Micro Ph Booklet

8/17/2019 Micro Ph Booklet

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A LAZAR LABORATORIES HANDBOOK

MICRO pH ME SUREMENT

PRIMER

Answers to your basic micro pH measurement questionswith helpful hints

Copyright Lazar Research Laboratories, Inc. 2000-2004


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Lazar Research Laboratories, Inc. Micro pH Measurement Primer 2

About Lazar Research Laboratories, Inc.

Lazar Research Laboratories, Inc., known as the Micro Measurement Experts™ have beencoaching researchers on measuring small samples for over 27 years. Our knowledge hashelped researchers in all scientific arenas including biotechnology, biomedical research,microchemistry, chemical engineering, environmental science, geology and more. Our familyof micro pH electrodes are the premier product for measuring pH in samples smaller than 1

millilter.

Free consultation

For all your micro measurement questionsCall us at 1-800-824-2066 (1-323-931-1204 international),fax us at 1-323-931-1204, or email us at [email protected] and we will put our 27 yearsof experience in the micro measurement field at your disposal. There is no cost or obligationfor this service.

Contact Lazar Research Laboratories, Inc.

Email: [email protected]

Website: http://www.lazarlab.com

Fax: 1-323-931-1434

Phone: 1-323-931-12041-800-824-2066 (toll free in the U.S. only)

Address:Lazar Research Laboratories, Inc.

731 North Labrea Avenue, Building 5Los Angeles, California 90038

U.S.A.

mailto:[email protected]:[email protected]://www.lazarlab.com/http://www.lazarlab.com/mailto:[email protected]:[email protected]


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TABLE OF CONTENTS

1. Micro pH Measurement Basics

2. Micro Measurement Hints

3. Recommended electrodes for measuring pH in various applications

• Standard pH Electrode

• NMR pH Electrode

• Micro Surface pH Electrode

• Micro Flow-Through pH Electrodes

4. Other Common Micro Measurements

• Redox Measurements

• p02 & pC02

• p02 in tissue samples

5. Measuring Ions in Micro Samples • Overview

• Hints

• Micro electrodes for K, Na, Cl, and other Ions

6. Placing an Order and Requesting Pricing Information


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1. MICRO pH MEASUREMENT BASICS

Micro volumes are generally considered those which are below 1

ml and all the way down to just a few microliters. Standard pHelectrodes whose technology has been continuously improvedover the last 60 years do not normally lend themselves to themeasurement of micro volumes. This is due to the fact that glasspH technology normally precludes the manufacture of very smallglass pH sensors which will function with the same accuracy,precision, and speed as standard size glass pH electrodes.

The problems that are encountered when the glass pH membrane isminiaturized are as follows:

1. High resistance - A standard glass electrode already has a very high output resistancewhich is on the order of several hundred megohms. The higher the resistance of theelectrode the weaker the signal is to the pH meter. Using ohms law we see that for the sameoutput voltage the higher the resistance the lower the current (signal strength) between thepH electrode and the reference electrode. The very low signal strength of a standard size pH

electrode requires that the output cable be specially shielded and that the pH meter have anultra high input resistance (normally 1 million megohms).The weak signal strength of thestandard glass pH electrode is particularly problematic with the presence of electrical noisefrom electrical appliances or even fluorescent lights in the laboratory. The lower the signalstrength the lower the signal to noise ratio. A low signal to noise ratio produces a signal whichis unstable and difficult to read. Standard size pH have been optimized in the last severalyears giving very stable accurate signals even though the signal strength is relatively low.

When a glass pH electrode is miniaturized the resistance of the electrode goes up inverselyproportional to the surface area of pH electrode. For example, if we take a standard size pHglass sensor (10 mm diameter) and reduce it to a micro pH electrode with a 1 mm glasssensor the resistance will increase by a factor of 100 (the surface area is related to thesquare of the diameter-10x10=100 1x1=1). The surface area of the 10 mm glass pH bulb is

100 times greater than the surface area of the 1 mm glass pH bulb.

Lazar Research Laboratories, Inc. has overcome the high resistance problem with small pHelectrodes by producing a solid state pH sensor which has an output resistance which issignificantly lower than any micro glass pH electrode. The lower resistance leads to asignificantly higher signal strength. The higher signal strength gives a higher signal to noiseratio and a corresponding more stable and accurate pH reading.

2. Fragility - In order to try to compensate for the increase in resistance with decrease in pHelectrode size, manufacturers have tried to decrease the thickness of the pH bulb whichsomewhat reduces the overall resistance. As we all know, standard size glass pH sensorsare already quite fragile. When the pH bulb is made even thinner this results in significantloss of strength in the bulb and frequent pH bulb breakage and replacement. Besides the

fragile pH bulb, the long thin glass stem of these micro glassp H electrodes makes them veryfragile and prone to breakage by even the smallest mechanical stress.


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Lazar Research Laboratories, has overcome the fragility problem by not only using a solidstate pH sensor which is unbreakable, but also using a totally flexible fluoropolymer pH stemwhich can be bent to 90 degrees and even dropped on the lab floor without breakage. Lazaris so confident that their micro pH electrode will not break, that it guarantees the electrodeagainst breakage for the life of the electrode.


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2. MICRO pH MEASUREMENT HINTS

1. Solution carryover - Solution carryover from one sample to another is more critical formicro samples than macro type samples because of the small volumes that are beingmeasured. One should exercise care in thoroughly rinsing the micro pH probe with liberal

amounts of DI water and then wiping dry with a lab paper wiper in going from one sample tothe next.

2. Reduction of Noise Pickup - In order to reduce noise pickup and thereby get the mostaccurate and stable results, micro pH measurements should be done in a lab environmentwhere electrical noise is minimized. This is simply done by not operating any mechanicaldevices such as lab mixers, pumps, etc. in the proximity of the sample during measurementand replacing any flickering (defective) fluorescent lights in the vicinity of thesample.

3. Stirring - Stirring of micro samples during measurement is often not feasible due to thesmall size of the samples. To get the most accurate results the pH buffer solutions that areused to calibrate the micro pH electrode should be placed in relatively small volumecontainers (2 to 10 ml) and should also not be stirred.

4. Ground loops - Occasionally users have tried to dip two different micro probes (e.g. pHand ion electrodes) into the same sample using two separate pH meters at the same time.Unless one is very careful, the common circuit ground (same power outlet) that the two pHmeters share can lead to a ground loop which may give an erroneous reading. If twoelectrodes need to be used in the same sample at one time with two different pH meters, it isbest to use pH meters that are battery powered.


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3. RECOMMENDATIONS FOR MEASURING pH in

VARIOUS APPLICATIONS

MICRO COMBINATION pH ELECTRODENMR MICRO pH ELECTRODEMICRO SURFACE pH ELECTRODE

• 96 well plates

• micro test tubes

• serum ups

• capillary tubes

• NMR tubes

• microcentrifuge tubes

We recommend the Ultra M® family of micro pHelectrodes for these applications for the followingreasons:

• MEASURE pH IN 1/10 OF A DROP. This electrode enables you to measure samples assmall as 5 microliters (1/10 of a drop)

• EXTREMELY SMALL SENSOR SIZE. Tip diameter of the Ultra M electrode is only 1mm.

• LOW IMMERSION DEPTH. Immersion depth for the Ultra M microcombination electrode is1 mm. For even lower immersion depths use the PHM-146 micro pH mono probe with animmersion depth of 0.1 mm. The Model PHR-146F micro flat surface pH probe is alsoapplicable to low immersion depth measurements.

• GUARANTEED UNBREAKABLE. Electrode features solid state sensor and fluoropolymercapillary tube making it virtually unbreakable. Electrode is guaranteed against breakage forthe life of the probe. Why settle for glass?

• MORE STABLE THAN GLASS ELECTRODES. The solid state design of the probe offersa much lower output resistance than glass probes of the same size giving a much morestable pH reading.

• BROAD pH RANGE. The pH range of the Ultra M combination pH probe is 1 to 12.

• COMPATIBLE WITH ALL LABORATORY pH METERS. The Ultra M micro comb. pHprobe is compatible with all major brand pH meters including Orion(R), Beckman(R)Corning(R), Fisher(R), and Radiometer(R). Specify meter when ordering.

MICRO NMR pH ELECTRODE A longer version of the standard micro combination pH electrode with same 1 mm pH sensor,same 2 mm stem diameter, but with longer 220 mm stem length.


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MICRO SURFACE pH ELECTRODE A micro combination pH electrode with 2 mm flat surface tip for measuring pH of smallsurfaces. This probe can also be used for isoelectric focusing studies.

ORDERING INFORMATION

Standard micro combination pH electrode Micro Comb. pH (U.S. Std. Conn) cat. no.PHR-146UMicro Comb. pH (BNC Conn) Cat. no.PHR-146B

NMR micro combination pH electrode with 220 mm stemMicro Comb. pH (U.S. Std. Conn) cat. no.PHR-146NMRUMicro Comb. pH (BNC Conn) Cat. no.PHR-146NMRB

Flat surface micro combination pH electrodeMicro Comb. pH (U.S. Std. Conn) cat. no.PHR-146FSUMicro Comb. pH (BNC Conn) Cat. no.PHR-146FSB

For Low Immersion MeasurementsMicro pH mono probe (U.S. Std.) Cat. no. PHM-146U(needs reference probe)Micro reference probe Cat. no. DJM-146

For Oxidation-Reduction measurementsMicro Redox probe Cat. no. ORP-146C


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MICRO FLOW THROUGH pH ELECTRODE SYSTEM

The Micro Flow Through pH Electrode System is therecommended method for flow-through cellmeasurement for the following reasons:

• USE IN BIOREACTOR, CELL CULTURE, AND ORGAN PERFUSION, HPLC. The pHmicro flow through system (60 micro liter internal volume) includes a special geometry flatpH electrode housed within a micro flow cell and is ideally suited for monitoring microflowing streams in biotechnology, organ perfusion, cell culture, and HPLC.

• ATTACHES DIRECTLY TO SILASTIC OR HPLC TUBING. End fittings on micro flowthrough pH flow cell attach directly to standard silastic tubing using hose barb fittings andstandard fluoro-polymer or PEEK HPLC tubing using 1/4-28 chromatography fittings.

• USE WITH ANY pH METER. The flow through pH electrode plugs directly into anystandard pH/mV meter. Electrode is available with all common pH meter connectorsincluding BNC, U.S. standard, Radiometer(R), and Metrohm (R).

• USE WITH CHART RECORDER. Output from micro flow through pH electrode can be fed

into a pH meter and the recorder output from the meter fed into a chart recorder forcontinuous monitoring of pH vs. time.

• USE WITH PC COMPUTER. Can be used with any PC that has an A to D data card, or usethe Lazar low cost A to D data logger which plugs into the serial port of a PC.

• BROAD FLOW RANGE. The standard micro flow cell has a flow range of 0 to 25 ml/min.Flow cells are also available for flow rates up to 500 ml/min.


Model FTPH-1A micro flow through pH electrode. Comes completewith micro flow through pH probe, micro flow through cell withinput and output ports, miniature hose barb fittings for silastictubing connection, 1/4-28 chromatography fittings for HPLCtubing, and connector cable to fit pH meter. Specify type ofconnector needed for pH meter being used (BNC, US Standard,Radiometer(R), Metrohm, other) when ordering.

Model PP-166 peristaltic pump. A variable speed peristalticpump with flow rates from 0 to 25 ml/min.


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4. Other Common Micro Measurements

pO2 & pCO2 MICRO ELECTRODES

We recommend the new p02 probe for micro p02 measurements for thefollowing reasons:

The new pO2 probe can be used to measure pO2 of tissues, whole cells, cell fractions, andvarious types of respiration studies. It can also be used to measure dissolved oxygen inbiological and environmental samples. The pCO2 probe can be used to measure pCO2 inblood, fermentation studies, and various tissues. Both probes have a 6mm probe diameter.The pO2 probe has a 2 mm tip and can measure down to 10 microliters.


DO-166MT-1 pO2 probe

GS-136C0-1 pCO2 probe

REDOX MEASUREMENTS A micro probe for oxidation-reduction measurements is also available. See ordering

information below.


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NEW pO2 NEEDLE PROBE

We recommend the new p02 needle probe for thefollowing applications:

• plant tissue• animal tissue

• cell cultures

• respiration studies

The new pO2 needle probe that can be used directly with a strip chart recorder or pH meterto measure pO2 of various. Unit comes complete with electronic signal conditioner for directhookup to your recorder or pH meter.


Order DO-166NP p02 probe


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5. HOW TO MEASURE IONS IN MICRO SAMPLES

Measuring other ions, such as K, Na and Cl in micro samples is similar to measuring pH inthese small samples. The same considerations apply such as using an electrode that has alow output resistance while at the same time having a nonglass body making it resistant tobreakage. For best results, use micro ion electrodes that are made specifically for the ion that

you want tomeasure making sure there are no significant interferences from other ions(see the table below).

Micro Ion Measurement Hints:When measuring ions in micro samples, always be sure to:

• Thoroughly rinse the electrode between different samples using deionized water.

• Maker sure that samples and standards are at the same temperature.

• Try to remove sources of electrical noise from near the area whereIon measurements are made.

.

Recommended electrodes for measuring ions in yoursmallest samples

• 96 well plates

• serum cups

• HPLC sample vials

• micro test tubes

• NMR tubes

• microcentrifuge tubes

The preferred method for measuring ions inmicro samples is Micro Ion Electrodes for thefollowing reasons:

• MEASURE COMMON IONS IN 1/10 OF A DROP OF LIQUID - these electrodes are thesmallest available anywhere.

• VIRTUALLY UNBREAKABLE. Electrodes feature fluoropolymer bodies with solid state

sensors, making them virtually unbreakable.• FAST, STABLE RESPONSE. Response time is typically 30 seconds or less making them

much faster than liquid membrane electrodes.

• LOW DETECTION LIMIT. All micro ion electrodes will measure down to 1 ppm (parts permillion), some electrodes like the sodium probe will measure down to 0.02 ppm.

• LOW IMMERSION DEPTH. Immersion depth for the ion probes is only 0.1 mm.


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ION ELECTRODE DESCRIPTION AND ORDERING INFORMATION

Electrode Type Conc. Range(ppm) Cat. No.

Bromide 0.08 to 80K ISM-146BR

Calcium 1 to 10K ISM-146CA

Chloride 1.5 to 35K ISM-146CLCopper 0.06 to 600 ISM-146CU

Cyanide 0.02 to 250 ISM-146CN

Iodide 0.01 to 120K ISM-146I

Potassium 2 to 3900 ISM-146K

Silver 0.01 to 110K ISM-146AG

Sodium 0.02 to 100K ISM-146NA

Sulfide 0.003 to 32K ISM-146S

Thiocyanate 0.5 to 19K ISM-146SCN

Reference electrode ------------ DJM-146


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6. HOW TO PLACE AN ORDER OR REQUEST PRICING

INFORMATION

by phone: 1-800-824-2066 in the U.S.1-323-931-1204 International

by email: [email protected]

by fax: 1-323-931-1434

by mail: Lazar Research Laboratories, Inc.731 North LaBrea Avenue, Suite 5Los Angeles, CA 90038U.S.A.

Note: Specifications and prices subject to change without notice

To get a brochure on the Lazar micro ion electrodes contact usvia email at [email protected] giving us your fax number andrequest brochure FIS.

METHODS OF PAYMENT

net 30 to companies with recognized credit ratingVisa or MasterchargeCOD, check, money order

Note: Specifications and prices subject to change without notice

To get a full brochure on the micro pH electrode including pictures contact Lazar ResearchLabs, Inc. at [email protected] giving your fax number and asking for brochure FPHR.
mailto:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]

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Micro Ph Booklet