Determination of Practical Quantitation Levels for Organic Compounds in Drinking Water

Oxenford, Jeffrey L.; McGeorge, Leslie J.; Jenniss, Stephen W.

doi:10.1002/j.1551-8833.1989.tb03193.x

Cited by 6 publications

(8 citation statements)

References 1 publication

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“…The fourth section, which deals with the toxic elements (e.g., heavy metals or inorganic chemicals [IOCs]), provides different detection limits for each approved method and does not include a requirement to conduct an MDL study (except for lead and copper under Lead and Copper Rule monitoring). The regulations state that results below these detection limits may be considered “zero” for averaging purposes and assume that accurate quantitation is possible right up to the detection limit, even though USEPA previously has formally distinguished between detection and quantitation (Oxenford et al, 1989; USEPA, 1984b).…”

Section: Analytical Concernsmentioning

confidence: 99%

Setting IOC Reporting Limits for Drinking Water Compliance—The California Approach

Kimbrough¹,

Cárdenas²,

Eaton³

et al. 2004

Journal AWWA

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Establishing meaningful reporting limits presents one of the more vexing problems associated with chemical monitoring under the Safe Drinking Water Act (SDWA). At very low concentrations, relative errors can be large, leading to an increase in false‐positives and false‐negatives. Even when a pollutant is correctly identified at concentrations in the region of detection, results can be inaccurate and imprecise. The California Division of Drinking Water and Environmental Management, the primacy agency for SDWA enforcement, established a study group to develop a new approach for reporting limits for metals based on the minimum reporting level (MRL) concept. A voluntary interlaboratory study was conducted to determine an appropriate basis for setting MRL values. Forty‐seven drinking water laboratories accredited by the state received a series of prepared solutions containing analytes of interest. Only analytic methods approved by the US Environmental Protection Agency for SDWA compliance monitoring were used. The major determinative of reporting limits was how many laboratories had the capability of producing accurate results at any given concentration. Other practical considerations included the toxicity and occurrence of the elements.

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Section: Analytical Concernsmentioning

confidence: 99%

Setting IOC Reporting Limits for Drinking Water Compliance—The California Approach

Kimbrough¹,

Cárdenas²,

Eaton³

et al. 2004

Journal AWWA

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“…First, interlaboratory studies may be conducted, in which a group of laboratories are challenged with low-level samples. 9,12,13 This approach may be the most defensible because it directly measures the quantitative abilities of an actual laboratory community. The lower limit of quantitation can then be set according to selected criteria of precision and accuracy.…”

Section: Determining Quantitation Levels For Regulatory Purposesmentioning

confidence: 99%

Determining quantitation levels for regulatory purposes

Sanders¹,

Lippincott²,

Eaton³

1996

Journal AWWA

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A quantitation level is proposed that should be quantifiable by a majority of laboratories. The authors describe an approach for calculating quantitation levels (QLs) that does not require changes in current laboratory practices. The reliable detection level (RDL), when defined as twice the concentration of the method detection limit (MDL), provides adequate protection against both false‐positive and false‐negative detection decisions. When analyte concentrations are at the RDL, the corresponding precision in the instrument response is adequate for analytical purposes. Therefore, the RDL (as determined by a single laboratory) is a reasonable lower limit of quantitation for that laboratory. To determine an interlaboratory QL suitable for regulatory purposes, median interlaboratory MDLs were multiplied by a variable factor (usually 4–7, determined from actual laboratory performance data). More than 80 percent of the laboratories surveyed had RDLs less than or equal to the calculated QL, indicating that adequate quantitation was attainable at this level and that the QL should be suitable for regulatory purposes.

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“…To address the need for a quantitation level procedure and for a verification of such a level, a number of procedures described in the literature (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14) were evaluated. These procedures are summarized in Table 1.…”

Section: Introductionmentioning

confidence: 99%

“…Quantitation level procedures are not defined consistently throughout the literature, but a quantitation level is typically used to describe a reporting level for data of known quality. To address the need for a quantitation level procedure and for a verification of such a level, a number of procedures described in the literature ( − ) were evaluated. These procedures are summarized in Table .…”

Section: Introductionmentioning

confidence: 99%

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Statistical Procedures for Determination and Verification of Minimum Reporting Levels for Drinking Water Methods

Winslow

Pepich²,

Martin³

et al. 2005

Environ. Sci. Technol.

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The United States Environmental Protection Agency's Office of Ground Water and Drinking Water has developed a single-laboratory quantitation procedure: the lowest concentration minimum reporting level (LCMRL). The LCMRL is the lowest true concentration for which future recovery is predicted to fall, with high confidence (99%), between 50% and 150%. The procedure takes into account precision and accuracy. Multiple concentration replicates are processed through the entire analytical method and the data are plotted as measured sample concentration (y-axis) versus true concentration (x-axis). If the data support an assumption of constant variance over the concentration range, an ordinary least-squares regression line is drawn; otherwise, a variance-weighted least-squares regression is used. Prediction interval lines of 99% confidence are drawn about the regression. At the points where the prediction interval lines intersect with data quality objective lines of 50% and 150% recovery, lines are dropped to the x-axis. The higher of the two values is the LCMRL. The LCMRL procedure is flexible because the data quality objectives (50-150%) and the prediction interval confidence (99%) can be varied to suit program needs. The LCMRL determination is performed during method development only. A simpler procedure for verification of data quality objectives at a given minimum reporting level (MRL) is also presented. The verification procedure requires a single set of seven samples taken through the entire method procedure. If the calculated prediction interval is contained within data quality recovery limits (50-150%), the laboratory performance at the MRL is verified.

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Determination of Practical Quantitation Levels for Organic Compounds in Drinking Water

Cited by 6 publications

References 1 publication

Setting IOC Reporting Limits for Drinking Water Compliance—The California Approach

Setting IOC Reporting Limits for Drinking Water Compliance—The California Approach

Determining quantitation levels for regulatory purposes

Statistical Procedures for Determination and Verification of Minimum Reporting Levels for Drinking Water Methods

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