Solid Waste-Determination of Dioxins-Isotope Dilution High Resolution-Gas Chromatography-High Resolution Mass Spectrometry (4)

8.

Data reliability

1.

The recovery rate of the internal standard extracted from all samples should be confirmed

2.

In view of the particularity of dioxin analysis, in addition to clarifying the detection limit of the instrument, the detection limit of the method should be confirmed according to the laboratory conditions and operators

3.

The blank experiment includes reagent blank and operation blank

4.

Parallel experiments take 10% of the total number of samples.

5.

The precision and accuracy of the method should be confirmed based on own laboratory conditions and personnel operations

6.

The standard solution should be stored in a sealed glass container and protected from light to avoid changes in mass concentration caused by the volatilization of the solution

7.

The sample pre-processing and instrument operators must be trained, and the recovery rate of the internal standard extraction of the blank experiment reaches the standard specified range and the operation is stable, before the sample pre-processing; the instrument operator needs to have a full understanding of the instrument and master skilled manual Tuning, the abnormal condition of the instrument can be judged by gas chromatography and mass spectrometry

The analysis process must be recorded in the whole process, and the report file must pass the three-level review before submitting

Nine, matters needing attention

(1) When using the Soxhlet extractor, proper temperature control and circulating condensate control should be used to prevent the extract from evaporating dry
.

(2) When the sample is concentrated by rotary evaporation, the vacuum degree should be slowly reduced, and it cannot be directly reduced to the target vacuum degree, otherwise the sample will easily boil and cause the loss of the target compound
.

(3) Dioxins are easy to remain in the injection port, so a low-adsorption liner and no glass wool should be used
.
If the sample is dirty, there is a potential threat of unclean handling, a small amount of inert glass wool should be placed to protect the inlet
.

(4) Analysts should understand the operation of dioxins analysis and related risks, and receive relevant professional training
.
It is recommended that the analysts in the laboratory perform routine physical examinations on a regular basis
.

(5) Laboratories should select low-quality concentration standard materials that can be used directly to reduce or avoid the operation of high-quality concentration standard materials
.

(6) Before the sample is analyzed, the instrument tuning resolution must be higher than 10000, and the proton number calibration is passed before the sample can be analyzed
.
At the same time, each batch of samples needs to be calibrated with standard solution (usually CS3) before analysis, and calibration is performed with standard solution every 24h
.

(7) The laboratory should be equipped with protective measures such as gloves, lab coats, masks and fume hoods
.

(8) The glassware is cleaned with a mixture of sodium hydroxide and absolute ethanol soaked in a mixture of sodium hydroxide and ethanol , and ultrapure water is ultrasonically rinsed.
It is allowed to dry naturally and rinsed with dichloromethane for 3 times before use to avoid baking the glassware
.