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Standard Solutions Resources

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.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 glasswareCompetitive 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.

The titration of carbonates (typically sodium carbonate) involves a weak base vs a strong acid (Hydrochloric 0.1N) and color change results with simple methyl orange are quite subjective, as the color change is very gradual. A good alternative is mixed methyl orange-xylene cyanole FF.
This will give a sharper color change within a narrower pH scale , the color changing from grey to violet with a minimal addition of titrant hydrochloric acid. Exaxol has this indicator available, catalog #M5056, for your convenience.

pH Buffer Calibration work requires calibration standards that are dependable and accurate to the specifications expected/listed. Providing your equipment is maintained well, measuring pH should not be a chore.Be sure you go through the meter checkout procedure for your meter according to manufacturer's directions. Also, perform a check on your electrode.

Electrode checks involve taking millivolt readings for the electrode when 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. Exaxol 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/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.

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/plasticware with dilute nitric or hydrochloric, depending on matrix. Rinse 3X with high purity DI water. Volumetric pipettes (class A calibrated) are a good tool for this.

Make calculations and have a second check done before proceeding, depending on final volume of stock solution required, back calculate for the balance of matrix solution (eg 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 ug/ml, and even 10,000 ug/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 (ug/ml). Below 20,000 is even preferred. QS to volume with appropriate matrix.

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 or 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 (μg/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 and 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 and conversion factors for all Ion Chromatography standards at hand and welcome your questions should they arise.

For years Exaxol has been a steady contributor to the leading and 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.

Exaxol is enhancing its current offering of conductivity standards to include a TDS (total dissolved solids) value right on the label for the user's convenience. The tolerance for a standard is a realistic and competitive 0.5%. The TDS values will be based on KCl.

Now, an analyst will be able to change modality on a meter without having to change necessarily the standard. For TDS standards not listed on our website just ask one of our customer service people for availability.

TDS is the measure of total dissolved solids in fresh water sources. It includes inorganics and organics that typically can pass through a 2 micron filter. Measurement occurs in reality via conductivity. Cations and anions emit charges and are a source of this "conductivity". There are benchtop as well as portable field versions of these meters for convenience.

Conductivity refers to the electrical conductivity a solution exhibits. Typically it is available as KCl and not NaCl. The units are expressed as micro Mho's/cm or micro Seimens/cm (Seimens unit was the convention in Europe, mho's in the US in the past).The opposite of conductivity is resistivity and its unit is microohms/cm. One can calculate, for convenience, one or the other having just one specification by calculating the reciprocal value. Resistivity it commonly used in water purification systems.

Hardness refers to the amount of calcium and magnesium in water. A hardness solution will have a conductivity, and a separate hardness value expressed in equivalent CaCO3 units and also a TDS value in ppm. But the opposite is not necessarily true. You can have a conductivity and TDS and NOT a hardness if no Ca or Mg ions are present. Exaxol offers standards for Conductivity, both conductivity combined with TDS, and water standards for drinking water/wastewater for hardness as well. Use our search box or click quick links at the left margin of our website.

Formazin has been used as a turbidity standard to test cloudiness in water for many decades. The standard unit of measurement is the NTU or nephelometric Turbidity Unit. Stock solutions are typically at 4000 NTU's. This concentration is stable for at least 1 year, although our customers frequently report stability/reliability/consistency up to the 2 year date from manufacture.

The nature of formazin is such that the particle size varies- between 0.01-10 microns, and because of this characteristic formazin resembles closely to what is described as "real world' samples. Formazin is an insoluble polymer formed by the reaction of 2 compounds.

Another benefit /advantage to formazin is that it is recognised worldwide as the only true primary standard for turbidity measurement. Of course, it is EPA approved. It is accepted and reliable for reporting of lab test results. All other "standards" are reliable only to the extent that they are traceable to formazin.

The other key benefit to a formazin turbidity standard is that it is compatible with any turbidity meter, unlike some modern synthetic substitutes which are sensitive to differences in turbidity meter brands. Formazin turbidity standards are also much more economical to use.

The one disadvantage of a formazin turbidity standard is stability with low concentrations. These must be prepared on a daily basis when required from a stronger 2000 or 4000 NTU solution. As always, any formazin standard needs to be shaken briefly before each use. Reproducible results from dilutions of Exaxol offers certified Formazin turbidity standards at competitive prices, and with a quick order turnaround. Different values of NTU are listed on our website with their respective shelf life.

Our embedding/mounting media is ideal for frozen tissue analysis for surgical pathology and frozen sectioning. It dries clear, does not curl, is non toxic, and there are no traces after drying. Supports tissue during cryotomy. Convenient squeeze bottle with yorker squirt tip.

With over 20 years experience in manufacturing histology /hematology products, as well as private labeling for national Brands, Exaxol offers this product at a fraction of the cost. 1.5 year shelf life. Also, convenient/cost saving 6- pack (6X 125ml bottles).

Hematoxylin stains are commonly employed for histologic studies, often employed to color the nuclei of cells (and a few other objects, such as keratohyalin granules) blue. The mordants used to demonstrate nuclear and cytoplasmic structures are alum and iron, forming lakes or colored complexes (dye-mordant-tissue complexes), the color of which will depend on the salt used. Aluminum salt lakes are usually colored blue white while ferric salt lakes are colored blue-black.

The three main alum hematoxylin solutions employed are Ehrlich's hematoxylin, Harris's hematoxylin and Mayer's hematoxylin. The name "haemalum" is preferable to "hematoxylin" for these solutions because haematein, a product of oxidation of Hematoxylin, is the compound that combines with aluminum ions to form the active dye-metal complex. Alum hematoxylin solutions impart to the nuclei of cells a light transparent red stain which rapidly turns blue on exposure to any neutral or alkaline liquid.

Alum or potassium aluminum sulfate used as the mordant usually dissociates in an alkaline solution, combining with OH of water to form insoluble aluminum hydroxide. In the presence of excess acid, aluminum hydroxide cannot be formed thus failure of aluminum hematoxylin dye-lake to form, due to lack of OH ions. Hence, acid solutions of alum hematoxylin become red. During staining alum hematoxylin stained sections are usually passed on to a neutral or alkaline solution (e.g. hard tap water or 1% ammonium hydroxide) in order to neutralize the acid and form an insoluble blue aluminum haematin complex. This procedure is known as "blueing".

When tap water is not sufficiently alkaline, or is even acid and is unsatisfactory for blueing hematoxlin, a tap water substitute consistibg of 3.5 g NaHCO3 and 20g MgSO4X7H2O in one liter of water with thymol (to inhibit formation of moulds), is used to accelerate blueing of thin paraffin sections. Addition of a trace of any alkali to tap or distilled water also provides an effective blueing solution;a few drops of strong ammonium hydroxide or of saturated aqueous lithium carbonate, added immediately before use, are sufficient for a 400 ml staining dish full of water. Use of very cold water slows down the blueing process, whereas warming accelerates it. In fact, the use of water below 10 degrees Celsius for blueing sections may even produce pink artifact discolorations in the tissue.

The straining of nuclei by hemalum does not require the presence of DNA and is probably due to binding of the dye-metal complex to arginine-rich basic nucleoproteins such as histones. The mechanism is different from that of nuclear staining by basic (cationic) dyes such as thionine or toludine blue. Staining by basic dyes is prevented by chemical enzymatic extraction of nucleic acids. Such extractions do not prevent staining of nuclei by hemalum.

EXAXOL Hematoxylin stains are mercury free and include a non toxic oxidizer as an aging additive.