Frequently Asked Questions

How long does an extraction take with an automated SPE system?

On average, an extraction can take anywhere from 15 - 20 minutes, with dirtier samples taking longer. The total run time will also be a function of the number of Pre-wet and Rinse steps that have been programmed into the method.

How much solvent is used during an extraction process?

Horizon Technology’s Automated Extractors use approximately 1/3 less solvent than with conventional LLE (liquid-liquid extractions). For a typical method, using a 47 mm disk, the total amount of solvent would be approximately 10 - 20 mLs for Prewetting and 15 - 20 mLs for final Rinsing. A typical method using a 90 mm disk will use about twice that volume.

My laboratory is concerned with solvent exposure.

The 1000XL and 3000XL Oil & Grease Machines come standard with an internal fan and hose ducting. This permits the systems to be operated directly on the lab bench. The SPE-DEX 4790 system has an internal fan, but the Vent Hose Kit is an option. If you plan to operate SPE-DEX 4790's on the bench, we recommend ordering the optional Vent Hose Kit at the time of purchase.

The fan pulls solvent fumes away from the technician and can be vented into a fume hood. This minimizes exposure to solvent fumes. Because the extraction process is automated, all of the solvents are contained in 2.5 Liter solvent bottles. Therefore, there is minimal handling of the solvents by the technician. Exposure levels have been tested and fall below the OSHA limits.

What solvents are compatible with the automated extractors?

Because the SPE-DEX® 1000XL & 3000XL Oil & Grease Machines are designed specifically for Method 1664A they can only be used with hexane and methanol. The use of other solvents will damage the extractors. Since the SPE-DEX 4790 was designed to perform all EPA approved SPE methods, it can handle all solvents. Some customers even use the SPE-DEX 4790 system for other internal R&D applications.

How are solvent volumes determined?

The volume of solvent delivered to the system is a function of the solvent bottle pressure; the length of time the internal solvent delivery valve (solenoid) stays open; the diameter of the solenoid valve opening; the diameter of the rinse tube and the number of Pre-wet and Rinse steps programmed. On the Spe-Dex® 4790 Extractors, an IR sensor regulates dispense time (or time the solenoid valve stays open) depending on whether a 47 mm or 90 mm disk is being used. For the 1000/3000XL Systems the dispense time is programmed into the Controller method.

Does the Controller come pre-programmed with EPA methods?

Yes. All of the currently approved EPA methods are pre-programmed into the Controller. These methods are simply called up by the operator, (EXAMPLE 525.2) and downloaded to the individual extractors.

Can I create my own methods in the 4700 Controller?

Yes. The 4700 Controller allows you to modify the pre-programmed EPA methods to create your own methods. The Controller simply asks which solvents will be used and the various times for soaking, air drying and rinsing the disk. The Controller can safely store about 200 individual methods in its non-volatile memory.

What are the differences between the SPE-DEX® 4790 Extractors, the SPE-DEX® 4770, and the Spe-Dex® 4750 Extractors?

1) Water Bottle Holder: Unlike the 4770 & 4750 Extractors in which the sample bottle sat loosely in the bottle holder, the 4790 requires a tight seal between the bottle holder and the sample bottle cap adapter. This is required, as the Water Inlet Valve now remains open during the entire water sample. In comparison, the 4770 & 4750 Water Inlet Valves opened and closed to introduce the water sample.

Therefore, since the Water Inlet Valve remains open until all of the water has been filtered, the sample bottle and cap adapter need to be firmly attached together to prevent air leaks. If you look into the bottle holder, you will notice a black o-ring. This o-ring provides the seal between the cap adapter and the bottle holder. As long as a good seal is maintained between the sample bottle/cap adapter and the bottle holder, the water sample can only flow out, as air is introduced into the bottle.

2) Loading the Sample Bottle: 4790 - Once the aluminum foil and cap adapter are in place, follow the procedures in the manual to load the sample bottle. Once the bottle is loaded into position, it is important to use a "clockwise" rotation to open the foil. If the bottle is rotated "counterclockwise" the cap adapter could be loosened from the bottle and allow an air leak to develop. This would cause an overflow of the water sample. Also, to prevent the aluminum foil from covering the solvent rinse opening, only rotate the bottle 3/4 of the way. Again, practice with the unit first - use an empty bottle with foil and observe how the foil opens. 4770 & 4750 – The rinse cone breaks the aluminum foil when loading the sample bottle.

3) Liquid Level Sensors: Unlike the 4770 & 4750 Extractors, which had fixed sensors, the 4790 sensors can be adjusted. This design was used in order to handle dirty samples that contain great amounts of particulate matter. Being able to move the sensors up (or down) is very useful.

Before running a water sample, inspect and adjust the height of the sensors. It is recommended to run a Purge method and visually inspecting the volume of Prewet solvent dispensed. Also, based on the vacuum setting, inspect the disk to ensure sufficient volume is left on the disk during the soaking cycle. The sensor assembly can be moved up or down until the desired Prewet volume is obtained. Once this sensor height is adjusted, it does not need to be changed, unless the operator elects to.

4) Water Inlet Valve: The 4790 Water Inlet Valve uses air pressure to open the valve. It is designed similar to a stopcock on a separatory funnel. The opening of the Water Inlet Valve is ½ “ in diameter. This is ideal for processing dirty samples that may not only be high in suspended solids but may have larger particles or chunks. The Water Inlet Valve opens during the sample-processing step and remains open until the entire extraction is complete. The Water Inlet Valve on the 4770 & 4750 Extractors operate on vacuum and have a diaphragm assembly that opens when vacuum is supplied to the valve. In this system, the Water Inlet Valve alternates between the open and closed positions during the sample-processing step to prevent the Disk Assembly from over filling. The diameter of the water path opening on this valve is 0.24 “. Therefore, the extraction of dirty samples with particulate material could be a problem causing the diaphragm to not seal properly and result in sample overflows. The 4770 Extractors were designed for the extraction of clean drinking water samples. The 4750 Extractors are similar in design to the 4770 Extractors. Although the 4750 Extractors were designed for Oil & Grease extractions, samples that are very dirty will be problematic. The 4790 Extractors were design to overcome this limitation.

5) Disk Holder Assemblies: The 4770 & 4750 Extractors have Disk Assemblies that can only accommodate 47 mm disks. The 4790 Extractors can accommodate two different size Disk Holder Assemblies. When running clean samples, the 47 mm Disk Holder Assembly is loaded onto the extractor platform and is used with 47 mm disks. For running dirty samples, the 90 mm Disk Holder Assembly is mounted on the platform and used with 90 mm disks. The Bakerbond Speedisks® can be used on all three extractors.

These are the main changes to the 4790. Internally, the main circuit board is now located in a higher position - not on the bottom. Also, the keypad is a membrane design so as to be impervious to liquids, plus, it is mounted higher up on the chassis. Two of the check valves have also been removed, which will make daily operation more reliable and user friendly.

What are typical Background values for the extractors?

First, let's discuss the background values typically found with method 1664A. A clean extractor system with clean solvents (and no disk), should give a background value of 0.5 - 0.75 mg. Based on the particular disk used, and the size of the disk (47 or 90 mm), the background value could range from 0.75 - 1.5 mg. Most of the higher backgrounds are a result of the SPE disk. Various steps can be taken to reduce these higher values.

With regards to background values for organic contaminates, the SPE-DEX 4790 model uses all PTFE, PEEK, and Kalrez components. Again, as long as the solvents are clean and no contaminating materials are used in the extractor, such as O-Rings, the background values are well below standard EPA method requirements.

I have difficulties with sample flow rates when using 3M Empore™ Oil & Grease disks. Is there anything that I can do?

Yes. There has been three generations of Disk Holder Assemblies. The old style snap fit assembly required one o-ring on the groove of the Insert that would hold the disk in place and form a tight seal. The second generation of Disk Holder Assemblies came in three parts, the Base Cup, the Riser and the Aluminum Locking Ring. No o-ring is needed when using a flat disk. However, when using the 3M Empore™ Oil & Grease disks the two o-rings are needed to provide a tight seal for optimal flow rates. The larger diameter, thicker o-ring is placed in the bottom outer groove of the Cup and the smaller diameter, thinner, o-ring is placed in the groove of the Riser, which is inserted into the Base Cup to hold the disk in place. The orientation of the Riser is such that the groove with the o-ring is face up and the flat edge is face down on the disk. The Aluminum Locking Ring is then screwed tightly onto this assembly. If the assembly is not tight, when vacuum is pulling, air will flow through the parts and slow the flow rates. A high amount of residual water may also be left on the disk after the Air Dry Time which can adversely effect recoveries.

The latest style of Disk Holder Assemblies also come in three parts but have been redesigned such that the o-rings are no longer used with the 3M disks. Instead, a red gasket is used to provide a better seal. The support screen is placed in the center of the Base Cup. The gasket is then placed into the Cup with the flat even side face down. The 3M Oil & Grease disk is placed into the center recess of the gasket. For the 90 mm assemblies, the Riser is inserted into the Cup with the grooved side face down on the disk. For the 47 mm assemblies, the side with the thin lip is inserted face down on the disk and the flat edge face up. Finally, tightly screw on the Aluminum Locking Ring. This design provides a better seal when using the 3M disks. For the flat disks, the gasket is eliminated and the orientation of the Riser in the Cup is reversed (flip over). Refer to the Operator Manual for detailed instructions and photos.