Inspection method for arsenic in traditional Chinese medicine

Arsenic salt is a toxic substance, and it is mostly introduced by inorganic reagents used in the drug production process

1.

(1) Arsenic Salt Inspection Method

The arsenic salt inspection method is applicable to the limit inspection of trace arsenic salt (calculated as As) in medicines

(2) Ancient Chua's Method

The principle of the ancient Chua’s method: the use of metal zinc and acid to generate new ecological hydrogen reacts with trace arsenite in medicines to generate volatile arsine hydrogen, and mercury bromide test paper produces yellow to brown arsenic spots, and Compare the arsenic spots produced by the quantitative standard arsenic solution under the same conditions to determine the limit of arsenic salt

2.

(1) Preparation of standard arsenic solution

Accurately weighed 105 ℃ dried to constant weight of 0.

(2) Mercury bromide test paper

Immerse the relatively loose medium-speed quantitative filter paper into the ethanol- made mercury bromide test solution, take it out after 1 hour, and dry it in the dark to get it

(3) Lead acetate cotton

Take 1g of absorbent cotton and immerse it in 12ml of an equal volume mixture of lead acetate test solution and water.

(4) Preparation of standard arsenic spot

1.

2.

3.

Three, matters needing attention

(1) Ancient Chua's Method

The reaction sensitivity is about 0.

(2) Standard arsenic spot or standard arsenic control solution

The preparation of standard arsenic spot or standard arsenic control solution should be carried out simultaneously with the inspection of the test product

(3) Sulfide

The test product and zinc particles may contain a small amount of sulfide, which generates H ₂ S gas in the acid solution, which interferes with the experiment.

(4) Quality of filter paper

The quality of the filter paper used to prepare the mercury bromide test paper has an impact on the color of the arsenic spots.

(5) Zinc particles

The zinc particles used in this method should be arsenic-free, and the size of the zinc particles affects the reaction speed.
In order to make the reaction speed and produce arsine gas suitable, zinc particles with a particle size of about 2mm should be selected
.
The reaction temperature is generally controlled at about 30°C, and it can be placed in a warm water bath in winter
.
If the reaction is too fast, the reaction temperature should be appropriately lowered so that the arsine gas can be absorbed uniformly
.

(6) Organic drugs

Traditional Chinese medicines are mostly organic drugs.
Because arsenic may be combined in an organic state in the molecule, organic destruction must be carried out first.
Otherwise, arsenic salts will not be easy to detect if the organic structure is not destroyed
.
The organic matter decomposition method includes the wet method (especially for those with high sugar content), that is, heating with acid-perchloric acid and sulfuric acid to decompose the organic matter; and the dry method (ashing method), which uses magnesium oxide, Calcium hydroxide, 10% magnesium nitrate solution, after evaporation to dry, 500 ~ 600 ℃ burning 3 ~ 4 hours to completely ash, and then check the arsenic content
.

Four, calculation

(1) Calculation of the concentration of standard arsenic solution

The mass of 1mol of arsenic trioxide is 197.
82g, containing 2×74.
92g of arsenic (As).
Weigh 0.
132g of arsenic trioxide and dissolve it in 1000ml of solution to prepare a stock solution.
The content of As per 1ml is:

The standard arsenic solution obtained after the stock solution is quantitatively diluted 100 times, contains 1.
0ug of As per 1ml
.

(2) Calculation of arsenic limit

When checking the limit, take 2.
0ml standard arsenic solution to make a control solution, and compare the color of the arsenic spot or absorption solution with the test solution under the same conditions to determine whether the arsenic content exceeds the regulation.
The arsenic limit can be calculated by the following formula :

If take 2.
0ml of standard arsenic solution, the concentration of standard arsenic solution is 0.
000001g/ml, and sample 1.
0g of the test product; then:

(3) Calculation of the sampling amount of the test product

If the arsenic limit is known to be one part per million, the standard arsenic solution is 2.
0ml, the concentration of the standard arsenic solution is 0.
000001g/ml, and the sample size of the test sample (g) is required
.