Cardinal Environmental Laboratories, LLC

Standard Operating Procedure

Procedure No.: 4030 Revision Date: 17/07

Subject: (Method 375.3) Sulfate, Total (Turbidimetric):

Approved by: Title: Date Revised:

Sulfate, Total (Turbidimetric)

Method 375.3

Scope and Application

This method is applicable to drinking, surface and saline water; and domestic and industrial wastes.

Matrix

Aqueous.

Description

Barium sulfate is precipitated with BaCl2 in an acetic acid medium. The BaSO4 suspension is measured on the spectrometer and sulfate is determined by comparing with a standard curve. The detection limit is 5ppm.

Definitions

Method Blank: aliquot of reagent water treated exactly as a sample including exposure to all glassware, equipment, solvents, reagents, internal standards, and surrogates used. Used to determine if interferences or analytes are present in the lab environment.

Duplicate Sample: sample analyzed second time exactly the same way as the first analysis. Used to calculate precision expressed as Relative Percent Difference (RPD).

Matrix Spike (MS) and Matrix Spike Duplicate (MSD): aliquots of sample to which known quantities of the analyte of interest is added in the laboratory. The MS and MSD are prepared and analyzed exactly as a field sample. The purpose is to quantify any bias or imprecision caused by the sample matrix. The background concentrations of the analyte(s) in the sample matrix must be determined in a separate aliquot and the measured values in the MS and MSD corrected for background concentrations.

QCS Quality Control Sample: A sample containing analyte(s) of interest at known concentrations. The QCS is obtained from a source different than the calibration standards. Purpose is to check performance using materials prepared independently from normal preparation procedures.

Precautions

General safety requirements (see procedure 0010)

Corrosives (see procedure (0020)

Sample Preservation

Samples analyzed for sulfate can be collected in either plastic or glass containers. They are unpreserved and stored at 4°C. Holding time before analysis is 28 days.

Apparatus

- Stir Plate - 1cm cell for spectrometer - Stir Bar - Filter apparatus

- 100ml beakers - Vacuum pump

- Volumetric Pipet, various - 0.45um filter paper

- Graduated Cylinder, various - Clock (with second hand) or timer

- Spectro meter

Reagents

- Sulfar 4 sulfate reagent powder; pillows available from Hach.

-  Sulfate standard; Commercially available 1ml = 1mg SO4

- QC sulfate standard; Commercially available 1ml = 0.100mg SO4

Procedure

1.0 Measure 25ml, or an aliquot made up to 25ml, into a 100ml beaker. If sample contains large amounts of suspended matter filter through a 0.45u filter before analysis.

1.1 Add 1 Hack Sulfauer 4 reagent pillow.

1.2 Stir to dissolve for 20 sec.

1.3 After 5 minutes read sample absorbance in a 1cm cell on the Milton Roy 601 Spectrometer at 420mm.

1.3.1 Once on, allow 1/2 hour for spectrometer to warm prior to analysis.

1.3.1.1 Adjust wavelength by keying 4,2,0 followed by the “‘’second function’’ key followed by the ‘’go to l‘’ key.

1.4 Place blank into 1cm cell and insert into spectrometer.

1.4.1 Zero the spectrometer to this blank by keying the ‘’second function’’ key followed by the ‘’zero’’ key.

1.5 Remove blank and insert standards and/or sample to be analyzed - read and record absorbances.

1.6 Standard Curve

1.6.1 Pipette the following volumes of the standard solution into separate 100ml beakers:

mls standard + mls ultrapure water = concentration/ppm

2.5 22.5 10.0

5.0 20.0 20.0

10.0 15.0 40.0

15.0 10.0 60.0

20.0 5.0 80.0

1.6.2 To each standard, continue with the method steps 1.1 - 1.7.

1.6.3 Record absorbance for each standard.

1.6.3.1 Absorbance data is input into excel file SO4STD.XLS to generate a linear coefficient. A printed copy of the current L.C. is found in the active L.C. file.

1.7 Calculation

SO4-2, ppm = (ABS)(LC)(25)

(sample volume in mls)

Quality Control

* Each analytical batch for sulfate must be accompanied by a method blank consisting of 25ml ultra pure water.

* Each analytical batch must also be accompanied by two standards.

* All weights, volumes, comments etc. for each batch must be entered in notebook form for data review.

* Every 5th sample of similar matrix shall be analyzed in duplicate and a % RPD calculated. Every 10th sample shall be analyzed as a duplicate spike and % RPD calculated. (See procedure 0110 for calculations).

* Any sample with an absorbance > 10% above the curve must be diluted and re-run.

* Failure to meet quality control acceptable limits requires corrective action.

(See procedure 0150).

If correlation coefficient is <0.995 reprep standards and rerun calibration curve. If standards are outside acceptable limits, reprep and reanalyze standards. If still outside acceptable limits, prepare a new standard curve and reanalyze standards and samples.

Method Performance

See QAPP section 5.2.

Aqueous Precision = 20%, Aqueous Accuracy = 97-123%.

Reference

Methods for Chemical Analysis of Water and Wastes

EPA 600/4-79-020 March 1983

pp 375.4-1 thru 375.4-3

Standard Methods for The Examination of Water and Waste Water

18th Edition 1992 Method 4500 - SO4-2

pp. 4-134

National Environmental Methods Index. April 1994. Method 375.3. 7 April 2004.

<http://www.nemi.gov>

Procedure 4030

Revised 17/07