Sonkir Soil pH Meter, MS02 3-in-1 Soil Moisture/Light/pH Tester Gardening Tool Kits for Plant Care, Great for Garden, Lawn, Farm, Indoor & Outdoor Use (Green)

 Sonkir Soil pH Meter, MS02 3-in-1 Soil Moisture/Light/pH Tester Gardening Tool Kits for Plant Care, Great for Garden, Lawn, Farm, Indoor & Outdoor Use (Green)

•  Kindly NOTE: This soil tester can not be applied to test pH value of any other liquid. If the soil is too dry the indicator will not move, and water it before testing.
• 3-IN-1 FUNCTION: Test soil moisture, pH value and sunlight level of plant with our soil meter, helps you specialize in grasping when you need to water your plant.
• ACCURATE & RELIABLE: Double-needle Detection Technology strongly enhances the speed and accuracy of detecting and analyzing soil moisture and pH acidity.
• EASY TO USE: No batteries needed, just insert the sensor probe into the soil about 2-4 inches, toggle switch to test moisture, pH, sunlight you would like to measure.
• INDOOR & OUTDOOR USE: Design to be lightweight and portable, easy to carry around for outdoor use, ideal soil test tool kit for home plants, garden, lawn and farm.

Soil analysis methods

It is very difficult to know what elements are present in the soil, so a generalized procedure for analyzing the elements present cannot be recommended due to the great diversity of the elements to be determined.

Soil analysis methods

The difficulties involved in determining the different elements in organic and inorganic samples are not fundamentally associated with the reliability of instrumental techniques, but with the choice of methods for sample preparation, which constitutes one of the most critical processes. of the analysis. In choosing the analytical technique, its sensitivity, precision and accuracy must be taken into account.

Both the most abundant elements and the trace elements are found in different compartments of the soil, the main forms in which the elements are found in the soil are as follows:

• Forming part of the crystalline network of the primary minerals, inherited from the starting material and secondary, formed as a consequence of the alteration processes.
• Adsorbed to oxides and hydroxides of iron, aluminum and manganese.
• Complexed or included in the structure of macromolecules.
• Retained by animal and plant waste.
• Forming part of the exchange complex and, therefore, associated with clays and humic compounds of the colloidal system.
• In soluble phase, forming part of the soil solution.

To obtain the total concentration of an element, it is necessary to extract all the forms of the element to be determined, including those that are part of the crystal lattice of primary and secondary minerals (silicates, clays, carbonates, etc.).

Usually, the reagents most used in the analysis of elements in soils have been a mixture of hydrofluoric and perchloric acid (HF + HClO 4 ) or aqua regia (HNO 3 + HCl). In some types of soils, the values ​​of total elements released by these two agents may present wide differences, so that when this occurs the aqua regia provides lower values. This makes it difficult to compare total element values ​​obtained by different extraction methods.



The total analysis of the elements present in the soil can be carried out using two different methods, a semi-quantitative method, X-ray fluorescence (X-ray fluorescence), as well as with a quantitative method, Argon Plasma Induced Emission Spectroscopy (ICP -MS).

SEMI-QUANTITATIVE METHOD

X-ray fluorescence (XRF)
The X-ray fluorescence (X-ray) technique is based on the principle that if an atom is bombarded with high-energy photons, some of its electrons are expelled. As other electrons fill in the vacant levels of energy occupied by the ejected electrons, they emit a quantum of radiation characteristic of that particular type of atom, hence each element has its own series of emission characteristics or X-ray fluorescence lines. .

X-ray fluorescence can be used to perform the analysis of the elements from the soil samples. Using this analytical technique, metals such as Cu, Mn and Zn, Ti and Zr can be determined at a normal concentration in the soil. Other heavy metals and metalloids (As, Cr, Ni and Pb) can also be determined, but in the case of Cd, Hg and Sn a previous pre-concentration of the sample is required.

Some applications of the FRX are, the following:

• Rapid qualitative determination of elements present in an unknown material with virtually no sample preparation and semi-quantitative determination using simple correction factors.
• Detection of all elements of the periodic table below B from the detection limit of a few ppm to 100%.
• Quantitative determination of all the elements in a sample (excluding elements with an atomic number below 5).
• Surface composition (1 µm) compared to volume (> 10 µm) using emission lines with different depth of penetration in certain samples (ceramics).

The FRX offers an impressive number of benefits. Generally, the method is non-destructive and can therefore be used without damaging the sample. Another advantage would be the precision and speed of the procedure. However, it also has some drawbacks; for example, it is not as sensitive a method as other optical methods. In the most favorable case, concentrations of a few ppm can be measured; furthermore, XRF methods are not considered suitable for light elements so that the difficulties in detection and in measurement progressively increase below atomic number 23 (Vanadium). Another disadvantage of this procedure is the high cost of the instruments. Despite this, X-ray analysis techniques are the most widely used in soil analysis.

QUANTITATIVE METHOD

Mass Spectrometry-Plasma (ICP-MS)
Many analytical methods require the sample to be in solution. This can be an inconvenience when working with soil samples, because the organic and inorganic components of the same require different treatment for their dissolution. The easiest method is the dissolution of the sample after previous heating, since all the organic matter is destroyed. Sequential treatment of soil samples with HF and HNO 3 is often effective even though inorganic residues must be treated again with HF and HNO 3 until completely dissolved.

The extraction method used, following the official procedure for soil analysis used by the United States Environmental Protection Agency (USEPA - “United States Environmental Protection Agency”), was the EPA-SW-846-3051 method. Through it, the oxidation of organic matter occurs using nitric acid and subjecting the sample to conditions of high temperature and pressure. In this way, it is not possible to solubilize the silicate fraction of the sample, so the real amount of the elements present in the soil cannot be quantified, although it dissolves those not bound to silicates. However, most of the heavy metals present as pollutants in soils belong to the latter type; thus,

Microwave digestion techniques at 8,000 ° C are among the newest methods for dissolving soil samples. Its main advantages lie in the fact that: it is more difficult to contaminate the sample, it produces a more complete dissolution of the sample and a lower loss of volatile elements. Its main disadvantage is the large amount of time required for the digestion process to complete.

ICP-mass determination is achieved by subjecting the flow of a gas at atmospheric pressure to the action of a magnetic field induced by a high-frequency current. The gas used, called plasmogen gas, is usually argon, although for certain applications it can be used in combination with a low proportion of some other gas. Due to the high plasma temperatures, matrix interferences are minimized. Argon is used for being an easily found material in a high degree of purity and for developing a chemically inert environment.




In addition, argon (Ar) itself together with a flow of water are responsible for cooling the system. ICP is a good source of ions, in which the gas or aerosol from the introduced sample is volatilized, automated and ionized at a very high temperature. Since the ion source (ICP) works at atmospheric pressure and the mass analyzer and detector work in a high vacuum regime, an interface has been developed that allows the transfer of ions to the mass spectrometer in charge of analyzing them.

In this interface, an ion jet is formed that is finally directed to the analyzer system, which can be of two types:

• the magnetic sector and the quadrupole ones, the latter being the most widespread due to their greater simplicity, scanning speed and lower cost.
• Quadrupole analyzers act as a filter, so that only those ions that meet a certain charge / mass ratio pass through them and reach the detector.
• The sample introduction system is pneumatic nebulization, where the liquid sample interacts with a gas stream in a nebulizer, generating an aerosol that passes through a spray chamber where large drops are eliminated and small ones are led to the plasma.