Industries Information

Autosamplers are automated sample loaders, usually robotic, used with chromatography, atomic absorption and other analytical technologies. Autosamplers are designed especially for laboratories that process large numbers of samples on a routine basis. They are used for a variety of tasks, ranging from general HPLC needs up to dedicated solutions for high sample throughput.  Most are designed to interface with PC systems, and some autosamplers can be remotely computer controlled.  Complete remote control of all operational parameters such as injection time, number of injections per vial, rinses, three auxiliary contact closures, and internal injection valve actuation are available by means of optional serial or parallel interfaces.

Autosamplers may use a variety of receptacles to accept sample or reagent injection. These include simple vials, wellplates, or graphite furnace sample cups.  Wellplates, also known as microplates, are plastic plates or cassettes containing a specified number (typically 96 or 384) of small wells arranged in rows.  Researchers commonly use them to conduct numerous chemical reactions at the same time. Graphite furnaces are used in atomic absorption spectroscopy to atomize a sample.  The sample crucible is usually a cup cut from hollow aluminum or magnesia tubing.  Syringes or injector valves are the usual methods used to inject materials into the testing receptacles. Some varieties of autosamplers are specifically configured for one type of receptacle platform, while others can use them interchangeably.

Autosamplers are used in a wide variety of applications.  These can range from analysis of Organic Volatile Impurities (OVIs), plastics, polymers, blood alcohol analysis, and flavors, to semiconductor applications and any ultratrace analysis of commonly occurring elements. Clinical applications including drinking water testing, wastewater analysis and reclamation projects, soil composition, toxicity analysis.  In addition, a range of QA/QC control procedures, such as the EPA protocols, can be automated using the optional Intelligent Sequencing Software.

 Specialty chromatographs and accessories are specialized or proprietary products related to chromatography and chromatography instruments. Chromatography is an analytical technique used in the chemical separation of mixtures and substances. It depends on the differential distribution of a solute between mobile and stationary phases. As the solute passes through the stationary phase, each constituent of the mixture separates at different speeds. These constituents can then be analyzed with chromatography instruments such as chromatograms, chromatographs, and ultra low pressure calibration devices. The proper selection of specialty chromatographs and accessories requires an analysis of product specifications and capabilities. Typically, a specialty chromatograph is used to perform chromatographic separation and to produce a specialty chromatogram, the pattern of bands of substances separated by a chromatograph column. Suppliers of specialty chromatographs and accessories are located across the United States and around the world.

Specialty chromatographs and accessories are used with many different types of chromatography and chromatography instruments. Common chromatographic techniques include thin layer chromatography (TL), high performance thin layer chromatography (HPTLC), high pressure liquid chromatography (HPLC), gas chromatography (GC), mass spectrometry (MS), and gas liquid chromatography (GLC). A high pressure liquid chromatograph (HPLC) uses a liquid mobile phase to separate the components of a mixture. The components are dissolved in a solvent and forced to flow through a chromatographic column under high pressure. Medium pressure liquid chromatography is used with substances that cannot be resolved chromatographically at atmospheric pressures. Gas chromatographs (GC) consist of a flowing mobile phase, an injection port, a separation column containing the separation phase, and a detector. For the detector, a gas chromatograph can use thermal conductivity, flame ionization, atomic emission, electron capture, photo ionization, flame photometric, chemiluminescence spectroscopy, and nitrogen phosphorous.

Specialty chromatographs and accessories are used in a variety of applications and industries. Examples include biochemistry, food and beverage processing, and the manufacture of pharmaceutical products. Specialty chromatographs and accessories are also used in the production of perfumes and the separation of chemical solvents.

Instrument calibration service providers calibrate various instruments including many types of process monitoring devices and analytical equipment including, flow instruments such as flow meters and sensors, gauges, totalizers or valve position indicators; pressure and vacuum instruments such as pressure sensors or gauges, meters, transducers or vacuum pumps; force, weight or mass instruments including strain gauges, load cells, scales or torque monitors; temperature instruments including thermocouple, RTD or thermistor type devices; humidity instruments including absolute or relative humidity, moisture content or dew point measuring devices; multimeter or electrical meters, either analog or digital; physical or dimensional instruments such as calipers, and micrometers, fiber optic or lightwave instruments including multiplexers, analyzers, isolators etc; rf or microwave instruments such as transmitters, receivers, antennas etc; generators; power supplies including any AC or DC power supply or conditioners; oscilloscopes or scopes or chart recorders; and signal or function analyzers.

Providers of instrument calibration services may have one of several calibration quality requirements.  These requirements include ISO / IEC 17025, ANSI / NCSL Z540-1, A2LA, ISO 9001, ISO 9002, NIST, or GMP / FDA.  ISO 17025 addresses the proficiency of the organization to perform the testing and calibration activities. It is a standard geared towards technical qualification and deals heavily with measurement uncertainties. This is layered on top of an ISO 9000 certification, which is a standard, used for total company quality system.  Formerly MIL-STD 45662A, American National Standard ANSI / NCSL Z540-1 is a requirements document titled "Calibration Laboratories and Measuring and Test Equipment - General Requirements."  A2LA is the American Association for Laboratory Accreditation.  A2LA accreditation is defined as formal recognition of an organization’s technical competency to perform specific tests, types of tests, or calibrations.  ISO 9001 sets out the requirements for an organization whose business processes range all the way from design and development, to production, installation and servicing.  ISO 9002 is for an organization, which does not carry out design and development. It does not include the design control requirements of ISO 9001 - otherwise, its requirements are identical.  Calibrations are traceable to National Institute of Standards and Technology.  GMP, or Good Manufacturing Practice, is a quality requirement for instruments involved in sanitary processing; such as pharmaceuticals or foods. FDA, or Food and Drug Administration, is a similar quality requirement.

Specific services offered by providers of instrument calibration services include, rapid turnaround, on-site calibration, pick up and delivery, calibration documentation, in-house contract lab services, and online documentation.  Rapid turnaround means the supplier offers quick turnaround on instrument calibration services, typically in a few days.  A supplier offering on-site calibration has personnel and/or equipment for on-site calibration work, eliminating the added expense of taking the instrument off line and shipping it.  The supplier offers pick-up and delivery services to minimize cost and time associated with using in-house personnel.  Documentation or test reports show calibration information such as "as found" and "as left" data, next scheduled calibration, etc with calibration documentation.  A supplier that offers in-house contract lab services has capabilities and resources for setting up an in-house contract lab for supplier - minimizing any downtime or lag in getting instruments quickly calibrated.  Supplier has online documentation system to access history, calibration certifications and recalibration notifications.

High performance liquid chromatograph (HPLC) detectors pass a beam of light through a column effluent as the fluid passes through a low-volume flow cell. Variations in light intensity are recorded and a chromatograph is generated. HPLC detectors use several detection methods. Ultraviolet (UV) detectors measure the ability of a sample to absorb light at one or more wavelengths. Light scattering detectors nebulize the effluent, vaporize the solvent, and then detect droplets in a light scattering cell. Electrochemical detectors measure the current from the oxidation/reduction reaction of an analyte at a suitable electrode. Radiochemical detectors use tritium or carbon-14 to detect the fluorescence associated with beta-particle ionization. Mass spectroscopy detectors ionize a sample and use a mass analyzer to detect the ion current. Nuclear magnetic resonance detectors irradiate nuclei that are placed between the poles of a strong magnet. The radiation is absorbed, the parallel nuclei enter a higher energy state, and each atom produces a spectra specific to its location and chemical composition. Some HPLC detectors measure the change in the refractive index of the column effluent passing through the flow cell. Others detect the fluorescence that occurs when compounds are excited by shorter wavelength energy and emit higher wavelength radiation.

Important specifications for HPLC detectors include dynamic range, detector wavelength, response time, flow cell volume and flow cell rate. Dynamic range allows for the quantification of unknown samples using a multi-point calibration curve. It indicates when the peak area is directly proportional to the solute amount so that, for example, doubling the solute amount results in a doubling of peak area. Detector wavelength indicates the emission wavelength. Response time is the amount of time between a solute’s entry into an HPLC detector and the generation of a chromatogram. Flow cell volume and flow cell rate are measurements of capacity and efficiency, respectively. Maximum pressure rating is another important specification to consider when searching for HPLC detectors.

HPLC detectors vary in terms of general features, display options, and interface options. General features include self-calibration, self-test diagnostics, data storage, and programmability. Devices with a built-in chromatograph and application software are commonly available. Some HPLC detectors are suitable for extreme temperatures. Others output an analog voltage, analog current, frequency, or pulse. Examples include amplitude modulation (AM), frequency modulation (FM), pulse width modulation (PWN), sine waves and pulse trains. Analog devices usually include an analog meter and a front panel with switches and knobs. Digital devices often provide a serial or parallel computer interface and a video display. Serial protocols include universal serial bus (UBS), RS232, RS422, and RS485.

High performance liquid chromatography (HPLC) is a separation technique that uses liquid mobile phase to separate the components of a mixture. The sample is first dissolved in a solvent, then forced to flow through a chromatographic column under high pressure. Within the column, the mixture is resolved into its component parts. Individual HPLC columns may use any one of a number of different phases or processes to induce this resolution including normally bonded phase, reversed phase, size exclusion, ion exclusion, and ion exchange.

Normally bonded phase HPLC columns are composed of a stationary bed, which is strongly polar in nature, and a mobile phase that is non-polar. Polar samples are thus retained on the polar surface of the column packing longer than less polar materials. This technique works well with water-sensitive samples, analytes that are insoluble in water, certain geometric isomers that are difficult to separate by reversed-phase, and class separations. Organic solvents used in normal-phase separations are more Mass Spectroscopy (MS) friendly than some of the typical buffers used in HPLC. In reversed-phase HPLC, operating conditions sometimes must be dramatically modified to allow compatibility with MS detection.

Reversed phase HPLC columns are the inverse of normal phase chromatography. The stationary bed is non-polar (hydrophobic) in nature, while the mobile phase is a polar liquid, such as mixtures of water and methanol or acetonitrile. The lower the polar differential, the longer the material is retained.

In size exclusion the HPLC column is filled with material having precisely controlled pore sizes, and the sample is screened or filtered by the stationary phase according to its solvated molecular size. Larger molecules are rapidly washed through the column, and smaller molecules penetrate the pores of the packing particles and elute later.

In ion exclusion the anions are retained longer on the stationary phase than on anion-exchange columns. Quantification is therefore simplified in the event large amounts of cationic contaminants are present in the sample.

In ion exchange, the stationary bed with the HPLC column has an ionically charged surface of opposite charge to the sample ions. This technique is used almost exclusively with ionic or ionizable samples. The stronger the charge on the sample, the stronger it will be attracted to the ionic surface and thus, the longer it will take to elute. The mobile phase is an aqueous buffer, where both pH and ionic strength are used to control elution time.

High performance liquid chromatographs (HPLC) use a liquid mobile phase to separate the components of a mixture. The components are dissolved in a solvent and forced to flow through a chromatographic column under high pressure. In the column, the mixture is resolved into its components. The components flow through a detector and a chromatogram is generated. Most high performance liquid chromatographs (HPLC) use high-pressure pumps to force solvents through packed stationary beds. Isocratic pumps use constant mobile phase composition to elute compounds. By contrast, gradient pumps vary the strength of the organic solvent to elute different compounds. Pumps with flow control are well-suited for high performance liquid chromatographs (HPLC) that deliver gradients automatically. Specifications such as flow rate, maximum pump pressure, and pump accuracy vary among devices. In simple systems, the sample is introduced with an injection valve. More complex high performance liquid chromatographs (HPLC) incorporate an autosampler with a microprocessor.   

High performance liquid chromatographs (HPLC) use several detection methods. Ultraviolet (UV) detectors measure the ability of a sample to absorb light at one or more wavelengths. Light scattering detectors nebulize the column effluent, vaporize the solvent, and then detect droplets in a light scattering cell. Electrochemical detectors measure the current from the oxidation/reduction reaction of an analyte at a suitable electrode. Radiochemical detectors use tritium or carbon-14 to detect the fluorescence associated with beta-particle ionization. Mass spectroscopy detectors ionize a sample and use a mass analyzer to detect the ion current. Nuclear magnetic resonance detectors irradiate nuclei that are placed between the poles of a strong magnet. The radiation is absorbed, the parallel nuclei enter a higher energy state, and each atom produces a spectra specific to its location and chemical composition. Some high performance liquid chromatographs (HPLC) measure the change in the refractive index of the column effluent passing through the flow cell. Others detect the fluorescence that occurs when compounds are excited by shorter wavelength energy and emit higher wavelength radiation.

High performance liquid chromatographs (HPLC) vary in terms of general features, display options, and interface options. General features include self-calibration, self-test diagnostics, data storage, and programmability. Devices with a built-in chromatograph and application software are commonly available. Some high performance liquid chromatographs (HPLC) are suitable for extreme temperatures. Others output an analog voltage, analog current, frequency, or pulse. Examples include amplitude modulation (AM), frequency modulation (FM), pulse width modulation (PWN), sine waves and pulse trains. Analog devices usually include an analog meter and a front panel with switches and knobs. Digital devices often provide a serial or parallel computer interface and a video display. Serial protocols include universal serial bus (UBS), RS232, RS422, and RS485.

 Gas chromatography detectors (GC detectors) identify solutes as they exit the chromatographic column. As solutes are eluted from the gas chromatography column they interact with the detector. The GC detector converts this interaction into an electrical signal that is sent to the data system. The magnitude of the signal is plotted versus time (from the time of injection) and a chromatogram is generated.  GC detectors use one of several technology types to identify solutes as they exit the column.  These methods include thermal conductivity, flame ionization, atomic emission, electron capture, photoionization, flame photometric, chemiluminescence spectroscopy, and nitrogen phosphorous.

Thermal conductivity GC detectors consist of an electrically heated wire or thermistor. The temperature of the sensing element depends on the thermal conductivity of the gas flowing around it. Changes in thermal conductivity, such as when organic molecules displace some of the carrier gas, cause a temperature to rise in the element, which is sensed as a change in resistance.

Flame ionization GC detectors consist of a hydrogen / air flame and a collector plate. The effluent from the GC column passes through the flame, which breaks down organic molecules and produces ions. The ions are collected on a biased electrode and produce an electric signal.

Atomic emission GC detectors simultaneously determine the atomic emissions of many of the elements in analytes that elute from the GC capillary column. As the eluant comes off the capillary column it is fed into a microwave powered plasma (or discharge) cavity where the components are destroyed and their atoms are excited by the energy of the plasma. The light that is emitted by the excited particles is separated into individual lines via a photodiode array.

Electron capture detectors use a radioactive Beta emitter (electrons) to ionize some of the carrier gas and produce a current between a biased pair of electrodes. When organic molecules contain electronegative functional groups, such as halogens, phosphorous, and nitro groups pass by the detector, they capture some of the electrons and reduce the current measured between the electrodes.

Photoionization GC detectors use ultraviolet light as a means of ionizing an analyte exiting from a GC column. Electrodes collect the ions produced by this process. The current generated is therefore a measure of the analyte concentration.

Chemiluminescence spectroscopy detectors use quantitative measurements of the optical emission from excited chemical species to determine analyte concentration. Usually the emission is measured from energized molecules rather than excited atoms. The bands of light determined by this technique emanate from molecular emissions and are therefore broader and more complex than bands originating from atomic spectra.

Nitrogen phosphorous GC detectors burn the compound in plasma surrounding a rubidium bead supplied with hydrogen and air. Nitrogen and phosphorous containing compounds produce ions that are attracted to the collector. The number of ions hitting the collector is measured and a signal is generated.

In specifying a GC detector the detection limit or sensitivity, dynamic range and temperature range are all important parameters.  GC detectors also have important parameters that are specific to each technology type.

 Gas chromatograph columns (GC columns) are tubes through which solutes being measured pass at a rate primarily determined by their physical properties and the temperature and composition of the column. The speed at which solutes move through the column can be weighed against a number of variables to determine its specific properties.  As each solute elutes from the column, it enters a heated detector. An electronic signal is generated upon interaction of the solute with the detector. This signal is recorded and plotted.

GC columns are either packed or capillary style. Packed GC columns are typically of glass or stainless steel coil construction. They are generally one to five meters in total length with an inner diameter of five millimeters.  These devices are filled with a stationary phase, or packing coated with the stationary phase. Capillary GC columns, also known as open tubular columns, are composed of two major parts: tubing and stationary phase. A thin film (0.1-10.0 micro meters) of high molecular weight, thermally stable polymer is coated onto the inner wall of small diameter tubing, usually 0.05-0.53 mm I.D.

Among capillary columns, there are three sub types to choose from. Support coated open tubular (SCOT) columns have an inner wall of the capillary that is lined with a thin layer of support material, such as diatomaceous earth, onto which the stationary phase has been adsorbed. Porous layer open tubular (PLOT) columns are capillary GC columns in which the stationary phase is based on an adsorbent or a porous polymer. Wall-coated open tubular (WCOT) columns consist of a capillary tube whose walls are coated with liquid stationary phase.

One of the most important specifications for GC columns is the material. Typically they are made of stainless steel, glass or a silicate glass such as alkali-borosilicate glass, borosilicate glass or alumina silicate glass. Length of the columns is very important as well, as are the inner diameter and the film thickness. Another factor to consider is the rated operating pressure required for the application.

Gas chromatographs separate organic chemical mixtures according to physical properties. Instruments consist of a flowing mobile phase, an injection port, a separation column with a stationary phase, and a detector. Differences in partitioning behavior between the mobile phase and the stationary phase cause the separation of compounds. Gas chromatographs use many different detection methods. Choices include: thermal conductivity detectors (TCD), flame ionization detectors (FID), atomic emission detectors (AED), electron capture detectors (ECD), photo-ionization detectors (PID), flame photometric detectors, and nitrogen phosphorous detectors. Gas chromatography that uses chemiluminescence spectroscopy is also available. Some gas chromatographs are used with agricultural chemicals and pesticides, cosmetics and fragrances, drugs and pharmaceuticals, electronics, energy and environmental applications, food and beverage processing, forensics and narcotics, industrial gases, medical and biological applications, or metals and welding. Others are used with organic and inorganic chemicals; paint, castings, and inks; paper, pulp and wood; petroleum products; plastics, polymers, and resins; or soaps and cleaners.  

Oven operation, pump specifications, and injection operation are the main parameters for gas chromatographs. Devices with a column oven carry specifications such as operational method and oven temperature range. There are two operational methods for columnar ovens: isothermal or constant-temperature, and variable or temperature-programmable. Flow control and inlet pressure range are common pump specifications. In terms of injection operation, parameters include number of injection ports, injection method, and column injection. For optimum efficiency, a sample should not be too large for a column, and is best introduced as a "plug" of vapor. There are two choices for column injection method: split/split-less and packed column. With split or split-less column injection, the injector has an additional set of gas lines, providing another path for the vaporized sample. This extra line is sometimes called a split line or vent. Importantly, the amount of gas that exits the split line controls the amount of sample that enters the column. With packed column injection, all samples enter the column - including the gaseous sample, solvent, and analyte.

Specifications for gas chromatographs may include user interface options, display options, additional output options, and general features and functionality. Local interfaces use an analog front panel, a digital front panel, or a computer interface with parallel or serial communications. Analog meters, digital readouts, and video displays are common choices for display options. Additional output options include: analog voltage, frequency or modulated frequency, analog current, and switch or relay contacts. Some gas chromatographs are programmable, self-calibrating, or include a built-in chromatogram. Others provide data storage options and are designed for extreme environments. Gas chromatographs that accept liquid samples and include self-test diagnostics are also available.