Transcript Glassware
Laboratory Glassware MLAB 1335 Immunology Serology Terry Kotrla, MS, MT(ASCP)BB Pipets (Pipettes) Laboratory instrument used to transport a measured volume of liquid. Three types of glass pipets used in the laboratory Volumetric Mohr Serological Mechanical Terms TC = To contain TD = To deliver Markings Pipets will be stamped with either a TD or TC. TD-blow out pipettes will have 2 frosted bands near the mouthpiece of the pipet. Volumetric Designed to transfer a fixed amount of liquid when filled to the mark, e.g. 10 mL and only 10 mL. There is generally only one "fill-line" on a volumetric pipet. For example a 5 mL volumetric pipette has one marking on it. This marking measures exactly 5 mL. of liquid, no more, no less. Volumetric Designed to deliver a single volume precisely, the volume will be indicated near the top of the pipet, At the top of the pipet is an etched ring. Fluid must be drawn up the pipet to above the ring indicating the volume and then released slowly until the bottom of the meniscus is exactly at the ring. To transfer this volume to a second container, touch the pipette tip to the inside of the new container and allow the liquid to drain out. Serological - TC A pipet marked TC, also known as a “blow out” pipet, has been calibrated "to contain" a specified volume of liquid. These pipets will have no base mark and graduations continue onto the tip. This means that ALL the measured liquid in the pipet must be delivered. A 5 mL serological pipette with one-tenth milliliter graduations can be used to obtain any desired volume of liquid in one-tenth milliliter increments between 0.1 mL to 5.0 mL, although volumes smaller than 0.2 mL are best measured with automatic pipets. Serological - TD TD pipets are not graduated to the tip and may have etched or colored rings around the top. Graduated “to deliver”, the base mark is at the top of the pipet. In this type of pipet the marking near the tip of the pipet should be the same as the total volume listed near the top of the pipet Serological - TD The majority of TD pipets are designed to be "blown out" by pushing a small amount of air out of the pipet, completely emptying it. These pipets are identified by an etched ring or two thin rings near the top of the pipet. Mohr – TC – to contain A pipet with this marking has been calibrated to contain a specified volume of liquid. These pipets have a single painted or frosted ring at the top and are allowed to simply drain with the tip placed against the side of the receiving vessel. To accurately transfer fluid with this type of pipet, the meniscus must be precisely on a calibration mark both at the beginning and at the end of a transfer. Mohr - TC To accurately transfer fluid with this type of pipet, the meniscus must be precisely on a calibration mark both at the beginning and at the end of a transfer. Near the top of this type of pipet you will find the total volume indicated and the size of the smallest gradations (i.e., 5 mL in 1/10, the total volume of the pipet is 5 mL, and it is graduated in 1/10 mL increments). Proper Use When filling a pipet, the tapered end is held beneath the surface of the liquid at all times. The liquid is drawn into the pipet by suction until the level is equal to or greater than the volume of liquid to be delivered. Since Mohr pipets are labeled with the zero mark at the top of the pipet you will need to subtract the amount you are going to pipet from the total volume of the pipet to determine the exact mark to fill the pipet to. For example if you are going to pipet 6.5 mL using a 10 mL pipet you would fill the pipet to the 3.5 mL mark. To determine the total volume of the pipet look near the top of this type of pipet. What volume does this pipet contain? Proper Use When reading the volume, ALWAYS view the pipette dead-on at eye level with the pipette held vertically, perpendicular to the ground. Pipettes are designed to be used with a hand pump or bulb, of which there are many varieties. Never use your mouth with a pipet! Mechanical or Automatic Mechanical pipets can be set to draw and dispense different volumes or be preset to deliver an exact volume. Used to accurately deliver very small volumes, microliters, of liquid. Although 0.1 mL could be delivered by a serological pipet most labs use mechanical, or automatic pipets. A volume of 0.1 mL is equal to 100 microliters Mechanical or Automatic Mechanical pipets are operated by depressing the plunger. On the downward stroke of the plunger there are TWO stops. The first offers firm resistance, and the second is a hard stop. To take up a volume in the pipet, place a tip on the end of the pipet. Depress the plunger to the first stop and insert into the sample to be transferred. Draw the liquid into the pipet by SLOWLY releasing the plunger. To dispense the liquid from the pipet, place the tip of the pipet into the opening of the well and slowly depress the plunger all the way to the second stop. When the liquid has been dispensed withdraw the pipet tip from the well BEFORE releasing the plunger. Glassware Glassware can be divided into 2 groups Non-volumetric glassware Beaker Flask Volumetric Glassware Volumetric Flask Graduated Cylinder Beaker Used for transferring liquid to another container or to transfer a small amount of reagent for use in procedures. Volume is not accurate, just an estimate. NEVER PLACE A REAGENT IN ANOTHER CONTAINER WITHOUT LABELING THE CONTAINER FIRST. Erlenmeyer Flask Features a conical base, a cylindrical neck and a flat bottom. They are marked on the side (graduated) to indicate the approximate volume of their contents. This is NOT used for ACCURATE measurement Erlenmeyer Flask – an FYI Like many other common pieces of glassware, Erlenmeyer flasks could potentially be used in the production of illegal narcotics. In an effort to restrict such production, some U.S. states (including Texas) have begun requiring permits to purchase such glassware, including Erlenmeyer flasks, as well as chemicals identified as common starting materials. Graduated Cylinder For rapid measurement of liquid volume. They are generally more accurate and precise for this purpose than flasks. This is a semi-accurate liquid measuring vessels. Reading the Volume 10 mL has approx 6.62 mL 100 mL 52.7 mL 25 mL has 11.5 mL Volumetric Flask A volumetric flask is used to measure very precisely one specific volume of liquid (100 ml, 250 ml, etc., depending on which flask you use). This flask is used to prepare a solution of known concentration. To make up a solution, first dissolve the solid material completely, in less fluid than required to fill the flask to the mark. After the solid is completely dissolved, very carefully fill the flask to the mL mark. The top is then sealed and the flask is inverted several times to mix. References Use of Serological Pipets http://tinyurl.com/5c9doe Volumetric Flask http://tinyurl.com/5sercn Measuring Volume Using a Graduated Cylinder a learning activity http://tinyurl.com/5z8r7c