The EPA on Monday, Aug. 3, 2009, announced in the Federal Register its approval of six alternative testing methods for use in measuring the levels of contaminants in drinking water and determining compliance with national primary drinking water regulations.

The newly approved methods are as follows:

EPA Method 524.3, Version 1.0

This is a gas chromatography/mass spectrometry (GC/MS) method for the determination of purgeable organic compounds in finished drinking waters. The method analytes are purged from the water sample using helium and trapped on a sorbent material. After purging, the trap is heated and back flushed with helium to transfer the analytes to a capillary GC column. Compounds eluting from the GC are directed into a mass spectrometer for mass analysis and detection. The analytes are identified by comparing the acquired mass spectra and retention times to reference spectra and retention times for calibration standards acquired under identical GC/MS conditions.

The concentration of each target analyte is calculated using the internal standard technique and response curves obtained via procedural calibration. The expansion of the method to include the option of selective ion monitoring makes this method sufficiently sensitive to measure dibromochloropropane (DBCP) and ethylene dibromide (EDB) at the concentrations required for drinking water compliance monitoring.

EPA Method 524.3 is an updated version of EPA Method 524.2, Revision 4.1 (USEPA 1995a), which is currently approved for analyses of compliance samples for 21 volatile organic contaminants and total trihalomethanes. The method development work is described in the method research summary (Zaffiro et al. 2009). The advantages of the new method include:

• Use of maleic acid, a common food preservative, to preserve samples, eliminating the requirement to ship a hazardous reagent (hydrochloric acid) to the field;
• Incorporation of features that allow users to take advantage of modern instrumentation to improve speed and data quality;;
• Increased flexibility in selection of method operating parameters; and;
• Addition of Method 524.3 as an approved method for DBCP and EDB.;

Approved methods for volatile organic contaminants and total trihalomethanes are listed at 40 CFR 141.24(e). EPA Methods 502.2; Revision 2.1 (USEPA 1995b) and 524.2; Revision 4.1 (USEPA 1995a) are approved for benzene; carbon tetrachloride; chlorobenzene; 1,2- dichlorobenzene; 1,4-dichlorobenzene; 1,2-dichloroethane; cis-dichloroethylene; trans-dichloroethylene; dichloromethane; 1,2-dichloropropane; ethylbenzene; styrene; tetrachloroethylene; 1,1,1-trichloroethane; trichloroethylene; toluene; 1,2,4-trichlorobenzene; 1,1-dichloroethylene; 1,1,2-trichlorethane; vinyl chloride; xylenes (total--measured as sum of o-xylene; m-xylene and p-xylene); and total trihalomethanes (sum of chloroform; bromodichloromethane; dibromochloromethane; and bromoform). EPA Method 551.1 (USEPA 1995c) is approved for carbon tetrachloride; tetrachloroethylene; 1,1,1-trichloroethane; trichloroethylene; EDB; DBCP; and total trihalomethanes. EPA Method 504.1, Revision 1.1 (USEPA 1995d) is approved for EDB and DBCP. Approved methods for total trihalomethanes are also listed at 40 CFR 141.131(b)(1).

The EPA has determined that, for each of the 24 contaminants, EPA Method 524.3 is equally as effective for measuring the contaminant as the methods currently listed in the regulations as approved for that contaminant.

Mitchell Method M5271

The EPA is approving the Mitchell Method M5271 for determining turbidity in drinking water.

Mitchell Method M5271 (Mitchell 2009a) uses laser nephelometry to measure turbidity in drinking water. The method is based on a comparison of the intensity of light scattered by the sample under defined conditions with the intensity of light scattered by a standard reference suspension. Readings are made using an on-line laser nephelometer with the following design criteria:

• Laser light source is monochromatic operated at a nominal wavelength of 650 +/- 30nm;
• Incident radiation and any convergence does not exceed +/-1.5 degrees in the measurement area;
• Distance traversed by incident light and scattered light does not exceed 10cm;
• Detector/light receiver is centered at 90 +/- 1.5 degrees to the incident light path and the light cone does not exceed +/- 30 degrees from 90 degrees; and
• Instrument incorporates a bubble trap and anti-fog windows. Sensor is horizontal and the windows are vertical. Windows are immersed in the sample stream.

Four approved methods for turbidity are listed at 40 CFR 141.74(a)(1). The performance characteristics of Mitchell Method M5271 were compared to the performance characteristics of approved EPA Method 180.1 (USEPA 1993a). The validation study report (Mitchell 2008a) summarizes the results obtained from the turbidimeters placed in series at three different public water systems. One water system used ground water and the other two plants used surface water sources. Measurements included at least one filter backwash at each of the surface water plants. The EPA has determined that the Mitchell Method M5271 is equally effective relative to EPA Method 180.1 that is already promulgated in the regulations at 40 CFR 141.74(a)(1). The basis for this determination is discussed in Wendelken 2009a.

A copy of the method can be downloaded from the National Environmental Methods Index (NEMI) at http://www.nemi.gov or obtained by contacting Leck Mitchell, PhD, PE, 656 Independence Valley Dr., Grand Junction, CO 81507.

Mitchell Method M5331

The EPA has determined that the Mitchell Method M5331 is equally effective relative to EPA Method 180.1 for determining turbidity in drinking water.

Mitchell Method M5331 (Mitchell 2009b) uses light-emitting diode (LED) nephelometry to measure turbidity in drinking water. The method is based on a comparison of the intensity of light scattered by the sample under defined conditions with the intensity of light scattered by a standard reference suspension. Readings are made using an on-line LED nephelometer with the following design criteria:

• LED light source is monochromatic operated at a nominal wavelength of 525 +/- 15nm;
• Incident radiation and any convergence does not exceed +/- 1.5 degrees in the measurement area;
• Distance traversed by incident light and scattered light does not exceed 10cm;
• Detector/light receiver is centered at 90 +/- 1.5 degrees to the incident light path and the light cone does not exceed +/- 30 degrees from 90 degrees; and
• Instrument incorporates a bubble trap and anti-fog windows. Sensor is horizontal and the windows are vertical. Windows are immersed in the sample stream.

Four approved methods for turbidity are listed at 40 CFR 141.74(a)(1). The performance characteristics of Mitchell Method M5331 were compared to the performance characteristics of approved EPA Method 180.1 One water system used groundwater and the other two plants used surface water sources. Measurements included at least one filter backwash at each of the surface water plants.

A copy of the method can be downloaded from NEMI at http://www.nemi.gov or obtained from Leck Mitchell, PhD, PE, 656 Independence Valley Dr., Grand Junction, CO 81507.

Orion Method AQ4500

The EPA has determined that Thermo Scientific's Orion Method AQ4500 is equally effective relative to EPA Method 180.1, which is already promulgated in the regulations at 40 CFR 141.74(a)(1). The agency is approving Method AQ4500 for the measurement of turbidity in drinking water.

Thermo Scientific's Orion Method AQ4500 (Thermo Scientific 2009) uses LED nephelometry to measure turbidity in drinking water. The method is based on a comparison of the intensity of light scattered by the sample at 90 degrees to the beam path with the intensity of light scattered by a standard reference suspension. Readings are made using a portable LED nephelometer with the following design criteria:

• White LED light source emits broadband light having peak intensities in the 400nm to 600nm range;
• Distance traversed by incident light and scattered light does not exceed 10cm;
• Detector/light receiver is centered at 90 degrees to the incident light path and the light cone does not exceed +/- 30 degrees from 90 degrees. The detector has spectral peak response between 400nm and 600nm;
• Pulsed light allows for synchronous detection, a technique by which ambient stray light leakage, as well as other electronic induced errors, are effectively cancelled out; and
• Color compensation is achieved using a dual-beam system with two photo detectors.

Four approved methods for turbidity are listed at 40 CFR 141.74(a)(1). The performance characteristics of Thermo Scientific's Orion Method AQ4500 were compared to the performance characteristics of EPA Method 180.1 (USEPA 1993a) listed at 40 CFR 141.74(a)(1) for measurement of turbidity. Two rounds of testing were conducted (Wendelken 2009c). The first was an ASTM round robin study comparing results from analyses of 28 samples of various types using turbidimeters with tungsten filament light sources as specified in EPA Method 180.1 and white LEDs as specified in Thermo Scientific Orion Method AQ4500.

A second study involved demonstration of performance at turbidities below 2 nephelometric turbidity units.

A copy of the method can be downloaded from NEMI at http:// www.nemi.gov or obtained from Thermo Scientific, 166 Cummings Center, Beverly, MA 01915, Phone: (800) 225-1480, www.thermo.com.

Systea Easy (1-Reagent)

The EPA has determined that the Systea Easy (1-Reagent) Nitrate Method is equally effective relative to EPA Method 353.2 and Standard Method 4500-NO₃- F-00. Furthermore, the agency identified the method as a "green alternative to other approved methods, which use cadmium, a known carcinogen, for the reduction of nitrate to nitrite." The EPA is approving this method for determining nitrate and nitrite concentrations in drinking water to comply with 40 CFR 141.23.

Systea Scientific LLC's Systea Easy (1-Reagent) Nitrate Method uses automated discreet analysis by spectrophotometry to determine concentrations of nitrate and nitrite combined or individually in drinking water. The method involves the following steps:

• Reduction of nitrate in a sample to nitrite using a non-hazardous proprietary reagent;
• Diazotizing the nitrite originally in the sample plus the reduced nitrate with sulfanilamide followed by coupling with N-(1-napthyl)ethylenediamine dihydrochloride under acidic conditions to form a highly colored azo dye;
• Colorimetric determination in which the absorbance of color at 546nm is directly proportional to the concentration of the nitrite plus the reduced nitrate in the sample;
• Measurement of nitrite individually by analysis of the sample while eliminating the reduction step; and
• Subtraction of the nitrite value from that of the combined nitrate plus nitrite value to determine nitrate individually.

Approved methods for nitrate and nitrite are listed at 40 CFR 141.23(k)(1). An inter-laboratory study (Systea Scientific LLC. 2008) was conducted to compare the performance characteristics of the Systea Easy (1-Reagent) Nitrate Method to the characteristics of the EPA Method 353.2 (USEPA 1993b) and Standard Method 4500-NO₃- F-00 (APHA 1997), which are listed at 40 CFR 141.23(k)(1) for nitrate and nitrite. Ten laboratories analyzed a variety of sample matrices using approved methods. The samples were also analyzed using the Systea Easy (1-Reagent) Nitrate Method.

Systea Easy (1-Reagent) Nitrate Method can be downloaded from NEMI at http://www.nemi.gov or obtained from Systea Scientific LLC, 900 Jorie Blvd., Suite 35, Oak Brook, IL 60523, Phone: (630) 645-0600.

Method ME355.01

The EPA is approving this method for determining cyanide concentrations in drinking water to comply with 40 CFR 141.23.

Method ME355.01, "Determination of Cyanide in Drinking Water by GC/MS Headspace" (Eaton 2009) uses direct headspace injection after acidification followed by Gas Chromatography/Mass Spectrometry (GC/MS) to determine the concentration of cyanide, as free cyanide, in drinking water. The method involves the following steps:

• Acidification of the sample;
• Heating the sample to 60 degrees Celsius with agitation;
• Direct injection of 1 milliliter of headspace onto the nitrogen-cooled cryotrap; and
• Analysis using temperature programmed GC/MS.

The performance characteristics of Method ME355.01 were determined in three laboratories by replicate analyses of fortified samples (Wendelken 2009e). The results were compared to the characteristics of EPA Method 335.4 (USEPA 1993c) and Standard Method 4500-CN-F-99 (APHA 1999) listed at 40 CFR 141.23(k)(1) for cyanide. The EPA has determined that Method ME355.01 is equally effective relative to each of these two methods. The basis for this determination is discussed in Wendelken 2009e.

Method ME335.01 can be downloaded from NEMI at http://www.nemi.gov or obtained from James Eaton, Ph.D, H & E Testing Laboratory, 221 State Street, Augusta, ME 04333, Phone: (207) 187-2727.