How to pre treat the plant when determining the lead content in the plant

The plant weighs 2g 5g sample (accurate to g, according to the content of lead and cadmium), cuts it, puts it in a porcelain crucible, first carbonizes it on an adjustable electric heating plate over low heat until it is smokeless, moves it into the muffle furnace 500 25 ash for 1h, cools, dissolves the ash with mol l nitric acid, washes the sample digest into (without filtration) 100 ml volumetric flask with a dropper, washes the porcelain crucible with a small amount of water for many times, and the lotion is combined in the volumetric flask and fixed to the scale, mixed well and set aside.

Experimental content and procedures].

1. Sample treatment (ashing method).

Weigh 2g 5g samples (accurate to g, according to lead and cadmium content), cut them, put them in a porcelain crucible, first carbonize them on an adjustable electric heating plate over low heat until smokeless, move them into the muffle furnace 500 25 ash for 1h, cool, dissolve the ash with mol l nitric acid, wash the sample digest into (without filtration) 100 ml volumetric flask with a dropper, wash the porcelain crucible with a small amount of water for many times, combine the lotion in the volumetric flask and set the volume to the scale, mix well and set aside;

2. Some parameter settings.

Select "Exploratory Mode" in the operation interface of the voltammetry electrometer software — Load Method — Select HMDE (Suspended Mercury Electrode)— Cell volume: 11 ml — Number of spikes: 2— Number of repetitions:

PB: 10 mg L— Spike: cd:

40μl；pb:40μl。Open the monitor.

Fourth, the standard addition method to determine the content of PD and CD elements in vegetables.

Add 1 ml of HAC-Naac buffer, 9 ml of distilled water, 1 ml of sample solution to the electrolysis vessel. After recording the determination curve of the sample, 10 mg l of lead standard solution and 40 l of cadmium standard solution were added twice with a pipette gun in order to measure the peak current respectively, and the content of lead and cadmium in vegetables was automatically calculated by the standard addition method.

The pre-treatment of trace element determination in plants can be digested by microwave, the application of microwave digestion technology in biomedical and pharmaceutical analysis, the digestion of biological samples is the earliest field of microwave application, and the processing samples include animal, plant, food and medical samples, etc., Microwave digestion overcomes the shortcomings of the traditional dry or wet high temperature, loss of volatile elements, and time-consuming.

Microwave digestion usually refers to the use of microwave heating of the digestion solution (various acids, some lyes and salts) and samples in a closed container to quickly dissolve various samples under high temperature pressurization conditions (there are also open container microwave digestion, not discussed). The two characteristics of closed vessel reaction and microwave heating determine the advantages of complete, fast and low blank, but inevitably bring the disadvantages of high pressure (the hidden danger of possible overpressure) and small sample volume to digest. High pressure (up to 100-150 bar), high temperature (usually 180-240 bar), and strong acid vapors put psychological pressure on the experimenter in terms of safety.

The current commercial microwave digestion system generally has temperature and pressure measurement and even temperature and pressure control technology, so it has a greater guarantee in safety.

This standard is suitable, but now it has been updated, yes.

When I do PB, because the unit has a microwave digestion instrument, the pretreatment is more convenient, and the sample (< nitric acid is directly put into the reaction tank, and the digestion program of the instrument is up to me.

If not, I'm using the wet digestion method, but pay attention to the fire, the digestive juice is easy to splash during the digestion process.

For plant samples, there is no need to use the soil method, you can refer to the digestion method in GB, the plant sample is easy to digest, and it is enough to use nitric acid directly, which does not have to be as troublesome as soil.