Industries Information

Titration instruments are used to determine the concentration of dissolved substances. Titration is based on a complete chemical reaction between the analyte and a reagent or titrant of known concentration that is added to the sample. The analyte is the substance which a laboratory test is designed to measure. The reagent or titrant is the substance that produces a chemical reaction in order to determine the presence of the analyte. There are two basic titration methods: manual and automatic. Manual titration is performed with a burette, a piece of laboratory glassware that has volumetric graduations along its length and a tap or stopcock on its bottom. Automatic titration is performed with an auto-titrator, an electrically-powered laboratory instrument that can be interfaced to a personal computer (PC). Typically, automatic titration instruments are used for repetitive titrations.

indication methods. Voltametry, a technique also known as the Karl Fischer water determination method, measures the concentration-dependent potential of a solution against a reference potential. Potentiometry, redox and precipitation measure the potential at a constant electric current. Photometry, complexometry, and turbidimetry measure the light transmission of a colored or turbid solution with a photometric sensor. With Titration instruments differ in terms of addition and indication methods. There are two titrant addition methods: volumetric and coulometric. Volumetric devices add the titrant directly to the sample. Coulometric devices generate the titrant electromechanically. There are many different titrationamperometry, the current flowing in a sample is measured at a constant potential. Titration instruments that measure conductivity include a conductivity meter while devices that measure temperature include a sensor. 

Selecting titration instruments requires an analysis of product specifications, features, display types, and computer interfaces. Product specifications for titration instruments include concentration range and reaction time. Some instruments provide data storage and temperature-compensation features. Others measure solids or gases. In terms of display types, titration instruments with analog or digital front panels are commonly available. Analog user inputs include potentiometers, dials and switches. Digital front panels can be setup or programmed using a digital keypad or menus. Titration instruments that can be controlled or monitored via a computer interface use serial or parallel communications and may include application software. RS232, RS485 and universal serial bus (USB) are common serial interfaces. The general-purpose interface bus (GPIB) is a common parallel interface.

Solid phase extraction (SPE) is an extraction method that uses a solid phase and a liquid phase to isolate one, or one type, of analyte from a solution. It is usually used to clean up a sample before using a chromatographic or other analytical method to quantify the amount of analyte(s) in the sample. The general procedure is to load a solution onto the SPE phase, wash away undesired components, and then wash off the desired analytes with another solvent into a collection tube. Solid-phase extractions use the same type of stationary phases as are used in liquid chromatography columns. The stationary phase is contained in a glass or plastic column above a frit or glass wool. The column might have a frit on top of the stationary phase and might also have a stopcock to control the flow of solvent through the column. Commercial SPE cartridges have 1-10 mL capacities and are discarded after use.

Separation techniques covers a wide range of instrumentation used to separate samples into their component parts for analysis and measurement. Centrifuges, capillary electrophoresis, laboratory filters, titration, Solid-phase extraction (SPE), and chromatography are major groupings within this family. Chromatography instruments are divided into two main areas, high performance liquid chromatographs (HPLC) and gas chromatographs (GC), and their related columns and detecting devices.

Sample dryers are used to remove liquids from a sample through techniques such as freeze drying, spray drying, and evaporation. Drying or dehydration is a mass transfer process that causes the removal of water. There are many types of sample dryers. Examples include freeze dryers and spray dryers. A spray dryer consists of a feed pump, atomizer, air heater, air disperser, drying chamber, and systems for exhaust air cleaning and powder recovery. Spray drying is the process of mixing and drying slurry to form a homogeneous mixture of powders. The powders are mixed with a solvent, and then the mixture is sprayed into the air, so that the solvent evaporates leaving the mixed powders. By contrast, a freeze dryer freezes the material and then reduces the surrounding pressure. Freeze drying allows the frozen water in the material to sublimate directly from the solid phase to gas.

Selecting sample dryers requires an analysis of performance specifications and application requirements. Some sample dryers use a two-stage process which drops the sample’s temperature twice, removing moisture in two individual trap assemblies. Drying can also be done by using evaporators to apply of dry, heated air. This causes the evaporation of surface water, which is replaced by water internally. The process of extreme drying is called desiccation. Desiccators create a dry environment with electronically controlled storage. Lyophilization technology uses the principle of freeze drying in preserving a perishable material. Operating conditions and sample dryer design are selected according to the drying characteristics of the product and powder specification.

Sample dryers are designed and manufactured to meet most industry specifications. They are used in many applications. Examples include pharmaceuticals, chemical synthesis, food preservation, semiconductor wafers, and obtaining absolute alcohol. Sample dryers should adhere to various food processing standards specified by the International Standards Organization (ISO).

Reactors (or bioreactors or fermenters as they are often called) are at the heart of the fermentation process. They are used for growing cells. Reactors are designed to meet the specific needs of the cells namely: optimal mixing, optimal temperature and optimal pH. In some cases, reactors continuously supply nutrients or precursors to produce a particular product. Bioreactors are often computer controlled to ensure that optimal conditions are met.

Reactors are available in a number of designs including bubble column, airlift, flocculated bed, fluidized bed, packed bed, and stirred tank.  Bubble column reactors are tall reactors, which use air alone to mix the contents. Airlift reactors are similar to bubble column reactors, but differ in that they contain a draft tube. The draft tube is typically an inner tube, which improves circulation and oxygen transfer and equalizes shear forces in the reactor.

Flocculated cell reactors retain cells by allowing them to flocculate. These reactors are used mainly in wastewater treatment. In fluidized bed reactors, cells are "immobilized" small particles, which move with the fluid. The small particles create a large surface area for cells to stick to and enable a high rate of transfer of oxygen and nutrients to the cells. In packed bed reactors, cells are immobilized on large particles. These particles do not move with the liquid. Packed bed reactors are simple to construct and operate but can suffer from blockages and from poor oxygen transfer.

Stirred tank reactors use mechanical stirrers (impellers) to mix the reactor to distribute heat and materials (such as oxygen and substrates).

Reactors use different measurement scales to read the reactions taking place.  From smallest to largest they are laboratory scale, pilot scale, and production or industrial scale. The laboratory scale is used for small-scale experiments of kinetics and yield studies.  They are primarily shake flasks and small bioreactors.  This scale is used to complete a preliminary economic evaluation of experiments. Pilot scale reactors are usually in the range of 100 to 1,000 liters and are utilized in kinetic and mass transfer studies.  They are used for economic evaluations, scale-up studies and downstream processing.  Reactors using the industrial scale are for commercial production applications in the range of 1,000 to 1,000,000 liters.  Their uses include commissioning, troubleshooting, improvement and optimization.

Laboratory shakers and rotators are used to blend or agitate samples within flasks or tubes. These devices consist of a housing containing the motor and control panels, upon which an agitation platform is attached. The platform may have simple grooves for supporting flasks and tubes horizontally as the device moves, or it may have basket style holders that keep the sample holders upright. Unlike mixers, which tend to shred or damage constituent sample materials, laboratory shakers generally leave sample material intact, although mixed. Many laboratory shakers are available with some form of temperature control to incubate, foster or retard reactions, or to maintain stasis.

There are many styles of laboratory shakers available, categorized by their manner of shaking motion. While this list is not all-inclusive, it does cover the most common styles. These are reciprocating, rocking, rolling, rotating, orbital, and wrist action.

In reciprocating motion devices, the shaker moves alternately backward and forward. Similarly, rocking motion devices are capable of a rocking or seesaw motion. Rolling devices slide from side to side with a slight upward, then downward tilt. Rotating shakers turn about an axis and function similarly to centrifuges, although they do not reach the same speeds.

Orbital shakers are the most common variety of laboratory shakers. They create an orbital (horizontal circular) shaking motion sufficient for mixing liquids in flasks and conducive to culturing cells. Most incubator style shakers are of this design.

Wrist or hand motion laboratory shakers duplicate the swirling motion of hand mixing. Instead of cradling flasks or tubes within the agitation platform, these devices have long arms attached to the housing, which swing and swirl when the device is turned on.

Some styles of agitation are better used for specific experimentation or research results. When in doubt, check with the manufacturer as to which of the laboratory shakers would be best for the given application.

Laboratory mixers are used to mix, emulsify, homogenize, disintegrate and dissolve samples. There are several basic types of products. Dual-shaft mixers use a three-wing or helical anchor to generate flow and remove mixed materials from the vessel wall. Double-planetary mixers use a rectangular or finger-shaped blade to feed material to an orbiting high speed dispenser (HSD). Single-stage rotor/stator devices use a stationary stator to turn an immersed rotor at high speeds. The blades pass each port in the stator and expel material at a high velocity into the surrounding mix. Multi-stage rotor/stator mixers increase shearing to produce smaller particle sizes and more homogenous batches. When two to four rotor/stator pairs are nested concentrically, the mixed material that moves outward from the center of the unit is subjected to a rapid, sequential shearing. Some mixers can be operated at variable speeds. Others are designed for continuous speeds.

Selecting laboratory mixers requires an analysis of performance specifications. Speed range and accuracy are usually measured in revolutions per minute (rpm). Viscosity range is measured in cycles per second (cps). Capacity, the size of the mixing vessel, is expressed in either liters (L) or gallons (gal). Operating temperature and operating range are measured in degrees Fahrenheit (F) or degrees Celsius (C). There are two sample introduction methods for laboratory mixers. Continuous devices accept a continuous flow of the sample. By contrast, batch mixers accept only a measured flow or volume. In terms of temperature control, laboratory mixers with an internal heating or cooling elements are commonly available. Heating elements are usually made of ceramic materials, powered electrically, and measured in watts (W). Smooth cooling shovels that rotate within a drum are used to ensure maximum contact without inter-particle friction.

Laboratory mixers vary in terms of user interface options, display types, and special features. Analog front panels include potentiometers, dials, switches or other manually-actuated inputs that allow operators to adjust ranges and control the output. Digital front with numeric keypads or menus are used to perform these same functions. Video displays consist of a cathode ray tube (CRT), liquid crystal display (LCD), flat panel display (FPD) or other multi-line display. Intrinsically safe (IS) laboratory mixers will not produce sparks, electrical energy or other thermal effects that would cause an explosion under normal or abnormal conditions. Some laboratory mixers are handheld, but not necessarily portable. Others mount on an overhead stand. Programmable mixers and devices that use a timer are used in many applications.

Laboratory filters are used to remove particulates from samples in laboratory-scale applications. They consist of a filter medium and housing or holder that constrains and supports the filter media in the sample’s path. There are several basic types of laboratory filters. Membrane filters are thin, polymeric films that contain thousands of microscopic pores. The size of the pores determines the size rating of the membrane. Typically, membrane filters are used in the quantitative separation or filtration of suspended matter from liquids and gases. Pre-filters are often placed upstream from membrane filters to reduce particulate loading and allow the membrane to operate more efficiently. Centrifugal filters are suitable for small-scale laboratory separations such as protein or nucleic acid desalting and concentration. These devices use centrifugal force to drive liquid through the filter. Increasing the centrifuge speed (G force) increases the pressure across the filter. Fouling is minimized by design features that cause the G force to reach the filter at an angle, sweeping accumulated molecules from the surface. Syringe filters consist of a filter element and housing assembly and are used in applications where a sample must be filtered before entering a syringe. Specialized and proprietary filters that are made from a variety of porous papers are also available. 

Laboratory filters vary in terms of configuration, sample type, filter paper measurement type, filter medium material and housing material. Configurations usually consist of a filter element, a housing element, or both a filter element and housing assembly. Filters that are used with solid, liquid or gaseous sample types are commonly available. There are two filter paper measurement types: qualitative and quantitative. Qualitative filter papers have an ash content that is ten times higher than quantitative filter papers. Common filter medium materials include cellulose, cellulose acetate, nitrocellulose, and regenerated cellulose; ceramic, carbon, and glass fiber materials; polytetrafluoroethelene (PTFE), polyvinylidene fluoride (PVDF), and polyvinylidene chloride (PVDC); and polypropylene (PP), polysulfone (PSU), and polyethersulfone (PES). Housing materials for laboratory filters include acrylics, plastic acrylics, modified acrylics, and polypropylene (PP).

Selecting laboratory filters requires an analysis of both physical specifications and performance specifications. Physical specifications include sample size, pore size, filtration area, and filter shape. Sample size, the maximum amount that filters can accept, is especially important for centrifugal filters and syringe filters. Pore size indicates whether particles of a specific size are retained with an efficiency rate less than 100%, typically 90% – 98%. Rating methods vary widely among manufacturers. The effective filtration area (EFA) is the total, usable filter area. As a rule of thumb, the larger the filter area, the faster the flow rate at a given pressure differential and the larger the throughput volume prior to clogging. Most filters are circular or rectangular in shape. Performance specifications for laboratory filters include particle retention size, flow rate, porosity, hold-up volume, and maximum pressure. Flow rate determines the volume of a liquid that flows through the filter at a fixed pressure and temperature. Hold-up volume is the maximum volume of a sample that a filter can retain.

Laboratory centrifuges are used for separating particles from solutions according to their size, shape, density, viscosity of the medium and rotor speed. The theoretical basis of this technique is the effect of gravity on particles (including macromolecules) in suspension. Two particles of different masses will settle in a tube at different rates in response to gravity. Centrifugal force (measured as xg, gravity) is used to increase this settling rate depending on the rotation to induce centrifugal force, which accelerates the separation of the liquid from the solids. Centrifugal force causes the solid phase to move through the liquid phase in a straight line and away from the center of rotation. Solid-phase characteristics such as particle density, size, shape, and consistency and the rotation speed for the laboratory centrifuges’ chamber (a basket or bowl, depending on the centrifuge type) of a given diameter also influence how fast the solid phase moves away from the center of rotation. The higher the rotation speed, the higher the G force exerted on the solid phase and the faster the solids accumulate.

The two most common types of laboratory centrifuges are analytical and preparative; the distinction between the two is based on the purpose of centrifugation. 

Preparative laboratory centrifuges are used to isolate specific particles. This classification is divided into two types: differential and density. Differential centrifuges are used to separate particles from a liquid medium or to separate particles of different masses into separate fractions of the supernatant. Density centrifuges work by spinning two fluids of different densities within a rotating container or rotor the heavier fluid is forced to the wall at the inside of the rotor while the lighter fluid is forced toward the center of the rotor.

Analytical laboratory centrifuges measure the physical properties of particle, such as sedimentation coefficient or molecular weight. Optimal methods are used in analytical ultra centrifugation. Molecules are observed by optical system during centrifugation, to allow observation of macromolecules in solution as they move in gravitational field. The samples are centrifuged in cells (tubes with quartz windows) having windows that lie parallel to the plane of rotation of the rotor head. As the rotor turns, the images of the cell (proteins) are projected by an optical system on to film or a computer. The concentration of the solution at various points in the cell is determined by absorption of a light of the appropriate wavelength (Beer’s law is followed). This can be accomplished either by measuring the degree of blackening of a photographic film or by the pen deflection

Laboratory balances are used to measure an object’s mass to a very high degree of precision. They consist of a beam with a friction-free fulcrum, a pointer which attaches to the beam and amplifies deviation from the balance position, and fractional weights which are applied along the beam’s measuring arm. Often, the weighing pan is sealed to prevent the ingress of dust or other contaminants. Samples are maintained at room temperature to prevent the formation of air currents inside the enclosure. Other sources of error for laboratory balances include buoyancy, friction, improper miscalibration, misalignment, condensation, evaporation, gravitational abnormalities, and seismic disturbances. For best results, laboratory balances provide high readability, a broad weighting range, and a high degree of accuracy.  

There are many types of laboratory balances. Examples include beam balances, equal-arm balances, unequal-arm balances, spring balances, analytical balances, moisture balances, top-loading balances, and platform balances. An equal-arm balance is the simplest type of beam balance. A uniform bar or beam is suspended at its exact center. By contrast, an unequal-arm balance is suspended at a point a very short distance from one of its ends. A spring balance consists of a coiled spring fixed to a support at one end, with a hook at the other to which the body to be weighed is applied. An analytical balance is designed for quantitative chemical analysis. A moisture balance is used to measure the moisture content in a material sample. A top-loading balance uses a glass or plastic breeze-break atop the scale. A platform balance is a form of equal-arm balance in which two flat platforms are attached to the top side of the beam, one at each end.  

Specifications for laboratory balances include capacity, resolution, platform width and length, display, interface, and ratings or certifications. Some laboratory balances have an analog display such as a needle. Others have a digital display such as a liquid crystal display (LCD), light-emitting diode (LED), or vacuum fluorescent display (VFD). Laboratory balances with remote displays are also available. There are four choices for laboratory balance interface: serial, parallel, universal serial bus (USB), and wireless. Ratings for laboratory balances include Ingress Protection (IP) standards, ratings from the National Electronic Manufacturers Association (NEMA), and certification by the National Type Evaluation Program (NTEP). Laboratory scales that sold in Europe must meet the Waste Electrical and Electronics Equipment (WEEE) directive from the European Union (EU).

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.