Technical Service - Frequently Asked Questions

For certain products, AccuStandard can prepare a second standard if only one lot is available. Ask the Customer Service Representative if this is an option.

Technical Mixtures, or tech mixes, can be mixtures of multiple chemicals or contain multiple isomers of the compound. Chromatograms of these products will have multiple peaks. These peaks are NOT impurities, but components of the product. The use of technical mixtures as reference materials is important for identity of substances (qualitative or quantitative), calibration, assessment of measurement and quality control. Contact our Technical Service Department for additional information.

A matrix blank is used for chlorine, sulfur and nitrogen standards to correct for native chlorine, sulfur or nitrogen content found in the matrix. Our matrices that we use for these standards have a small amount of these elements present in them naturally, and our standards do not correct for the native content.

The intention is for the blank to be run for the appropriate element content, and then have the returned value from the analysis subtracted from the values obtained from the standards in the calibration curve to identify the true element content of the standard. From these corrected values, the true calibration curve can be established. This is why the blank is required for all sulfur, nitrogen and chlorine sets we offer unless the concentration is high enough that the small amount of native elements will not affect the results.

Like most Organic Chemical Reference Material manufacturers, AccuStandard uses ampules. There are many positive reasons for using ampules. One of the most important is that once sealed, they provide a long term, air tight and relatively inert environment that protects the product for long term storage. Ampules preserve the concentration of the analytes since neither the analytes nor the solvent can escape. Ampules do have some inconveniences associated with them, such as snapping them without breaking them and not being able to use a pipette in the neck of the ampule. When snapping ampules, we suggest using an AccuSnap to protect your hands. Alternatively, a folded paper towel, or thick gloves can also provide protection. To transfer from an ampule to another container we suggest either using a clean narrow tipped disposable Pasteur pipette. Once the transfer has been made, the designated portion of the AccuStandard label can be removed from the ampule and attached onto the transfer container for easy identification. To dilute the standard directly from the ampule, we suggest using a CLEAN glass syringe.

Certain chemicals, due to their structure, are more likely to react than others. The conditions that increase this reactivity are time, temperature, solvent, other analytes present, air, light and pH. For example, aldehydes and ketones form adducts when methanol is used as the solvent, certain acids will form salts with bases such as amines, and anthracene will react with oxygen in the air to form anthraquinone. AccuStandard works to formulate the most stable solutions possible, but we cannot change the nature of the chemistry of unstable chemicals so some products will have a short expiration to reflect their anticipated usable shelf life.

Certain of the Chemical Reference Standards are thermally labile. This means they are highly susceptible to change at room temperature or above. For this reason, AccuStandard states the storage conditions on the label. In some of these cases, AccuStandard also recommends that the product ship in a “Cold PAK”, which is a styrofoam container that has an ice pack in it. The purpose of the Cold Pak is to delay the exposure of the product to higher temperatures. The purpose is NOT to keep the product frozen. The product will not immediately go out of specifications when the Cold PAK melts or when the product reaches room temperature. Temperature related effects would begin to exhibit themselves at various times (up to many months) after this happens. The Cold Pak simply delays exposure to higher temperatures. When a product is shipped with a Cold Pak, the customer should also consider requesting next-day delivery (where available) and should avoid having the shipment sent on a Friday unless it is approved for Saturday Delivery.

Sometimes precipitation or crystallization may appear in a product. This can occur with products that are close to saturation and have gotten cold. If this happens, the solution should be warmed to room temperature and then the sealed ampule should be sonicated for approximately fifteen minutes. Invert the ampule several times and allow the sample to return to room temperature. The standard is now ready for use. If the sealed product has crystals at the top of the outside of the ampule, it may indicate a pinhole break in the seal. In this case, please call AccuStandard Customer Service for assistance.

“Sonicate” is written on the label of products with high component concentrations or cold-temperature storage items because some of the analytes may begin to fall out of the solution under these conditions. This precipitation may be so slight that it cannot be detected visually, however, it could affect the outcome of the analysis. If sonication is recommended, the product should be warmed to room temperature and then the sealed ampule should be sonicated in an ultrasonic bath for at least fifteen minutes. Invert the ampule several times to achieve homogeneity and allow the sample to return to room temperature before using.

Even though it doesn’t look like the product is in there, it is. Small amounts (5-10 mg) of powder often are spread over the surface of the vial and cap. If the chemical is a liquid it may coat the walls as a thin layer invisible to the eye. To recover all of the contents contained in a vial of neat material please use the procedure described below:

1. Wipe the outside of the vial (containing the Standard) clean and dry (including the cap).
2. Weigh the entire unit on an analytical balance. Record the weight to the nearest 0.1 mg.
3. Carefully transfer the contents to a volumetric flask using a suitable solvent. Rinse the cap and vial several times to assure a complete transfer.
4. Dry inside and outside of the vial and cap with mild heat or inert gas.
5. Weigh the empty dry vial on the same analytical balance to the nearest 0.1 mg and calculate by difference the amount of material transferred.

Volatile Analytes, especially gases, can be troublesome to analyze. To provide the best possible standard we suggest the following procedures:

1. Keep the ampules cool (follow the storage conditions on the label).
2. Prior to use, invert the ampule several times to ensure the gases are in the solution, not in the headspace. Mixing too vigorously can cause the gases to be lost as well.
3. Use freshly opened ampules whenever possible.
4. When transferring, take care to avoid losses of the very volatile components. For example, holding the barrel of a syringe in your hand can warm it enough to lose some of the most volatile components.
5. If using the purge and trap (PT) system is giving questionable results, try a direct liquid injection. If the results are not as expected, there may be a problem with the PT apparatus.

Poor recoveries on these analytes can result from an injector port problem. Try cleaning the port or replacing the liner. Most times this will correct the problem. Removing the first few inches of a capillary column can also help. Since elevated temperatures contribute to the breakdown problem, using cool on-column injection method scan be used to avoid this issue.

Since Phenols and Nitrosamines can react with the active sites on a column, they can sometimes give inconsistent results from run to run. By saturating these sites, the problem should go away. To do this, run a standard that is between 2 to 5 times higher than your highest calibration point. This can be repeated if necessary until the problem is alleviated. Alternatively silylation can be performed on the column (contact column manufacturer for more details).

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FedEx:

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Agility Logistics (Intl Only)

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