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Balance calibration.pptx
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- 2. Balance Calibration USP Chapter no. 41Balances USP Chapter no. 1251 Weighing of analytical balance EP Chapter no. 2.1.7
- 3. Important term andexcel formula Least count Sprit level Acceptance criteria Tolerance True value versus Display value Operating range Accuracy versus Precision Standard deviation Percentage Relative Standard Deviations correlation coefficients Mean Scale interval Nominal value versus Certificate value
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- 5. Repeatability or Measurement of Uncertainty Criteria- NMT 0.10% Formula = 2∗𝑆𝐷 𝑠𝑚𝑎𝑙𝑙𝑒𝑠𝑡 𝑛𝑒𝑡 𝑤𝑒𝑖𝑔ℎ𝑡 x 100 Smallest net weight = 2000 x SD If SD less than 0.41d than Smallest net weight = 2000 x 0.41d where d is scale interval Readability (smallest value read by balance) Smallest net weight determine the operating range 1 mg to 220 gm. E.g.- 5 gm. for 10 times Nominal value = Smallest net weight Least count = d Mean Standard deviation Uncertainty = 2∗0.41𝑑 𝑜𝑟 𝑆𝐷 𝑆𝑡𝑎𝑛𝑑𝑎𝑟𝑑 𝑊𝑒𝑖𝑔ℎ𝑡 x100
- 6. Accuracy Criteria- ±0.10% Formula = 𝑐𝑒𝑟𝑖𝑓𝑖𝑐𝑎𝑡𝑒 𝑤𝑒𝑖𝑔ℎ𝑡 −𝑜𝑏𝑠𝑒𝑟𝑣𝑒𝑑 𝑤𝑒𝑖𝑔ℎ𝑡 𝑐𝑒𝑟𝑡𝑖𝑓𝑖𝑐𝑎𝑡𝑒 𝑤𝑒𝑖𝑔ℎ𝑡 x 100 E.g., -50 mg, 01gm,10 gm and 100 gm. The degree of agreement between a measured value and the accepted reference value. The degree of closeness of the determined value to the nominal or known true value under prescribed conditions. This is sometimes termed trueness. Check accuracy using different standard weight from 5 to 100% of balance capacity.
- 7. Sensitivity Test weightnear to balance capacity is selected Formula = 𝑐𝑒𝑟𝑖𝑓𝑖𝑐𝑎𝑡𝑒 𝑤𝑒𝑖𝑔ℎ𝑡 −𝑜𝑏𝑠𝑒𝑟𝑣𝑒𝑑 𝑤𝑒𝑖𝑔ℎ𝑡 𝑐𝑒𝑟𝑡𝑖𝑓𝑖𝑐𝑎𝑡𝑒 𝑤𝑒𝑖𝑔ℎ𝑡 x 100 The repeatability or reproducibility of individual measurements expressed as standard deviation (SD), or Relative Standard deviation (RSD). Check 5 times weight as selected for linearity by loading & unloading specific weight. Calculate % RSD for observed weight. Criteria- NMT 0.05%
- 8. Linearity Criteria- NMT0.05% Formula = 𝑜𝑏𝑠𝑒𝑟𝑣𝑒𝑑 𝑤𝑒𝑖𝑔ℎ𝑡 𝑟𝑒𝑎𝑑𝑖𝑛𝑔 1 −𝑜𝑏𝑠𝑒𝑟𝑣𝑒𝑑 𝑤𝑒𝑖𝑔ℎ𝑡 𝑟𝑒𝑎𝑑𝑖𝑛𝑔 2 𝑜𝑏𝑠𝑒𝑟𝑣𝑒𝑑 𝑤𝑒𝑖𝑔ℎ𝑡 𝑟𝑒𝑎𝑑𝑖𝑛𝑔 1 x 100 The linearity of an analytical procedure is its ability (within a given range) to obtain test results which are directly proportional to the concentration (amount) of analyze in the sample. Check 5 different weight. Plot graph of actual weight against observed weight. It should be linear. Calculate correlation coefficients and it should not be less than 0.99%
- 9. Eccentricity Criteria- NMT0.05% for corner and ±0.10% center Formula = 𝑤𝑒𝑖𝑔ℎ𝑡 𝑎𝑡 𝑐𝑒𝑛𝑡𝑒𝑟 −𝑤𝑒𝑖𝑔ℎ𝑡 𝑎𝑡 𝑐𝑜𝑟𝑛𝑜𝑟 𝑤𝑒𝑖𝑔ℎ𝑡 𝑎𝑡 𝑐𝑒𝑛𝑡𝑒𝑟 x 100 Test weight should be more than 30% of balance capacity. Eg-100 gm weight used Weigh 1/3rd of the maximum capacity of balance in the 4 corners & center of the pan of the balance. Calculate % RSD for observed weight.