© 2007 NSFNSF/ANSI 42 – 2007e
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NSF/ANSI Standard
for Drinking Water Treatment Units –
Drinking water treatment units –
Aesthetic effects
3Definitions to be added to NSF/ANSI 330
X.XReporting Limit: “The “Reporting Limit” (RL) for an analyte is the maximum level, for an undiluted sample, to which a laboratory may report a particular analyte as “Not Detected”.”
X.X Method Detection Limit (MDL): the minimum concentration of a substance that can be measured and reported with 99% confidence that the analyte concentration is greater than zero and is determined from analysis of a sample in a given matrix containing the analyte.
Note: Many times there is more to the analytical method than just doing a reaction or submitting it to direct analysis. For example it might be necessary to heat a sample that is to be analyzed for a particular metal with the addition of acid first (this is called digestion). The sample may also be diluted or concentrated prior to analysis on an instrument. Additional steps in an analysis add additional opportunities for error. Since detection limits are defined in terms of error, this will naturally increase the measured detection limit. This detection limit (with all steps of the analysis included) is called the MDL. The practical method for determining the MDL is to analyze 7 samples of concentration near the expected limit of detection. The standard deviation is then determined. The one-sided t distribution is determined and multiplied versus the determined standard deviation. For seven samples (with six degrees of freedom) the t value for a 99% confidence interval is 3.14. Rather than performing the complete analysis of seven identical samples, if the Instrument Detection Limit is known, the MDL may be estimated by multiplying the Instrument Detection Limit or Lower Level of Detection by the dilution prior to analyzing the sample solution on the instrument. This estimation, however, ignores any uncertainty that arises from performing the sample preparation and will therefore probably underestimate the true MDL.
X.XInstrument Detection Limit: The IDL is the analyte concentration that is required to produce a signal greater than three times the standard deviation of the noise level.
X.X Level of Quantitation (LOQ): The LOQ is the limit at which we can reasonably tell the difference between two different values. The LOQ is drastically different between labs so another detection limit is commonly used that is referred to as the Practical Quantitation Limit (PQL).
Note: Just because we can tell something from noise does not mean that we can necessarily know how much of the material there actually is.
X.X Practical Quantitation Limit (PQL): The PQL is defined simply as about 5 times the MDL.
X.X Total Allowable Concentration: The maximum concentration of a non-regulated contaminant permitted in a public drinking water supply as defined by annex A of NSF/ANSI 60.
4Materials
4.1Materials in contact with drinking water
POE drinking water treatment units shall conform to the protocol and criteria in NSF/ANSI 61.
POU drinking water treatment units shall conform to the protocol and criteria in this section. Materials in contact with drinking water shall not impart levels of extractable contaminants that exceed the Total Allowable Concentration (TAC) MCC or MDWL values specified in tables 1, 2 and 3when evaluated and tested in accordance with 4.2.Contaminants that extract from products when tested in accordance to section 4.2 that are not listed in Tables 1, 2 and 3 shall be evaluated in accordance to NSF/ANSI 61 Annex D & E (TAC) concentrations and/or Annex A if the contaminant is not listed in the Annex D & E tables.
At a minimum, metallic products shall be evaluated to the TAC levels in Table 1 and products made from non-metallic components shall be evaluated to the TAC levels in Tables 2 and 3 when evaluated and tested in accordance with 4.2.
NOTE – The concentration of active agents or additives used in the drinking water treatment process shall be evaluated in the product water as specified in 6.10. The concentration of active agents or additives used in the drinking water treatment process shall not be evaluated during extraction testing.
4.1.1Complete formulation information on any material not certified as specifically compliant with the sections of the U. S. Code of Federal Regulations, Title 21, listed in table 3, shall be reviewed to determine whether the material presents a health effects concern in contact with drinking water and to assess the material's potential for contributing contaminants to the drinking water.
NOTE – As a minimum for those materials requiring submission of formulation information, the complete chemical identity or proportion by weight (in some cases approximate weights or proportions may suffice), ingredient sources of supply, documentation regarding the health effects concern of each ingredient in the material, and documentation regarding the suitability of each ingredient for use in potable-water-contact material shall be provided.
4.1.2The product shall be tested in accordance with 4.2.3. If the product does not impart a concentration of an extractable contaminant at a level that exceeds the TAC either the MCC, MDWL, or advisory concentrations in tables 1, 2, or 34, the product shall be deemed to have met the requirements of 4. . If the product does impart a concentration of an extractable contaminant at a level that exceeds the advisory concentration, but not the MCC or MDWL, the product shall be deemed to have met the requirements of 4, but the manufacturer shall be notified of the concentration of the extractable contaminant, and a new product sample(s) shall be immediately retested in accordance with 4.2.3.6. For the parameters in table 4, the required follow-up analyses shall also be performed after the product has been exposed according to 4.2.3.6, if they were not performed as part of the initial exposure under 4.2.3.2.
4.1.3Whole-system extraction testing may be waived if components, when separately tested, meet the requirements of this Standard and are assembled in a manner that does not introduce any new components, increase the surface area-to-volume ratio of previously evaluated components, or present potential concern based on cumulative factors.
4.2Materials evaluation
4.2.1Analytical methods
All analyses shall be conducted in accordance with the applicable method(s) referenced in 2.
Reporting Limit:The laboratory must have validated the particular analytical method to this level following the procedures as established in the referenced method. The laboratory shall have evaluated its MDL (method detection limit) and LOQ (limit of Quantitation) in reference to the “RL”. In all cases, the MDL must be less than the RL, and preferably, the LOQ should also be below the RL. Further, to ensure accurate quantitation, when preparing its calibration standards, the lowest calibration point should be at or less than the RL.
For extracted techniques (i.e., 625), regarding the concentration of the lowest calibration point, the laboratory should apply the concentration factor due to sample preparation. For example, if for a typical sample one liter extracted, and the extract concentrated to 1.0 milliliter, for a factor of 1000, if the RL is set to 0.2 ug/L, then the lowest calibration point should be at or below 0.2 mg/L.”
4.2.2Exposure water
Systems and components shall be exposed to locally available tap water that has been adjusted to contain 50 ± 5 mg/L total dissolved solids and 0.5 ± 0.05 mg/L free available chlorine, and to have a pH of 6.75 ± 0.25. Exposure water used to evaluate systems or components shall be 23 ± 2 C (73 ± 3 F). Any existing concentrations of extraction testing parameters listed in tables 1, 2, and 3 4found to be present in the exposure water shall be subtracted from the values obtained in the analysis of the extractant water.
4.2.3Exposure
4.2.3.1The system or component(s) of a system shall be installed, flushed, and conditioned in accordance with the manufacturer's instructions using the exposure water specified in 4.2.2 at an initial inlet static pressure of 340 kPa (50 psig).
4.2.3.2The system or component(s) shall be refilled with the exposure water specified in 4.2.2 and maintained for 24 h at a temperature of 23 ± 2 C (73 ± 3 F). A 2-L water sample shall then be collected in accordance with 4.2.3.3. The system or component(s) shall be flushed according to the manufacturer’s instructions, refilled, and maintained for another 24 h at a temperature of 23 ± 2 C (73 ± 3F). A second 2-L water sample shall be collected in accordance with 4.2.3.3. The system or component(s) shall again be flushed according to the manufacturer’s instructions, refilled, and maintained for a third period of 24 h at a temperature of 23 ± 2 C (73 ± 3 F). A third 2-L water sample shall be collected in accordance with 4.2.3.3.
4.2.3.3A minimum sample volume of 2 L shall be collected at each sample point. If the water-holding volume of the product is greater than 2 L, the entire volume shall be collected in a suitable collection vessel, and a 2-L subsample obtained from this volume. If the water-holding volume of the product is less than 2 L, sufficient samples shall be exposed to provide the required 2-L volume of extractant water.
4.2.3.4All samples collected shall be composited and analyzed in accordance with 4.2.1.
4.2.3.5Systems with adsorptive or absorptive media shall be tested with and without the media. Testing without media shall include removal of the media from the system, as well as removal of any non-media materials or ingredients that cannot be disassociated from the media or materials that would be released into the effluent of the system in the absence of the physical barrier provided by the media. An example is the binder used to produce carbon blocks. Normalization or adjustment for changes in wetted surface area from the normal configuration shall be taken into account. For instance, carbon block end caps will have more wetted surface area exposed without the carbon block attached; therefore, an appropriate adjustment in the end caps included in the exposure shall be made.
4.2.3.6If the level of an extractable contaminant exceeds an advisory concentration in table 1, 2, or 4, the 72-h test exposure sequence in 4.2.3.2 shall be repeated three times using a new product sample(s). The extractant water from the third 24-h exposure of the third 72-h exposure sequence shall be analyzed to determine whether the concentration of the extractable contaminant has been reduced to a concentration less than or equal to the advisory concentration.
4.3Gas chromatography/mass spectroscopy (GC/MS) analysis
4.3.1General requirements for GC/MS analysis
When determined to be required by a toxicologist following a product-specific formulation review, Semi-volatile and Volatile Mass Spectral scans shall be performed on non-metal products or components, and shall include full-range scans to monitor for non-target compounds.
Testing for Semi-Volatiles (EPA Method 625 and Volatiles EPA Method 524.2) shall be conducted using the required Target Compounds in Tables 2 and 3 and the laboratory’s reporting limit shall be no greater than the reporting limits listed in Tables 2 and 3.
Contaminants are considered either as “Target Compounds” (targets)or as “Tentatively Identified Compounds” (TICs). Target compounds are those analytes for which the analytical system has been specifically validated, and for the samples in question specifically calibrated in accordance with the referenced analytical procedure. Contaminants that have been identified and quantified by comparison to authentic standards shall be compared to the acceptable exposure concentration as determined in accordance with NSF/ANSI 61 Annex D and NSF/ANSI 61 Annex E. TICs are identified by comparison of the spectrum of the unknown to the mass-spectral reference library utilizing “Probability Based Matching” (as available from instrument manufacturers) as well as interpretation by the GC/MS chemist. The laboratory shall report the TIC with the best match factor except in the following circumstances.
- Due to the complex nature of GCMS interpretation and identification, when reviewingthe list of possible matches for any particular TIC peak, the laboratory has the authority to assign the identification to a compound “hit” with a lower numeric match factor from the library search algorithm.
- The laboratory may determine that none of the returned compounds by the automated search algorithm is a good match for the unknown peak. In this case the compound is reported as a “Unknown”
- The laboratory may utilize manual spectral interpretation to identify the peak in question.
The library used during the analysis shall be NIST version 2007 or more current version. For TICs, the concentration is estimated by comparison of its total ion area response to the total ion area response of the nearest internal standard. For TIC’s, a response factor of “1” (one) shall be utilized for the purposes of calculating the TICs estimated concentration.
Note: To ensure clear communication of the potential range in concentration of tentatively identified compounds, as part of the laboratory report shall be the typical range of response factors from their 524.2 and 625 calibrations (based upon the required compound lists within this standard). Because reporting this range is to give clearer understanding of the potential range in concentration to the user of the TIC concentrations, it is acceptable for the laboratory to determine this range on an annual basis. An example of an appropriate laboratory statement would be; “when performing concentration estimates for tentatively identified compounds, the laboratory utilizes an estimated response factor of “1”. In performing methods 524.2 and 625 the typical response factors for calibrated compounds are 0.2 to 2.0 and 0.1 to 1.5 respectfully. Because these factors are applied as a reciprocal, this would mean an overall potential concentration range for any particular TIC from 0.5 the reported concentration to about 10 times.”
TICs that have been identified and quantified by comparison to a known mass spectrum, or by spectral interpretation by a qualified chemist, or both shall be compared to the acceptable exposure concentration as determined in accordance with Annex A and Annex D & Eof NSF/ANSI 61. The concentration threshold for all TICs and unknowns shall be no greater than 3.0 ppb. Upon toxicological review, TICs may require verification of identification and quantitation as a target compound. This would necessitate performing the requisite validation studies utilizing an authentic standard of the compound in question. In addition, the product manufacturer shall assist the testing laboratory in the identification of an authentic standard for the compound and an appropriate analytical method, if applicable, so that confirmatory identification and quantification can be performed.
Contaminants that are detected by GC/MS analysis but are not identified and quantified against a known mass spectrum or authentic standard shall be evaluated as follows:
a)The laboratory shall report the molecular weight or, if no molecular ion is identifiable by the GC/MS chemist, a minimum value for the molecular weight (ifor example, if the highest mass ion for the TIC has an m/z of 143, then report MW >=143).
b)The laboratory shall report chemical class information if this determination is possible.
c)The laboratory shall report the presence of the common halogens chlorine and bromine utilizing their characteristic “M+2” patterns.
d)The product material formulation(s) shall be reviewed for potential identification of the unknown contaminant(s) as an ingredient or byproduct;
e)The manufacturer shall be notified and requested to provide supporting information that enables identification of the unknown contaminant(s);
f)Structure activity relationships (SAR) shall be utilized when sufficient structural identification of the unknown contaminant(s) can be made; and
g)Alternative methods of analysis that may identify the unknown contaminant(s) shall be considered, such as classifying the unknown into a chemical class.
Contaminants that can be identified after performing one or more of the above steps shall be compared to the acceptable exposure concentration as determined in accordance with Annex Dand Annex Eof NSF/ANSI 61. In addition, the product manufacturer shall assist the testing laboratory in the identification of an authentic standard for the compound and an appropriate analytical method, if applicable, so that confirmatory identification and quantification can be performed when needed.
Contaminants detected by GC/MS analysis for which no identification can be made after performing the above steps shall not be considered in the determination of product compliance to this Standard. When unknown contaminants are detected in the extractant water, the testing laboratory shall report the analytical results to the product manufacturer.
Notes:
- The product manufacturers should assist the testing laboratory in a continuing effort to indentify the unknown contaminant(s) until specific identification is achieved.
- Items “b” and “c” above may be automated utilizing software available from NIST available with their mass-spectral database.
The minimum instrument operation requirements for GC/MS analysis shall be in accordance with USEPA Method 625 with the addition of the following modifications:
–The average chromatographic peak area of each internal standard in the calibration curve shall be determined. The chromatographic peak area of each internal standard in the continuing calibration shall be greater than 50% and not more than 200% of that average;
–While a continuing calibration check (CCC) is performed, concentrations of 10% of the target compounds for each analysis (e. g., base/neutral, base/neutral/acid, acid) shall be allowed to fall outside of the range of 70% to 130% (outlier) of the true value. None of the concentrations shall be allowed to fall below 50% or above 200% of the true value. If a positive sample analyte result is identified for any outlier, a second CCC shall be performed. If the second CCC determines the sample analyte result no longer to be an outlier, the sample shall be reanalyzed. However, if the second CCC also determines the analyte to be an outlier, a new calibration curve shall be determined and the sample shall be reanalyzed; and
–If commercially available mass spectral libraries are utilized, a minimum size of 100,000
compounds shall be required.
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© 2007 NSFNSF/ANSI 42 – 2007e
Table 1 – Extraction testing parameters (Metals)Parameter / Total Allowable Concentration (TAC)
mg/L / Reporting Limit (RL) mg/L / Reference Method(s)
aluminum / 0.5 / 0.100 / 200.7, 200.8
antimony / 0.006 / 0.001 / 200.8, 200.9
arsenic / 0.010 / 0.001 / 200.8, 200.9
barium / 2.0 / 0.100 / 200.7, 200.8
beryllium / 0.004 / 0.001 / 200.7, 200.8, 200.9
cadmium / 0.005 / 0.001 / 200.8, 200.9
chromium / 0.1 / 0.010 / 200.7, 200.8, 200.9
copper / 1.3 / 0.100 / 200.7, 200.8
lead / 0.015 / 0.001 / 200.8, 200.9
manganese / 0.3 / 0.010 / 200.7, 200.8
mercury / 0.002 / 0.001 / 200.8, 245.1
nickel / 0.1 / 0.010 / 200.7, 200.8
selenium / 0.05 / 0.001 / 200.8, 200.9
thallium / 0.002 / 0.001 / 200.8, 200.9
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