ISO 7106 Determination of oil content in Liquefied anhydrous ammonia

Detection Target

Determination of oil content in liquefied anhydrous ammonia

Overview

This solution conforms to the ISO 7106 Liquefied anhydrous ammonia for industrial use — Determination of oil content — Gravimetric and infra-red spectrometric methods. This International Standard specifies two methods for the determination of the oil content non volatile at about 105 °C, of liquefied anhydrous ammonia for industrial use, namely: a gravimetric method and an infra-red spectrometric method. The gravimetric method is applicable to products having an oil content equal to or greater than 10 mg/kg. The infra-red spectrometric method, being more sensitive, is applicable to products having an oil content greater than 1 mg/kg. Principle At room temperature, after evaporating the liquid ammonia sample, the oil in the residue is extracted using Tetrachloroethylene. The absorbance of the organic phase is measured at a fixed wavelength of approximately 3.42 μm (corresponding to the strongest absorption band of the asymmetric vibration of CH groups) to determine the oil content in anhydrous liquid ammonia.

Operating Conditions

1. Apparatus and Accessories

   1) HKL-7106 FTIR Spectrometer for oil content in Liquefied anhydrous ammonia

   2) Liquid Test Accessory: Stoppered quartz cuvette (1 cm path length)

2. Others

   1) Tetrachloroethylene (C₂Cl₄)

   2) Paraffin oil standard solution

3. Test Conditions

   1) Resolution: 4 cm^-1

   2) Scan times: 32

   3) Detector: Pyroelectric Infrared Detector

Preparation of Test Solution

1. Remove the oil-containing platinum evaporation dish from the desiccator.

2. Add 10 ml of Tetrachloroethylene (C₂Cl₄) to dissolve the oil.

3. Transfer the solution to a 50 ml volumetric flask.

4. Rinse the dish 2–3 times with additional C₂Cl₄, then dilute to the mark with C₂Cl₄ and mix thoroughly for analysis.

Standard Curve Preparation

1.Inject paraffin oil standard solutions (containing 0.25 mg, 0.50 mg, 1.00 mg, 1.50 mg, 2.00 mg, and 2.50 mg of paraffin oil) sequentially into stoppered quartz cuvettes. Using C2Cl₄ as the background, measure the absorbance at ~3.42 μm (2924 cm⁻¹), corresponding to the maximum absorption peak of CH stretching vibrations. 

2. Plot the standard curve with absorbance (y-axis) against paraffin oil mass (x-axis) (see figure below).

Conclusion

The infrared spectrometric method with standard curve calibration enables accurate and rapid determination of oil content in anhydrous liquid ammonia. The calibration curve demonstrates near-perfect linearity with R²=1, fully meeting quantitative analysis requirements.