Calibration balances

A 10-mL volumetric pipet was calibrated following the procedure just outlined, using a balance calibrated with brass weights having a density of 8.40 g/cm. At 25 °C the pipet was found to dispense 9.9736 g of water. What is the actual volume dispensed by the pipet ... 

Quality assurance measures such as pre-analytical checks on instrumental stability, wavelength calibration, balance calibration, tests on resolution of chromatography columns, and problem diagnostics are not included. For present purposes they are regarded as part of the analytical protocol, and IQC tests their effectiveness together with the other aspects of the methodology. 

If, as is usual, the sample has a lower density than the stainless steel balance calibration weight, the buoyancy effect of air on the sample mass means that a litre of water would indicate a weight of 1.05 g less than expected. Where weights of sample components are expressed as percentages or ratios, this error almost reduces to zero. This correction is usually ignored and considered well within acceptable experimental error (Jeffery et al., 1989, p. 76). 

Laboratory personnel commonly give one of three common responses to someone who points out the traceability requirements of ISO/fEC 17025 Its ok we have our balances calibrated every year, and when it is further pointed out that calibration extends to the chemical aspects of the measurement, I am sure it is ok to use this analytical-reagent-grade material to make a calibration solution, or we make measurements in such complex matrices, a suitable CRM just does not exist. The first comment stems from the rather physical or engineering flavor of the section in ISO/IEC 17025 (section 5.6) (ISO/IEC 2005), although traceability of calibration materials is mentioned. 

A moisture balance calibrated to indicate an 8% moisture content can be used to monitor weight loss and may be useful until experience is gained. The calibration can be performed as a gravimetric determination on a sample analyzed in parallel. This measurement can also be used to estimate an 8% moisture content relative to the initial sample weight. 

Verify the balance calibration by placing a 10 g and a 100 g weight on the balance pan. Use forceps take care not to touch the weights with your hands at any time. 

Were balances calibrated If so, how often Are logs available ... 

Calibration weights should only be used to calibrate or verify the accuracy of a balance. Calibration weights should never be used to make weight determinations. They should never be handled directly with hands, and they should be stored in safe locations away from environmental dangers. 

A horizontal audit examines one aspect of the analysis. For example, a horizontal audit might check the balance used to weigh samples for analysis. Is the balance calibration checked as required by the quality system Has it been regularly serviced Have the weights used to perform the balance calibration themselves been calibrated ... 

Calibration of balances calibration of ultraviolet grating for wavelength accuracy exchange of lamps system suitability testing analysis of quality control samples and evaluation of results using control charts. 

Calibration factor A load value in engineering units that a transducer will indicate for each volt of output, after amplifier gain and balance. Calibration factor is usually expressed in relation to FS. 

Uncertainty associated with the balance calibration, tfcaifb106, defined by... 

Certain variables— water quality, calibration of analytical balances, calibration of volumetric glassware and pipettes, stability of electrical power, and the temperature of heating baths, refrigerators, freezers, and centrifuges—should be monitored on a laboratorywide basis because they wiU affect many of the methods in the laboratory (see Chapter 1). In addition, there wiU be certain variables that relate more directly to individual analytical methods, and these require... 

In all quantitative TG investigations, it is necessary to characterize the reactant, and this may require both chemical (elemental) analysis, together with structure determination for those solids that exhibit polymorphism (where reactivity can vary with crystal form). The reaction identified must be consistent with both mass change and compositional evidence (which also confirms the balance calibration). Several aspects of sample examination and reaction characterization that merit consideration are mentioned in the following paragraphs ... 

Reference standards have to be used in those methods for calculating content within samples for example where the procedure asks for a calibration curve that requires weighing of substances on a mass balance (calibrated previously by certified masses). See also Sect. 29.1. 

In the ORNL s isopiestic system (Holmes et al., 1978 Holmes and Mesmer, 1986), operating at temperatures and pressures up to 250 °C and 3.5 MPa, a number of electrolyte solutions, placed in different metallic cups, attain an equilibrium with a common vapor phase at a well-controlled temperature. The equilibrium compositions are determined by weighing the cups in place (inside of the pressure vessel) with an electromagnetic balance calibrated frequently using a set of standard masses interspersed with the solution cups (Figure 1.7). 

Concept Assessment 1-1. No, an experimental result contrary to that predicted by a hypothesis is reason to reject a hypothesis, not its proof. 1-2. The product (mg) is the same for the unknown and the "weights" of known mass, regardless of the value of g. The measured mass with a two-pan balance is the same on the moon as on Earth. The single pan electronic balance measures weight, which is converted to a "mass" reading. With such a balance calibrated on Earth, the "mass" will appear less when measured on the moon. 1-3. To find the one temperature, substitute t(°C) = t(°F) into the... 

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