The Analysis of Total Petroleum Hydrocarbons. Hazel Davidson Technical Marketing Manager Derwentside Environmental Testing Services

Transcription

1 The Analysis of Total Petroleum Hydrocarbons Hazel Davidson Technical Marketing Manager Derwentside Environmental Testing Services

2 Derwentside Environmental Testing Services DETS is an independent testing laboratory with over 100 staff. We offer analytical testing on a variety of matrices including : Soils, water, gases, waste, asbestos and fuels We offer: A personal service and designated point of contact Accreditation to ISO for most determinands and sampling Accreditation to MCERTs for soils and waters Flexible testing protocols Technical support and training for clients DETS dependable data, dependable delivery

3 Petroleum Hydrocarbons Composition of TPH Common refinery products Behaviour of TPH in soil Sampling precautions VPH/EPH methods Example chromatograms TPH forensics

4 Characteristics of Petroleum Hydrocarbons Thousands of compounds derived from crude oil Varying in appearance from pale yellow condensates to black tars, with SG of <1 ( ) Toxicity, mobility and environmental persistance of compounds is highly variable Crude oil: predominantly C + H, plus N, S + O

5 Properties of Petroleum Products (1) Generally with increasing molecular size (usually recorded as carbon number ) there is: increase in boiling and melting points lower vapour pressure increase in density decrease in water solubility stronger adhesion to soils and therefore less mobility in subsurface conditions

6 Properties of Petroleum Products (2) Oil Fraction C Range Boiling Pt. Sol. in H 2 O Density % Arom. Gasoline C 4 -C O C Moderate Kerosene C 10 -C O C Moderate/ 0.81 <15 & Jet Fuel Low Diesel Fuel & C 12 -C O C Low Light Fuel Oils Heavy Fuel Oils C 19 -C O C V. low Motor Oils & C 20 -C O C V. low 0.90 < 15 Lube Oils Bitumen > C 35 > 500 o C Insol

7 Behaviour in Soil B. Pt Density (g/cm 3 ) Solubility (mg/l) o C in water Benzene Toluene Pentane MTBE ,000 Octane < 1 Eicosane nc solid < 1 Triacontane nc solid < 1

8 Behaviour in Soil Hydrocarbons will break down or be removed by: Sorption Degradation microbial or chemical Dispersion Volatilisation Advective flow carried along by groundwater Diffusive flow movement along a concentration gradient The environment (soil matrix, moisture content, ph, TOM, particle size, etc.) will significantly affect the rate of the above

9 Behaviour in Soil

10 Sampling for VPH Soils Suitable for GRO, chlorinated solvents, TML/TEL It is good practice to take duplicates for each of the above analyses Also supply a tub of soil for moisture content No headspace Waters Volatile organic compounds as above, including VFAs and dissolved gases It is good practice to take duplicates, as above Minimise aeration and agitation when sampling No headspace, check by inverting vial 60 g glass jar 40 ml vial with PTFE septum

11 Sampling for EPH Extractable organics e.g. EPH, oils, grease, PAHs Waters - 1 x 500 ml or 1 litre coloured glass bottle, either no preservative or acid (H 2 SO 4 or HCl) Soils 1 x 250 g glass jar ALL ORGANIC SAMPLES SHOULD BE STORED IN GLASS VESSELS AT 5 o C

12 Analysis - Hydrocarbon Groups PIANO - parafins - isoalkanes - aromatics - naphthenes - olefines

13 Methods of Analysis Infra red (IR) limited use Gas Chromatography Flame Ionisation Detector (GC- FID) GCMS MTBE, PAHs and biomarkers

14 TPH - Gas Chromatography VPH by headspace EPH by extract analysis Modified US EPA methods Detection limits: Soil : 5 mg/kg Water : 0.01 mg/l

15 Volatile Petroleum Hydrocarbons (VPH) Also known as petrol range organics (PRO) or gasoline range organics (GRO) Carbon range C 5 - C 10, typically up to 400 compounds Includes n- and iso-alkanes, e.g. pentane, dimethylpentane, octane; and naphthenes (cycloparaffins) Includes mono-aromatics, e.g. benzene, toluene, ethyl benzene, and xylenes Can include methyl tertiary butyl ether (MTBE), but GCMS gives greater certainty of identification

16 VPH - GCFID Headspace method Column DB 1 MS length 10 m, diameter 0.1mm Rapid turnaround Minimal sample handling Inexpensive Detection to 10 ppb Total volatiles (C 5 - C 12 ) + BTEX + banding

17 Benzene ring BTEX by GC-FID

18 Unleaded Petrol

19 Extractable Petroleum Hydrocarbons (EPH) Requires solvent extraction Carbon range C 10 - C 40 with speciation Column DB HP 1MS length 15 m, diameter 0.25mm Includes aliphatics, aromatics and hetero-compounds Includes internal standards Identification of diesel, kerosene, lube oil, plus degree of weathering Detection limit : Soils 5 mg/kg Waters 0.01 mg/l

20 SCA TPH Working Group Over 10 years in progress Round robin trials Samples provided by Shell As received soil is preferable Comparison of solvents Analysis by GCFID, not IR Standard in draft format (80% done)

21 Solvent Extraction HEXANE/ACETONE DCM/METHANOL DCM/PENTANE CYCLOHEXANE FREON 112 Image by ALcontrol Laboratories

22 Solvent comparison Mineral O il Aromati cs NSO Hexane / Acetone DCM / Methanol DCM / Pentane Cyclohexane Freon 112 Solvent Ratio Polarity Total Extract Mineral Oil Aromatics NSO Hexane / Acetone 1/ DCM / Methanol 10/ DCM / Pentane 3/ Cyclohexane Freon

23 Liquid/liquid extraction Stir bar liquid/liquid Solid Phase Extraction (SPE) DNAPLs and LNAPLs Issues to consider: Extraction of Waters Solubility in water generally low Dissolved, colloidal, or product layer? To filter or not to filter?

24 Identification Known Sample Retention Time Quantification Calibration Standards Banding Retention Time Quality QC Blanks Duplicates Calibration Checks Proficiency Testing Gas Chromatography

25 Chromatograms Diesel & Lube oil Fuel Oil Diesel Bio Fuel Kerosene Sample with possible PAHs

26 Polar hydrocarbons Possible Interferences in TPH analysis Oxygenated fuels Non-Petroleum compounds Biogenic material Plant oils and waxes Coal material Fats

27 Cleaned up EPH and Mineral Oil ISO Definition of mineral oil (drinking water): Compounds in the range C 10 - C 40 which are not retained by a silica column, using a non-polar solvent. Chemically, this consists of aliphatics (nalkanes, iso-alkanes and cyclo-alkanes) only. A cleaned up EPH requires a moderately polar solvent for elution only the polar NSO compounds will be retained on the column

28 Speciation Breakdown of TPH into narrow carbon band ranges (CWG) Includes VPH and EPH Includes aliphatics & aromatics Used in risk assessment packages such as RBCA

29 NON-POLAR SOLVENT POLAR SOLVENT VERY POLAR SOLVENT have more have more A A A affinity for solid phase over solvent affinity for phase A over solvent have more affinity for solvent than both phase A and B Separation B B B has no affinity for either solid phase and will elute with solvent has more affinity for solvent and will elute with solvent Image by ALcontrol Laboratories MINERAL OIL (NON-POLAR) P.A.H S (POLAR) NSO S (VERY POLAR)

30 Aliphatic Fraction Aromatic Fraction Combined Aliphatic and Aromatic Standard

31 Advantages Rapid analysis VPH & EPH in one run Lower costs Disadvantages TPH Screen by Rapid GC (C 6 C 40 ) Incomplete resolution of all peaks Higher detection limits Suitable for soils only

32 TPH Forensics analysis Four main questions: What is it? What was the source? When did it happen? Who was responsible?

33 Ageing of petroleum products Ageing = weathering + biodegradation Most Affected C 10 -C 20 n-alkanes Alkylated aromatics 2 and 3 ring aromatics Most affected C 35 -C 10 alkanes Least Affected C 20+ alkanes Cyclo naphthenes C 4 -C 6 ring aromatics Least affected Iso-prenoids Pristane Phytane C 6 -C 2 ring aromatics

34 Ageing of petroleum products Diesel fresh and degraded Most commonly used ratios: nc 17 /Pristane nc 18 /Phytane Pristane/Phytane Images by ALcontrol Laboratories

35 GCFID Methods Advantages Covers the full TPH range Good sensitivity (10 ug/l for components) Carbon chain speciation Provides a fingerprint Identify individual analytes i.e. BTEX Identifies different products Identifies degree of weathering Good recovery efficiency Disadvantages Slower, and slightly more expensive

36 TPH Method Summary VPH by headspace GC-FID for gasoline range organics (C 5 C 10 ) EPH by GC-FID for diesel and lube oil range organics (C 10 C 40 ) Cleaned up EPH to remove polars Speciated TPHCWG for aliphatic and aromatic banding (C 5 C 44 ) TPH screen for VPH and EPH combined (C 6 C 40 )

37 The Analysis of Total Petroleum Hydrocarbons Thank you