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Agilent UltiMetal Plus Stainless SteelDeactivation for Tubing, Connectors, andFittings
Technical Overview
Introduction
Modern GC and GC/MS instruments are important analytical tools for accurate andreproducible measurement of many compounds at low ppb level in a wide variety ofmatrixes [1]. For accurate analyte measurement, compounds need to survive thejourney through the flow path. The flow path can contain different metalcomponents, which need to be deactivated when compounds are more (re)activethan alkanes, for example pesticides, alcohols, or very polar compounds. In thistechnical overview, Agilent UltiMetal Plus deactivated stainless steel tubing andstainless steel connectors and fittings were tested and compared to bare stainlesssteel and products that were deactivated by different methods. Because analystshave to investigate reactive components at ever lower detection limits, UltiMetaldeactivation chemistry, developed in the 1980s, is now improved and known asUltiMetal Plus. UltiMetal Plus technology is applied specifically to steel andstainless steel surfaces, and can be used safely when stainless steel products aredefined or prescribed in a method. UltiMetal Plus technology provides a significantimprovement. Agilent and non-Agilent products are compared in this study.
Tubing and fittings are widely used in various industries and GC applications. Theinertness of tubing and connectors is important, especially when used in the GCflow path.
Breakdown or adsorption of analytes is affected by different factors, including:
• Surface inertness
• Surface area
• Contact time
• Concentration or amount
• Type of analyte
• Temperature
2
Analytes can show reversible interaction, causing peaktailing. They can also show irreversible interactions(adsorption or reaction to the surface or catalytic breakdown),resulting in lower recoveries. A combination of both effects ispossible.
Tubing can be divided in stainless steel transfer lines (often1/16 inch), capillary tubing (used in GCs as guard columns),and tubing for connecting instruments or installations (1/16,1/8, and 1/4 inch). Stainless steel capillary tubing is analternative for commonly used fused silica. Figure 1 showsthe use of stainless steel transfer lines.
Figure 1. Examples of 1/16 inch stainless steel transfer lines in the flowpath. For the analysis of (re)active components these should bedeactivated.
A. Plumbing to a valve and sample loop
B. Gas sample inlet
Figure 2. Examples of some Agilent UltiMetal Plus-treated parts. Theoutside of the GC column is Agilent UltiMetal coated for increasedinertness.
Tubing is not the only component of the flow path. Parts ofconnectors (Figures 2 and 3 show examples of an inert GCcoupling) and fittings are also involved. Deactivation of theseconnectors and fittings is very important. The inertness ofUltiMetal Plus Flexible Metal ferrules has been described inan application note [2]. Although the contact area for ferrulesin the flow path is very small, there is an improved inertnessfor certain compounds. Agilent, therefore, decided to add anUltiMetal coating to the outside of the stainless steel tubing,as small areas of the exterior are exposed to analyteinteraction. Experiments demonstrated that the UltiMetalexternal coating improved the inertness of the flow path.
3
Figure 3. Examples of critical connections and active sites in a GC flow path. A) installation in a GC inlet, B) Agilent CPM Union, inert (p/n G3182-60580)connecting a fused silica column to stainless steel Agilent UltiMetal Plus tubing. There is a small area of the outside of the column that is in the flowpath, (correct length after ferrule is 0.1 to 0.5 mm). C) cutting Agilent UltiMetal Plus deactivated tubing creates a relatively small area of inactive barestainless steel (red). For short pieces of Agilent UltiMetal Plus tubing with a fixed length, the tubing end can be deactivated as well.
UltiMate Union, inert
Metal on the outside of the column in the flow path
Flexible Metal ferrule
A
Metal on the outsideof the column in theflow path
Inlet C
Because tubing has to be cut during installation, a small areaof bare stainless steel will be exposed in the connection. Thiscannot be easily avoided. Exposure of analytes to metal(oxides) on the cutting edge does not occur with fused silicatubing as the synthetic quartz is metal-free.
Results and Discussion
Test methods A tandem-column setup was used to verify the inertness ofthe connector or tubing (Figure 4). The compounds were firstseparated on a reference GC column, which was followed bya connector and a piece of tubing. The tubing was connectedto a flame ionization detector (FID). As system inertness isinfluenced by the total flow path, a system test wasperformed to establish the base level inertness profile. Tomeasure small differences in system activity, a high degree ofinitial inertness was required. The amount of analyteintroduced in the column setup was calculated from theinjection volume, split ratio, and concentration of the testmixture. Peak asymmetry and relative or absolute recoveriesof several test components were the key parameters used tocompare the inertness of connector and tubing parts.
B
Figure 4. Principle of a tandem- or post-column test.
Inlet (split mode) Detector (FID)
Connector
Reference column Tubing
relative recovery % =peak area inert alkane
peak area probe
absolute recovery % =relative recovery ref set
relative recovery
StandardsTwo test mixtures were used in the experiments [4,5], asshown in Tables 1 and 2.
Improved performanceThe inner surface area for columns and tubing is relativelylarge (Table 3). As the contact time between analyte andsurface is relatively long, the inertness of tubing for guardcolumn and transfer lines is of critical importance. A highperformance deactivation chemistry for the tubing is requiredto achieve optimal chromatographic analyses. This high levelof system inertness will translate into more symmetrical peakshapes with less tailing, improvement of critical separations,greater linearity of responses, and lowering of detectionlimits.
4
Table 1. Test Mix 60 (0.1 mg/mL Cyclohexane or Dichloromethane)
Compound
1 1-Octanol
2 n-Undecane
3 2,6-Dimethylphenol
4 2,6-Dimethylaniline
5 n-Dodecane
6 Naphthalene
7 1-Decanol
8 n-Tridecane (used as 100% reference)
9 Decanoic acid ME
Table 3. Comparison of Surface Area of Different Components of a GC flowPath (10 m for Tubing)
Component Area (cm2)
Tubing 0.25 mm (0.5 mm od) 79
Tubing 0.32 mm (0.5 mm od) 100
Tubing 0.53 mm (0.8 mm od) 166
Tubing 0.75 mm (1/16 inch od) 236
Tubing 1 mm (1/16 inch od) 314
Tubing 2.1 mm (1/8 inch od) 659
Tubing 4.3 mm (1/4 inch od) 1,350
Agilent Ultimate Union (p/n G3182-60580) (1.8 mm) 0.05
GC column (30 m × 0.25 mm) 237
Open Agilent liner (4 mm id) 99
Table 2. Very Inert Mix in Dichloromethane (Split 1:75)
Peak no. Compound ng*
1 Methane
2 Propionic acid 1
3 iso-Butyric acid 1
4 n-Butyric acid 1
5 Octene 0.5
6 Octane 0.5
7 1-Nitrobutane 1
8 4-Picoline 2
9 Trimethyl phosphate 5
10 1,2-Pentanediol 2
11 Propylbenzene 1
12 1-Heptanol 1
13 3-Octanone 1
14 Decane (used as 100% reference) 1
* The calculated on-column amount after a split injection depended on thesplit ratio used.
The surface area of the liner is relatively high compared tothat of tubing. How critical this part is depends on theinjection technique. For a split injection, where the contacttime with the liner surface is less than 1 second (for example,for an 800 µL liner with a split flow of 100 mL/min, the totalliner volume is flushed twice every second), this is far lesscritical compared to a splitless injection of 1 minute, with onlycolumn flow through the liner.
5
Although the Agilent Ultimate Union has a relatively low innersurface area, this critical stainless steel part also needsdeactivation to shield active sites as much as possible.Besides scratches on the inner surface of the connector,broken fused silica is prone to introduce high activity in a
connection. By following the connector installationinstructions, an inert and leak-tight connection can be madeusing UltiMetal Plus Flexible Metal ferrules [3]. The effect ofa damaged and non-inert connector is shown in Figure 5.
7.27.06.86.66.46.26.05.85.65.45.25.04.84.64.44.24.03.83.63.43.23.02.82.62.42.22.01.81.61.41.21.00.80.60.40.20
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12
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61.73
2.36
2.48
2.73
2.923.69
3.954.12
5.42
6.14
6.86
1.261.32
1.732.36
2.48
2.73
2.923.69
3.95
4.12
5.416.14
6.86
RT (min)
pAX offset: 0Y offset: 22
1-DecanolAs 1.2RR 77%
1-DecanolAs 2.6RR 50%
1
2
34
5
6
78
9
A
B
Figure 5. When an Agilent Ultimate Union is damaged or broken, fused silica becomes part of the flow path (B). The peak shape of compounds in even the lesscritical Test Mix 60 is affected. As well as the lower relative 1-decanol recovery (area 1-decanol/area n-tridecane), tailing or asymmetry alsoincreased. After replacement of the damaged connector with properly deactivated Agilent UltiMetal Plus, the inertness of the system was restoredimmediately (A).
Before a tandem test can be used, a system test is performedto test the reference column alone, and tested again afteradding a connector and piece of tubing or column. When thesystem test is done to certain specifications (peak shape andrecovery), it can be used for testing.
Because analysts often use a piece of tubing as a retentiongap or guard column before the analytical column, this canprovide different results compared to testing post-column.Figure 6 compares a piece of 2 m × 0.53 mm UltiMetal Plusguard installed after the reference column (tandem) or beforethe column (reversed-tandem).
6
Experiments showed that the post-column setup under theseconditions appeared to be more challenging for testinginertness. Interactions for the different probes aresummarized in Table 4. The fact that the test mixture was notseparated when using a reversed-tandem setup, and elutedas a band of solvent and probes, is a possible explanation for
the differences in peak shape. Although the linear velocity atthe inlet was lower, this did not result in a more critical test.In the tandem setup the probes eluted as small bandsthrough the column and only direct effects of the column withan individual probe were tested.
pAX offset: 0Y offset: 20
4-picolineA
s 2.5
Abs. recovery 100%
4-picolineA
s 1.7
Abs. recovery 98%
1110.5109.598.587.576.565.554.543.532.521.510.50
4240383634323028262422201816141210
8642
1.79
1.92
2.21
2.33
2.79 3.09
3.333.45
4.21
4.63
6.62 7.197.91
8.84 9.78 10.75
1.72
2.01
2.14 2.60 2.90
3.14
3.25
4.02
4.43
6.436.99
7.71
8.64 9.58 10.54
RT (min)
Tandem setup
Reversed-tandem setup
2 3 4
5
6
7
8
910
11
12 13 14
1
1. MethanePropionic acidiso-Butyric acidn-Butyric acidOcteneOctane1-Nitrobutane4-PicolineTrimethyl phosphate
1,2-PentanediolPropylbenzene1-Heptanol3-OctanoneDecane
No. Compound ng
2.3.4.5.6.7.8.9.
10.11.12.13.14.
1110.50.5125
21111
Figure 6. Comparison pre-(reversed) and post (tandem) testing of 2 m x 0.53 mm Agilent UltiMetal Plus guard column (p/n CP6576). An Agilent J&W VF-5ms,30 m × 0.25 mm, 0.25 µm (p/n CP8944) GC reference column was used and the tubing was connected using an Agilent Ultimate Union (p/n G3182-60580) with Agilent UltiMetal Plus Flexible Metal ferrules. The very critical test mix (Very Inert Mix) was employed to test the inertness ofthe deactivated stainless steel tubing in the ng range [4]. Results were compared to the reference system test to calculate absolute recovery. Probeswere injected using a split injection (1 µL, split 1:75), the oven was set at 60 °C and hydrogen was used as carrier gas (constant flow at 1.35 mL/min).
Table 4. Surface Interactions for Test Probes Using a Very Inert Mix
Probe Category Interaction
Propionic acid (coelution with cyclohexane) Acid Basicity
i-C4 acid Acid Basicity
n-C4 acid Acid Basicity
C8= Alkene Polarity
n-C8 Alkane (n-C8) Inert (hydrocarbon marker)
Nitrobutane Alkane with NO2 group Dipole
4-Picoline (4-methyl pyridine) Base Acidity/silanol
TMP (trimethylphosphate) Base Acidity/silanol (retention index shift depends on amount silanol)
1,2-Pentanediol Di-alcohol Silanol/metal impurity (a diol for the assessment of column damage (impact ofoxygen/water – two very common contaminants), and silanol groups.)
n-Propylbenzene Aromatic (inert) Inert
1-Heptanol Alcohol Silanol (interaction with residual Si-H)
3-Octanone Ketone Polarity
n-Decane Alkane (n-C10) Inert (hydrocarbon marker)
7
Testing different kinds of tubingSome examples of different types of Agilent UltiMetal Plustubing are summarized in Table 5.
Testing guard columnsGuard columns installed in front of the analytical columnprotect it from matrix contamination introduced by injectingdirty samples. As guard columns are part of the sample flowpath, their inertness is important. The temperature stability ofthe UltiMetal Plus guard columns was tested up to 450 °C(Table 6). The results clearly illustrate the temperaturerobustness of the UltiMetal Plus deactivation layer, withminimum tailing and stable retention after many hours of hightemperature exposure.
Table 5. Different types of Agilent UltiMetal Plus tubing and their uses.
Product type Use
Guard column, capillary Guard column or retention gap
Capillary tubing Direct replacement for RestekSilcoNert 2000 (Sulfinert) tubing
Transfer lines, 1/16 inch od Used for transfer liner, plumbing GCand valves
Bulk tubing, 1/16, 1/8, and 1/4 inch Used for gas sampling and generalpurpose
Table 6. Testing an Agilent UltiMetal Plus guard column (25 m × 0.53 mm) using Test Mix 60(120 °C, constant hydrogen flow at 3 mL/min) after heating at 450 °C for several hours.
Time at 450 °C (h)
Retention factor (%)
Asymmetry, 1-decanol
Retention index, 1-decanol
Retention index, decanoic acid ME Bleed (pA)
0 100 1.4 1,270.1 1,306.1 16.5
4 99 1.4 1,270.1 1,306.0 15.4
8 98 1.5 1,270.0 1,306.0 15.2
12 96 1.4 1,270.0 1,306.1 14.7
20 94 1.3 1,270.0 1,306.0 14.9
8
0
0 0.2 0.4 0.6
0.69 1.143 4
5
6
7
8
910
11
12 13 14
1.29
1.37
1.43
1.77
1.96
2.863.12
3.44
3.86 4.29 4.73
4.40 4.853.96
3.52
3.202.941.80
1.44
1.38
1.301.150.68
0.7273 0.92
2.00
0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6RT (min)
2.8 3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4 4.6 4.8 5.0
20
40
60
80
100
120
140
160
180
200
220
240
260X offset: 0Y offset: 140
pA
Agilent UltiMetal Plus guard
4-PicolineAvg. corr. A
s 2.3
Avg. abs. recovery 103%
Biodiesel guard, non-Agilent
4-PicolineAvg. corr. A
s 6.6
Avg. abs. recovery 103%
Figure 7. Tandem testing of a 2 m × 0.53 mm id Agilent UltiMetal Plus guard and a biodiesel guard from a non-Agilent supplier with the Very Inert Mix(hydrogen constant flow at 4.7 mL/min, oven 60 °C. See Table 2 for peak identification and calculated on-column amounts). An Agilent J&W VF-5ms,30 m × 0.25 mm, 0.25 µm (p/n CP8944) GC reference column was used with an inert Agilent CPM union (p/n G3182-60580) and Agilent UltiMetalPlus Flexible Metal ferrules.
Megabore guard columns, 0.53 mmA 2 m × 0.53 mm guard column was tandem tested with theVery Inert Mix and compared to a non-Agilent guard column(Figure 7). Nearly symmetrical peaks and high recovery wereobtained for the UltiMetal Plus guard while the non-Agilentguard column generated more peak tailing.
9
Narrow bore guards, 0.25 mmSimilar results were obtained for a narrow bore, 5 m ×0.25 mm UltiMetal Plus Guard column in comparison to anon-Agilent guard column (Figure 8). Low tailing profiles andhigh recovery for the most challenging test probes wereobtained for the Agilent tubing.
Agilent UltiMetal Plus Guard
non-Agilent deactivated tubing
02468
1012141618202224262830323436384042444648
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0 12.5 13.0 13.5
1.922.05
2.53
2.84
3.08
3.20
3.99
4.41
1.62
2.06 2.53 2.84
3.07
3.18
3.98
4.42
6.46 7.79
8.74 9.72 10.717.04
6.507.76
8.74 9.69 10.657.07
RT (min)
X offset: 0Y offset: 25
pA
Figure 8. Tandem testing of 5 m × 0.25 mm Agilent UltiMetal Plus guard column versus a non-Agilent product using a Very Inert mix (hydrogen constant flow at1.35 mL/min, oven 60 °C). An Agilent J&W VF-5ms, 30 m × 0.25 mm, 0.25 µm (p/n CP8944) GC reference column was used with an inert Agilent CPMunion (p/n G3182-60580) and Agilent UltiMetal Plus Flexible Metal ferrules.
10
Figure 9. Uniform performance over total length of 30 m × 0.25mm id Agilent UltiMetal Plus-treated tubing. The column (number 9300205) was divided into sixpieces and tandem tested with Test Mix 60. See Table 2 for peak ID.
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60
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90
95
100
105
110
115
120
0 0.5 1.0 1.5
1.53
2.893.16
3.374.23
4.524.70
6.14 6.947.74
1.63
3.04
3.32
3.54 4.43 4.73 4.92
6.41
1. 1-Octanol2. n-Undecane3. 2,6-Dimethylphenol4. 2,6-Dimethylaniline5. n-Dodecane6. Naphthalene7. 1-Decanol8. n-Tridecane9. Decanoic acid ME
7.248.07
1.63
3.04
3.32
3.544.43
4.73 4.93
6.427.25
8.08
Beginning of tubing
Example #
9300205
End of tubing
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5RT (min)
X offset: 0Y offset: 20
pA
1.63
3.04
3.32
3.544.43 4.73 4.92
6.417.25
8.07
1.63 3.05
12
34 5 6
7 8 9
3.32
3.554.43 4.73 4.93
6.42 7.258.08
1.63
3.04
3.32
3.544.43 4.72 4.92
6.41 7.248.06
UltiMetal Plus treatment of 0.25 mm tubing, 30 mTo demonstrate inertness over the total length of the columnafter UltiMetal Plus treatment, a 30 m column (0.25 mm id)was tested in pieces approximately 5 m. Piece 6 was slightlyshorter than 5 m and, therefore, this section had shorterretention times for Test Mix 60 (Figure 9).
Four columns were tested. Peak asymmetry and absoluterecovery data for 1-decanol are shown in Table 7. In additionto some variation from different pieces in the column, therewas some inertness variation in the four channels whentandem testing.
UltiMetal Plus deactivation was equal over the whole lengthof the tubing.
11
Tandem testing UltiMetal Plus tubing, 0.53 mmFigure 10 is a comparison of a tandem test of UltiMetal Plus0.53-mm tubing. The inertness of the original UltiMetalproduct, UltiMetal Plus tubing, and tubing from a non-Agilentsupplier was compared.
Figure 10. Tandem test of 5 m × 0.53 mm tubing (hydrogen constant flow at 1.35 mL/min, oven 60 °C). See Table 2 for peak identification and calculatedon-column amounts. An Agilent J&W VF-5ms, 30 m × 0.25 mm, 0.25 µm (p/n CP8944) GC reference column was used with an inert Agilent CPMunion (p/n G3182-60580) and Agilent UltiMetal Plus Flexible Metal ferrules.
All stringent probes eluted and inertness was acceptable,although trimethylphosphate and 1,2-pentanediol showedmore tailing. Compared to the original UltiMetal tubing, theinertness improved significantly with UltiMetal Plustechnology. The non-Agilent product gave slightly moretailing.
Agilent UltiMetal Plus CP6581
non-Agilent deactivated tubing
Agilent UltiMetal CP6540
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
33
35
37
39
41
43
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0 12.5
2.66
2.78
3.27
3.58
3.793.90 4.70
5.23
7.60
9.58
7.99
10.46 11.38
8.47
RT (min)
X offset: 0Y offset: 15
pA
2.62
1
23
4
5
67
8
910
11
12 13 14
2.75
3.22
3.54
3.75
3.874.66
5.15
7.41
9.45
7.88
10.3711.31
8.42
2.59
2.78
2.26 2.71 3.29
3.65
3.803.93 4.74
5.40
7.93
9.98 10.8111.89
8.76
Table 7. Tandem Test Results for 1-Decanol (Test Mix 60) with Four 30 m × 0.25 mm Agilent UltiMetal Plus Stainless Steel Columns; Every 5-m Piece wasTested
Column number
9300209 9301597 9300205 9300202
Piece Asymmetry Absolute recovery (%) Asymmetry
Absolute recovery (%) Asymmetry
Absolute recovery (%) Asymmetry
Absolute recovery (%)
1 1.1 96 1.3 98 1.1 93 1.3 100
2 1.1 96 1.4 97 1.2 97 1.3 104
3 1.1 95 1.2 98 1.1 93 1.3 101
4 1.1 96 1.3 102 1.2 93 1.4 105
5 1.2 95 1.2 93 1.2 89 1.3 103
6 1.3 89 1.3 96 1.2 92 1.2 107
avg 1.1 94 1.3 97 1.2 93 1.3 103
rsd (%) 7 3 5 3 4 3 4 3
12
Transfer lines, 1/16 inchThe plumbing of GCs and switching valves relies mostly on1/16 inch transfer line tubing. To minimize loss of activecomponents, the inertness of transfer lines is also a keyparameter. In Figure 11 test results are shown for anUltiMetal Plus deactivated transfer line. Untreated stainlesssteel tubing is highly active, and many probes are irreversiblyadsorbed and do not elute. The performance of non-Agilenttubing exceeded that of regular stainless steel, but wasinferior to UltiMetal Plus tubing.
Figure 11. Transfer lines of 1/16 inch × 0.75 mm tandem tested as 1-m pieces using the Very Inert Mix split 1:20 (amounts are 3.75x lower, as mentioned inTable 2) (hydrogen constant flow at 4.7 mL/min, oven 60 °C). A Megabore Agilent J&W VF-5ms, 30 m × 0.53 mm, 0.5 µm GC reference column(p/n CP8974) was used.
Agilent UltiMetal Plus CP6573
non-Agilent 1/16 in deactivated tubing
Bare stainless steel
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60
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70
75
80
85
90
95
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110
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120
125
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0 12.5 13.0 13.5 14.0 14.5 15.0 15.5 16.0
1.90
3.15
3.55
3.89
4.045.03
5.62
8.24
11.219.00 12.45 13.7714
14
1312
11
11
109
8
76
5
4
3
2 (+CH)
CH
5 + 6
1
9.96
RT (min)
X offset: 0Y offset: 45
pA
1.78
1.79
2.55
2.552.54
4.10
3.143.54
3.86
4.02
5.00
5.60
8.2411.17
11.77
14.63
8.98 12.38 13.69
9.90
4-PicolineA
s 4.3
4-PicolineA
s 5.7
1. MethanePropionic acidiso-Butyric acidn-Butyric acidOcteneOctane1-Nitrobutane4-PicolineTrimethyl phosphate1,2-PentanediolPropylbenzene1-Heptanol3-OctanoneDecane
No. Compound ng
2.3.4.5.6.7.8.9.
10.11.12.13.14.
3.83.83.81.91.93.87.518.87.53.83.83.83.8
13
Bulk tubingThree different standard types of bulk tubing are available:1/16 inch od (1 mm id), 1/8 inch od (2.1 mm id), and 1/4 inchod (4.3 mm id). The results in Figure 12 are for 1/8 inch tubing(1 m). Due to the large internal volume, a Megabore VF-5msGC column was used. Because there are no specialdeactivated connectors available to reduce 1/8 inch to1/16 inch, standard metal connectors were UltiMetal Plusdeactivated and used to connect a 1-m piece of tubing. As a
Figure 12. Tandem test of different 1 m × 1/8 inch tubing with Test Mix 60 using a Megabore Agilent J&W VF-5ms, 30 m × 0.53 mm, 0.5 µm GC referencecolumn (p/n CP8974) (hydrogen constant flow at 4.7 mL/min, oven 120 °C). The inside of the column can be checked visually (rainbow color, in thiscase blue-purple).
1/8 inch tubing with internal Agilent UltiMetal Plus treatment
Agilent UltiMetal Plus SS1-Decanol
Bare SS
Agilent UltiMetal SS
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54
0.2 0.6 1.0 1.4 1.8 2.2 2.6 3.0 3.4 3.8 4.2 4.6 5.0 5.4 5.8 6.2 6.6 7.0 7.4 7.8 8.2 8..6
3.20
3.43
3.63
3.21
3.41
3.61
4.38
4.36
6.13
6.11
4.65
4.67
4.63
6.84
6.80
7.559
8
7
65
431
2
4.81
4.85
4.79
RT (min)
X offset: 0Y offset: 15
pA2.02 3.44
6.87
7.50
7.52
1.Test mix 60 (0.01%)1-Octanol
2. n-Undecane3. 2,6-Dimethylphenol4. 2,6-Dimethylaniline5. n-Dodecane6. naphthalene7. 1-Decanol8. n-Tridecane9. Decanoic acid ME
system reference set, a short piece (3 cm) of UltiMetal Plusdeactivated 1/8 inch tubing was used with two reducingunions, without cutting off the tubing (completelydeactivated). Metal ferrules were used to connect the fusedsilica tubing to the reducing union.
Compared to bare stainless steel and UltiMetal-treated steel,improved inertness was obtained with the UltiMetal Plustechnology.
14
Comparison of capillary tubing and deactivatedfused silicaThe inertness of several steel deactivated tubing types, aswell as deactivated fused silica, was compared (Figure 13,Table 8). The system test, shown above (A), illustrates theinitial inertness profile. Subsequent chromatograms showinertness performance of different tubing types (5 m × 0.53 mm) with the same reference column andconnector.
12.51211.51110.5109.598.587.576.565.554.543.532.521.51
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140
135
130
125
120
115
110
105
100
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90
85
80
75
70
65
60
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50
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20
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0
2.34
2.66
2.78 3.273.58
3.79
3.90 4.70
5.23
7.60 7.998.47
9.58 10.46 11.38
2.26
2.59
2.71
2.78 3.293.65
3.803.93 4.74 5.40
7.93
8.769.98 10.81 11.89
2.31
2.62
2.75
3.223.54
3.75
3.87 4.66
5.15
7.41 7.888.42
9.45 10.37 11.31
2.15
2.24
2.67 3.163.47
3.72
3.85 4.65
5.09
7.20 7.78 8.54 9.52 10.50 11.54
2.53
2.66
3.12
3.43
3.68
3.79
4.59
5.02
7.08 7.64 8.369.32 10.29 11.25
1.261.85
2.32
2.62
2.86
2.98
3.77
4.18
6.21 6.78 7.528.45 9.42 10.39
RT [min]
pA
X offset: 0Y offset: 23
A
B
C
D
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E
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14131211109
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Figure 13. Comparison of different types of tubing, 5 m x 0.53 mm, using the Very Inert Mix. A) system check Agilent J&W VF-5ms (p/n CP8944) and AgilentCPM union (p/n G3182-60580); B) non-polar (apolar) deactivated fused silica; C) Agilent UltiMetal Plus guard, stainless steel (p/n CP6577); D) AgilentUltiMetal Plus tubing, stainless steel (p/n CP6581); E) Agilent UltiMetal tubing, stainless steel (p/n CP6540); F, non-Agilent inert deactivated tubing.Tubing was tested using the tandem setup with the Very Inert Mix at 60 °C at constant hydrogen flow of 1.35 mL/min. On-column amounts andcomponents are given in Table 2 (split 1:75, 1 µL injection).
A B C D E F
Compound AS RR (%) AS RR (%) AS RR (%) AS RR (%) AS RR (%) AS RR (%)
Propionic acid 0.5 45 1.1 47 1.3 45 2.8 40 6.4 38 1.6 44
i-C4 acid 0.3 49 0.8 50 1.0 49 2.0 42 3.7 45 1.5 48
n-C4 acid 0.3 49 0.8 49 1.0 48 2.1 41 1.9 35 1.6 46
C8= 1.0 50 1.0 51 1.0 51 1.0 52 0.9 56 0.9 52
n-C8 1.0 50 1.0 50 1.1 50 1.0 50 1.0 54 1.0 51
Nitrobutane 1.2 53 1.1 53 1.1 52 1.1 51 1.2 52 1.1 53
4-Picoline 1.5 169 3.1 169 2.4 168 10.1 162 18.0 137 15.5 164
TMP 1.2 101 6.5 102 4.6 100 51.5 81 60.7 83 60.0 71
1,2-Pentanediol 1.1 105 2.0 104 2.5 99 21.5 98 coelutes 28.5 101
n-Propylbenzene 1.0 107 1.1 107 1.0 107 1.0 111 1.3 156 1.0 115
1-Heptanol 1.1 82 1.4 83 1.5 82 5.6 80 9.6 80 16.9 79
3-Octanone 1.1 80 1.2 80 1.1 80 1.5 80 1.4 80 2.3 80
n-Decane 1.0 100 1.0 100 1.0 100 1.0 100 1.0 100 0.9 100
15
These data show UltiMetal Plus guard tubing had similar orbetter inertness for the active probes in the test mixturecompared to apolar deactivated fused silica. UltiMetal Plusstainless steel guards had excellent inertness performanceand are a more robust replacement for deactivated fusedsilica tubing.
UltiMetal Plus tubing, temperature stability andflexibility The temperature stability of the external UltiMetal coating ofa GC column was tested at 450 °C and compared to regularstainless steel (Figure 14). The exterior appearedmechanically stable and its color was unchanged afterthermal exposure.
Table 8. Comparison of Different Types of Tubing, 5 m × 0.53 mm, Using the Very Inert Mix
Figure 14. The external appearance of a GC column, 0.53 mm id, coated with Agilent UltiMetal after five days at 450 °C, with an untreated stainless steel columnas reference. Both columns were thoroughly rinsed before the start (A). After heating, the untreated column was oxidized to a brown color but theAgilent UltiMetal deactivated column kept its rainbow appearance (B,C).
A
B C
RR = Relative recovery, compared to n-decaneAS (asymmetry) was measured at 10% peak heightA) system check Agilent J&W VF-5ms (p/n CP8944) and Agilent CPM union (p/n G3182-60580); B) non-polar (apolar) deactivated fused silica; C) AgilentUltiMetal Plus guard, stainless steel (p/n CP6577); D) Agilent UltiMetal Plus tubing, stainless steel (p/n CP6581); E) Agilent UltiMetal tubing, stainless steel(p/n CP6540); F, non-Agilent inert deactivated tubing.
16
Bending UltiMetal-treated stainless steel tubing has somelimitations in terms of the minimum radius that can beattained. The UltiMetal layer can be damaged by extremebending, which can influence the inertness of the flow path.In this test, the outside of the tubing was visually checked forchanges after bending. For tubing of 1/8 and 1/4 inch od,standard pipe bending tools can be used. For 1/16 inchtubing, a 2-cm radius or larger can be safely employed. A1 m × 0.25 mm id capillary tube was wound to diameters of2.5 and 10 cm (Figure 15) and tested for inertness using theUS EPA8270 short mix.
An example chromatogram of the tandem test using theEPA8270 short mix is shown in Figure 16.
Damage of the deactivation layer after bending would affectthe inertness of the tubing. Measurements showed nochange in the inertness for UltiMetal Plus and non-Agilentdeactivated tubing, leading to the conclusion that nosignificant mechanical stability differences exist between thetwo. Figure 17 shows a comparison for the most stringenttest probe (2,4-dinitrophenol). The differences observed werewithin variations of the measurement.
Figure 15. Flexibility test to compare 0.25 mm Agilent UltiMetal Plus tubingbent to diameters of 2.5 and 10 cm.
Figure 16. Tandem test chromatogram for the EPA8270 short mix using GC/FID (20 ng level, 40 ng for internal standards). A 1-µL sample was injected (splitlessmode, 0.75 minutes at 30 mL/min, 250 °C) on an Agilent 7890A GC with split/splitless inlet using a G4513B autosampler. Helium was used as carriergas at a constant flow rate of 3 mL/min. An Agilent J&W HP-5ms, 50 m × 0.32 mm, 0.52 µm GC column (p/n 19091S-112) was programmed from40 °C (1 minute) at 15 °C/min to 310 °C (0 minutes). A 5-ppm test standard in dichloromethane was used with 40-ppm internal standards (deuteratedPAHs) included.
1. N-Nitrosodimethylamine 2. Aniline 3. 2,4-Dinitrophenol 4. 4-Nitrophenol 5. 4,6-Dinitro-2-methylphenol 6. 4-Aminobiphenyl 7. Pentachlorophenol 8. Benzidine 9. 3,3-Dichlorobenzidine10. Benzo(b)fluoranthene11. Benzo(k)fluoranthene
IS 1 Dichlorobenzene-d4IS 2 Naphthalene-d8IS 3 Acenaphthene-d10IS 4 Phenanthrene-d10IS 5 Chrysene-d12IS 6 Chrysene-d12
4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00
1,000,000
2,000,000
3,000,000
4,000,000
5,000,000
6,000,000
7,000,000
8,000,000
9,000,000
1
2
IS 1
IS 2
IS 3
3 45
6
7
IS 4
8
9, IS 5
10
11
IS 6
17
Conclusions
Compared to bare stainless steel, Agilent UltiMetal Plustreated stainless steel provided greatly improved inertness.Compared to non-Agilent tubing, an equal or better inertnesswas obtained. The deactivated exterior of UltiMetal Plustubing delivered the extra benefit of improved inertness whenconnecting the tubing to the instrument or connectors. Forinert, leak-tight and robust connections, the use of AgilentUltiMetal Plus connectors, ferrules, and fittings isrecommended.
References
1. Anon. “UltiMetal Plus – Advanced Chemistry forStainless Steel Surface Deactivation” TechnicalOverview, Agilent Technologies, publication number5991-3357EN (2014).
2. Ken Lynam “Agilent Inert Flow Path EnhancementsImprove Drugs of Abuse Testing” Application Note,Agilent Technologies, publication number 5991-1859EN(2013).
3. Anon. “Agilent Ultimate Union Kits (G3182-61580 andG3182-61581)” Installation Guide, Agilent Technologies,publication number G3182-90580 (2013).
4. J. Luong, R. Gras, W. Jennings. J. Sep. Sci. 30, 2480(2007).
5. Anon. “Agilent J&W Ultra Inert GC Columns: A New Toolto Battle Challenging Active Analytes” TechnicalOverview, Agilent Technologies publication number 5989-8665EN (2008).
0
0.2
0.4
0.6
0.8
1
1.2
2,4 dnp 2,4 dnp
Nor
mal
ized
rec
over
y (±
std
ev)
Analytical columnPre analytical column and unionAgilent UltiMetal Plus tubing (Av n = 3)Non-Agilent tubing (Av n = 3)Post analytical column and union
Diameter 10 cm Diameter 2.5 cm
Figure 17. Comparison of Agilent UltiMetal Plus tubing and non-Agilenttubing bent to diameters of 2.5 and 10 cm (1 m stainless steeltubing, 0.25 mm id, 0.5 mm od, n = 3).
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Agilent shall not be liable for errors contained herein or for incidental or consequentialdamages in connection with the furnishing, performance, or use of this material.
Information, descriptions, and specifications in this publication are subject to changewithout notice.
© Agilent Technologies, Inc., 2014Printed in the USAMay 6, 20145991-4499EN
