Note:Autosampler Control:
Selecting the Syringe Speed (AS/AS50)
The speed at which the AS and AS50 syringes move can vary between a speed of 1 (the slowest) to 5 (the fastest). You can select the syringe speed on the Control Panel or in the Program.
Select a slower speed for more viscous samples and to ensure the backpressure at the inject port and needle seal remains below 690 kPa (100 psi). The maximum allowed speed depends on the syringe size and the tubing IDs and lengths. See the syringe speed and tubing size guidelines below for details.
Note:
If a concentrator column is installed, a speed of 1 or 2 is required to ensure the backpressure does not exceed the maximum allowed.
Selecting Different Aspirate and Dispense Speeds
If the AS has Moduleware Version 2.02 (or later) installed, different speeds can be selected for aspirating versus dispensing liquids. For example, if the AS is loading sample, you can select a faster syringe speed for aspirating sample from the vial and a slower speed for dispensing sample to the loop or concentrator column. Selecting a slower speed reduces the backpressure at the inject port and needle seal.
You can select different aspirate and dispense speeds for the following functions: Flush, Prime, Load, Reagent Flush, Reagent Prime, and Concentrate (see 
Dionex AS/AS50 Autosamplers for a list and description of the various aspirate and dispense speed commands).
Notes:
If you do not include aspirate and dispense syringe speed commands in a program, the autosampler uses the speeds selected in the previous program or on the control panel (whichever are the most recent).
If the autosampler does not support separate aspirate and dispense speeds, the SyringeSpeed command determines the speed for both aspirating and dispensing liquid when the autosampler is loading the loop and performing other operations.
Syringe Speed and Tubing Size Guidelines (For All AS and AS50 Autosamplers)
The AS and AS50 are capable of delivering sample at a maximum pressure of 690 kPa (100 psi). Refer to the formula and tables below to select the appropriate tubing sizes and sample or prep syringe speed to keep the total backpressure below 690 kPa (100 psi).
Use the following formula to determine the backpressure produced by the tubing lengths, syringe size, and syringe speed:
backpressure = cm of tubing x kPa (psi)/ml/min/cm (from Table 1) x ml/min (from Table 2 or Table 3)
Example: 30 cm of 0.254 mm tubing x 1.6 kPa/ml/min/cm x 2.40 ml/min (5 ml syringe at speed 2) = 115 kPa
Tip:
When calculating the total backpressure, include the needle seal tubing and the sample loop. If you are calculating the backpressure for an AS or AS50 that is set up for sequential injections, also include the diverter line (the line that connects the diverter and injection valves).
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Table 1: Tubing Volume and Backpressure |
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Backpressure in kPa (psi) per |
Volume in ml per |
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0.127 mm (0.005 in) |
25 kPa (3.6 psi) |
0.13 |
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0.178 mm (0.007 in) |
6.5 kPa (0.94 psi) |
0.25 |
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0.254 mm (0.010 in) |
1.6 kPa (0.23 psi) |
0.51 |
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0.330 mm (0.013 in) |
0.55 kPa (0.079 psi) |
0.86 |
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0.508 mm (0.020 in) |
0.10 kPa (0.014 psi) |
2.03 |
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Table 2: Flow Rates Provided by the Sample Syringe |
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Sample Syringe |
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100a, 250, 500, and 1,000 ml |
1 |
0.06 |
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2 |
0.12 |
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3 |
0.24 |
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4 |
0.60 |
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5 |
1.20 |
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5 and 10 mlb |
1 |
1.80 |
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2 |
2.40 |
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3 |
4.80 |
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4 |
7.20 |
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5 |
15.00 |
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a) The maximum flow rate for a 100 ml syringe is 0.60 ml/min. |
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Table 3: Flow Rates Provided by the Prep Syringe |
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Prep Syringe |
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250, 500, and 1,000 ml |
1 |
0.03 |
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2 |
0.09 |
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3 |
0.24 |
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4 |
0.60 |
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5 |
1.20 |
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2.5, 5, and 10 mla |
1 |
1.80 |
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2 |
2.40 |
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3 |
4.80 |
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4 |
7.20 |
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5 |
15.00 |
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a) In general, if you are using a 5 or 10 ml syringe, select a syringe speed of 1 or 2. |
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