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1、BRITISH STANDARD BS 7532:1991 Method of test for Accuracy and precision of mechanical handpipettes of capacity less than 50 4L down to and including 10 4L Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 13:33:19 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7532
2、:1991 This British Standard, having been prepared under the direction of the Laboratory Apparatus Standards Policy Committee, was published under the authority of the Standards Board and comes into effect on 31 January 1992 BSI 03-1999 The following BSI references relate to the work on this standard
3、: Committee reference LBC/27 Draft for comment 91/52110 DC ISBN 0 580 20230 5 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Laboratory Apparatus Standards Policy Committee (LBC/-) to Technical Committee LBC/27, upon which the following
4、 bodies were represented: Association of Clinical Biochemists British Glass Manufacturers Confederation British Laboratory Ware Association Department of Trade and Industry (Laboratory of the Government Chemist) Department of Trade and Industry (National Weights and Measures Laboratory) Institute of
5、 Medical Laboratory Sciences Medical Sterile Products Association South Western Regional Health Authority Amendments issued since publication Amd. No.DateComments Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 13:33:19 GMT+00:00 2006, Uncontrolled Copy, (c) BSI
6、 BS 7532:1991 BSI 03-1999i Contents Page Committees responsibleInside front cover Forewordii 0Introduction1 1Scope1 2Definitions1 3Apparatus1 4Reagent1 5Conditions of test1 6Procedure2 7Calculation and interpretation of results2 8Test report3 Table 1 Variation of the apparent density in air of disti
7、lled or deionized water with temperature3 Publication(s) referred toInside back cover Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 13:33:19 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7532:1991 ii BSI 03-1999 Foreword This British Standard has been prepared
8、 under the direction of the Laboratory Apparatus Standards Policy Committee. It supersedes DD 154:1986 which is withdrawn. It describes a method for determining the accuracy and precision of mechanical handpipettes of capacity less than 50 4L down to and including 10 4L. The method may also be suita
9、ble for mechanical handpipettes with a capacity less than 10 4L. BS 6018, originally published in 1981, described a gravimetric method of test for the accuracy and precision of mechanical handpipettes down to 50 4L. In seeking to extend the method to lower capacities, a number of problems were encou
10、ntered, especially the increase in errors due to evaporation. The BSI Committee therefore considered a number of other methods but all of these were found to have deficiencies. The method finally chosen was basically that of BS 6018 with the following major differences. a) The control of conditions
11、and especially the relative humidity in the test room is tighter. b) Evaporation is reduced by using a tall and narrow weighing vessel and allowance is made for any evaporation that occurs. The method was originally issued as a Draft for Development in order to gain sufficient experience and informa
12、tion on which to base a British Standard. In the event, the Draft for Development proved satisfactory with only minor technical changes which have been incorporated in the text of this British Standard. BS 7532 has also been aligned, where relevant, with BS 6018:1991. A British Standard does not pur
13、port to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front
14、cover, pages i and ii, pages 1 to 4, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Licensed Copy: London South Bank University, London South
15、 Bank University, Fri Dec 08 13:33:19 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7532:1991 BSI 03-19991 0 Introduction It has been shown experimentally that, when using or testing a mechanical handpipette, the errors due to the operator and his technique and due to evaporation become proportional
16、ly greater as the measured volume decreases. In measurement of small volumes they may well be the major source of error, yet they are not due, in the main, to the pipette itself. Variations in technique which have been shown to cause variation in results include the method of removing excess water f
17、rom the tip on sampling, the depth and angle of tip immersion and the method of removal of the dose from the tip. Evaporation can be minimized and corrected for by working speedily yet consistently and by the choice of vessel. The drift which occurs with electronic balances can be minimized by switc
18、hing on some hours before use. It is important to stress that the method described here tests the pipette plus operator plus technique and one pipette may seemingly perform differently: a) with various operators; or b) with the same operator under various conditions. Warmth transmitted by the hand t
19、o the mechanical handpipette during normal use may affect the performance of some pipettes. In order that any variation due to this might be seen, it is recommended that the instrument be neither pre-conditioned (warmed) before, nor isolated from handwarming during testing. 1 Scope This British Stan
20、dard describes a method of test for determining the accuracy and precision of the volume delivered by mechanical handpipettes of capacity less than 50 4L down to and including 10 4L in the temperature range 16 C to 25 C. NOTE 1The method may also be applicable to handpipettes down to 1 4L. NOTE 2The
21、 method applicable to handpipettes down to 50 4L is described in BS 6018. NOTE 3The titles of the publications referred to in this standard are listed on the inside back cover. 2 Definitions For the purposes of this British Standard, the following definitions apply. 2.1 mechanical handpipette a hand
22、-held semi-automatic pipette with a detachable tip, used for transferring and dispensing a measured volume of liquid by displacement with or without an interface 2.2 accuracy (of a mechanical handpipette) the closeness of agreement between the nominal volume and the mean volume obtained by testing i
23、n accordance with this British Standard NOTEIt is quantified by the inaccuracy of the mean, expressed as a percentage error. 2.3 repeatability (of a mechanical handpipette) the closeness of agreement between the results of successive measurements of the same volume and carried out subject to all of
24、the following conditions: a) the same method of measurement; b) the same observer; c) the same measuring instrument; d) the same location; e) the same conditions of use; f) repetition over a short period of time. NOTERepeatability is expressed as the coefficient of variation (in %). 3 Apparatus 3.1
25、Analytical balance, capable of being read to 0.01 mg with a repeatability of 0.02 mg. NOTE 1A balance which tares rapidly is an advantage. NOTE 2There is evidence that, if a balance readable to 0.001 mg and with a repeatability of 0.002 mg is used, the method described may be extended to mechanical
26、pipettes having a capacity down to 1 4L (but see foreword and clause 0). 3.2 Water containers, comprising two 100 mL capacity beakers. 3.3 Weighing vessel, comprising a flat bottomed glass or plastic tube, of dimensions 75 mm 12 mm. NOTEThe weighing vessel is tall and narrow, tall enough to have sev
27、eral centimetres of airspace above the liquid level yet not so narrow as to impede pipette manipulation. 3.4 Stop watch or timer, accurate to 1 s. 3.5 Thermometer, accurate to 0.1 C. NOTEA 0 C to 40.5 C, 100 mm immersion type thermometer, complying with BS 593 is suitable. 4 Reagent 4.1 Water, fresh
28、ly distilled or deionized complying with grade 3 of BS 3978. 5 Conditions of test 5.1 Test room The test shall be carried out in a room with a stable environment having a relative humidity maintained at 55 10 % r.h. and a temperature between 16 C and 25 C. NOTE 1Precautions should be taken to avoid
29、draughts from open doors, windows or air conditioning units. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 13:33:19 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7532:1991 2 BSI 03-1999 NOTE 2It is recommended that the temperature during the test is within 2 C
30、 of the starting temperature. 5.2 Cycle time The cycle time shall be kept to a minimum. NOTEThe cycle time should not exceed 60 s. It is important that the routine of each cycle is as regular as possible and that, each cycle is performed as quickly as possible. 6 Procedure 6.1 Place the instruments
31、to be tested together with one of the water containers (3.2), containing approximately 50 mL of water (4.1), in the test room for at least 1 h before the test to enable them to reach equilibrium temperature. The water in this container is to be used for filling the pipette to be tested and is herein
32、after referred to as the test water. 6.2 Place 1 mL of water (4.1) in the weighing vessel (3.3). Place this and the second water container (3.2) containing 50 mL of water (4.1) in the case of the balance (3.1) for at least 1 h before the test to enable them to reach equilibrium temperature and humid
33、ity. 6.3 If using an adjustable pipette, set the capacity to the required value. Do not alter the setting of an adjustable pipette during a sequence of ten weighing cycles (see 6.4 to 6.10). NOTEPipettes of adjustable capacity should be tested at the manufacturers recommended maximum and minimum cap
34、acity values and at two or more intermediate capacity values, one of which should be below the mid-point of the range. 6.4 Prepare the mechanical handpipette for the weighing cycle, fitting the tip recommended or supplied by the manufacturer if appropriate and filling and expelling water not less th
35、an five times using the test water. 6.5 Measure and record the temperature of the test water to the nearest 0.1 C. 6.6 Note the time to the nearest second or start the stop watch (3.4). 6.7 Place the weighing vessel (3.3) (with added water) on the balance pan and record its mass (m0) to the nearest
36、0.01 mg, or use the tare facility. Whilst the balance is stabilizing, fill the pipette from the test water, immersing the tip 2 mm to 4 mm into the water. Release the button slowly. Lift the pipette vertically and cleanly from the surface of the water. NOTEPrecautions should be taken in handling the
37、 weighing vessel to avoid direct hand contact, e.g. by the use of lint-free cotton gloves. 6.8 Remove the weighing vessel from the balance pan. Expel the contents of the pipette into the vessel, immersing the tip of the pipette 2 mm to 4 mm into the water. Lift the pipette vertically and cleanly fro
38、m the surface of the water. NOTEIt is important for consistency of results that the depth to which the tip is immersed as described in 6.7 is as close as possible to that described in 6.8. 6.9 Place the weighing vessel on the balance pan and record its mass (m1) to the nearest 0.01 mg. If the facili
39、ty is available, tare the balance. 6.10 Repeat the steps described in 6.7 to 6.9 until 10 weighing cycles have been carried out to obtain a series of masses, m2, m3, .m10 for each of the consecutive weighing cycles. If the tare facility is available use it after recording the value of each dose mass
40、. Record the total mass of the vessel and 10 doses (m11). 6.11 Note the time to the nearest second or stop the stop watch and calculate half the total time for the 10 weighing cycles. 6.12 When the final weighing of the 10 weighing cycles has been completed, allow the weighing vessel to stand in the
41、 balance case for a period equal to half the total test time (calculated in 6.11). 6.13 Remove the weighing vessel from the balance case and allow it to stand on the work bench for a further period equal to half the total test time (calculated in 6.11). 6.14 Place the weighing vessel on the balance
42、pan and record its mass (m12) to the nearest 0.01 mg. 6.15 Measure the temperature of the remaining test water to the nearest 0.1 C and calculate the mean test temperature. 7 Calculation and interpretation of results 7.1 Calculation of dose volumes 7.1.1 Calculation of mass loss Calculate the mass l
43、oss per cycle (in g) from the following equation: Loss per cycle = (m11 p m12)/10 where 7.1.2 Calculation of corrected dose mass If the tare facility has not been used calculate 10 values for the mass of successive doses by subtraction, i.e. m1 p m0, m2 p m1, etc. Add to each dose mass the mass loss
44、 per cycle from 7.1.1 to obtain a series of dose masses corrected for evaporation. m11is the mass of the weighing vessel and 10 doses at the end of 10 weighing cycles (in g) (see 6.10); m12is the mass of the weighing vessel and 10 doses after standing (in g) (see 6.14). Licensed Copy: London South B
45、ank University, London South Bank University, Fri Dec 08 13:33:19 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7532:1991 BSI 03-19993 7.1.3 Conversion to dose volumes Convert each dose mass (in g) to a dose volume (x 4L) by multiplying by 1 000 and dividing by the apparent density in air of water (
46、in g/mL) at the mean test temperature (see Table 1). Table 1 Variation of the apparent density in air of distilled or deionized water with temperature 7.1.4 Mean volume delivered Add the ten values for the dose volumes together and divide by 10 to obtain a mean volume delivered(in 4L). 7.2 Accuracy
47、Calculate the error of the handpipette, A, expressed as a percentage from the equation: where Compare this value with the manufacturers published information. 7.3 Standard deviation Calculate the standard deviation (s) from the volume delivered from the equation: where Compare this value with the ma
48、nufacturers published information. 7.4 Coefficient of variation Calculate the coefficient of variation (Cv), expressed as a percentage, from the equation: Cv = 100s/ where Compare this value with the manufacturers published information. 8 Test report The test report shall include the following: a) i
49、dentification of the pipette; b) the method of test, e.g. “In accordance with BS 7532”, and the date of test; c) the nominal volume at which the test was carried out (see 6.3); d) the mean temperature at which the test was carried out (see 6.15); e) the accuracy (see 7.2); f) the standard deviation (see 7.3); g) the coefficient of variation (see 7.4). TemperatureApparent density TemperatureApparent density Cg/mLCg/mL 16 17 18 19 20 0.99789 0.99772 0.99754 0.99735 0.99715 21 22 23 24 25 0.99694 0.99672 0.99649 0.99624 0.99599 NOTEThese density values ta
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