i standard methods. What is the percentrecovery? Specificity Does the method identify and measure your parameters of interest? What steps are taken to ensure

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Few techniques give quick, accurate and uncomplicated read out of moisture content as well as moisture balances using infrared drying. "Thermogravimetric scales are ideal when you need to know the precise moisture content of a material, whether it's raw ingredients or when the final product is mixed and ready t o go," says Walter Krywolap, Moisture Analyzer Product Manager for Sartorius Corp., Edgewood, NY Moisture content affects the processing performance of many materials and will affect the shelf life

of finished products. Analyzers are placed at key points in many processes: snack food manufacturers making different varieties of potato chips check for percent moisture in their blend of oils, sugars and spices. Thermogravimetric analysis entails weighing a sample before and after drying. The difference between the

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Infrared rays h #fall molecules in a sample to the same temperature.Arizona Instrument's MRY-2000 ma sture balance (below) uses diglfal technology for detection of moisture levels down tO'.Oa5% in as little as two minutes. ,,

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initial and final weight yields is the moisture content of the sample, and is expressed as percent moisture or percent solids. Krywolap adds that moisture balances measure both water and volatile substances in the sample, such as fats, oils, alcohols, organic solvents and flavorings. Infrared drying "heats every molecule to the same temperature," avoiding surface cooling that can occur in conventional ovens, Krywolap says. In conventional oven drying, circulating hot air warms the sample from the outside-in. As the moisture evaporates it cools the sample surface, making time a factor. Infrared rays, conversely, penetrate samples without impedance from 2 to 5 mm then convert to heat energy. Top layers transmit heat to underlying layers through contact with adjacent molecules. The higher the sample's conductivity the faster and more

uniformly it heats; Krywolap says results can generally be obtained in under 15 minutes. Typical sample size ranges from .5 to 10 grams. REPRESENTATIVE SUPPLIERS Arizona Instrument Phoenix, AZ 602-470-1414; fax 602-470-1888. Circle 225 CSC Scientific Co. Farfax, VA. 800-458-2558; fax 703-280-5142. Circle 226 Ken villa Park, CA. 714-630-5100; fax 714-630-5105 Circle 227 Sartorius Corp. Edgewood, NK 800-635-2906fax 516-254-4261. Circle 228

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particle size directly affects product properties such as solubility, reactivity, strength, structure, flow, taste and texture. Particle size aiiaiyzers employed for routine q,iality control often use laser ;d [fraction to give continuous readings of the distribution of particle sizes within a samplpj. ; Diffractive measuremeas are Ibased on principles such asathe Mie ' scattering theory, an absolute measurement that corre'lates the gle of diffracted light to particle [,.e, explains Andrew Malcolmson, AD Engineer at Insitec, San amon, CA. Detectors record a urrent proportional to the intensity f the scattered light that hits them: he smaller the particle the wider the ngle of scattering and the lower the tensity of scattered light. Along with computations for etermining how differently sized icles will scatter light, particle ysis instruments incorporate her models to relate intensity of tered light to the volumetric ibution of particle sizes present e material. Results are figurable and systems are cally set up to measure the ratio distribution of particles of a size to the total number of s in the material. lcolmson notes that although erica1 particles are ideal for active measurements, they are often encountered in real esses. Most particle analysis ware compensates for irregularly ed particles, approximating their ering angles into spherical ivalents. The advantage with instems is that this compenoccurs continuously and es out error" for more e measurements, he says. ec's EPCS instrument (see makes up to 1,000 size tion measurements per in pneumatic powder or flow streams. A multi-line unit was to be available this fall enables the user to place e taps in up to six different nd monitor them with the

same unit using a single solid-state diode laser. Detection of scattered light in the EPCS is on a logarithmically scaled solid-state ring detector. Size distributions are based on the analysis of 30 detector rings. An alternative technique that is beginning to find some application in the food industry is offered by

Particle Sizing Systems, Santa Barbara, CA. In contrast to laser diffraction and other "ensemble techniques,'' where a large number of particles of every size contribute simultaneously to the measured signal, single-particle optical sensing (SPOS) is a "conceptually simpler approach" that separates and measures individual particles, sa PSS Marketing Director Kerry . . Hasapidis. "There's no mathemadeal fitting or complex deconvolution algorithms because you're measuring each particle at each diameter one at a time." PSS's Accusizer is fully automated and combines continuous dilution with particle size distribution analysis. Essentially, particles in gas or liquid suspension flow through a sensor containing a small photozone with a laser diode as its source. Particles pass one at a time through this illuminated region, each giving rise to a detected pulse, the magnitude of which depends on the diameter of the particle and the respective cross-section of light that is obscured. The pulse height analyzer compares detected pulse heights with a standard calibration curve for sensor response, displaying the size distribution continuously in real time using absolute particle counts versus

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diameter for each diameter channel spaced logarithmically over the total size range covered by the sensor. The particle size distribution of the sample is constructed one particle at a time, so Hasapidis says collected data is much more precise. "Outliers can be detected and measured, where in ensemble techniques they would be part of the background and have no effect on the overall scattered light signal,'' he notes. With the Accusizer, "If you routinely run a sample whose mean diameter is 20 microns and suddenly you start to unknowingly introduce 50-micron particles, the instrument is capable of detecting as few as one or two of the 50-micron outliers." The key to this method is sufficient dilution of the sample.to avoid particle coincidence in the optical sensor. The Accusizer incorporates a proprietary automatic dilution method that quickly and continuously dilutes a fully concentrated sample suspension to the optimal concentration for particle size determination. A few drops of liquid suspension or several milligrams of dry powder are introduced, then filtered diluent is fed into the mixing chamber. The resulting positive pressure causes the suspension to exit the chamber and flow through the sensor. REPRESENTATIVE SUPPLIERS Coulter Gorp. Miami, FL. 305-380-8312; fax305-380-8312. Circle 229 lnsitec Measurement Systems San Ramon, CA. 510-837-1330;fax 510-837-3864. Circle 230 Malvern Instruments Inc. Southborough, MA. 508-480-0200;fax 508-460-9692. Circle 231 Particle Sizing Systems Santa Barbara, CA. 805-968-1497; fax 805-968-0361. Circle 232

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Though analog systems are still common, in-line digital refractometers are fast becoming the industry standard because of the improved versatility and performance of digital optics and microprocessor technology. Refractometry is well-suited to measurement of liquid concentration J because of the direct relationship between the refractive index of a iiquitll h

which light travels through the materials; a medium's index of refraction is the ratio between speed of light in a vacuum and the speed through the particular medium. A liquid's refractive index is also a function of temperature, so process refractometers must be fitted with a temperature sensor for continuous compensation.

In-line refractometers focus a beam of light onto the interface between the prism and liquid product. Reflected light falls on the CCD sensor; the shadow-line moves from as concentration

Focusing Lens

' Photocells and its percent concentration. In many processes liquid concentration of raw ingredients and finished product must be measured and controlled, so refractometers are commonly used at critical or value-added stages of production, categorized as concentrating, diluting or reconstituting, blending, and alarm/ divert applications. Refractive index measurements can be converted to "Brix ( % sucrose by weight dissolved in water) and other working units. Roger Ver Mulm, Director of Sales for Maselli Measurements, Stockton, CA, explains that the refractive index is a measure of the bending of light rays as they move between media of differing densities. Refraction occurs because of the differing speeds with

When rays are focused at the interface of two materials (in a process refractometer this would be the refractometer's prism and the liquid being measured) some rays will have an angle of incidence at a right angle to the media interface. Rays with incoming angles less than this "critical angle of incidence'' will refract into the material while those with greater incoming angles are reflected back to the refractometer's measuring cell. The instrument is more accurately called a critical angle refractometer, Ver Mulm says, because it measures the angle at which light rays change from refraction to reflection. Digital circuitry enhances detection of this "shadow line," which can be sharp, ..' .,

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blurry or gradual. The shadow line position corresponds to the refractive index, delineating light and dark areas, its position moving from right to left across the detector window as product concentration increases. With a digital device called a CCD (charged coupled device) even an extremely blurry shadow lines can be detected to a linear resolution of several thousandths of an inch, or better than an equivalent 0.05 "Brix, says Ver Mulm. Microprocessors can run more complex algorithms for better shadow-line detection, improved temperature compensation and wider operating ranges. Maselli's UR-15 process refractometer, for example, can operate freely between 23 and 250°F over a 0-85 "Brix range. The operator can fine-tune the compensation at the working point, Ver Mulm says, and alternative ranges to "Brix for products such as HFCS, citric acid or ethyl alcohol can be programmed based on empirical or derived data. The process value is displayed continuously; electrical output signals, such as dry relay contacts, are used for highllow alarms, divert or on/off; and serial communications such as an RS-485 interface. In-line refractometers such as Maselli's can be installed directly in line or in a sample loop with dedicated pump. In-line zero calibration, says Ver Mulm, is checked by comparing measurements with a standard methodology, such as a laboratory refractometer,following a defined sample collection procedure. Off line, zero and span calibration can be checked with standardized sucrose samples or with actual product samples of known concentrations. REPRESENTATIVE SUPPLIERS Leica, Optical Products Div., Buffalo, IVY 716-686-3000; fax 716-686-3085. Circle 233

Masel// Measurements, Stockton, CA. 209-474-9178; fax 209-474-9241. Circle 234

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's an energy measurement of how tightly water is structurally or chemically bound in a food product. Measurements are expressed as the ratio of water vapor pressure above any sample to the water vapor pressure of pure water at the same temperature, or equilibrium relative humidity ERH is measured after an equilibration period when the sample is

?$ Water activity, or. A ,

placeo 'n a sea.ea ciiamoer or enclosure. ERH is achieved naturally as the water vapor coming out of the sample material reaches equilibrium with the water in the sealed environment. This primary method is found in systems such as Rotronic Instruments' portable AWC (see photo), where samples are placed in disposable plastic cups, sealed, then pierced with a probe after equilibrium is ,

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atta nea. Tile sensor imineoiate q begins to detect the changing A, which is displayed on an LCD readout. Results are obtained in 10 minutes on average. Water activity affects the growth and activity of microorganisms and other destructive agents. Steve Teare, Marketing Manager for Decagon Devices, Pullman, WA, says ,A is not yet fully utilized by food com-

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panies as a quality control tool. For some products, A, must be record.*,' ed for regulatory requirements, and the data is required of suppliers by a growing number of processors. Decagon's AquaLab hastens the equilibrium process with something called the chilled-mirror dew point technique, a primary, ADAC-approved method. ERH is achieved with a stainless steel mirror that is repeatedly cooled and heated, repeatedly forming dew and driving it off. The ...*r instrument's fan circulates air in the sensing chamber, speeding up this , equilibration process. Each time dew forms on the mirror, the AquaLab :: measures the temperature and A, of the sample, saving these values to I compare to previous values as it repeats its readings. When the A, values of consecutive readings are less than ,001 apart, the measurement is complete. ma

The COMPUTRAC MAX-2000

provided along with ~romptr

for startin$ tho n m lest.

Automatic operation requires minimal user skills Programmable test parameters for 30 food products Storage of 74 test results Detects moisture levels from 50ppm-1009b * Parameter changes and menu system access code Graphical, interactive user interface Statistical analysis package Multiple test temperatures can be automatically calibrated with an NET-traceable module. Accommodates sample weights of 150mg - 40 grams

The faster a moisture problem is detected the sooner it can be corrected to improve overall qualib. The COMPUTRAC MAX-2000, utilizing the latest digital balance technology, combines the precision of a laboratory instrument with the durability, speed and ease-of-use required of a production floor model.

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REPRESENTATIVESUPPLIERS Decagon Devices -2: Pullman, WA. 509-332-2756,fax 509-332-5158 -1

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Rotronic lnstrument Corp. 4114 E. Wood Street Phoenix, AZ 85040-1941 (800) 290-1414 Fax (602) 470-1888 !

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ItMllR 1903

Though traditional nuclear magnetic resonance spectroscopy is generally perceived as a high-skill laboratory technique, there has been substantial activity in the development of rugged, low-resolution NMR instruments for routine production control. NMR is a non-invasive, nondestructive technique that requires minimal sample preparation and can give results in under a minute. Pulsed NMR spectrometers apply microsecond bursts of radio frequency (RF) energy to the sample, which is inserted in a probe that contains a coil between two magnet poles. According to Terry Suscavage, NMR Application Specialist with Oxford Instruments' Analytical Systems Division, Concord, MA, measurements are based on the magnetic resonance phenomenon that occurs in the nuclei of the hydrogen atoms in a sample. The high-power magnet and RF pulse are used to generate a signal from the

solidhiquid ratio technique, which is used for the analysis of edible fats where the fats exist as either a dispersion of solid particles in a liquid or a dispersion of liquid droplets in a solid. This measurement is solid fat content, or SFC. The American Oil Chemists Society has approved NMR as an official technique for SFC. NMR can also be used to measure the total moisture and/or oil content

in foods and oilseeds. Many NMR instruments can be calibrated against an appropriate reference.techniques to perform total fat content measurements, as well.

REPRESENTATIVE SUPPLIERS Oxford Instruments, Analytical Systems Oiv., Cbncord, MA. 800-447-4717; fax5OSr 71 0204 Circle 236

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hydrogen atoms in a sample. The principle relies on the fact that the hydrogen nuclei have magnetic dipoles that align themselves in the strong magnetic field (4,700 Gauss). An RF pulse of 20 MHz produces resonance in the hydrogen nuclei, which absorb the energy and generate a signal that can be measured. The signal's intensity is proportional to the concentration of hydrogen in the sample, and the free induction decay of the signal indicates how the hydrogen is bound-either solid or liquid-In the sample. Calibration curves are generated or a ratio calculation is employed to quickly analyze samples. Pulsed NMR can be used to measure sample properties in several ways, Suscavage says. One is a CIRCLE 190 ON READER SERVICE CARD

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Nitrogen analysis using flash combustion coupled with a modified gas chromatograph is an attractive alternative to Kjeldahl methods. Richard Hancock, Product Manager for CE Elantech, a Lakewood, NJ, distributor for Fisons Instruments, says such instruments are in fairly widespread use in research laboratories but that larger companies and a growing contingent of smaller firms are using them in qualib .~ control capacities, as well. "If you have one technician running afew Kjeldahl analyses a day, I'm not sure the instrument would justify itself." he savs. "But for anyone concerned about solvents and their disposal, nitrogen analyzers are a much more convenient technique." Nitrogen analyzers such as Fisons' NA 2000 operate completely unat-

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tended, accommodate samples up to .5g and give results in 3-5 minutes. The NA 2000 can be linked to a process control system via PC, "but

their organic components. Temperatures in the combustion tube can reach 1,800"C (see photo), converting all nttroaen in the samole to diatomic nitrogen molecules ' independent of their chemical bond, matrix and physical state of the sample. Carrier gases then transport the combustion gases into the GC

column for separation of nitrogen. Quantitative detection is via a thermal conductivity detector. Then, factors based on the particular sample matrix are applied to the total nitrogen measurement to yield the protein content. The technique is AOAC-approved for various foodstuffs, including grains and meats. For most materials, precision is as good or better than wet chemistry. Calibration is to NlST standards, which are run as samples. Standards should be run periodically as unknowns, Hancock says, and if there is any drift the unknown can be reset as a standard and results will be adjusted accordingly. The Fisons unit will maintain calibration for at least a shift and generally longer.

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REPRESENTATIVE SUPPLIERS CE Elantech, Lakewood, IVJ. 908-370-5559: fax 908-370-3888. Circle 237

SGS INTERNATIONAL CERTIFICATION SERVICES, INC.

Phone: 201-935-1500 * Fax: 201-935-4555

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I becoming one of the most common -fixtures in processing environments for qualitative measurement of bulk constituents. Dr. David Honigs, President of Katrina Inc., a Hagerstown, MD, manufacturer of NIR instrumentation, points to a handful of successful applications: rocessed cheeses, milk blending and itandardization, fat in chocolate, fat and moisture in meat products, protein in slurries and whey, and moisture in caramel. These constituents and others such as protein and sugar have typical absorptions and an ensuing refiectance spectrum for light in the NIR range. In transmittance NIR, waves pass through the material and are measured; with reflectance, waves that reflect off the product are measured. Reflectance is effective for powders, Honigs says, but transmission NIR is generally better suited for food processes because reflectance measurements can be thrown

suchas protein coatings and oil on the surface of a product. When the instrument is set up to pinpoint a particular absorption, Honigs explains, simple, "local" Calibrations are employed. In a typical configuration, three beams are applied to the material of interest: one measures the target analyte, one measures overlapping absorptions, and the third measures background. Conversely, when the entire NIR spectrum is garnered from the material, more complex "global" mathematics are used to "put the spectrum into a format that makes it easier to pick up useful wavelengths, You get information about a constituent from ail wavelengths and weigh each according to its ability" Though complex models are slightly more accurate they are harder to set up, use and maintain. Ongoing calibration is the cornerstone to effectively operating an on-line NIR sensor. A good approach is to collect

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rainina samo es rom iiie ne o teach t i e instrument about a particular process. "The lab Is often the Achilles heel in gening an NIR system up and running," Honigs says. "The method depends on solid lab analysis. It requires a lot of samples over one or two weeks of production, and the measurement has to be rugged." Verification is important: Users need to be vigilant of hidden variables such as different people doing the calibrations, or different people setting different process set points. Typical light sources include light emitting diodes and tungsten lamps. Detectors include Silicon (most effective at 400-700 nm) and Geranium (500-1,650 nm), which generate electrons when the light hits them. Lead Sulfide, another common detector, changes its resistance in reaction to the light. Fiber optics can be employed, as well. NIR units are often positioned close to a value-added point in the process, such as after blending, in the cookina phase, or after swaration. Linkkdio a process control system, they enable both feed-forward and reverse-feed process control. "Processed cheese manufacturers use the data to adiust wraaaer

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If so, you need the right kind of particle size analyzer one that doesn't miss the details. Our NEW AccuSlzer" 770 Is different from all the rest. Designed with prcven optical technology. Innovative electrcnics and Autodilution". the 770 succeeds where alternate technologias fail. Wide dynamic size range: 0.5-2500 micrcns Autodilution (pat.). solvenLcompatible Fast cyde lime (< 5 mln ) easy to w e Automalic ON-IhE samp ing capab city Compauble wilh NICOMP"370 SJbmicran Particle S zel moaule. 0 003 5 Wm NEW Zeta Potential mod. ar opl on

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temperature or other cooking processes," says Allen Bickel, Food

is that it's "an easy, direct technique that requires no sample preparation of any kind." Transmission cells can '

or can contact the material via dip probes. Bypass lines can be installed for sampling but are not necessary, and Bickel adds that many food companies are interested in noncontacting configurations, such as a beam transmitted across product as it progresses along an open conveyor. Moisture Register Products, La Verne, CA, offers such asystem for moisture analysis called the BSP901. Positioned over a conveyor, a 1 stabilized NIR source is focused on the material and reflected lightis filtered at two different wavelengths, one sDecific for moisture and the

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displayed. A new Remote Operator system from the company provides calibration programming and an RS*L 232 linkfor the BSP-901.

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W C , Inc., trusted for pharmaceutical analyses for ten years. announces HPLC columns for challenging food industry applications.

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Food Pack Gas Analysis

REPRESENTATIVE SUPPLIERS Bran + Luebbe lnc. Buffalo Grove, IL. 708-520-0700; fax 708-520-0855. Circle 238 Katrina lnc. Hagerstown, MD. 301-733-9397; fax 301-739-3428. Circle 239

Servomex Model 1450

Moisture Register Products La Verne, CA. 909-392-5833; fa 909-392-5838. Circle 240

Combined 0,and COz Fast High Efficiency Readings Sample Volume Down to 8ml Resolutions Down to 0.1% 0, and CO, Simple to Use Low Maintenance

NlRSvstems Inc. si/& spring, MD. 301-680-9600; fax 301-236-0157. Circle 241 South Norwalk, CT. 203-855-9136; fax 203-838-9868

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ItMtMLR 1991

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FOOD OPT l!

The main performance advantage of FT-IR spectrometers is the "capability of collecting the entire infrared spectrum in one scan," says Bertrand Lanher, Dairy and Beverage Marketing Manager for Perstorp Analytical Inc., Dairy, Beer and Beverage Unit. This is made possible by a device called an interferometer, which consists of a beam splitter, and a moving and a fixed mirror. The beamsplitter splits a single infrared beam into two beams of equal intensity and phase which reflect off the mirrors. The beams recombine in the beamsplitter to create a series of interfering waves. The combination of these interferences results in an interferogram which includes all available spectral information in one sub-second scan. Each position of the moving mirror can be related to a wavelenath. This means that a continuous scan will collect a theoretically continuous pectrum. Specific wavelengths ca

THE PRINCIPLE Fixed Mirror Moving Mirror

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then be selected by software from the entire spectrum, which enables

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analyses to be performed. "You can calibrate the system for as many components that you have the time and computing power for," Lanher

The mathematics used to calibrate FT-IR instruments fall into two general categories largely dependent on whether the product's spectra constitute a simple or a complex system. Lanher explains that simple systems are characterized by few well-defined absorption wavebands that allow the definition of discreet variables; here, simple mathemtatical tools such as multilinear regression suffice to calibrate the instrument. Complex systems, on the other hand, do not allow definition of discreet and mathematical soft ' variables modeling tools are required. Such conditions are somewhat observed in MIR spectra and often in the NIR region, where "numerous overtones /I and recombination bands create ills resolved and highly overlapped spectra," he says. "However, NIR spectrometry is useful for identifying compounds that cannot be observed in the MIR region." An example is the direct measurement of casein in milk, a crucial measurement for cheese makers.

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OMEGA ENGINEERING, INC. .................. RSX100 TELt 243-359-1560, FAX# 203-359-7700 "Process measurement and control instruments includes temperalure pressure, flow pH. and recording equipment."

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Lanher adds that along with quantitative analyses, some users of Anadis' Aegys Mi200 FT-IR analyzer employ the unit in a pass-fail mode for incoming raw materials and finished product checks. Pattern recognition software proprietary to Perstorp Analytical is used to fingerprint product constituents for quick comparative screens.

automatic data storage. PC lnteliace."

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REPRESENTATIVESUPPLIERS Perstorp Analytical Inc. Silver Spring, MD. 301-680-9600; faX 301-236-0157.

Circle 235

CE EUNTECH, INC. ......................... RSb134 TELX 908-370-5559, FAX# 908-370-3888 "NA2000 NitlOgenlPrOtein Analyzer. Dynamic flash combustion is utilized to determine nitrogen and protein in large samples. Conforms to AOAC 990.03.992.15.992.23, & 993.13." Colorlec.. ................................. RSU163 TEL#908-236-2311. FAX# 908-236-7865 "Color Instruments and PC software forthe fieid and processing plant.' OECAGON OEVICES. INC.. .................... RSrlO5 TE.I 503.332.1756 'Mi 503-332-5'58 A o . ~ n P c n D s ' i : r CP. cz,~n~:i.res .,at? CI.' I. ' tor f i o d quality and saietv Water aclivitv is used for predicting shelllife." EM SCIENCE..

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RSPllO

TEL# 609-354-9200, FAX# 609-423-4389 "The Reflectoquant System .A revolutionary new test technology which uses system dedicated test Stripsfor testing a wide variety of ions."

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INSITEC, INC. RS1166 TELX 837-1330. FAX# 837-3864 "EPCS - In-process. real-time pailicle sizing of powders after grinders. dryers, mills. lor quality and process control."

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LEICA, INC. RSXl9O TEL# 716-686-3000. FAX#: 716.686-3085 "Leica overs a full range of temperature compensated laboratory and hand-held refractometers for measuring refiaclive index and %solids." M I N O J A CORPORAllON . . . . . . . . . . . . . . . . R S n l l Z ls'.rl-"t5,scllr ? . I lr T~.* ?I:--ZMJX f;:A* zct-a2j-.1?7.1 "Measurement equ'lpment to ensure that your food color is exactly whet it should be...from R&O through processing and pmd~ction."

Large sample size. Cost effective operation. WItltR 1091

ROTRONIC INSTRUMENT CORP ...............R S X I l 9 TEL# 516-427-3898, FAX# 516-427-3902 "System provides measurementof water activity of powders. granuiates & pellets of food products or chemicals."

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SARTORIUS CORPORATION., RSX14Z TEL#: 51645414249, FAX# 516-254-4261 "Saftorius'l. a manufacturer of precision weighing instruments h u d i n g lab balances, moisture a n a l y m and scales for counting formulating and checkweighing." SERVOMEX COMPANY, INC.. .................. RSX123 TEL# 617-769-7710. FAX# 617-769-2834 "Headspace gas analyzers for food packages." SUPREX CORPORATION.. .................... US1187 TELI 412-826-5200, FAX# 412-826-5215 "Suprex is the market ieader in the robust, routine application of Supeicritical fluid extraction to fat analysis and pesticide residue sampie preparation." TESIO, INC. ............................... RSb140 TELX 201-252-1720, FAX# 201-252-1729 '"The Testostor 171 Datalogger monitors temperature and/or humidity for process, storage, and transporalion Of perishable goods. RH drifts lessthan 1 % per year,' YMC, INCORPORATED.. ..................... RSX18O TELt 800-962-6311, FAX# 910-343-0907 "YMCs Short hioh efficiencv HPLC columns in over 30 stationary phasesiuppoti f a i l anaiflical method development and 5 minute OA assays." For more intormetion from these suppliers, circle thn appropriate RSX on the Reader Service Card.

Phn: 908-376-5559 Fax: 908-370-3888 CIRCLE 134 ON READER SERVICE CARD