren (Gruppe C) Teil 3: Bestimmung der Absorption im Bereich der UV-Strahlung, SpektralerAbsorptionskoeffizient (C 3)SupersedesDIN 38404-3:1976-12www.beuth.deDocument comprises 12 pages Translation by DIN-Sprachendienst.In case of doubt, the German-language original should be consulted
4、 as the authoritative text.08.07Physical and physicochemical parameters (group C) DIN 38404-3:2005-07 2 Contents Page Foreword. 3 Introduction 3 1 Scope . 3 2 Normative references . 4 3 Terms and definitions 4 4 Principle. 4 5 Interferences . 5 6 Designation . 5 7 Reagents 6 8 Apparatus 6 9 Sampling
5、 and sample preparation 6 9.1 Sampling 6 9.2 Sample pretreatment 6 10 Procedure 7 10.1 Determination of spectral absorption. 7 10.2 Turbidity compensation . 7 11 Evaluation 7 11.1 Spectral absorption, () . 7 11.2 Turbidity correction 8 12 Expression of result . 8 13 Test report . 8 14 Results of int
6、erlaboratory testing . 9 Annex A (informative) Explanatory notes 10 Bibliography. 12 DIN 38404-3:2005-07 3 Foreword This standard has been prepared jointly with Wasserchemische Gesellschaft (Water Chemistry Society), a specialist group of the Gesellschaft Deutscher Chemiker (German Chemists Society)
7、 (see Annex A). Expert assistance and specialized laboratories will be required to perform the analyses specified in this standard. Existing safety instructions shall be observed. When using the standard, a check shall be made on a case-by-case basis as to whether and to what extent additional bound
8、ary conditions have to be specified. See Annex A for a list of other parts of DIN 38404 and of groups A to T of the German standard methods. Amendments This standard differs from DIN 38404-3:1976-12 as follows: a) The analytical method has been modified. b) Apparatus and reagent requirements have be
9、en added. c) Allowance has been made for the effect of particulates. d) The results of interlaboratory testing have been included. e) The standard has been editorially revised. Previous editions DIN 38404-3:1976-12 Introduction Since many organic substances have absorption bands in the UV range, the
10、 spectral absorption, (), at 254 nm can be used to determine the total content of dissolved organics in water, especially if there is little fluctuation in their qualitative composition. CAUTION Users of this standard should be familiar with standard laboratory practice. It is not claimed that all t
11、he safety problems associated with the use of the standard have been dealt with exhaustively here. It is therefore the responsibility of the user to take appropriate safety precautions and to ensure that these comply with national regulations. 1 Scope This standard specifies a method of determining
12、absorption in the UV range as a measure of the total content of dissolved organics in undiluted water samples of every kind, including those that are highly coloured or turbid. However, the method does not detect some organic compounds, for example short-chain aliphatics, pure alcohols, pure sugar,
13、etc. If the sample contains not only truly dissolved, but also undissolved substances, the measurement does not yield the spectral absorption, (), but the spectral attenuation coefficient () (see DIN EN ISO 7027). DIN 38404-3:2005-07 4 2 Normative references The following referenced documents are in
14、dispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. DIN 38404-4, German standard methods for the examination of water, wastewater and sludge P
15、hysical and physicochemical parameters (group C) Determination of temperature (C 4) DIN 38404-5, German standard methods for the examination of water, wastewater and sludge Physical and physicochemical parameters (group C) Determination of pH value (C 5) DIN EN ISO 5667-3, Water quality Sampling Par
16、t 3: Guidance on the preservation and handling of water samples DIN EN ISO 7027, Water quality Determination of turbidity ISO 3696, Water for analytical laboratory use Specification and test methods 3 Terms and definitions For the purposes of this standard, the following terms and definitions apply.
17、 3.1 spectral absorption, (), at 254 nm the attenuation of UV light per unit path length on passing through a water sample NOTE The absorption of the water sample measured at a wavelength, , of 254 nm is a measure of the content of the dissolved chromophoric organic substances. 3.2 spectral diffusio
18、n coefficient (turbidity coefficient), s(), at 254 nm the attenuation of UV light by particulates per unit path length on passing through an absorption-free water sample 3.3 spectral attenuation coefficient, (), at 254 nm the sum of the spectral absorption coefficient and the spectral diffusion coef
19、ficient () = () + s() NOTE This is the light attenuation due to all the dissolved and undissolved components. 3.4 corrected spectral attenuation coefficient at 254 nm the spectral attenuation coefficient corrected for the scattered light component as defined in this standard 4 Principle The method i
20、s based on measuring the attenuation of a light beam as a result of absorption in the water sample. This absorption obeys the Lambert, Beer and Bouguer law, which may be expressed as: dcA = tr0lg (1) DIN 38404-3:2005-07 5 where A is the absorbance; tris the intensity of the light after passing throu
21、gh the sample; 0is the intensity of the incident light; is the logarithm to the base 10 of the molar absorptivity; c is the concentration, in mol/l; d is the path length of the cell, in cm. It is preferable to restrict the measurement range to one absorbance unit, since the absorption will then be a
22、 linear function of concentration and path length, i.e. tr= f(c,d), but the range should not under any circumstances exceed two absorbance units since this leads to measurement errors due to scattered light in many types of equipment. The substances dissolved in the water must have an absorption max
23、imum near 254 nm. In addition to the many organic substances that have absorption bands in the UV, there are some inorganic substances, such as nitrate ions, that absorb below 250 nm. This problem is minimized by working at a wavelength of 254 nm or more, but nitrate ion concentrations of more than
24、10 mg/l may still cause some interference. 5 Interferences Particulates in the water cause interference by attenuating and scattering the incident light. Fairly large concentrations can be substantially reduced by filtration through a membrane filter with a pore size of 0,45 m, but this may itself r
25、esult in interferences due, for example, to atmospheric oxidation, precipitation during filtering or UV-absorbing substances being leached out of the filter material. However, membrane filtration will not be necessary if any turbidity is compensated for by the method described in subclause 10.2. Int
26、erference may also be caused by the outgassing of dissolved gases (oxygen, carbon dioxide), by contaminants on the inside walls of the cell and skin grease on its beam entrance and exit walls. 6 Designation Designation of the method of determining spectral absorption in the UV absorption range, spec
27、tral absorption coefficient (C 3): Method DIN 38404 C 3 DIN 38404-3:2005-07 6 7 Reagents 7.1 Optically pure water Use only grade 1 water conforming to ISO 3696. This can be prepared by passing about one l of distilled or deionized water through a membrane filter with a pore size of 0,1 m that has be
28、en soaked for about one hour in distilled or deionized water. Discard the first 50 ml. Use only filters that have been shown not to release any organic contaminants. NOTE There is no need to clean the filter if the water treatment system is fitted with a suitable filter. 8 Apparatus The following eq
29、uipment shall be used. 8.1 Photometer or spectrophotometer for continuous or batch measurement, capable of measuring in a range from about 200 nm to 750 nm, or 8.2 Filter photometer for continuous or batch measurement at 254 nm and 550 nm, fitted with a spectral line filter having a bandwidth of 10
30、nm. 8.3 Fused quartz cells, having a path length, for example, of 1 cm and 5 cm. 8.4 pH meter. 8.5 Thermometer, having 0,1 C scale intervals and capable of measuring temperatures between 10 C and +50 C. 8.6 Membrane filter, having a pore size of 0,1 m and being free of organic contaminants. 8.7 Seal
31、able glass bottles, e.g. of nominal capacity 1 000 ml. 9 Sampling and sample preparation 9.1 Sampling Collect the samples in glass bottles (as in subclause 8.7) and perform the analysis as soon as possible, within no more than 24 hours (cf. EN ISO 5667-3) of collection. If delay is unavoidable, stor
32、e the samples in the dark at (4 3) C avoiding contact with air, especially if there is a possibility of redox reactions, and keeping the temperature constant. 9.2 Sample pretreatment Shake the unfiltered sample so as to distribute any particulates evenly and not to disperse the constituents. Analyse
33、 samples containing particulates immediately after shaking them. Fill the clean cell, first with optically pure water and then rinse and fill it with sample liquid. Tap it gently to remove any air bubbles. Treat filtered samples in the same way. DIN 38404-3:2005-07 7 10 Procedure 10.1 Determination
34、of spectral absorption Turn on and set up the spectrophotometer or filter photometer as specified by the manufacturer. Adjust the zero using optically pure water as reference; the zero should be within 0,005 absorbance units. NOTE 1 If high accuracy is required, adjust the zero five times at interva
35、ls of about ten seconds. An increase of more than +0,005 absorbance units in the vicinity of the measurement wavelength may be due to contamination of the cell or to adhering substances redissolving. A meaningful measurement is only possible when the zero signal has stabilized. NOTE 2 In the case of
36、 double-beam instruments, adjust the zero after every sample measurement, making sure that reading fluctuations stay within narrow limits (observe the manufacturers information). When carrying out series of measurement with a single-beam photometer, always check the zero between consecutive sample m
37、easurements in order to detect any reading fluctuations, minimize cell errors and avoid entrainment. Check the zero at least at the end of a measurement series. Measure the sample at 254 nm and, in the case of samples containing particulates, make further measurements at 550 nm for the correction pr
38、ocedure in subclause 10.2. If necessary, determine the pH value as specified in DIN 38404-5 and the temperature as specified in DIN 38404-4 in parallel with every measurement. 10.2 Turbidity compensation To compensate for undissolved constituents, determine the spectral attenuation coefficient at 25
39、4 nm, (), and at 550 nm, (ref), using, for example, a continuous process photometer and take the difference (see subclause 11.2). 11 Evaluation 11.1 Spectral absorption, () Calculate the spectral absorption, (), using equation (2): fdA )()( = (2) where A() is the sample absorbance at wavelength , in
40、 nm; d is the optical path length of the cell, in mm; f is the factor for converting the spectral absorption to m1(here, f = 1 000). NOTE Most spectrophotometers will provide a direct reading of the absorbance. In the case of instruments that give a reading of the transmission, T = (tr/0), calculate
41、 the absorbance using equation (3): A = lg T (3) DIN 38404-3:2005-07 8 11.2 Turbidity correction If the water sample is turbid, calculate the corrected spectral attenuation coefficient using equation (4) (absorbance reading) or (5) (transmission reading); ()corr= () ()ref(4) ()fdAA550254corr)(= (5)
42、where ()corris the corrected spectral attenuation coefficient, in nm; ()refis the spectral attenuation coefficient at 550 nm; () is the spectral attenuation coefficient at 254 nm. See equation (2) for A, d and f. 12 Expression of result The analytical results obtained using this standard are subject
43、 to a certain degree of uncertainty that has to be taken into account in interpreting them. Methods have been developed for determining measurement uncertainty that make it possible to estimate the uncertainty from laboratory validation data, routine quality assurance (range or mean-value control ca
44、rds) and validation and approval interlaboratory testing. The measurement uncertainty is preferably reported as an expanded uncertainty, the combined standard measurement uncertainty, expressed as the standard deviation or coefficient of variation, being multiplied by an expansion (coverage) factor
45、of 2. This corresponds to a confidence level of about 95 %. In the present standard, to estimate the measurement uncertainty, the reproducibility coefficient of variation, CVR, obtained in the validation interlaboratory test was multiplied by 2 (see Table 1). The expanded measurement uncertainty, U,
46、 of the method derived from this may only be used as a guide in determining the laboratory measurement uncertainty and cannot replace the in-house measurement uncertainty obtained from laboratory data. NOTE The measurement uncertainty depends on concentration and type of sample and is greatest for l
47、ower concentrations. Normally, the values of the spectral absorption, () and of the spectral attenuation coefficients, () and ()corr, are reported to the nearest 0,1 m1. EXAMPLE Spectral absorption, (), at 254 nm with = 1 nm: 1,8 m1. 13 Test report The test report shall refer to this method and may
48、include the following details: a) identification of sample; b) sampling and sample preparation; DIN 38404-3:2005-07 9 c) whether the spectral absorption, (), or the corrected spectral attenuation coefficient, ()corr, is being reported; d) if necessary, the pH value; e) the temperature if of relevanc
49、e for the test result; f) whether the sample was filtered; g) expression of result as in clause 12; h) an indication of any deviation from this standard and of any circumstances that may have affected the result. 14 Results of interlaboratory testing An interlaboratory test carried out in October 2004 yielded the results shown in Table 1. Further information on the interlaboratory test is contained in the validation document. Table 1 Results of interlaboratory
