Soil Analytical Procedures

In Aridisols (Figure 2.6), both the occurrence of clay in the lower horizon and the occurrence of high pH and salt contents greatly affect the retention of components. For these soils, analytical procedures must be potentially impervious to high pH and salt content, or steps must be taken to remove salts or to change the pH before analysis. 

IR is not typically used in common soil analytical procedures, although it has been used to investigate various soil components, the most common being humus and its various subcomponents (see Figure 14.6, top spectrum). It has also been used to identify soil clays, both crystalline and amorphous. Many IR spectra can be accessed on the Web via government laboratory sites. 

A soil sample was taken from a field, transported back to the laboratory by road and stored for three weeks prior to analysis. The analytical procedure consisted of drying the soil in an oven at 100°C for 24 h before the analyte was extracted using 200 cm of dichloromethane. This extract was reduced in volume to 200 til and a 20 p.l aliquot then analysed by HPLC. A calibration was set up by measuring the response from a number of solutions containing known concentrations of the analyte. The resnlt obtained from the unknown , after suitable mathematical manipulation, indicated the original soil sample contained 20 0.05 mgkg of the analyte. Comment on the accuracy of this result. 

A form of this approach has long been followed by RT Corporation in the USA. In their certification of soils, sediments and waste materials they give a certified value, a normal confidence interval and a prediction interval . A rigorous statistical process is employed, based on that first described by Kadafar (1982,), to produce the two intervals the prediction interval (PI) and the confidence interval (Cl). The prediction interval is a wider range than the confidence interval. The analyst should expect results to fall 19 times out of 20 into the prediction interval. In real-world QC procedures, the PI value is of value where Shewhart (1931) charts are used and batch, daily, or weekly QC values are recorded see Section 4.1. Provided the recorded value falls inside the PI 95 % of the time, the method can be considered to be in control. So occasional abnormal results, where the accumulated uncertainty of the analytical procedure cause an outher value, need no longer cause concern. 

The method for chloroacetanilide soil metabolites in water determines concentrations of ethanesulfonic acid (ESA) and oxanilic acid (OXA) metabolites of alachlor, acetochlor, and metolachlor in surface water and groundwater samples by direct aqueous injection LC/MS/MS. After injection, compounds are separated by reversed-phase HPLC and introduced into the mass spectrometer with a TurboIonSpray atmospheric pressure ionization (API) interface. Using direct aqueous injection without prior SPE and/or concentration minimizes losses and greatly simplifies the analytical procedure. Standard addition experiments can be used to check for matrix effects. With multiple-reaction monitoring in the negative electrospray ionization mode, LC/MS/MS provides superior specificity and sensitivity compared with conventional liquid chromatography/mass spectrometry (LC/MS) or liquid chromatography/ultraviolet detection (LC/UV), and the need for a confirmatory method is eliminated. In summary,... 

Anticipated persistence and mobility of agrochemical and degradates Anticipated variability in soil residues and cost constraints Depends upon specific analytical procedures (and associated LOQ) and available sample storage and processing capabilities Necessary for most dryland and irrigated cropping scenarios... 

Table 4 Tepraloxydim analytical results used to determine efficacy of soil homogenization procedure...

Some agrochemicals bind strongly to the soil component as bound residues, which cannot be extracted without vigorous extraction procedures. In this case, an acidic (e.g., hydrochloric acid, sulfuric acid) or alkaline solution (e.g., sodium hydroxide, potassium hydroxide) can be used as an extraction solvent, and also heating may be effective in improving the extraction of the residues. Analytical procedures after the extraction are the same as above, but a filtration procedure may be troublesome in some of these situations. However, these procedures are rare exceptions or are needed for specific chemicals that are stable under such harsh extraction conditions. 

The analysis of steroid sexual hormones and related synthetic compounds in WW, soil, sludge, and sediment samples is a challenging task. This is due to both the complex environmental matrices and the requirement of low detection limits. Therefore, the use of complicated, time- and labor-consuming analytical procedures is necessary. 

The fact that soil always contains water, or more precisely an aqueous solution, is extremely important to keep in mind when carrying out an analytical procedure because water can adversely affect analytical procedures and instrumentation. This can result in an over- or under-determination of the concentrations of components of interest. Deactivation of chromatographic adsorbents and columns and the destruction of sampling tools such as salt windows used in infrared spectroscopy are examples of the potential deleterious effects of water. This can also result in absorbance or overlap of essential analytical bands in various regions of the spectrum. 

Salts, in addition to causing the soil to be basic, can have deleterious effects on analytical procedures. For example, significant error can occur if a potassium-selective electrode is used to determine potassium in a high-sodium soil (see Chapter 9). As discussed in Chapter 14, other salts could cause inaccurate results when atomic absorption analysis of a soil extract is carried out. 

Soils develop by the action of the soil forming factors on soil parent materials including material transported by different agents. The result of these soil forming factors is the formation of soil horizons, different colors, and peds. Each of these factors has a pronounced effect on a soil s chemistry. Knowledge of the soil type and profile description can provide the soil chemist, analyst, or researcher with valuable information about the characteristics of soil relevant to the development of extraction, analytical, and instrumental analytical procedures. It also is the place to start when investigating the failure of a procedure. 

Humus and organic matter can have a dramatic effect on analytical results as shown in the work by Gerke [16]. Metal complexes, particularly aluminum and iron, were found to complex with phosphate. These complexes, which accounted for 50-80% of the phosphate present, were not detectable by standard phosphate analytical procedures. When developing a soil analytical method, it is essential that the method be either applicable to soils of all organic matter contents or that variations of the procedure applicable to soils of differing organic matter be developed [16-19],... 

A first step in deciding on an analytical procedure to use or a species to look for is to understand that the species of interest may be in one of four soil compartments (see Figure 6.3) the solid (both inorganic and organic), the liquid (soil solution), the gaseous (soil air), or the biological (living cells). It is also important to remember that molecules and ions can move between compartments and interconvert between species. 

A number of techniques have been developed to directly volatilize soil components and contaminants and introduce them into the carrier gas of a gas chromatograph. Such procedures avoid the time and cost of extraction, cleanup, and concentration and also avoid the introduction of contaminants during the extraction process. However, these methods are not universally applicable and caution must be used when applying new or untested analyses or analytical procedures [2-5],... 

Hyphenated methods involve both separation and identification of components in one analytical procedure and are commonly used in investigating soil chemistry. These investigations can involve one separation step and one identification step, two separation steps and one identification step, and two separation and two identification steps. Hyphenated analytical method instruments are arranged in tandem, without the analyte being isolated between the applications of the two methods. This leads to a very long list of possible combinations of instrumentation and, potentially, any separation method can be paired with any identification method. The list of hyphenated methods is long, although only a few methods are commonly used in soil analysis as can be seen in the review by DAmore et al. [1],... 

Two-dimensional GC can be used to separate complex mixtures of polyaromatic compounds, and MS used to subsequently identify the compounds. In this method, the original sample is injected into a gas chromatograph with one type of column. As the components exit the first GC, they are fed into a second GC, with a different column, for further separation and finally into a mass spectrometer. In this way, compounds that coeluted from the first column are separated on the second. Focant et al. [19] were able to separate polychlorinated dibenzo-p-dioxin (PCDD), polychlorinated dibenzofuran (PCDF), and coplanar polychlorinated biphenyl (cPCB) using this type of analytical procedure, including isotope dilution TOF-MS. These compounds are frequently found as contaminants in soils surrounding industrial settings thus, the ability to separate and identify them is extremely important [6,12,19],... 

Analytical procedures can be classified in two ways first, in terms of the goal of the analysis, and second, in terms of the nature of the method used. In terms of the goal of the analysis, classification can be based on whether the analysis is qualitative or quantitative. Qualitative analysis is identification. In other words, it is an analysis carried out to determine only the identity of a pure analyte, the identity of an analyte in a matrix, or the identity of several or all components of a mixture. Stated another way, it is an analysis to determine what a material is or what the components of a mixture are. Such an analysis does not report the amount of the substance. If a chemical analysis is carried out and it is reported that there is mercury present in the water in a lake and the quantity of the mercury is not reported, then the analysis was a qualitative analysis. Quantitative analysis, on the other hand, is the analysis of a material for how much of one or more components is present. Such an analysis is undertaken when the identity of the components is already known and when it is important to also know the quantities of these components. It is the determination of the quantities of one or more components present per some quantity of the matrix. For example, the analysis of the soil in your garden that reports the potassium level as 342 parts per million (ppm) would be classified as a quantitative analysis. The major emphasis of this text is on quantitative analysis, although some qualitative applications will be discussed for some techniques. See Workplace Scene 1.1. 

Of the analytical procedures used for the determination of LAS in soils (Table 6.7.1), most methods rely on (Soxhlet) extraction with methanol, followed by clean-up on SPE cartridges (RP-C18 and/or SAX) and final quantitative measurements by HPLC—UV/FL. Applying this protocol, detection limits were achieved ranging between 0.05 and 5 mg kg-1 depending on the matrix, the enrichment factor and the optical detection system employed. 

The analytical technique assumes that the calculated diffusion coefficients for various individual pollutants represent average values throughout the length of the soil column. Although the interactions established between the pollutant and the soil cause continuous alteration in the transmissivity characteristics of the soil, the procedure which uses the analytical solution can only provide average values, because the values of Ce are obtained at the outlet end of the test sample. Thus, a representative diffusion coefficient should be calculated for individual layers in the soil column, and/or each pore volume passage of ef-... 

Analytical Procedure. After thawing, each field sample was immediately divided into 4 quarters and subsamples of approximately lOOg of moist soil taken from each for analysis. A... 

Abstract in late 2008, soil and stream sediment orientation surveys were carried out to provide optimized field and analytical procedures for use in property and regional-scale exploration programs on MinCore s Tameapa property in Sinaloa Mexico. The property is host to two advanced mineral prospects named Pico Prieto (copper-molybdenum porphyry) and Venado (molybdenum-copper structurally controlled porphyry) that were first explored in detail by Las Cuevas during the 1970s and early 1980s. 

Finding 14. Analytical procedures for the chemical agents and their most toxic degradation products have not been specified and may need to be developed, particularly when these agents and products occur in media such as concrete, soils, and spent carbon. 

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