Assessing total nitrogen in surface-water samples--precision and bias of analytical and computational methods

Rus, David L.; Patton, Charles J.; Mueller, David K.; Crawford, Charles G.

doi:10.3133/sir20125281

Cited by 10 publications

(7 citation statements)

References 15 publications

(15 reference statements)

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“…Over the range of concentrations analyzed, the RSD for nitrate was very low. The RSD for TN is well within the range reported [25]. The higher error rate obtained with 2 ppm of nitrate and 2 ppm of TKN is being re-evaluated in our laboratories at the current time.…”

Section: Theoretical Tkn (Ppm)supporting

confidence: 83%

Simplified Method for the Determination of Total Kjeldahl Nitrogen in Wastewater

Hicks

Kuns

Raman³

et al. 2022

Environments

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The increase in total Kjeldahl nitrogen (TKN) concentrations is correlated with increases in cyanobacterial bloom biomass. Standard methods for the measurement of TKN are tedious, costly, time-consuming and involve the use of hazardous catalysts, such as mercury, high temperatures and significant amounts of toxic acids and bases. Since TKN plays a pivotal role in influencing algal blooms, there is an urgent need to develop simpler, safer and more accurate methods for the determination of TKN. The simplified TKN method (s-TKN™) developed by Hach® offers several advantages over the traditional TKN method, including eliminating the use of mercury, requiring low sample and reagent volumes and being cost-efficient and user-friendly. This communication presents preliminary results comparing the efficacy of s-TKN™ and the standard method, using commonly used primary standards and waste, estuarine and lake water matrices. For all primary standards analyzed, the s-TKN™ method exhibited good accuracy across a wide range of concentrations. The repeatability for the glycine–para-toluene sulfonic acid (Gly-PTSA) standard using the s-TKN™ method was 4.1% at the highest concentrations analyzed, with overall repeatability across concentrations comparable to the standard EPA method. For wastewater, estuarine and lake matrices, a good correlation (r2 = 0.9917) between the two methods and no statistical difference in the values (p > 0.05) were obtained between two methods. Preliminary studies indicate that the s-TKN™ method has the potential to reduce the expenditure associated with the cost of analysis and has the potential to be a safer and cheaper alternative, while providing comparable analytical results to the standard method.

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Section: Theoretical Tkn (Ppm)supporting

confidence: 83%

Simplified Method for the Determination of Total Kjeldahl Nitrogen in Wastewater

Hicks

Kuns

Raman³

et al. 2022

Environments

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“…Our answer based on three lines of evidence is: mostly. First, the accuracy of both methods was high and similar to prior laboratory studies using a limited number of well‐controlled procedures (Rus et al ). Second, evidence for one method or another consistently over‐ or underestimating TN was inconsistent; and finally, regressions of samples simultaneously analyzed by both approaches were difficult to distinguish from a 1 : 1 relationship.…”

Section: Discussionsupporting

confidence: 70%

“…Our analyses of USGS‐SRS and LAGOS‐NE data sets were intended to provide a variety of perspectives on biases and potential interchangeability of TN results derived from direct and combined approaches. Several prior studies have compared TN methodologies both within direct (e.g., Bronk et al ; Vandenbruwane et al ) and combined (reviewed by Saéz‐Plaza et al ) approaches, as well as between TN‐d and TN‐c methods (e.g., Smart et al ; Maher et al ; Patton and Kryskalla ; Rus et al ). However, these comparisons have all been laboratory investigations that considered a small number of protocols (usually 2 or 3) that were well known and well controlled by the authors.…”

Section: Discussionmentioning

confidence: 99%

“…Note both axes are log10 transformed to visualize the data. methodologies both within direct (e.g., Bronk et al 2000; Vandenbruwane et al 2007) and combined (reviewed by Saéz-Plaza et al 2013) approaches, as well as between TN-d and TN-c methods (e.g., Smart et al 1981;Maher et al 2002;Patton and Kryskalla 2003;Rus et al 2012). However, these comparisons have all been laboratory investigations that considered a small number of protocols (usually 2 or 3) that were well known and well controlled by the authors.…”

Section: Discussionmentioning

confidence: 99%

“…For example, high NO 2 +NO 3 ‐N concentrations that may be common in settings such as agriculturally dominated landscapes (Stanley and Maxted ) can interfere with the accuracy of TN measurements by the Kjeldahl method (Schluter ). Alternatively, methods based on sample oxidation may not be effective in converting some classes of organic N compounds to NO x , especially in the presence of high sediment concentrations (Bronk et al ; Maher et al ; Rus et al ). Such issues would reasonably lead to an expectation that the use of different methods would reflect prevailing limnological conditions across broach geographic regions.…”

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confidence: 99%

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Comparison of total nitrogen data from direct and Kjeldahl‐based approaches in integrated data sets

Stanley

Salazar

Lottig³

et al. 2019

Limnology & Ocean Methods

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There are multiple protocols for determining total nitrogen (TN) in water, but most can be grouped into direct approaches (TN‐d) that convert N forms to nitrogen‐oxides (NOx) and combined approaches (TN‐c) that combine Kjeldahl N (organic N +NH3) and nitrite+nitrate (NO2+NO3‐N). TN concentrations from these two approaches are routinely treated as equal in studies that use data derived from multiple sources (i.e., integrated data sets) despite the distinct chemistries of the two methods. We used two integrated data sets to determine if TN‐c and TN‐d results were interchangeable. Accuracy, determined as the difference between reported concentrations and the most probable value (MPV) of reference samples, was high and similar in magnitude (within 3.5–4.5% of the MPV) for both methods, although the bias was significantly smaller at low concentrations for TN‐d. Detection limits and data flagged as below detection suggested greater sensitivity for TN‐d for one data set, while patterns from the other data set were ambiguous. TN‐c results were more variable (less precise) by many measures, although TN‐d data included a small fraction of notably inaccurate results. Precision of TN‐c was further compromised by propagated error, which may not be acknowledged or detectable in integrated data sets unless complete metadata are available and inspected. Finally, concurrent measures of TN‐c and TN‐d in lake samples were extremely similar. Overall, TN‐d tended to be slightly more accurate and precise, but similarities in accuracy and the near 1 : 1 relationship for concurrent TN‐d and TN‐c measurements support careful use of data interchangeably in analyses of heterogeneous, integrated data sets.

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Water quality related to Conservation Reserve Program (CRP) and cropland areas: Evidence from multi-temporal remote sensing

Yin

Wang²,

Zhu³

et al. 2021

International Journal of Applied Earth Observation and Geoinfor

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Assessing total nitrogen in surface-water samples--precision and bias of analytical and computational methods

Cited by 10 publications

References 15 publications

Simplified Method for the Determination of Total Kjeldahl Nitrogen in Wastewater

Simplified Method for the Determination of Total Kjeldahl Nitrogen in Wastewater

Comparison of total nitrogen data from direct and Kjeldahl‐based approaches in integrated data sets

Water quality related to Conservation Reserve Program (CRP) and cropland areas: Evidence from multi-temporal remote sensing

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