What Precautions should be taken for correct weighing of Laboratory Samples?

在决定之后对样本需要的衡量平衡you have to start the actual weighing.You have to keep in mind that the accuracy and precision of your results is largely dependent on the reliability of your weighing. It is at this stage that you have to take adequate precautions and adhere to the standard operating procedures to ensure reliability of your reports.

Balance Calibration

• Weighing of samples is always against standard reference weights. Ensure that your laboratory has a set of certified standard weights and their calibration is validated as per the prescribed procedure through a recognized national calibration laboratory
• Keep your balance always calibrated using standard calibration procedures against daily, weekly and monthly schedules
• Standard weights should never be touched with hands

Environmental Control

• Horizontal positioning of balance should be daily checked with the help of inbuilt spirit level
• The balance should be kept on a vibration free support
• Balance should be kept in an area with controlled temperature and humidity
• 硅胶袋应放置在称重室内，以防止室外湿度。袋子应定期充电或更换。
• Balance should not be exposed to direct sunlight as this can cause temperature variations inside the weighing chamber
• 余额不应位于门或窗户旁边，因为打开和关闭导致航空料。
• Always weigh samples after closing the weighing chamber doors
• Keep the inside of the weighing chamber and surrounding bench space scrupulously clean so as to avoid errors and cross contamination of samples.

Handling of Weights

• Weights should not be touched with bare hands as grease or oil from hands can lead to errors. Always use a pair of clean forceps
• Place weights gently onto the pan. The weights should be kept in the centre of the pan so as to avoid errors due to eccentricity
• After use weights should not be left outside on the work bench but kept inside the slots in the weight box and keep the box closed so as to avoid minimum environmental exposure

Weighing of Samples

• 每次使用适当尺寸的清洁刮刀
• Butter paper weighing can introduce errors. Instead weigh the sample quantity required in the volumetric flask and after weighing of samples make up the volume with the diluent
• 允许阅读在录制前稳定
• Accurate weighing of samples of small amounts requires additional precautions such as use of disposable gloves, use of head caps to prevent fall of hair or dandruff and use of face mask to prevent breath from disturbing the reading
• Reading should be recorded directly into the laboratory notebook. Making note of readings on scrap paper, filter paper or hands should be strictly forbidden
• 将打印机添加到余额，以便直接打印在重量滑动上以避免转录错误。保护重量滑动以及实验室记录。

Weighing of samples is a critical component of any analytical determination. You can eliminate errors by adopting the recommended weighing practices as a regular habit.

Please feel free to share your experiences and offer your suggestions and comments