Why we need new Total Nitrogen parameter and methods for CWA reporting. William Lipps Chief Science Officer, Eurofins Eaton Analytical August 2018

Transcription

1 Why we need new Total Nitrogen parameter and methods for CWA reporting William Lipps Chief Science Officer, Eurofins Eaton Analytical August 2018

2 Full Service Laboratories Eurofins Lancaster Laboratories Env. Lancaster, PA Eurofins Calscience Garden Grove, CA Eurofins Spectrum Analytical Agawam, MA North Kingstown, RI Centers of Excellence Eurofins Air Toxics Folsom, CA Eurofins Eaton Analytical Monrovia, CA South Bend, IN Eurofins Frontier Global Sciences Bothell, WA Eurofins QC Southampton, PA

3 The current EPA definition for Total Nitrogen is TKN plus nitrate/nitrite Measure TKN Measure NO3/NO2-N TN

4 TKN = modification of 1883 digestion/distillation

5 Which TKN procedure (Part 136 methods)? Manual Digestion + Distillation SM 4500-N org B or C 4500-NH 3 C, D, G, F Digestion + Direct Analysis EPA (on-line distillation/digestion) By Difference S-TKN ASTM D3590 A EPA ASTM D1426 EPA (block) SM 4500-N org D ASTM D3590 B USGS I-4515

6 Which TKN digestion procedure (Part 136 methods)? Sample Volume Water Removal Digestion 25 ml 160 C for 1 hour 380 C for 1.5 hour 10 ml 220 C for 30 minutes Up to 500 ml Boil down to ml 370 C for 15 minutes Heat to fumes at C then 30 minutes 5 50 ml Boil 30 minutes Heat to fumes at C then 30 minutes 25 ml 220 C for 1 hour 380 C for 1 hour

7 TKN suffers from low recovery of some organics 120 TKN Recovery in Various N compounds

8 EPA Calculated TN can be lower than combustion TN TN (Calculated) TN (Combustion)

9 EPA Calculated TN can be higher than combustion TN TN (Calculation - mg/l) TN (Combustion Analysis - mg/l)

10 Sometimes EPA Calculated TN can be lower than measured NH 3 -N TKN NOx-N TN (EPAcalc) NH 3 -N TN (D8083) TKN < NH 3 -N?

11 A low TKN results in low bias for Organic Nitrogen calculations (negative?) mg/l N Organic Nitrogen (EPA) - Organic Nitrogen (ASTM) Organic Nitrogen (EPA) Organic Nitrogen (ATP)

12 New methods are needed that measure Total Nitrogen as a single result, and not TKN Organic Nitrogen NH3-N NOx-N TN

13 ASTM D8003 = TN (and TP) by 120 C alkaline persulfate digestion and ion chromatography Digest on your COD Block to Nitrate Only one hour digestion Safer reagents less hazardous Nitrate (TN and NO 3 -N) is measured by Ion Chromatography Calculate TKN by difference (TN-NO 3 -N) % Recovery Nicotinic Acid Urea Glycine Ammonium

14 The method is capable of measuring analytes in the high sulfate matrix

15 Chromatogram and recovery with chloride present % Recovery mg/l Chloride

16 D8083 and new SM TN methods Schematic of a TOC + TN Analyzer Decomposition : 720 with Pt catalyst TN Analysis Formation of NO 2*, -> NO 2, Photon Emission Obtain a TN Result (~ every 5 minutes)

17 120 TKN and Catalytic Oxidation Recovery in Various N Compounds TKN CC

18 HTCO (TNb) methods obtain near equal results with persulfate TN on unknown samples TN TNb Sample 1 Sample 2 Sample 3 Sample 4 Sample 5

19 Comparison of EPA TN and new TN (SM) TKN+NOx vs TN (mg/l) y = x R² =

20 % Recovery of Various Nitrogen Compounds

21 120% 100% MS Percentage Recoveries (%) and Conductivity using NO3 and NH3 STD's for TN analysis (SM study) 103% 102% 111% 106% 104% 102% 110% 103% 106% 103% 108% 106% 106% 107% 104% 103% 99% 96% % 82% 80% % % % % AE93054 AE93053 AE93023 AE93024 AE93051 AE93050 AE90609 AE89665 AE90585 AE90584 % Recovery NO3 % Recovery NH3 Conductivity 0

22 Sample Avg certified value % recovery sx %RSD % % % % % % % % % % % % % % % % % % % % LCS % %

23 Some of the problems with the TKN method for TN Time consuming hour digestion Separate distillation and/or analysis Uses hazardous reagents Boiling sulfuric acid Metal catalyst (Hg, Cu, Se?) Must run NO 3 + NO 2 separately Not applicable to all N compounds

24 Issues with TKN procedure Digestion time varies per lab Digestion temperatures vary per lab Digestion vessels Macro in flask Micro in block To distill or not to distill? Where is the study that compares all these versions of the same method?

25 Why should we have a new TN parameter and methods? Better data (one result) Faster results Safer for lab personnel No addition or subtraction (of method results) TKN result may not be reliable (bias high or low?)

26 Any Questions? William Lipps Eurofins Eaton Analytical, LLC