Nutrients: analytical methods, detection limits, and holding times - USEPA/SuRGE GitHub Wiki
Filtered samples (0.45um) are collected for nitrite + nitrate (no2.3), nitrite (no2), ammonium (nh4), and reactive phosphorus (op). Unfiltered samples are collected for total nitrogen (tn) and total phosphorus (tp). Samples collected by the ADA field crew are analyzed at the ADA General Parameters Laboratory. SAll samples collected in 2020 were analyzed at the ADA General Parameters Laboratory. All other samples are analyzed in CIN.
Analyte detection limits (dl) are assessed annually by each lab. Detection limits may differ by lab and year of analysis. Separate tables are provided below for ADA and CIN.
Please note that the analyte names and units used below are consistent with the SuRGE chemistry data objects, but may differ from those in the data files provided by the laboratories. See Wiki page Chemistry units, names, and data sources for the official list of analyte names and units to be used in the SuRGE data objects.
See emails from Bill Wright for MDL (1/20/2022) and RL (9/6/2022). These values are consistent with manual inspection of standard curves used for 2023 data (2023_ESF-EFWS_NutrientData_Updated05012024_AKB_JB.xlsx)
| Analyte | Analyte Container and volume | Analytical method | Year | Detection limit | Reporting limit | Preservation and Holding times | Lab |
|---|---|---|---|---|---|---|---|
| -no2 -TNO2 in raw data |
A single 30 mL HDPE bottle for TNO2,3, TNH4+, and TRP. Transferred to Lachat tubes in lab | Latchat QuikChem Method 10-107-04-1-J. N-(1-naphthyl)ethylenediamine dihydrochloride method | 2016-2023 | 6 ug_n_l | 20 ug_n_l | 24 hours @ 5oC or 28 days at -20oC | CIN |
| -no3 -TNO3 in raw data |
A single 30 mL HDPE bottle for TNO2,3, TNH4+, and TRP. Transferred to Lachat tubes in lab | Latchat QuikChem Method 10-107-04-1-J. N-(1-naphthyl)ethylenediamine dihydrochloride method | 2016-2023 | 6 ug_n_l | 20 ug_n_l | 24 hours @ 5oC or 28 days at -20oC | CIN |
| -no2.3 -TNO2.3 in raw data |
A single 30 mL HDPE bottle for TNO2,3, TNH4+, and TRP. Transferred to Lachat tubes in lab | Latchat QuikChem Method 10-107-04-1-J. N-(1-naphthyl)ethylenediamine dihydrochloride method | 2016-2023 | 6 ug_n_l | 20 ug_n_l | 24 hours @ 5oC or 28 days at -20oC | CIN |
| -nh4 -TNH4 in raw data |
A single 30 mL HDPE bottle for TNO2,3, TNH4+, and TRP. Transferred to Lachat tubes in lab | Latchat QuikChem Method 10-107-06-1-B. Alkaline phenol-based method. | 2016-2023 | 6 ug_n_l | 20 ug_n_l | 24 hours @ 5oC or 28 days at -20oC | CIN |
| -op -TRP in raw data |
A single 30 mL HDPE bottle for TNO2,3, TNH4+, and TRP. Transferred to Lachat tubes in lab | Latchat QuikChem Method 10-115-01-1-B. Molybdate based method | 2016-2023 | 3 ug_p_l | 5 ug_p_l | 24 hours @ 5oC or 28 days at -20oC | CIN |
| tp | A single 30 mL HDPE bottle for TP and TN. Transferred to 10 mL glass screw cap tubes with teflon liners in lab. | Latchat QuikChem Method 10-115-01-4-E. Offline acid persulfate digest | 2016-2023 | 5 ug_p_l | 5 ug_p_l | 24 hours @ 5oC or 28 days at -20oC | CIN |
| tn | A single 30 mL HDPE bottle for TP and TN. Transferred to 10 mL glass screw cap tubes with teflon liners in lab. | Latchat QuikChem Method 10-107-04-4-A. Offline alkaline persulfate digest. | 2016-2023 | 25 ug_n_l | 30 ug_n_l | 24 hours @ 5oC or 28 days at -20oC | CIN |
Separate results for no2 and no3 only provided in 2021.
2021 ADA data reports a NH4 MDL determination on 6/2/2021. The MDL is reported as 2 or 1.71 ug_l, across the various 2021 data reports. Presumably 2 ug_l is simply rounding up of the 1.71 ug_l value. Using 1.71 ug_l here.
no2.3 and nh4 MDL was reassessed late in the 2022 season (9/8/2022). Prior to this the MDL was based on the 6/2/2021 determination. Here we adopt the 9/8/2022 results for all 2022 samples.
no2.3 and nh4 MDL was reassessed late in the 2023 season (8/30/2023). Prior to this the MDL was based on the 9/8/2022 determination. Here we adopt the 8/30/2023 results for all 2023 samples.
| Analyte | Analyte Container and volume | Analytical method | Year | Detection limit | Reporting limit | Preservation and Holding times | Lab |
|---|---|---|---|---|---|---|---|
| no2.3 | A single 125 mL HDPE bottle. Transferred to Lachet tubes in the lab. | Analysis Using Lachat Flow Injection Analyzers Analysis Method 10-107-04-2-A. K-GCRD-SOP-1151-0 | 2021 including 2020 samples analyzed in 2021 |
10 ug_n_l MDL determination on 1/5/2021 |
50 ug_n_l | Filtered and acidified to pH of <2 with H2SO4 store cold at @ 4oC up to 28 days | ADA |
| no2 | A single 125 mL HDPE bottle. Transferred to Lachet tubes in the lab. | Analysis Using Lachat Flow Injection Analyzers Analysis Method 10-107-04-2-A. K-GCRD-SOP-1151-0 | 2021 | 12 ug_n_l MDL determination on 1/5/2021 |
50 ug_n_l | Filtered and acidified to pH of <2 with H2SO4 store cold at @ 4oC up to 28 days | ADA |
| no3 | A single 125 mL HDPE bottle. Transferred to Lachet tubes in the lab. | Analysis Using Lachat Flow Injection Analyzers Analysis Method 10-107-04-2-A. K-GCRD-SOP-1151-0 | 2021 | 10 ug_n_l MDL determination on 1/5/2021 |
50 ug_n_l | Filtered and acidified to pH of <2 with H2SO4 store cold at @ 4oC up to 28 days | ADA |
| nh4 | A single 125 mL HDPE bottle. Transferred to Lachet tubes in the lab. | Analysis Using Lachat Flow Injection Analyzers Analysis Method 10-107-06-1-O. K-GCRD-SOP-1151-0 | 2021 including 2020 samples analyzed in 2021 |
1.71 ug_n_l MDL determination on 6/2/2021 |
10 ug_n_l | Filtered and acidified to pH of <2 with H2SO4 store cold at @ 4oC up to 28 days | ADA |
| op | A single 125 mL HDPE bottle. Transferred to Lachet tubes in the lab. | Analysis Using Lachat Flow Injection Analyzers Analysis Method 10-115-01-1-A. G-GWERD-SOP-1151-0 | 2021 including 2020 samples analyzed in 2021 |
2 ug_p_l MDL determination on 8/28/2020 |
25 ug_p_l | Store cold at @ 4oC up to 48 hours | ADA |
| tp | A single 125 mL HDPE bottle. Transferred to Lachet tubes in the lab. | Analysis Using Lachat Flow Injection Analyzers Analysis Method 10-115-01-3-A. G-GWERD-SOP-1151-0 | 2021 including 2020 samples analyzed in 2021 |
2 ug_p_l MDL determination on 1/12/2021 |
100 ug_p_l | Acidified to pH of <2 with H2SO4 store cold at @ 4oC up to 28 days | ADA |
| tn | A single 125 mL HDPE bottle. Transferred to Lachet tubes in the lab. | Analysis Using Lachat Flow Injection Analyzers Analysis 10-107-04-3-P. G-GWERD-SOP-1151-0 | 2021 including 2020 samples analyzed in 2021 |
69 ug_n_l MDL determination on 2/1/2021 |
100 ug_n_l | Acidified to pH of <2 with H2SO4 store cold at @ 4oC up to 28 days | ADA |
| no2.3 | A single 125 mL HDPE bottle. Transferred to Lachet tubes in the lab. | Analysis Using Lachat Flow Injection Analyzers Analysis Method 10-107-04-2-A. K-GCRD-SOP-1151-0 | 2022 | 21 ug_n_l MDL determination on 9/8/2022 |
100 ug_n_l | Filtered and acidified to pH of <2 with H2SO4 store cold at @ 4oC up to 28 days | ADA |
| nh4 | A single 125 mL HDPE bottle. Transferred to Lachet tubes in the lab. | Analysis Using Lachat Flow Injection Analyzers Analysis Method 10-107-06-1-O. K-GCRD-SOP-1151-0 | 2022 | 32 ug_n_l MDL determination on 9/8/2022 |
100 ug_n_l | Filtered and acidified to pH of <2 with H2SO4 store cold at @ 4oC up to 28 days | ADA |
| op | A single 125 mL HDPE bottle. Transferred to Lachet tubes in the lab. | Analysis Using Lachat Flow Injection Analyzers Analysis Method 10-115-01-1-A. G-GWERD-SOP-1151-0 | 2022 | 2 ug_p_l MDL determination on 6/8/2022 |
50 ug_p_l | Store cold at @ 4oC up to 48 hours | ADA |
| tp | A single 125 mL HDPE bottle. Transferred to Lachet tubes in the lab. | Analysis Using Lachat Flow Injection Analyzers Analysis Method 10-115-01-3-A. G-GWERD-SOP-1151-0 | 2022 | 10 ug_p_l MDL determination on 3/9/2022 |
100 ug_p_l | Acidified to pH of <2 with H2SO4 store cold at @ 4oC up to 28 days | ADA |
| tn | A single 125 mL HDPE bottle. Transferred to Lachet tubes in the lab. | Analysis Using Lachat Flow Injection Analyzers Analysis 10-107-04-3-P. G-GWERD-SOP-1151-0 | 2022 | 61 ug_n_l MDL determination on 3/9/2022 |
100 ug_n_l | Acidified to pH of <2 with H2SO4 store cold at @ 4oC up to 28 days | ADA |
| no2.3 | A single 125 mL HDPE bottle. Transferred to Lachet tubes in the lab. | Analysis Using Lachat Flow Injection Analyzers Analysis Method 10-107-04-2-A. K-GCRD-SOP-1151-0 | 2023 | 35 ug_n_l MDL determination on 8/30/2023 |
100 ug_n_l | Filtered and acidified to pH of <2 with H2SO4 store cold at @ 4oC up to 28 days | ADA |
| nh4 | A single 125 mL HDPE bottle. Transferred to Lachet tubes in the lab. | Analysis Using Lachat Flow Injection Analyzers Analysis Method 10-107-06-1-O. K-GCRD-SOP-1151-0 | 2023 | 27 ug_n_l MDL determination on 8/30/2023 |
100 ug_n_l | Filtered and acidified to pH of <2 with H2SO4 store cold at @ 4oC up to 28 days | ADA |
| op | A single 125 mL HDPE bottle. Transferred to Lachet tubes in the lab. | Analysis Using Lachat Flow Injection Analyzers Analysis Method 10-115-01-1-A. G-GWERD-SOP-1151-0 | 2023 | 2 ug_p_l MDL determination on 8/1/2023, same results as 6/8/2022 determination |
50 ug_p_l | Store cold at @ 4oC up to 48 hours | ADA |
| tp | A single 125 mL HDPE bottle. Transferred to Lachet tubes in the lab. | Analysis Using Lachat Flow Injection Analyzers Analysis Method 10-115-01-3-A. G-GWERD-SOP-1151-0 | 2023 | 29 ug_p_l MDL determination on 4/13/2023 |
100 ug_p_l | Acidified to pH of <2 with H2SO4 store cold at @ 4oC up to 28 days | ADA |
| tn | A single 125 mL HDPE bottle. Transferred to Lachet tubes in the lab. | Analysis Using Lachat Flow Injection Analyzers Analysis 10-107-04-3-P. G-GWERD-SOP-1151-0 | 2023 | 30 ug_n_l MDL determination on 4/13/2023 |
100 ug_n_l | Acidified to pH of <2 with H2SO4 store cold at @ 4oC up to 28 days | ADA |