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Fast Mineral Oil Analysis using LTM
Matthew S. Klee, Ph.D.Agilent Technologies
Wilmington, Delaware, USA
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Mineral Oil Analysis(HOI: hydrocarbon oil index)• Mineral Oil analysis is in top 5 of current
environmental analyses (next to VOCs, PAHs, pesticides)
• Analysis is done by GC-FID (replaces old extraction – FTIR analysis)
• Technique is similar to “TPH” (Total Petroleum Hydrocarbon) analyses done in the U.S.A.... #1 LTM application in U.S.A.
Ref: ISO 9377-2, ISO 9377-4, EN 14039, DIN H53,…
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What is included in “Mineral Oil” analysis?
Any mixture of compounds that:1. are extracted by hydrocarbon solvent (from soil or
water)2. are not adsorbed by Florisil (used for cleanup)3. elute from an apolar column between decane
(C10) and tetracosane (C40)
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Typical HOI analytical procedure
1. ExtractWater: extract 1 L water with hexaneSoil: extract by ASE
2. Clean-upFlorisil (removes polar and semi-polar solutes such as sterols and lipids)
3. Concentrate to 1 mLN2 purge
4. Analyze extract by “discrimination free” injection, GC-FID, area sum between C10 and C40
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Analytical requirements
Non-discriminatory injection:– COC
• concerns about dirty samples– PTV– SSL (splitless)
• concerns about discrimination against high boilersLow bleed column
– Must elute C40 (thin film, high phase ratio)– Needs to separate solvent and 1st peak (decane)
• can be problematic with splitless injection (wide solvent peak), so low initial temperature is required
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Typical GC-FID conditions
Agilent S/Sl: 1 µL injection in SL mode
Others: COC or PTV (if S/Sl discriminates)
Column: 5-25 m x 0.25-0.53 mm ID 0.1-0.5 µm HP-1 or HP-535-40°C init to 300-350°C
Current disatisfier: Cycle time (~ 20-30 min without cool-dow)Limited ramp rate or lab GCsCool-down time
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Typical Hydrocarbon Index Analysis by GC(Application note 5988-0621EN)
15 m x 0.53 mm id x 1.5 µm HP-1He: 7.4 mL/min, constant flow35°C (1.5 min) → 60°C@ 5°C/min→ 350°C (5 min) @ 15°C/min
4.20
7
13.3
31
22.5
35
pA
10
20
30
40
50
60
70
80
90
min5 10 15 20 25
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The LTM Advantage
• Total cycle time for an analysis can be cut by a factor of 3 or more (compared to same columns in air oven and LTM)
• 1-4 independent column modules per GC– Dual column module configurations allow simultaneous
parallel analyses– Each module can have a different column type– Temperature programs for modules are independent
• Compatible with CFT devices for splitting, multidimensional separations, and/or for backflush
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LTM method 1 (hot splitless)
1 µL splitless injection, 320°CGC oven: 340°CFID: 340°CLTM: 10 m x 0.32 mm ID x 0.1 µm DB-5HT• 40°C (0.5 min) → 240°C @ 200°C/min → 340°C (0.5 min)
@ 100°C/min (3 min total)Carrier: He • 120 kPa (0.5 min) → 160 kPa @ 40 kPa/min → 180 kPa
(0.5 min) @ 20 kPa/min
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n-Alkane test mixture
C10 C20
C40
0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.20 2.40 2.60 2.800
400000
800000
1200000
1600000
2000000
2400000
2800000
Time
Response
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n-Alkane test mixture
Retention time repeatability (n=6)• C10: tR = 0.812 min, s = 0.001 min, RSD = 0.06%• C20: tR = 1.501 min, s < 0.001 min, RSD < 0.01%• C40: tR = 2.633 min, s = 0.003 min, RSD = 0.10%Peak Area repeatability• C10: mean area = 4265145, RSD = 0.86%• C20: mean area = 4578586, RSD = 1.05% • C40: mean area = 4117178, RSD = 0.85% Discrimination test• Relative peak area C40/C20 = 0.899 (RSD: 1.31%)
(criterion: > 0.80)
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Calibration diesel/motor oil 400 mg/L
0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.20 2.40 2.60 2.800
400000
800000
1200000
1600000
2000000
2400000
2800000
Time
Response
Motor oil
Diesel
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Mineral Oil calibration
Calibration from 40 – 1000 mg/LLinearity: r² > 0.999Repeatability at 400 mg/L: • RSD on peak area = 0.64%LOD: < 25 mg/L
R2 = 0.9991
0
200
400
600
800
1000
1200
0 200 400 600 800 1000 1200
mg/L
Are
a (x
10-6
)
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Calibration 100 mg/L
0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.20 2.40 2.60 2.80
50000
150000
250000
350000
450000
550000
Time
Response
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Extra benefit: sensitivity gain
0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.000
200000
400000
600000
800000
1000000
1200000
1400000
1600000
1800000
2000000
2200000
2400000
2600000
2800000
Time
Response_
Signal: SENS-TEST07.D\FID1A.chSignal: SENS-TEST05.D\FID1A.ch (*)
21 min run3 min run
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HOI analysis with LTM - conclusions
• Sample analysis cycle time is reduced to 5 min!• Analysis time: 3 min• Cool-down time to 40°C < 2 min
• Meets all method requirements with hot splitless and Agilent ALS
• Excellent repeatability, linearity• High sensitivity (“signal compression”)• Dual column module configuration with
simultaneous injection and parallel analyses will maximize throughput