ES Industries has been producing HPLC columns for over 25 years. During this period of time, we have gained extensive insight into and an in-depth understanding of the factors affecting the quality and consistency of HPLC columns. This has resulted in the transformation of our company and an adaptation of a Quality Focus Program which is incorporated into every facet of our production process.
The Quality Focus Program
The ES Industries Quality Focus Program (QFP) required a critical review of our manufacturing processes and an institution of strict quality control procedures. The review process included all steps starting with the silica, bonding reagents, bonding procedures, batch testing, column packing, and ending with the final column test. The QFP is composed of five key steps which begins with the application of a systematic method for each packing material.
Ultra High Purity Spherical Silica
The finest silica based HPLC columns start with the highest quality spherical silica. High quality columns can not be manufactured from low quality silica. High quality spherical silica results from the control and measurement of several key parameters.
Metal Free Silica
One of the most important parameters to control during the production and use of silica is metal content. Metals are considered to be the primary impurity in silica and reversed-phase packings because metal contamination will result in undesirable effects. Metal impurities are strong adsorption sites for complexing solutes. Chelating analytes can bind directly to metal ions causing poor peak shape. Metal ions can also increase the acidity of adjacent silanol groups, resulting in tailing of basic compounds. The presence of metal ions can influence bonding of the stationary phase, reducing coverage and increasing residual silanols.
Metal contamination generally stems from the silica preparation process and from the synthesis of bonded phases. At ES Industries we utilize only the finest synthetically produced metal free ultra-high purity silica available. The metal free character of this silica material is carefully protected from contamination. This includes possible contamination from reagents, equipment, and material handling which are monitored and minimized. The silica is tested for metals several times before the packing materials are used to produce HPLC columns. These procedures ensure that ES Industries HPLC Columns can provide repeatable performance for even the most challenging analysis. The chromatographer can rest assured that a difficult separation is not the product of an uncontrolled metal interaction.
Controlled Particle Size, Pore Size, Surface Area, and Surface Hydroxylation
The most efficient and durable columns are produced from monodispersed particles. Unfortunately, even the highest quality spherical silica available is not monodispersed. There is a distribution of particle sizes associated with all silica material. The key to high performance spherical silica is to achieve the tightest particle size distribution possible. HPLC columns produced from a tight distribution of silica particle sizes are reliable for analysis of closely eluting components. Many analysis fail because they were developed on columns containing widely dispersed silica particles. This wide dispersion leads to fluctuations in column efficiencies and can ultimately lead to breakdown in resolution of separated components. At ES Industries we obtain precise measurements of particle distributions for all bulk silica utilized. Only the bulk silica that conforms to the set parameters for tight particle size distribution is released for use in production. These strict tolerances ensure that all columns produced at ES Industries meet the highest efficiency requirements.
Other specific parameters affecting column performance include pore size distribution and surface area consistency. Without a tight pore size distribution a bulk silica material will contain many micropores. These micropores will produce poor peak shapes for many components and are an undesirable silica feature. At ES Industries we only use silicas that meet the highest requirements for pore size distribution.
Surface area consistency is critically important to bonded phase reproducibility. Surface area measurements are carefully reviewed at ES industries and only silicas with consistent surface areas can be used for Chromegabond® columns. As a final step, we treat all of the qualified silica before bonding to ensure that the particle surface is completely hydroxylated. A hydroxylated surface ensures that complete surface coverage is produced during phase bonding reactions. Unreacted silanol groups can lead to peak tailing and adsorption of critical analyte components. The treatment process maximizes bonded phase coverage while minimizing the number of silanol groups. Our proprietary surface hydroxylation procedure yields the best deactivated columns available commercially.
Bonding Reagents and Bonding Chemistry
Once the high-quality ultra-pure silica has been established, bonding of the stationary phase is the next critical step. ES Industries has extensive knowledge and experience in developing and producing bonded reagents for HPLC stationary phases. We are experts in the production and purification of HPLC grade stationary phase bonding reagents. We have developed technology that primarily consists of monomeric bonding chemistries. Our reagents reliably bond to the silica particle surface. We have discovered that bonding strategies, which depend on polymeric bonding reagents, are unpredictable and yield stationary phases with poor reproducibility. In addition, bonding reagent purification is critically important to stationary phase consistency and reproducibility. Many off-the-shelf bonding reagents are low purity, and many contain significant amounts of isomers. These impurities and isomers can lead to variability in the final bonded stationary phase. At ES Industries we carefully purify and analyze the composition of all bonding reagents to ensure consistent stationary performance.
The quality of the bonded phase does not end with stable bonding chemistry or highly purified reagents. The bonding process is completed when the stationary phase is thoroughly washed to remove reaction by-products, catalysts, and unreacted chemicals. This cleansing procedure is a necessity for production of stable and repeatable packing materials. Without this step the packed column bed would be unstable and baseline performance would be unacceptable. At ES Industries we subject all of our packings to a battery of washing procedures including high pressure solvent washing and super critical fluid extraction. These washing procedures yield high quality packings that produce columns of unmatched performance and stability.
Column Packing and Hardware
One of the most important parts of the whole HPLC column production sequence is the packing of the column. Stationary phases have been carefully prepared and washed, but unless these materials are packed with the highest precision possible, the integrity of the packing material can be lost. Over the last 25 years of HPLC column production, we have developed and refined techniques for packing columns. As a result of our experience, we now utilize the most advanced column packing technology in the industry. This technology enables us to pack the finest columns available across a wide variety of internal diameters from 0.5 mm to 4 inch and in lengths from 10 mm and 500 mm.
A significant part of our superior packing technology resides in unsurpassed column hardware. Only end fittings and column tubing of the highest quality and performance is acceptable for ES Industries. Stainless steel column tubing with highly polished, mirrored finished internal bores are used. In addition to our strict performance criteria for stainless steel columns, we apply the same requirements to PEEK and glass lined columns. As a result, the chromatographer can be confident that they are receiving the highest quality column hardware in the industry.
At ES Industries every step of our column production sequence is strictly monitored and controlled by an extensive battery of tests. These tests are applied at each step including silica particle formation, bonding reagents and reactions, column hardware, and packing. These tests ensure the quality of the final product with each assay designed to measure a customer-critical parameter.
The final batch test for each product is carefully designed and tailored to test the performance standard set for each phase. In addition to batch testing, each column is tested individually to check the integrity and performance of the packed bed.
Every ES Industries column is guaranteed to deliver the highest plate counts and most symmetrical peaks for even the most difficult analysis. We are confident that our Quality Focus Program will deliver the highest quality and most reliable HPLC columns available to the HPLC chromatographer.