A LAZAR LABORATORIES HANDBOOK MICRO ph MEASUREMENT PRIMER. Answers to your basic micro ph measurement questions with helpful hints

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1 A LAZAR LABORATORIES HANDBOOK MICRO ph MEASUREMENT PRIMER Answers to your basic micro ph measurement questions with helpful hints Copyright Lazar Research Laboratories, Inc

2 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 been coaching researchers on measuring small samples for over 27 years. Our knowledge has helped researchers in all scientific arenas including biotechnology, biomedical research, microchemistry, chemical engineering, environmental science, geology and more. Our family of micro ph electrodes are the premier product for measuring ph in samples smaller than 1 millilter. Free consultation For all your micro measurement questions Call us at ( international), fax us at , or us at service@lazarlab.com and we will put our 27 years of experience in the micro measurement field at your disposal. There is no cost or obligation for this service. Contact Lazar Research Laboratories, Inc. service@lazarlab.com Website: Fax: Phone: (toll free in the U.S. only) Address: Lazar Research Laboratories, Inc. 731 North Labrea Avenue, Building 5 Los Angeles, California U.S.A.

3 Lazar Research Laboratories, Inc. Micro ph Measurement Primer 3 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

4 Lazar Research Laboratories, Inc. Micro ph Measurement Primer 4 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 ph electrodes whose technology has been continuously improved over the last 60 years do not normally lend themselves to the measurement of micro volumes. This is due to the fact that glass ph technology normally precludes the manufacture of very small glass 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 is miniaturized are as follows: 1. High resistance - A standard glass electrode already has a very high output resistance which is on the order of several hundred megohms. The higher the resistance of the electrode the weaker the signal is to the ph meter. Using ohms law we see that for the same output voltage the higher the resistance the lower the current (signal strength) between the ph 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 an ultra high input resistance (normally 1 million megohms).the weak signal strength of the standard glass ph electrode is particularly problematic with the presence of electrical noise from electrical appliances or even fluorescent lights in the laboratory. The lower the signal strength the lower the signal to noise ratio. A low signal to noise ratio produces a signal which is unstable and difficult to read. Standard size ph have been optimized in the last several years 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 inversely proportional to the surface area of ph electrode. For example, if we take a standard size ph glass sensor (10 mm diameter) and reduce it to a micro ph electrode with a 1 mm glass sensor the resistance will increase by a factor of 100 (the surface area is related to the square 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 ph electrodes by producing a solid state ph sensor which has an output resistance which is significantly lower than any micro glass ph electrode. The lower resistance leads to a significantly higher signal strength. The higher signal strength gives a higher signal to noise ratio 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 ph electrode size, manufacturers have tried to decrease the thickness of the ph bulb which somewhat reduces the overall resistance. As we all know, standard size glass ph sensors are already quite fragile. When the ph bulb is made even thinner this results in significant loss 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 very fragile and prone to breakage by even the smallest mechanical stress.

5 Lazar Research Laboratories, Inc. Micro ph Measurement Primer 5 Lazar Research Laboratories, has overcome the fragility problem by not only using a solid state ph sensor which is unbreakable, but also using a totally flexible fluoropolymer ph stem which can be bent to 90 degrees and even dropped on the lab floor without breakage. Lazar is so confident that their micro ph electrode will not break, that it guarantees the electrode against breakage for the life of the electrode.

6 Lazar Research Laboratories, Inc. Micro ph Measurement Primer 6 2. MICRO ph MEASUREMENT HINTS 1. Solution carryover - Solution carryover from one sample to another is more critical for micro samples than macro type samples because of the small volumes that are being measured. 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 to the next. 2. Reduction of Noise Pickup - In order to reduce noise pickup and thereby get the most accurate and stable results, micro ph measurements should be done in a lab environment where electrical noise is minimized. This is simply done by not operating any mechanical devices such as lab mixers, pumps, etc. in the proximity of the sample during measurement and 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 the small size of the samples. To get the most accurate results the ph buffer solutions that are used to calibrate the micro ph electrode should be placed in relatively small volume containers (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. ph and 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 ph meters share can lead to a ground loop which may give an erroneous reading. If two electrodes need to be used in the same sample at one time with two different ph meters, it is best to use ph meters that are battery powered.

7 Lazar Research Laboratories, Inc. Micro ph Measurement Primer 7 3. RECOMMENDATIONS FOR MEASURING ph in VARIOUS APPLICATIONS MICRO COMBINATION ph ELECTRODE NMR MICRO ph ELECTRODE MICRO 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 ph electrodes for these applications for the following reasons: MEASURE ph IN 1/10 OF A DROP. This electrode enables you to measure samples as small 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 is 1 mm. For even lower immersion depths use the PHM-146 micro ph mono probe with an immersion depth of 0.1 mm. The Model PHR-146F micro flat surface ph probe is also applicable to low immersion depth measurements. GUARANTEED UNBREAKABLE. Electrode features solid state sensor and fluoropolymer capillary tube making it virtually unbreakable. Electrode is guaranteed against breakage for the life of the probe. Why settle for glass? MORE STABLE THAN GLASS ELECTRODES. The solid state design of the probe offers a much lower output resistance than glass probes of the same size giving a much more stable 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. ph probe 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.

8 Lazar Research Laboratories, Inc. Micro ph Measurement Primer 8 MICRO SURFACE ph ELECTRODE A micro combination ph electrode with 2 mm flat surface tip for measuring ph of small surfaces. 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-146u Micro Comb. ph (BNC Conn) Cat. no.phr-146b NMR micro combination ph electrode with 220 mm stem Micro Comb. ph (U.S. Std. Conn) cat. no.phr-146nmru Micro Comb. ph (BNC Conn) Cat. no.phr-146nmrb Flat surface micro combination ph electrode Micro Comb. ph (U.S. Std. Conn) cat. no.phr-146fsu Micro Comb. ph (BNC Conn) Cat. no.phr-146fsb For Low Immersion Measurements Micro ph mono probe (U.S. Std.) Cat. no. PHM-146U (needs reference probe) Micro reference probe Cat. no. DJM-146 For Oxidation-Reduction measurements Micro Redox probe Cat. no. ORP-146C

9 Lazar Research Laboratories, Inc. Micro ph Measurement Primer 9 MICRO FLOW THROUGH ph ELECTRODE SYSTEM The Micro Flow Through ph Electrode System is the recommended method for flow-through cell measurement for the following reasons: USE IN BIOREACTOR, CELL CULTURE, AND ORGAN PERFUSION, HPLC. The ph micro flow through system (60 micro liter internal volume) includes a special geometry flat ph electrode housed within a micro flow cell and is ideally suited for monitoring micro flowing streams in biotechnology, organ perfusion, cell culture, and HPLC. ATTACHES DIRECTLY TO SILASTIC OR HPLC TUBING. End fittings on micro flow through ph flow cell attach directly to standard silastic tubing using hose barb fittings and standard 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 any standard ph/mv meter. Electrode is available with all common ph meter connectors including 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 for continuous monitoring of ph vs. time. USE WITH PC COMPUTER. Can be used with any PC that has an A to D data card, or use the 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. ORDERING INFORMATION Model FTPH-1A micro flow through ph electrode. Comes complete with micro flow through ph probe, micro flow through cell with input and output ports, miniature hose barb fittings for silastic tubing connection, 1/4-28 chromatography fittings for HPLC tubing, and connector cable to fit ph meter. Specify type of connector needed for ph meter being used (BNC, US Standard, Radiometer(R), Metrohm, other) when ordering. Model PP-166 peristaltic pump. A variable speed peristaltic pump with flow rates from 0 to 25 ml/min.

10 Lazar Research Laboratories, Inc. Micro ph Measurement Primer Other Common Micro Measurements po2 & pco2 MICRO ELECTRODES We recommend the new p02 probe for micro p02 measurements for the following reasons: The new po2 probe can be used to measure po2 of tissues, whole cells, cell fractions, and various types of respiration studies. It can also be used to measure dissolved oxygen in biological and environmental samples. The pco2 probe can be used to measure pco2 in blood, 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. ORDERING INFORMATION 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.

11 Lazar Research Laboratories, Inc. Micro ph Measurement Primer 11 NEW po2 NEEDLE PROBE We recommend the new p02 needle probe for the following 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 meter to measure po2 of various. Unit comes complete with electronic signal conditioner for direct hookup to your recorder or ph meter. ORDERING INFORMATION Order DO-166NP p02 probe

12 Lazar Research Laboratories, Inc. Micro ph Measurement Primer HOW TO MEASURE IONS IN MICRO SAMPLES Measuring other ions, such as K, Na and Cl in micro samples is similar to measuring ph in these small samples. The same considerations apply such as using an electrode that has a low output resistance while at the same time having a nonglass body making it resistant to breakage. For best results, use micro ion electrodes that are made specifically for the ion that you want to measure 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 where Ion measurements are made.. Recommended electrodes for measuring ions in your smallest samples 96 well plates serum cups HPLC sample vials micro test tubes NMR tubes microcentrifuge tubes The preferred method for measuring ions in micro samples is Micro Ion Electrodes for the following reasons: MEASURE COMMON IONS IN 1/10 OF A DROP OF LIQUID - these electrodes are the smallest 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 per million), 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.

13 Lazar Research Laboratories, Inc. Micro ph Measurement Primer 13 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-146CL Copper 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 to 32K ISM-146S Thiocyanate 0.5 to 19K ISM-146SCN Reference electrode DJM-146

14 Lazar Research Laboratories, Inc. Micro ph Measurement Primer HOW TO PLACE AN ORDER OR REQUEST PRICING INFORMATION by phone: in the U.S International by by fax: by mail: Lazar Research Laboratories, Inc. 731 North LaBrea Avenue, Suite 5 Los Angeles, CA U.S.A. Note: Specifications and prices subject to change without notice To get a brochure on the Lazar micro ion electrodes contact us via at service@lazarlab.com giving us your fax number and request brochure FIS. METHODS OF PAYMENT net 30 to companies with recognized credit rating Visa or Mastercharge COD, 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 Research Labs, Inc. at service@lazarlab.com giving your fax number and asking for brochure FPHR.