PROCEDURE. Alkalinity by Titration. Alkalinity, Carbonate and BiCarbonate Analysis by Titrimetric Procedure

Transcription

1 Page:1 of 8 Alkalinity, Carbonate and BiCarbonate Analysis by Titrimetric Procedure 1.0 Purpose This procedure provides for analysis for water samples containing Alkalinity. Alkalinity is a total of Carbonate, BiCarbonate and Hydroxide species. 2.0 Applicability This procedure applies to samples being analyzed for Alkalinity, Carbonate, and BiCarbonate at the Cotter Corporation (N.S.L.) Cotter Canon City Milling Facility s Analytical Laboratory. Samples analyzed by this procedure are water samples from the Cotter Canon City Milling Facility and surrounding areas, including samples from the Schwartzwalder Mine in Golden Colorado. These samples are derived from wells, surface runoff, streams or rivers, tailings and previous mining operations. 2.1 Summary of the Method Total alkalinity is measured by titrating the water sample with sulfuric acid to a ph endpoint of ~4.5. Once the water sample reaches a ph of 4.5, the three main forms of alkalinity (bicarbonate, carbonate, and hydroxide) have been neutralized When titrating for total alkalinity, there are 2 equivalence points, where the ph changes rapidly with small amounts of acid these lie near ph 8.3 and 4.5. These points can be determined by measuring ph as the acid is added, or by choosing indicators that change color at the ph value of the equivalence point Samples are preserved by refrigeration at 4º C. 2.2 Interferences Substances, such as salts of weak organic and inorganic acids present in large amounts may cause interference in the electrometric ph measurements Carbon Dioxide in the air can combine with H 2 O and form Carbonic acid. The Carbonic acid provides bicarbonate and carbonate for buffering like CaCO 3, which can decrease the ph.

2 Page:2 of Other Documents Oil and grease, by coating the ph electrode, may also interfere, causing sluggish ph meter response. 3.1 References Quality Assurance Program Plan for Environmental and Occupational Sampling and Monitoring Studies for the Cotter Corporation Canon City Milling Facility and Lincoln Park, Colorado Superfund site. Revision May 22, EPA, Total Alkalinity, USEPA Buret Titration Method, USEPA accepted, adapted from Standard Methods for the Examination of Water and Wastewater 2320 B Cotter Analytical Procedure SOP 3-3, Calibration and Verification of Laboratory Balances and Weights Cotter Analytical Procedure SOP 3-4, Calibration and Verification of Laboratory Pipettes Material Safety Data Sheets (MSDS). 3.2 Appendices None 3.3 Exhibits None 4.0 Equipment and Materials 4.1 Equipment Analytical balance, to g, Scientech or Auto pipettes, µl, µl, µl, µl, µl etc Buret, 25 ml Class A, Self Zeroing with Stopcock ml graduations, 1000 ml reservoir, VWR or

3 Page:3 of Disposable, 125 ml polypropylene, specimen cups, VWR or Graduated Cylinders, Class A, 100, 250 and 500 ml, Kimble or Magnetic stirring plate, VWR or Orion ph meter with probe, or Pipette tips, μl, μl, µl, µl Eppendorf or Polypropylene Specimen bottles, 125 ml, StarPlex or Teflon stir bar, 1.5 VWR or Volumetric Flasks, class A (1000 ml), VWR or 4.2 Materials and Reagents 5.0 Responsibility Alkalinity Standard/Control, 1000 ppm (µg/ml) as CaCO 3 (0.010 M Na 2 CO 3 ) - NIST Traceable with certification, Orion Application Solution Thermo Scientific or Dilute 10.0 ml of 1000 ppm standard/control to 100 ml with deionized water ASTM Type II Deionized Water Buffers: Red ph 4, Yellow ph 7, Blue ph 10, BDH or N Sulfuric Acid Reagent, used as titrant, VWR or 5.1 Analyst Perform sample analysis by titrating the sample for Total Alkalinity determination.

4 Page:4 of Peer Reviewer Verify preparation and analysis of samples as per this method. 5.3 Quality Assurance Coordinator Review of sample preparation/analysis and QA parameters. 5.4 Laboratory Manager Review sample preparation/analysis and QA parameters as a function of data review. 6.0 Prerequisite Information 6.1 Definitions 6.2 Safety At ph 10, hydroxide (if present) reacts to form water. At ph 8.3, carbonate is converted to bicarbonate. At ph 4.5, it is certain that all the carbonate and bicarbonate are converted to carbonic acid. Below this ph, the water is unable to neutralize the sulfuric acid. Note: The following steps are performed as frequently as necessary to prepare samples for analysis Review MSDS for reagents used in this procedure Analyst shall wear appropriate protective clothing and equipment to prevent splashes from coming in contact with skin or eyes. 6.3 Preparation QC Standards LCS Spike Using a graduated cylinder transfer 90 ml DI water to a clean disposable specimen cup and pipette ml (1000ul) of the 1000 ppm Total Alkalinity Standard, Place Teflon stir bar in cup and place on stirrer and titrate as per the procedure listed in Matrix Spike

5 Page:5 of Quality Control Transfer the same amount of sample as used for the Original sample and the Duplicate to a disposable sample cup and pipette ml of the 1000 ppm Total Alkalinity standard, Place stir bar in cup and place on stirrer and titrate as per the procedure listed in Any discrepancies to this procedure will be noted on the case narrative for each batch of samples Verify that balances and auto pipettes to be used in this procedure have received Quality Control checks as per SOP 3-3 and SOP Preparation Blank Analyze a Preparation Blank with each batch of 20 samples or less For aqueous sample Preparation Blanks, DI water is used in the same volume as the sample volume The result of the Preparation Blank should be below the MDL of the method. If not, note any discrepancies in the case narrative for that batch of samples Laboratory Control Sample, LCS Analyze a LCS sample with each batch of 20 samples or less The LCS is prepared as per section 6.4. The percent recovery is calculated according to the following: LCS R *100 s Where: R: Percent Recovery LCS: Laboratory Control Sample Results s: amount of spike added (in concentration units)

6 Page:6 of The Percent Recovery for the LCS shall be within the required control limits of %. If the recovery is not within control limits note any discrepancies in the case narrative and refer to Lab Manager before reanalyzing batch to resolve any problems that may have arisen Duplicate Analyze a duplicate sample with each batch of 20 samples or less RPD, Relative Percent Difference of less than or equal to 20 % and an RD, Relative Difference less than or equal to 1 are the acceptance ranges as per section of Reference (QAPP) If the RPD and/or the RD are not within control limits note any discrepancies in the case narrative and refer to Lab Manager before reanalyzing batch to resolve any problems that may have arisen Matrix Spike Analyze a Matrix Spike with each batch of 20 samples or less The aliquot used for the Matrix Spike must be a duplicate of the aliquot used for sample analysis For aqueous samples the added analyte concentration must be the same as that used in the Laboratory Control Sample. The LCS is prepared as per section Calculate the percent recovery for the Matrix Spike as follows: R C s C *100 s Where: R: Percent Recovery C s : Measured concentration in spiked sample matrix C : Measured concentration in un-spiked sample

7 Page:7 of Procedure s: amount of analyte added to sample matrix The recovery of the Matrix Spike should be within the designated acceptance range of %. If it is not within control limits note any discrepancies in the case narrative and refer to Lab Manager before reanalyzing batch to resolve any problems that may have arisen. 7.1 Confirm ph meter calibration A three point calibration using a 4 ph buffer, a 7 ph buffer and a 10 ph buffer. Follow manufacturer s instructions for calibrating of the ph meter. 7.2 Sample Procedure ph buffers should be at room temperature when calibrating the meter T i t r a t i o n 7.3 Calculations Samples should be at room temperature before starting analysis Place appropriate size sample in sample cup. Record volume on worksheet Stir sample with magnetic stirring plate and stir bar such that air isn t drawn into sample Place ph probe in the opposite side of the sample cup that the Buret discharges to. Measure ph of sample using the ph meter Titrate using 0.02 N Sulfuric acid from a Class A buret to ph 8.3. Record volume of titer used on worksheet, continue titrating to ph 4.5. Record volume of titer used on worksheet Total Alkalinity as CaCO 3 :

8 Page:8 of 8 CaCO 3 mg/l = Total ml of Titrant * 1000 ml/sample volume ml Bi-Carbonate, as HCO 3 : HCO 3 mg/l = ml of Titrant 1 st endpoint * 1000 ml/sample volume ml Carbonate, as CO 3 : CO 3 mg/l = Total Alkalinity as CaCO 3 mg/l Bi-Carbonate as HCO 3 mg/l 8.0 NOTES: 8.1 Lab wastes are disposed to Pond 3 through piping.