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GC detection of drugs in the eight points of the organic sol

Source:未知 Posted:2015-08-12 23:11 Browse:

(1) Unless otherwise specified, the gas chromatograph to detect the drug residue in the headspace conditions may be selected organic solvents: A. headspace equilibrium temperature should be selected according to the boiling point of the test residual solvent. The residue of higher boiling solvent, is usually higher equilibrium temperature; but this time the test should take into account the thermal decomposition characteristics, try to avoid the volatile thermal decomposition products produced by the interference of gas chromatograph results of the test. B. Headspace equilibration time is generally 30 to 45 minutes to ensure the test solution gas - liquid two-phase have enough time to reach equilibrium. Headspace time is usually not too long, as more than 60 minutes, may cause airtight vial deteriorates, resulting in reduced quantitative accuracy. C. control solution for the test solution and must use the same headspace condition.
 
(2) headspace gas chromatography to verify quantitative methods: when using headspace for the test and reference substance in the matrix are not exactly the same, it should be considered in the process of vapor-liquid equilibrium matrix effects (test solution Differences between the composition of the reference solution headspace gas - liquid equilibrium). Since the standard addition method can eliminate the test solution and reference solution matrix matrix matrix effects caused by different influences, it is usually the standard addition method to verify the accuracy of quantitative methods.
 
(3) the exclusion of interfering peaks: the samples of unknown impurity or thermal degradation of the volatile matter easily on the determination of residual solvent interference. Interference in the chromatographic system including the unknown measured in the same thermal degradation impurities or volatile substance and analyte retention value (co peak); or thermal degradation products with the same structure of the analyte (e.g. methoxy pyrolysis generating methanol). When the determination of residual organic solvents overruns, but failed to determine whether the test or unknown impurities on the determination of the volatile thermal degradation interference effects, should preclude the presence of interference by a test. Interference of first class, usually in another polar opposite of the same color column system was measured for the sample and then compare different measurement results chromatographic system approach. As the two results are consistent, then you can eliminate the interference assay has a total peak; if both results are inconsistent, it indicates that there are a total of assay interference peaks. The second type of interference, usually by measuring the control sample known not to contain the solvent to be judged.
 
Determination (4) nitrogen-containing basic compound: General GC stainless steel tubing, injector liner and other nitrogen-containing basic organic amine compound having a strong adsorption, resulting in the detection sensitivity. Should be inert silicon material or nickel steel pipe; when measured by solution directly into the sampling method, the test solution should not acidic, so as not to react with the acid analyte easy vaporization.
    Usually less polar column packing or column by alkali-treated analysis of nitrogen-containing basic compound, if the amine-specific analysis for analysis column, the better. Containing basic compound should not be used for the determination of gas chromatography, such as N- methylpyrrolidone and the like, can be used other methods such as by ion chromatography.
 
(5) Detector selection: residual halogen-containing solvents such as chloroform and other elements using an electron capture detector (ECD), is easy to obtain a high sensitivity.
 
(6) Since different laboratories in the determination of the same test may be used different experimental methods, internal standard and when the determination results in Pass Fail edges to internal standard or standard addition method prevail.
 
 (7) headspace equilibrium temperature is generally lower than the dissolution of the test should be used having a boiling point of the solvent 10 ℃, to meet the detection sensitivity can be; for the high-boiling solvent, such as dimethylformamide, 2-methoxyethanol, 2- ethoxyethanol, ethylene glycol, N- methylpyrrolidone, with headspace sensitivity of the assay as a direct injection, usually not measured by headspace way.
 
(8) the use of retention qualitative gas chromatograph is the most commonly used qualitative methods. Changes in the flow rate of carrier gas chromatographic system, carrier gas temperature and the column temperature will make the reservation is changed, thus affecting the qualitative results. Adjusting the relative retention time (RART) only by the nature of the stationary phase column temperature influence and, as a more reliable qualitative analysis parameters.