1. Accuracy and Uncertainties of Mercury Fractionation in Hydrocarbons using CV-AFS Dr Bin Chen Dr Warren Corns P S Analytical. Orpington, United Kingdom

2. Mercury in Crude Oil, Gas Condensates and Refined Products?
Important feedstock for many industrial applications.
Detrimental effect on refining operations such as poisoning of catalysts & corrosion of aluminium alloys and cryogenic cold boxes due to Hg induced embrittlement
Product quality defines price! Less than 1ppbw required for high spec Naphtha. Measurement and sampling is therefore critical.
Optimisation, design and monitoring efficiency of Hg removal strategies.
Hg Speciation/fractionation important to understand the fate and transport of Hg across the process

3. Hg Species?
Mercury Classification
Forms of Mercury
Elemental Hg
Hgo(gas), Hgo (dissolved) , Hgo (solids)
Particulate Hg
HgS, Hg (solid associated), Hg (insoluble)
Inorganic Hg
Hg2+, Hg22+
Organometallic Hg
R-Hg+ ,R-Hg-R, Hg thiolates - Unknowns??
Complexity of sample matrix and number of potential species of Hg inhibits the use of a single approach for determining all Hg species
Fractionation Methods are therefore used

4. The Fractionation Method
Hg Total
CV-AFS
Particulate Hg
HgS
Aqua Regia
Other Particulate Hg
Nitric Acid
Volatile Hg
Purge & Trap
Dissolved Hg
KCl extraction
Ionic Hg
Aqueous Phase
Unknown Hg
Organic Phase
Organic Hg
GC-AFS

5. Total, Dissolved & Particulate Hg
Sample
(1-3 g)
Aqua Regia reflux (10 ml, 3 hrs)
CV-AFS
T-Hg
Filtered Sample (0.45µm, 1-3 g)
Aqua Regia reflux (10 ml, 3 hrs)
CV-AFS
Total Dissolved Hg
T-Hg – D-Hg = P-Hg

6. Volatile Hg Hgo and R2Hg species Sample (5-50 g) Bubbler
Argon 250 ml/min for 30 min
Gold trap AFS
Bubbler is washed with diluted HCl/NH2OHHCl between samples

7. KCl Extraction 40% KCl, 0.5% HCl, 0.1 g/L NH2OHHCl
Filtered Sample (0.45µm, 10 g)
Shake with KCl (10 ml, 0.5 hrs)
Bromination of the aqueous phase
KCl extractable ionic Hg
Organic phase, AR or direct
Non extractable Hg (organic?)

8. Organometallic Hg R-Hg-R, R-Hg+ , Hgo
Filtered Sample
(0.45 µm)
Direct Injection
GC-AFS
Pyrolyser 8000C
Detection as Hg0
Samples analysed with and without gold trap inline of AFS detector to confirm that signal is Hg

9. MDL and LODs Hg, ng/g MDL LOD Volatile Hg 0.001 0.0001 Total Hg 0.05
Dissolved Hg
Ionic Hg
Organic Hg by GCAFS 1

10. Hg Fractionation in Condensates Example data
Sample A
Sample B
Sample C
Sample D
Sample E
Sample F
Sample G
Sample H
Sample I
Total Hg
1.00
1.24
780.80
8.17
420.74
73.73
168.30
925.30
Dissolved Hg
0.73
0.66
552.70
0.00
19.82
0.44
0.50
14.00
2.30
Ionic Hg, KCl
0.57
0.36
13.60
3.95
18.59
0.18
0.23
0.25
Unknown Hg, non - KCl NA
NA (0.23)
539.10
Organic Hg
Particulate Hg
0.27
0.58
226.20
4.06
400.92
73.29
167.80
923.00
Volatile Hg
0.10
0.07
1.90
0.01
0.06
0.84
0.05
0.24
0.35
Fraction Sum
0.94
(94%)
1.01
(81%)
(100%)
8.02
(98%)
419.57
74.31
(101%)
168.03
(99%)
923.60
NA = Not Analysed - Only analysed if summation of fractions is poor
ND = Not detected, MDL= 1ng/g
All results in ng/g (ppbw)
Fraction Sum = summation of columns in yellow
Results have higher confidence if total Hg and Fraction Sum are in good agreement

11. Hg Fractionation in Crude Oil Example DataB1 B2 B3 B4 B5 B6 B7 B8
Total Hg
538.24
98.79
60.80
37.04
62.56
46.79
42.38
84.83
96.00
Dissolved Hg
43.44
7.72
9.12
4.25
11.82
7.79
6.69
13.13
4.99
Ionic Hg, KCl
19.06
4.73
7.59
3.43
6.08
4.46
3.82
6.60
0.74
Unknown Hg non-KCl NA
Organic Hg ND
Particulate Hg
494.80
91.07
51.68
32.79
50.74
39.00
35.69
71.70
91.01
Volatile Hg
24.25
0.20
0.10
0.08
0.12
0.33
0.25
0.37
Fraction Sum
538.11
(100%)
(97%)
59.37
(98%)
36.30
57.02
(91%)
39.12
(84%)
39.84
(94%)
78.55
(93%)
92.12
(96%)
NA = Not Analysed - Only analysed if summation of fractions is poor
ND = Not detected. MDL = 1ng/g
All results in ng/g (ppbw)
Fraction Sum = summation of columns in yellow
Results have higher confidence if total Hg and Fraction Sum are in good agreement
Sample B – Same plant sampled at different periods

12. Hg Fractionation in Naphtha Example Data
Sample A
Sample B
Sample C
Sample D
Sample E
Sample F
Total Hg
6.05
14.45
4.40
161.3
18.91
14.93
Dissolved Hg
4.33
13.15
2.30
161.2
1.36
0.49
Ionic Hg
1.61
1.86
1.90
160.6
2.35
0.09
Unknown Hg, non-KCl
NA (2.70)
NA (10.94) NA
Organic Hg ND
Particulate Hg
1.72
1.30
2.20
17.54
14.4
Volatile Hg
0.03
0.05
0.01
6.3
Fraction Sum
3.36
(56%)
3.21
(23%)
4.11
(93%)
166.9
(103%)
19.9
(105%)
14.52
(97%)
NA = Not Analysed – ( Calculated shortfall in summation)
ND = Not Detected, MDL = 1ng/g
All results in ng/g (ppbw)
Fraction Sum = summation of columns in yellow
Results have higher confidence if total Hg and Fraction Sum are in good agreement.

13. Sampling Uncertainties for Liquid Hydrocarbons
Depressurization and stabilization might release volatile Hg compounds such as elemental mercury vapour.
Potential Loss of Mercury on sampling components. Materials and speed loop should be carefully considered.
Losses of Mercury from association with particulates and aqueous phase. Sample filtration devices and sample point selection should be carefully considered.
Losses and species conversion of Mercury during storage and shipping of samples. Sample containers and storage conditions are critical.
Sample homogenization is required prior to measurement.
Shipping regulations often require metal containers!

14. Measurement Uncertainty Questions?
How does Homogenization and Filtration of sample affect accuracy. Solids and free water issues.
Is the particulate Hg measurement influenced by Hg scavenging solids collected on the filter?
What Hg species do we extract with each fractionation step?
More research is needed to identify the ionic and organic species present. KCl extracted aqueous phase requires a full digestion inorganic divalent Hg is unlikely species.
In most cases summation data compared to total Hg is very good. On some samples however summations can be lower? Our results indicate that missing portion is present in organic phase after KCl extraction. Analysis of this fraction will know be included for all samples.
Do mercury removal sorbents trap all Hg species?
Lack of CRM’s for this application and Inter-lab proficiency schemes

15. Questions?
Thank you for your attention