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GB/T 9722-2006 English PDF (GBT9722-2006)

GB/T 9722-2006 English PDF (GBT9722-2006)

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GB/T 9722-2006: Chemical reagent -- General rules for the gas chromatography

This Standard specifies requirements for instruments by chemical reagent gas chromatography and analysis methods. The detectors used include thermal conductivity detectors and flame ionization detectors. The chromatographic columns are packed column and capillary column.
GB/T 9722-2006
GB
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
ICS 71.040.030
G 60
Replacing GB/T 9722-1988
Chemical reagent - General rules for the gas
chromatography
ISSUED ON: JANUARY 23, 2006
IMPLEMENTED ON: NOVEMBER 01, 2006
Issued by: General Administration of Quality Supervision, Inspection and Quarantine;
Standardization Administration of the People's Republic of
China.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative references ... 4
3 Terms and definitions ... 4
4 Method principle ... 5
5 Reagents and materials ... 5
6 Instruments ... 5
7 Selection of test conditions ... 7
8 Methods of operation ... 8
9 Quantitative method ... 14
10 Method error ... 17
11 Environmental requirements and safety matters ... 18
Annex A (normative) Illustration diagrams and calculation formulas for related terms ... 20
Chemical reagent - General rules for the gas
chromatography
1 Scope
This Standard specifies requirements for instruments by chemical reagent gas chromatography and analysis methods. The detectors used include thermal conductivity detectors and flame ionization detectors. The chromatographic columns are packed column and capillary column.
This Standard is applicable to determination of main ingredients and impurities of organic chemical reagents that contain volatile ingredients.
2 Normative references
The provisions in following documents become the provisions of this Standard through reference in this Standard. For dated references, the subsequent amendments (excluding corrigendum) or revisions do not apply to this Standard, however, parties who reach an agreement based on this Standard are
encouraged to study if the latest versions of these documents are applicable. For undated references, the latest edition of the referenced document applies. GB/T 4946, Terms of gas chromatography
JJG 700-1999, Verification Regulation of Gas Chromatograph
No. 250 Gas Cylinder Safety Supervision Regulations issued by Quality and Technology Supervision Bureau [2000]
3 Terms and definitions
For the purposes of this document, the terms and definitions defined by GB/T 4946 as well as the followings apply.
3.1 asymmetric factor (f)
a parameter that describes the degree of asymmetry of chromatographic peaks; see Annex A for diagram
3.2 height of an effective plate (Heff)
6.3 Stability of the whole machine
Use hydrogen as carrier gas (when using thermal conductivity detector) or nitrogen as carrier gas (when using flame ionization detector). Use dinonyl phthalate (mass fraction is 20%) to apply on white diatomaceous earth carrier (0.18mm~0.25mm) as the stationary phase. Column length is 2m. Column
temperature is 80??C. Appropriately select carrier gas flow rate. The sensitivity of the instrument shall be close to the requirements of the sensitivity of the whole machine. The baseline drift value of the instrument within 10min shall not be greater than 1% of the full scale.
6.4 Sensitivity of the whole machine
6.4.1 Instrument that uses thermal conductivity detector
Take benzene as sample. The test conditions are the same as 6.3. The
sensitivity is calculated as ST. The value is expressed in milligrams per millivolt (mV?€?mL/mg). The sensitivity shall not be less than 1000 mV?€?mL/mg. Calculate according to formula (1):
Where,
A - Arithmetic mean of benzene peak area, in millivolt minutes (mV?€?min); FC - Value of the corrected carrier gas flow rate, in milliliters per minute (mL/min); m - Benzene injection volume value, in milligrams (mg).
Refer to Annex A for the calibration of carrier gas flow rate.
When using a recorder to record the peak area, the half-height width of the benzene peak shall not be less than 5mm, the peak height is not less than 60% of the full scale of the recorder. The peak area A in formula (1) is calculated according to formula (2):
Where,
A - Benzene peak area, in millivolt minutes (mV?€?min);
C1 - Value of recorder sensitivity, in millivolts per centimeter (mV/cm); and the thickness of the fixative film;
e) Temperature: column temperature, vaporization chamber temperature,
detection chamber temperature;
f) Degree of separation: according to the requirements of method precision and accuracy, specify the degree of separation of the measured
component and its difficult-to-separate substance (retain two significant digits);
g) Asymmetric factor: according to the requirements of method precision and accuracy, specify the asymmetry factor of the main peak; the calculation method is shown in Annex A (retain two significant digits);
h) Height of an effective plate: on the basis of meeting the requirements of degree of separation and asymmetry factor, specify the height of an
effective plate of the column; see Annex A for the calculation method
(retain two significant digits);
i) relative retention value (reserve to two decimal places);
j) Injection volume: shall be controlled within a linear response range. Each impurity peak and internal standard shall be clearly recorded at the
injection volume. When using the normalization method, the main peak
height (or after attenuation) shall account for more than 70% of the full scale on the recorder;
k) Bridge flow, split ratio, makeup and other instrument conditions;
l) Quantitative method.
NOTE: The separation of difficult-to-separate substance pairs and the retention value relative to the main body can be determined according to needs. Carrier gas flow rate, column temperature, vaporization chamber temperature, split ratio and makeup and injection volume conditions can be adjusted according to the specific instrument performance during operation.
8 Methods of operation
8.1 Chromatographic column
8.1.1 Filling column
8.1.1.1 Fixative coating
Dissolve the fixative in the solvent. Make it a homogeneous solution. Soak the carrier in the solution (heat to reflux if necessary). Stir gently or shake well. Do not crush the carrier. Place in a fume hood. Volatilize and dry the solvent under infrared light.
The mass fraction of the fixative is calculated in w. The value is expressed in %. Calculate according to formula (4):
Where,
m1 - Value of fixative mass, in grams (g);
m2 - value of carrier mass, in grams (g).
8.1.1.2 Pretreatment of empty column
First remove the mechanical impurities in the column. Use nitric acid solution (mass fraction is 105) to wash. Use water to wash to neutral. Then use sodium hydroxide solution (100g/L) to wash. Finally, use water to wash to neutral. Bake to dry.
8.1.1.3 Packing of chromatographic column
Tighten one end of the pretreated empty column with glass fiber and copper wire mesh. Connect to vacuum pump for decompression and evacuation. Add stationary phase at the other end. At the same time conduct moderate vibration. Pack the carrier evenly and tightly into the chromatographic column.
8.1.1.4 Ageing of chromatographic column
The aging chromatographic column shall be slowly heated in nitrogen gas flow. After the temperature rises below the maximum use temperature of the fixative, keep for more than 4h (the temperature must not be too high to prevent loss). After aging, the temperature shall be gradually reduced in the carrier gas. 8.1.2 Capillary column
There are currently available capillary columns for different purposes on the market. The user can choose according to the nature of the sample.
8.2 Determination of carrier gas flow rate
8.2.1 Determination of carrier gas flow rate of thermal conductivity
detector
9 Quantitative method
9.1 Correction factor
This Standard adopts the mass correction factor of component i relative to the main body.
9.1.1 Principle of adopting correction factor
For the individual components listed in the technical indicators, the correction factor is used regardless of the mass fraction. Among the tested components, whether a correction factor is added to homologues with relatively close carbon numbers or substances with small differences in thermal conductivity, shall depend on the specific circumstances.
9.1.2 Determination of correction factor
Use weighing method (to the nearest of 0.0001g) to prepare several standards that are similar to the components to be corrected. Determine according to the determination conditions of the sample. The determination result is rounded off at 95% confidence level. Calculate the average (retain two significant digits). The correction factor is expressed as fi. The value is calculated according to formula (9):
Where,
As - Value of main body peak area, in square centimeters (cm2) or millivolt minutes (mV?€?min);
mi - Value of component i mass, in grams (g);
Ai - Value of component i peak area, in square centimeter (cm2) or millivolt minutes (mV?€?min);
ms - Value of main body mass, in grams (g).
NOTE: When preparing the standards, if there is no pure product, the mass fraction can be measured by other methods for correction
9.2 Normalization method
When the normalization method is used for quantification, the following Where,
ms - Value of mass of added internal standard substance, in grams (g);
Ai - Value of peak area of component i, in square centimeters (cm2) or millivolt minutes (mV?€?min);
fs,i - Value of correction factor of component i compared with internal standard substance;
m - Value of sample mass, in grams (g);
As - Value of peak area of internal standard substance, in square centimeters (cm2) or millivolt minutes (mV?€?min).
9.4 External standard method
When the external standard method is used for quantification, the following requirements shall be met:
a) The external standard solution is prepared by weighing method (to the nearest of 0.0001g). Its concentration shall be close to the mass fraction of the component to be tested;
b) The injection volume shall be within the linear range of the detector. All the components to be tested shall flow out under the test conditions. Repeat the test for the same sample.
The mass fraction of the component tested by external standard method is calculated in wi. The value is expressed in %. Calculate according to formula (12):
Where,
Ei - Mass fraction (%) of component i in standard sample;
Ai - Peak area of component i, in square centimeters (cm2) or millivolt minutes (mV?€?min);
AE - Peak area of component i in standard sample, in square centimeters (cm2) standard deviation RSD. Value is expressed in %. Calculate according to formula (14):
Where,
wi - Mass fraction of the ith measurement, in %;
- Arithmetic mean of the mass fractions of n injections, in %;
n - Number of measurements;
i - Value of injection number.
10.2 Accuracy
Accuracy is calculated by the recovery rate r of component i. Value is expressed in %. Calculate according to formula (15):
Where,
m2 - Value of component i mass detected after component i is added in sample, in milligrams (mg);
m1 - Value of component i mass detected in sample, in milligrams (mg);
ma - Value of added component i mass, in milligrams (mg).
11 Environmental requirements and safety matters
11.1 Environmental requirements
The instrument shall be placed under the condition that the room temperature is 5??C~35??C and the relative humidity is lower than 85%. Prevent the intrusion of corrosive gas, vibration, direct sunlight and strong magnetic field from damage to the instrument. The operation site shall have good ventilation. 11.2 Safety precautions
Annex A
(normative)
Illustration diagrams and calculation formulas for related terms
A.1 Carrier gas flow rate after calibration, Fc
The carrier gas flow rate after calibration is calculated in Fc. The value is expressed in milliliters per minute (mL/min). Calculate according to formula (A.1):
Where,
F0 - Value of carrier gas flow rate at the outlet of detector measured by soap film flowmeter at room temperature, in milliliters per minute (mL/min); TC - Value of column temperature, in Kelvin (K);
Tr - Value of room temperature, in Kelvin (K);
pw - Value of saturated vapor pressure of water at room temperature, in megapascal (MPa);
p0 - Value of atmospheric pressure, in megapascal (MPa);
j - Pressure gradient correction factor.
Pressure gradient correction factor j is calculated according to formula (A.2): Where,
pi - Value of injection inlet pressure, in megapascal (MPa).
A.2 Asymmetry factor f
See Figure A.1 for the illustration diagram of asymmetry factor.

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