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FAQ
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What is Solid Phase Extraction?
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What is Solid Phase Extraction?
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Solid Phase Extraction, often referred to as SPE, is a sample preparation technique wherein analytes are concentrated by adsorption on a solid-phase substrate such as C18. This is followed by elution with a suitable solvent to yield a purified extract of the compounds of analytical interest. SPE is used in place of liquid-liquid extraction (LLE).
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What types of phases are used in SPE?
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What types of phases are used in SPE?
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Solid phases are available as small silica particles with various carbon functional groups such as C18 or C8 bonded to the silica surface. They may also be composed of polymeric gels such as styrene divinylbenzene (SDB). These solid-phases are in the form of micron sized particles.
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How is SPE conducted?
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A polypropylene cartridge, packed with the appropriate solid phase, is placed in a vacuum apparatus and a water sample containing the analyte(s) of interest is drawn through the cartridge. The solid phase in the cartridge captures the analyte(s). A small quantity of solvent is then used to release the analytes (elution) from the solid phase. The extraction solvent may then be evaluated by an appropriate analytical instrument such as GC or HPLC.
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What are the benefits of using SPE?
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What are the benefits of using SPE?
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There are many benefits to using solid-phase extraction:
- Reduced solvent usage saves money
- No phase separation problems (emulsions)
- Analytes are concentrated in a small solvent volume for increased analytical sensitivity
- Extracted solutions are free of interferences that could plug injectors
- Multiple extractions can be conducted simultaneously
- Extractions can be automated
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Why should I do SPE when I already do LLE(liquid liquid extraction)?
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Why should I do SPE when I already do LLE(liquid liquid extraction)?
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Mixed Mode SPE removes the matrix effects without compromising the recovery.
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I do not have a vacuum manifold. Can I perform elution thru centrifuge?
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I do not have a vacuum manifold. Can I perform elution thru centrifuge?
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Unless you are using an Ultra Centrifuge i.e. one that can separate
proteins by differentials, then you'll never get the sorbent dry enough to
have reproducible results. So the answer is NO.
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I am trying to register but i cannot sumbit?
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I am trying to register but i cannot sumbit?
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Make sure your password meets the requirements (6 chars - numbers and letters).
Also check to see if you have filled out all of the required (*) fields.
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When extracting heroin from urine should I expect to find codeine?
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When extracting heroin from urine should I expect to find codeine?
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Yes and No
If the subject used Heroin derived solely from the pharmaceutical industry, then it should have some Heroin (Diacetylmorphine), some 6-mam, some morphine, some morphine glucuronides. That’s because the starting material is Diacetylmorphine.
IF the starting material comes from the opium poppy, then it may contain codeine, codeine gluc, papaverine, thebaine, noscapine, acetyl codeine, and the morphine constituents and that’s because those opioids originate in the latex of the poppy.
The codeine morphine discussion has prevailed for years, Codeine can demethylate to morphine at about a ratio of around 10:1, some people are poor metabolizers and don’t demethylate as readily as others and thus their ratio is higher (morphine has better analgesic effects than does codeine), it’s a genetic thing. So they pump up the amount of codeine they take. But morphine is not known to re-methylate in vivo (only on badly manufactured SPE columns).
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We use a lot of Acetonitrile in our extractions. How can i cut down on it?
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We use a lot of Acetonitrile in our extractions. How can i cut down on it?
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The quick answer is no we do not use a lot of acetonitrile in UCT extractions. In 2 analyses is the use of aceto prominent
1 Is THC (Blood and Urine): CSTHC
In the blood extraction: Aceto can be replaced with either methanol or acetone (carefully adding them to the sample dropwise).
In the urine extraction, the Aceto is used to wash the SPE column in either as a 5% solution with 0.1 M Acetate buffer, or 0.1 M HCl: this again can be replaced with a low level of methanol in the wash.
With the SSTHC, the precipitation step is the same, the wash is currently 85% DI water 15% Aceto and 1 % Ammonium Hydroxide, this could be altered to a lower % of methanol (approx, 7-10%) and increase the DI Water content.
2 Is the Benzo analysis which currently uses 20% Aceto in 0.1 M phosphate buffer, this again can be replaced with approx. 10% methanol, or alternatively the column can be washed with DI Water, 0.1 M acid, dried, washed with hexane, Dried, then eluted with Dichloromethane/ IPA/ Ammonium Hydroxide (78: 20:2). The other alternative, is the CSBNZ which consumes only 5% Aceto, and I have it on good authority that this step can be removed and replaced with Dichloromethane/ IPA/ Ammonium Hydroxide (78: 20:2).
In all the other analyses, the sample is diluted with 0.1 M phosphate buffer, the washes are DI Water, 0.1 M acid, and methanol. Elution solvents can be either Dichloromethane/ IPA/ Ammonia, or Ethyl Acetate/ Ammonia, those that do use aceto i.e. ethyl acetate/ aceto/ ammonia can be converted to use either IPA or methanol.
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I’m having problems recovering planar compounds from C18. Shouldn’t this be easy?
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I’m having problems recovering planar compounds from C18. Shouldn’t this be easy?
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Always specify Enviro-Clean® C18 products. Enviro-Clean® cartridges use inert materials that allow for excellent recoveries of planar compounds.
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We are fractionating aliphatic and aromatic hydrocarbons using the XRSIHT13M15 column. Occasionally we get breakthrough of the aromatic fraction in the aliphatic fraction. Why is this?
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We are fractionating aliphatic and aromatic hydrocarbons using the XRSIHT13M15 column. Occasionally we get breakthrough of the aromatic fraction in the aliphatic fraction. Why is this?
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The XRSIHT13M15 uses heat treated silica to provide enough theoretical plates to separate the two types of compounds. Moisture will deactivate the silica and cause a reduction in theoretical plates resulting in some of the lighter aromatics eluting in the aliphatic fraction. Use the XRSIHT13M15 as soon as the end caps are removed from the column to prevent deactivation from room humidity.
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I’m having problems extracting pesticides from honey using the QuEChERS approach. It seems pretty straight forward. What could be going wrong?
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I’m having problems extracting pesticides from honey using the QuEChERS approach. It seems pretty straight forward. What could be going wrong?
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The two most common mistakes when using the QuEChERS approach are not hydrating the sample and adding the sample to the salts before adding the solvent. The sample should always be at least 80% moisture since water is very important for the extraction. Also, if the sample directly contacts magnesium sulfate, the magnesium sulfate will pull the moisture out of the sample reducing the extraction efficiency. Always add the solvent before adding the sample.
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All of my pesticides are recovering great except Aldrin. What can I do to improve Aldrin recoveries?
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All of my pesticides are recovering great except Aldrin. What can I do to improve Aldrin recoveries?
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Low Aldrin recoveries can be caused by the water in the extracts bonding the Aldrin to sodium sulfate during extract drying. Rinsing the sodium sulfate with plenty of methylene chloride will improve recoveries.
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When I performed oil and grease liquid/liquid extraction (Method 1664A) I used a filter paper funnel to hold my sodium sulfate. Now I am told that I can’t do that when performing 1664 by SPE. Why is that?
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When I performed oil and grease liquid/liquid extraction (Method 1664A) I used a filter paper funnel to hold my sodium sulfate. Now I am told that I can’t do that when performing 1664 by SPE. Why is that?
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When performing 1664 using large volumes of solvent, the solvent rinses the oil and grease standard through the filter paper. With SPE, much less solvent is used and the standard becomes trapped in the paper giving low recoveries. Use either glass wool or a sintered frit to hold your sodium sulfate.
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My Diesel Range Organics (DRO) recoveries aren’t as high as I would like them to be. How can I get better recoveries?
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My Diesel Range Organics (DRO) recoveries aren’t as high as I would like them to be. How can I get better recoveries?
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Since many of the components of DRO are very volatile, special care must be taken when spiking QC, drying the sorbent and handling the extracts. Below are some tips.
- Always add your spike in a water soluble solvent.
- Keep your sorbent dry times to 10 minutes or less.
- Concentrate your extracts carefully. A K-D ampoule with a micro-Snyder column is recommended.
- Do not store your extracts with headspace in the vial.
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Can a user control flow to EACH position on the manifold?
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Can a user control flow to EACH position on the manifold?
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Each individual position cannot be controlled. Only each row (1-4) can be adjusted or controlled. The design of the PPM allows a uniform flow to each individual position even at times where a tube may be empty. The flow is controlled by the black dials and the toggle switch on the front of the PPM. The toggle switch position for Full Flow/ Dry Flow should be used when drying columns. The pressure should be adjusted to the highest possible pressure (usually up to 120 psi) but that will depend on the pressure of the gas source.
It is not necessary to plug any of the holes on the PPM (as you would on a vacuum manifold) because the design of the manifold and the fritted plates will for each row keep the flow to each position at al times. This is an advantage over vacuum where pressure can be lost if a position is left open or a tube goes dry too fast. The PPM eliminates the need for individual stopcocks at each position when using a vacuum manifold.
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