ALLOWAY METHOD OUTLINE Standard Laboratory Method SM4500-Cl -G Parameter Residual Chlorine & Free Chlorine Method DPD Colorimetric Test Kit Date Issued Originator: Section Supervisor: QA Manager Date: Date: Date: Page 1 of
1.0 Scope of Application CHLORINE RESIDUAL FREE AND TOTAL COLORIMETRIC, DPD 1.1 This method is applicable to drinking, surface and saline waters, and domestic and industrial wastes. 1.2 The range of this method is 0.01 to 3.60 mg/l (Based on HACH DR 00). Dilutions of samples can be performed for concentrations exceeding the linear range of calibration. 1.3 The reporting level is 0.05 mg/l. 2.0 Summary of Method 2.1 DPD reagent is added to test samples. In the presence of oxidizing materials a red color is produced proportional to the concentration of oxidizing materials present. 2.2 The presence of other oxidizing materials other than chlorine (e.g. Bromine, Oxidized Manganese) act as a positive interference. 3.0 Definitions 3.1 Accuracy-The degree of agreement between an observed value and an accepted reference value. Accuracy includes a combination of random error (precision) and systematic error (bias) components which are due to sampling and analytical operations; a data quality indicator. 3.2 Aliquot - A portion of the field sample to be processed through the analytical steps. 3.3 Analytical Batch Composed of prepared environmental samples (extracts, digestates, or concentrates) which are analyzed together as a group. An analytical batch can include prepared samples originating from various environmental matrices. 3.4 Calibration To determine, by measurement or comparison with a standard, the correct value of each scale reading on a meter, instrument, or other device. The levels of the applied calibration standard must bracket the range of planned or expected sample measurements. 3.5 Calibration Curve The graphical relationship between the known values, such as concentrations, of a series of calibration standards and their instrument response. Page 2 of
3.6 Continuing Calibration Check - A check standard analyzed periodically to evaluate whether the analytical process remains in control. These results are compared to the initial calibration. 3. Duplicate Analyses- The analyses or measurements of the variable of interest performed identically on two sub-samples of the same sample. The results from duplicate analyses are used to evaluate analytical or measurement precision but not the precision of sampling, preservation or storage internal to the laboratory. 3.8 Homogeneous Sample - A sample which has an even distribution of material. 3.9 Instrument Detection Limit - The minimum concentration of an analyte that can be measured with 99% confidence that the analyte concentration is greater than zero. Determine the IDL with seven replicates of standard solution at the instrument with no specific analytical preparation. 3.10 Method Detection Limit - The minimum concentration of an analyte that can be measured with 99% confidence that the analyte concentration is greater than zero. Determine the MDL with seven replicates of standard solution taken through the preparative and analytical procedures. 3.11 Initial Calibration - A series of standards analyzed to produce a calibration curve in order to develop a linear system. 3.12 Internal Standard A known amount of standard added to a test portion of a sample as a reference for evaluating and controlling the precision and bias of the applied analytical method. 3.13 Laboratory Control Sample A sample matrix, free from the analytes of interest, spiked with verified known amounts of analytes from a source independent of the calibration standards or a material containing known and verified amounts of analytes. It is generally used to establish intra-laboratory or analyst/technician specific precision and bias or to assess the performance of all or a portion of the measurement system. 3.14 Matrix- The component or substrate that contains the analyte of interest. 3.15 Matrix Spike A sample prepared by adding a known mass of target analyte to a specified amount of matrix sample for which an independent estimate of target analyte is available. Matrix spikes are used, for example, to determine the effect of the matrix on a method s recovery efficiency. Page 3 of
3.16 Matrix Spike Duplicate A second replicate matrix spike prepared in the laboratory and analyzed to obtain a measure of the precision of the recovery for each analyte. 3.1 Quality Assurance An integrated system of activities involving planning, quality control, quality assessment, reporting and quality improvement to ensure that a product or service meets defined standards of quality with a stated level of confidence. 3.18 Quality Control The overall system of technical activities whose purpose is to measure and control the quality of a product or service so that it meets the needs of users. 3.19 Reagent Blank or Method Blank A sample consisting of reagent(s), without the target analyte or sample matrix, introduced into the analytical procedure at the appropriate point and carried through all subsequent steps to determine the contribution of the reagents and of the involved analytical steps. 3.20 Reporting Limit - The practical quantitation level for an analyte, greater than the MDL, accounting for dilutions and matrix specific concerns. 3.21 Sample Duplicate Two samples taken from and representative of the same population and carried through all steps of the sampling and analytical procedures in an identical manner. Duplicate samples are used to assess variance of the total method including sampling and analysis. 4.0 Interferences 4.1 A high alkalinity of the sample or acidity may not develop the full amount of color or it may cause the color to instantly fade. 4.2 Manganese or Chromium (Cr 6 ) may interfere. The addition of potassium iodide and sodium arsenate will compensate for this. 4.3 Highly colored samples interfere with the color measurement and can be corrected by zeroing the spectrophotometer on the sample. 5.0 Safety 5.1 The toxicity or carcinogenicity of each chemical and reagent used in this method has not been precisely defined. However, each one must be treated as a potential health hazard, and exposure to these chemicals should be minimized. Each analyst is responsible for adherence to the procedures outlined in the Chemical Hygiene Plan. Material Safety Data Sheets are kept in the laboratory. Page 4 of
5.2 Some method analytes have been tentatively classified as known or suspected human or mammalian carcinogens. Pure standard materials and stock standard solutions of these compounds should be handled with suitable protection to skin, eyes, etc. 5.3 Safety glasses and lab coats must be worn when handling samples and solvents. Safety glasses must be worn when handling glassware. 6.0 Equipment and Supplies 6.1 HACH DR00 colorimeter. 6.2 DPD Total Chlorine and Free Chlorine Reagent powder pillows..0 Reagents and Calibration Standards.1 1000 mg/l DPD Potassium permanganate solution (KMn0 4) : Dissolve 0.891 grams of potassium permanganate in 800mL of deionized water. Dilute to mark in 1000mL volumetric flask..1.1 10 mg/l DPD standard: Pipet 10mL of the 1000mg/L KMn0 4 solution (.1) into a 1000mL volumetric flask and dilute to mark with deionized water..1.2 2.0 mg/l DPD standard: Pipet 20mL of the 10mg/L standard (.1.1) into.1.3 1.5 mg/l DPD standard: Pipet 15mL of the 10mg/L standard (.1.1) into.1.4 1.0 mg/l DPD standard: Pipet 10mL of the 10mg/L standard (.1.1) into.1.5 0.5 mg/l DPD standard: Pipet 5mL of the 10mg/L standard (.1.1) into.2 DPD Total Chlorine Reagent.3 DPD Free Chlorine Reagent. 8.0 Sample Collection, Preservation, and Handling 8.1 Sample preservation is not practical for this determination. Sample analysis should be performed within 15 minutes of sample collection. Samples not Page 5 of
analyzed within 15 minutes must be qualified on the final report as estimates due to holding time exceedance. 8.2 The laboratory will analyze samples as soon as possible after receipt. 9.0 Calibration and Standardization 9.1 Known amounts of a potassium permanganate solution are used as standards to verify the calibration of the DR00 colorimeter (see section.0). Calibration is performed initially and thereafter every three months; records are kept in the laboratory so that any rapidly deteriorating equipment can be replaced. 9.2 Each calibration standard concentration must be within 10% of the true value before proceeding. 10.0 Quality Control 10.1 The test kit is to be standardized every three months by analyzing the calibration standards listed in section.0. 10.2 A duplicate sample must be analyzed for every ten samples or at least once if fewer than ten samples are analyzed. 10.2.1 The RPD limit for the duplicate is 20%. The sample analyzed in duplicate is qualified if the RPD exceeds the limit. 10.3 The instrument is zeroed on each sample prior to the addition of DPD reagent. 11.0 Analytical Procedures 11.1 Fill two test tubes with the sample. 11.2 Add HACH Reagent (either for free chlorine or total chlorine) to one of the tubes and mix. 11.3 For free chlorine, immediately compare the color of test sample to the permanent standards. Also read the untreated sample. 11.4 For total chlorine, allow a three-minute reaction time before making the visual comparison. 12.0 Calculations and Quantitative Analysis 12.1 Measure accurately the amount of the resulting solution for your individual kit off the HACH spectrophotometer in terms of mg/l. Page 6 of
13.0 Data Assessment 13.1 The primary analyst bears the responsibility of producing accurate data. A documented review is performed that includes a check of the following parameters: Calibration verification, QC criteria, calculation checks, Data entry into the LIMS 13.2 The initial data review is documented on the worksheet or bench sheet and dated by the primary analyst. An individual trained in the analytical procedure must perform a secondary review. 13.3 Data qualifiers are used whenever deviations occur while analyzing the samples. The qualifiers are included on the Certificate of Analysis that is presented to the client. Qualifiers include: samples that were not analyzed within 15 minutes of collection, failed duplicate and estimated or elevated reporting limit due to sample matrix interference. 14.0 Report Generation 14.1 A Certificate of Analysis is generated after each analysis run is complete. The report includes the EPA Method Number, sample identification, date and time sampled, date and time received, quantitative result, analysis date and time, and analyst initials. 15.0 Waste Management and Pollution Prevention 15.1 Samples are disposed of according to the Alloway SOP on Sample Disposal. For those samples which are deemed to be hazardous materials, these must be lab packed and removed by a third party firm. 15.2 For information about pollution prevention that may be applicable to laboratory practices consult "Less is Better for Laboratory Chemical Management for Waste Reduction" available from the American Chemical Society Department of Government Relations and Science Policy. Address: 1155 16 th St. N.W. Washington, DC 20036. 16.0 References 16.1 Standard Methods for the Examination of Water and Wastewater, 20 th Editions, SM4500Cl-G (DPD Colorimetric) 1.0 Revision History 1.1 Revision issued to update format, add DPD reagents, add calibration curve acceptance criteria, remove EPA Method 330.5 as a reference, add reporting level, add holding time and add duplicate limits. Page of