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Competence in Volume Measurement EXCELLENCE in MEASUREMENT ACCURACY Volumetric Instruments

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Competence in Volume Measurement EXCELLENCE in MEASUREMENT ACCURACY Volumetric Instruments Competence in Volume Measurement EXCELLENCE IN MEASUREMENT ACCURACY Volumetric instruments Volume measurement is of fundamental importance What are volumetric instruments? in the laboratory. Volumetric flasks, graduated cylinders, burettes and pipettes are standard Glass and plastic labware for measuring liquid equipment in any analytical laboratory. VITLAB is one volumes are the most frequently used apparatus in of the leading manufacturers of plastic laboratory the laboratory. There is a big difference between products and liquid handling instruments, and offers volumetric instruments for exact measurements, decades of experience in the development and including volumetric flasks, volumetric and graduated production of products for volume measurement. pipettes, graduated cylinders and burettes, on the one hand, and apparatus in which the scale is Basically, volumetric instruments can be made from intended solely as an approximate guide. plastic or glass, and fall under accuracy class AS, A This second type of apparatus includes graduated or B. It is important for the user to be clear about beakers, Griffin beakers, Erlenmeyer flasks, etc. the accuracy required for the application. Accurate The scale here is made to the same precision as in measurements require more than just precision graduated cylinders, for example, but the larger measurement instruments - proper handling is diameter leads to larger reading errors. also necessary. For this reason, the most important This relationship between the error limits, and the classification terms and their correct usage are inner diameter of the instrument at the menis- explained in the following. If you have any additional cus that is formed by the liquid to be measured, is questions on the topic volume measurement, please described in ISO 384:2015. do not hesitate to contact us. The draft standard defines the basic and metrological requirements for the construction and design of the volumetric instruments, and describes three accuracy classes (AS, A and B). VITLAB volumetric instruments Volumetric flasks Graduated cylinders Pipettes Burettes 2 www.vitlab.com Materials Plastic volumetric instruments Plastic products from VITLAB offer many advantages: • The high break resistance significantly reduces the risk of injury (none of the sharp edges as when glass breaks) and ensures a long service life • Excellent chemical resistance (e.g., even against NaOH, KOH, and HF) • The light weight makes it easier to use • Modern manufacturing techniques yield plastics with very smooth surfaces, which together with their hydrophobic properties make cleaning easy • Only pure, approved plastics are used - no additives that can lead to interferences in lab work • Many of the products made of polypropylene are approved for use with food 3 Manufacturing the blanks Only the highest quality plastic granulates are used in manufacturing our products, which guarantees that the instruments produced down the line will have the desired properties. Thus, polymethylpen- tene (PMP) is used exclusively for instruments of accuracy class A (volumetric flasks and graduated cylinders). This high-performance plastic offers near- glass transparency, and very good dimensional sta- bility after the production process. These are two of the critical requirements for producing Class A prod- The fluoroplastic PFA is a special case. Although this ucts. Moreover, PMP exhibits very good chemical and fluoroplastic copolymer doesn't have the excellent thermal resistance. transparency of PMP, it offers by far the best chemical and thermal resistance. Fine workmanship Polypropylene (PP) is used for the Accuracy Class B likewise offers outstanding dimensional stability, products, as well as volumetric and graduated thus enabling application in the manufacture of pipettes, graduated beakers, Griffin beakers and Class A volumetric flasks. Erlenmeyer flasks. This material has a good dimen- sional stability after the production process, and also High-quality blanks and strict statistical testing of exhibits good chemical and thermal resistance. the required quality characteristics are fundamental in producing high-quality volumetric instruments. For example, the blanks must withstand thermal stresses from controlled heating and cooling. This is a pre- requisite for achieving the best possible mechanical strength, with a volume that remains constant dur- ing subsequent thermal stresses. 4 www.vitlab.com Scales and labeling Techniques Cleaning Various techniques are used for the labels on our To maintain the long-term readability of the scale, products and for imprinting the scales. Volumetric do not clean imprinted volumetric instruments at flasks and pipettes are imprinted by standard temperatures exceeding 60 °C. Obviously, laboratory methods using high-quality inks, but PFA is an dishwashers can be used. These are gentler than exception because of its surface structure. A special immersion baths. Due to the low weight, we process makes it possible to apply the ring mark recommend using washing nets. in color, but imprinting within acceptable quality limits cannot be done for PFA products due to their If aggressive cleaning methods (higher temperatures, completely smooth and highly inert surfaces. more concentrated detergents) are to be used, we recommend products with raised scales without inks. Thus, the labels are engraved on the volumetric flask Compared to glass, the wall thickness of an injection- surface using a laser. This labeling method is thus molded plastic exhibits only very small differences. extremely durable. The color dyes used for PMP and This is due to the high pressures employed in injection PP products are matched individually to the plastic, molding, whereby products can be produced with and are applied using a silk screen printing or hot highly accurate surface contours and volumes. stamping process. 5 Labeling of volumetric instruments Example for a graduated cylinder Front Manufacturer Class A indicates Nominal volume, graduation and the highest accuracy volume units Maximum Calibration (In, TC) and reference error tolerance temperature Back Recycling code 20 Material DE-M marking for conformity certified products according to Maximum use temperature the German Measurement and Calibration Regulation DE-M Country of manufacture Lot number 01 Designation of the standard The labeling below must be printed on every Moreover, VITLAB imprints the following volumetric instrument: additional information, for example, on graduated cylinders: • Nominal volume • Units symbol: ml or cm³ • Country of manufacture • Reference temperature: 20 °C • Error limit • Calibration: Ex (TD) or In (TC) • Trademark • Class: A, AS or B • Standard, e.g., DIN 12681 • Waiting time (if necessary): in the format “Ex + 5 s” • Lot number • Manufacturer’s name 6 www.vitlab.com Labeling of volumetric instruments Certificates Quality certificate The quality assurance developed according to DIN EN ISO 9001 forms the basis for issuing factory calibration certificates, which serve as the quality certificates. These VITLAB factory test certificates are normally available in the form of a lot certificate, and an individual certificate can be obtained upon request. All test results are documented and archived for at least 7 years, so that individual results for any production times during this period can be accessed when the lot number or serial number is known. Lot certificate Individual certificate Quantity shipped per packing unit. Obtainable upon request prior to ordering. The following information is included: The following information is included: • Lot number, e.g. 13.01 (production year/lot) • Lot number and individual serial number, e.g., • Mean volume and standard deviation for the lot 13.02.1234 (year/lot/serial number) • Date of issue • Measured volume and measurement uncertainty • Date of issue Certificate of conformity Conformity for volumetric instruments means: Compliance of an instrument with the authorization for the legally regulated area in accordance with the German Measurement and Calibration Regulation. The DE-M marking certifies that the device meets the demands of the German Measurement and Calibration Regulation. This eliminates the need for a written Declaration of Conformity. Since there are no longer any DIN/EN/ISO standards for some of the plastic products, such as volumetric flasks, VITLAB uses the standards for the corresponding glass products. 7 Calibration Calibrations for volumetric measurements are The standard reference temperature, i.e., the basically of two types: “In” (TC) and “Ex” (TD): temperature at which the volumetric instruments are calibrated, is 20 °C. If a calibration or measurement Type “In”: The contained quantity of liquid is to be carried out at a different temperature, the corresponds to the volume printed on the instrument measured values ​​must be corrected accordingly. (volumetric flasks and graduated cylinders). Type “Ex”: The delivered quantity of liquid Accuracy classes corresponds to the volume printed on the instrument (pipettes and burettes). Volumetric instruments fall into two accuracy classes: Due to the hydrophobic properties of the materi- Class AS/A: Volumetric instruments of Class AS/A als, the measured and dispensed volumes are sub- offer the highest accuracy. For class stantially the same in plastic volumetric instruments AS volumetric instruments, calibrated (i.e., “In” = “Ex”). to deliver (TD, Ex), the additional ‘S’ means swift delivery (concerns pipettes VITLAB calibrates
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