Custom Multi-element Standards

Custom Standard Request Form

Exaxol welcomes orders for custom multi-element ICP standards as well as other custom standards. Exaxol custom standards are carefully prepared using our high purity standardized solutions that are directly traceable to NIST. The quality of our custom standards is evidenced by the loyalty of our customers who continue to trust us with their custom blend needs year after year. Each custom blend is submitted to a triple check QC Procedure which verifies: elements, concentration, lot numbers, expiration date, aliquots, pipets, and matrices. All certification data is included on the Certificate of Analysis which is signed and certified by two chemists.

* Most custom standards guaranteed for one year.

* Guaranteed accuracy of +/-0.5% of the stated value.

* Made from: The highest purity starting materials (typically 99.999% ) 18 Megaohm Type I Water High Purity Acid Matrices Calibrated Class A precleaned glassware

* Competitive pricing and unsurpassed quality, and service.

Call us if you would like to discuss any questions concerning your special multi-element needs at: 727-524-7732 or 1-800-739-2965. Quotes for custom standards are returned to you within 24 hours. You may use your own records to submit data to us or use our custom request form. We recommend keeping the total concentration of elements in a custom standard below 20,000ppm to minimize potential precipitation problems. Orders are usually shipped within 3 business days from the order date, and rush service is available at no extra charge providing our lab schedule permits.

Contribution to Scientific Publication

For years Exaxol has been a steady contributor to the most comprehensive publication on high purity compounds "Purification of Laboratory Chemicals" by Wilfred Armarego and Christina Li Lin Chai. Information and data provided by Exaxol includes metal impurities detected by ICP-MS on various purified inorganic compounds, most of which include starting material grade and source of manufacture.

ICP-MS results are listed showing decreasing levels with subsequent recrystallizations providing the reader with an idea of what to expect as typical results for a given grade or source. Also, advice on the purification procedures of several inorganic compounds were provided over the years.

For more information on the book "Purification of Laboratory Chemicals", go to Elsevierdirect.

How Exaxol Produces ICP Standards

Multiple quality control steps are observed when preparing our high purity ICP standards and ICP-MS standards. We begin with the purification of the starting materials. This purification is time consuming, but the final, high purity product is our goal. Stoichiometry is controlled during this process, allowing for the streamlining of the standardization checks later on. The purified product is then checked for trace impurities by ICP-MS. Typically, each starting material has a purity between 99.998% to 99.9999%. Other ingredients include high purity acids and ASTM Type I water (18 megaohm). Our glassware is pre-cleaned and pipets, burets and flasks are class A certified and re-tested with documentation. Our semi-micro mettler balance is calibrated regularly with NIST weights. Each batch of stock standard is carefully tested and recorded with lot number, test results via classical wet chemistry, standards used, and standardized to a tolerance of +/-0.3% of specified value. A final check is done by Inductively Coupled Plasma DIRECTLY against the NIST standard reference material. These results are transferred to our certificate sent with each standard. Most standards have a guaranteed shelf life of 18 months from the order date, with the exception of a few elements which have a guaranteed shelf life of one year from the order date.

Ion Chromatography-Analytes & Sources

Often, IC standards are described by an element or by an ionic specie which is the source of the element. An example is nitrogen (element) and Ammonium (ionic specie/polyatomic cation). It is easy to confuse concentration values for such a standard unless one is specific about the "title" of the ionic standard. A ammonium standard of 1000ppm (ug/ml) is for the cation NH4+ at 1000ppm, not Nitrogen at 1000ppm. The nitrogen value is much less, of course due to the hydrogens being factored out of the calculation. Where one talks of a nitrogen standard from an ammonium source the value of nitrogen then becomes 1000ppm, and the ammonium is therefore much higher in value, since you must ADD the hydrogens to the ppm weight.

Likewise, when talking of a nitrogen standard one needs to specify the source. Different sources are ammonium, nitrate, nitrite. Ammonia as a source is actually not accurate as in aqueous solution ammonia ionized to NH4 with water. An "ammonia" standard in aqueous form is not accurate/does not exist. Yes, you can report the value as ammonia if you factor out the extra hydrogen from ammonium, but the actual ion chromatographic results are due to ammonium adsorption/resolution.

A phosphate-phosphorous standard of 1000ppm is P at 1000, not PO4 at 1000. Also, a phosphorous, source phosphate is also P at 1000. A phosphate 1000ppm standard has a 1000ppm value of the PO4, not P. The P will be much less from factoring out the oxygens. This is basic chemistry but it continues to be a source of confusion/mistakes for ordering the correct standard from a standards supplier. We at Exaxol are aware of this and are ready to offer clarification at the time of order minimizing errors down the line. Exaxol has gravimetric/conversion factors for all Ion Chromatography standards at hand and welcome your questions should they arise.

Inside Look at Exaxol

Blending Elements for ICP, ICP-MS, ICP-OES Standards

Blending stock standards for your own custom in house internal standard takes a little time but is very economical provided you already have the stock standards available. Pre-rinse all glassware/plastic ware with dilute nitric or hydrochloric acid, depending on matrix. Rinse 3 times with high purity deionized water. Volumetric pipettes, class A calibrated, are the tool of choice for accurately dispensing aliquots of standard. Take the time to perform the necessary calculations and have a second check done before proceeding. Depending on the final volume of stock solution desired, back calculate for the balance of matrix solution needed (e.g. 2% nitric, etc), and add first to the flask enough matrix so that addition of the stock will not go over flask volume. This also will prevent concentrated stock from possible precipitation with other elements (likely with higher concentrations such as 50,000 μg/ml, and even 10,000 μg/ml). Stock solutions in HF must be made in plastic based flasks. Plastic pipettes are also a must. Generally, keep total concentration of blended elements below a maximum of 30,000ppm (μg/ml) but below 20,000ppm is preferred. Finally, q.s. to volume with appropriate matrix.

pH Buffer Calibration Verification

pH Buffer Calibration work requires calibrated standards that are dependable and accurate as expected to the specifications listed. Providing your equipment is maintained well, measuring pH should not be a chore. Be sure you go through the meter check out procedure for your meter according to manufacturer's directions. Also, perform a check on your electrode. To our surprise, a prominent brand of high quality electrodes did not include the electrode check out procedure in their owner's manual. But with a quick phone call, their tech person explained it to us. Electrode checks involve taking millivolt readings for the electrode while in buffers 7 and 4, then subtracting the difference, and checking that that figure falls within their parameters. Failure of the electrode will result in erratic readings and drift.

Three point calibrations give the most accurate results. For less demanding work, 2 point is useful and quicker.

Buffers sold in the lab market, both by Exaxol and our respected competitors are traceable to NIST Standard Reference Material. Exaxol, in 2003, did some internal testing and found that of 3 brands obtained, not one was within the 0.1 pH unit tolerance guaranteed by the manufacturer, and total variation between the 3 was a staggering 0.5 units.

NIST Traceable means that the manufacturer is using these materials provided by NIST, drying the appropriate ones (some should not be dried), weighing them on a semi micro balance, and dissolving the salts in high purity, carbonate free water to volume. These prepared standards are then used to calibrate the meter before measuring and testing the values of the buffers manufactured in house. This is repeated again for extra accuracy.

Exaxol performs these steps in preparing high quality standards for pH measurement. Our buffers are cataloged as B0470 for your convenience.