**2. Glyphosate residues in soil**

#### **2.1 Environmental fate of glyphosate**

## *2.1.1 Glyphosate in the soil*

Given the widespread use of glyphosate, the investigation of the relationship between glyphosate and soil ecosystem is critical and has great significance for its valid application and environmental safety evaluation. Although herbicides containing glyphosate are not intentionally applied directly to the soil, they may contaminate soils in and around the treated areas, via spray drift during their application and after being washed off from leaf surfaces with rainfall.

The fate of glyphosate in soil is complex and attributed to mineralization, degradation, immobilization, and leaching. Several studies trying to identify and understand the mechanisms that control the fate of chemicals as a source of environmental contamination have been published in previous years, especially in soils and water. Some were conducted with the acid form of glyphosate and others with formulated products, since glyphosate is not introduced into the environment as pure active ingredients but as formulated products containing co-formulant chemicals (adjuvants) and other additives. In a recent review, Mesnage et al. presented an overview of the most common surfactants containing co-formulants in glyphosatebased herbicides and explained whether the presence of such surfactant (e.g., Triton CG-110) has the potential to affect adsorption, leaching, and mineralization of glyphosate in the soil [9].

The fate of glyphosate depends on soil composition, its physicochemical properties (texture, organic matter content, pH), its biological properties (microbial community, climatic conditions), the chemical properties of the specific pesticide, as well as the timing between precipitation and pesticide application [10–13]. A recent study by Muskus et al. showed that temperature, pH, and total organic carbon

**123**

**Figure 1.**

*Glyphosate Residues in Soil and Air: An Integrated Review*

(TOC) variations influenced the mineralization kinetics of glyphosate as well as the amount of extractable glyphosate and the extent of bio-NER formation over time in

Glyphosate degrades at a relatively rapid rate in most soils, with a half-life estimated to be between 7 and 60 days. The relatively rapid degradation of glyphosate has the advantage of limiting its role in polluting the environment, especially soil and water resources. However, its degradation could increase the pollution risk by its metabolites: aminomethylphosphonic acid (AMPA) and/or sarcosine. The degradation of the herbicide molecule as described in the literature (**Figure 1**) can follow two paths: the first is based on the breakdown of the carbon-nitrogen bond and leads to the formation of AMPA (main metabolite of glyphosate) via glyphosate oxidoreductase which is further degraded to carbon dioxide, while the second way is based on the splitting of the carbon-phosphorus (C-P) bond that is mediated by C-P lyase enzyme and results in the formation of sarcosine and glycine [15–20]. However, AMPA also exists in the environment as a photodegradation product of

Glyphosate is a small, amphoteric molecule characterized by three polar functional groups. These are the phosphonomethyl, amine, and carboxymethyl groups arranged in a linear manner. As a result of the presence of those groups in its structure, glyphosate is an ionic compound (log KOW = −3.20), highly polar and

0.7, 2.2, 5.9, and 10.6, 8 meaning that the speciation of the molecule is dependent upon the pH value of the solution. Three pKa values, 0.9, 5.6, and 10.2, characterize AMPA. Over the pH values commonly found in soils, mono- and divalent anions are

This coefficient value indicates a high absorption in the soil. Glyphosate adsorption to soil, and later release from soil, varies depending on the characteristics and

Glyphosate is soluble in water, but it also binds onto soil particles under certain conditions, particularly in clays. Numerous laboratory studies have shown that the absorption constant of the molecule in the soil varies between 8 and 377 dm3

at 20°C). GPS is a polyprotic acid with four pKa values,

/kg.

*DOI: http://dx.doi.org/10.5772/intechopen.93066*

aminopolyphosphonates in water [21].

the predominant species present [6, 22].

*Main glyphosate biodegradation pathways in the environment [5].*

soluble in water (10.5 g L<sup>−</sup><sup>1</sup>

a German soil [14].

*Glyphosate Residues in Soil and Air: An Integrated Review DOI: http://dx.doi.org/10.5772/intechopen.93066*

*Pests, Weeds and Diseases in Agricultural Crop and Animal Husbandry Production*

amino acids phenylalanine, tyrosine, and tryptophan [3].

crops grown around the globe by interfering with the synthesis of the aromatic

Since then, its use in agricultural and nonagricultural settings has steadily increased from a total of 0.6 Mg applied in 1974 to a total of 125.5 Mg applied in 2014, and it is currently the most widely used herbicide in the United States and throughout the world [4, 5]. Monsanto's last commercially relevant US patent expired in 2000. Nowadays, GLY formulations that are used as a broad-spectrum systemic herbicide have been widely applied in agronomic crops and orchards. Furthermore, GLY formulations are currently approved by regulatory bodies and marketed worldwide by many agrochemical companies, such as Bayer, Dow AgroSciences, and Monsanto, in different solution strengths and with various

GLY approval is renewed in the European Union (EU) on 16 December 2017, while its approval expires on 15 December 2022. Therefore, GLY can be used as an active substance in plant protection products (PPPs), until 15 December 2022. GLY has been thoroughly assessed, under an intense debate due to a concern about its effects on the environment and human health, by the Member States, the European Chemicals Agency (ECHA), and the European Food Safety Authority (EFSA) in recent years [6, 7]. An important prerequisite for GLY upcoming renewal as an ingredient in PPPs is that GLY should not adversely affect the environment and human and animal health as delineated by European

Given the widespread use of glyphosate, the investigation of the relationship between glyphosate and soil ecosystem is critical and has great significance for its valid application and environmental safety evaluation. Although herbicides containing glyphosate are not intentionally applied directly to the soil, they may contaminate soils in and around the treated areas, via spray drift during their application and after being washed off from leaf surfaces with rainfall.

The fate of glyphosate in soil is complex and attributed to mineralization, degradation, immobilization, and leaching. Several studies trying to identify and understand the mechanisms that control the fate of chemicals as a source of environmental contamination have been published in previous years, especially in soils and water. Some were conducted with the acid form of glyphosate and others with formulated products, since glyphosate is not introduced into the environment as pure active ingredients but as formulated products containing co-formulant chemicals (adjuvants) and other additives. In a recent review, Mesnage et al. presented an overview of the most common surfactants containing co-formulants in glyphosatebased herbicides and explained whether the presence of such surfactant (e.g., Triton CG-110) has the potential to affect adsorption, leaching, and mineralization

The fate of glyphosate depends on soil composition, its physicochemical properties (texture, organic matter content, pH), its biological properties (microbial community, climatic conditions), the chemical properties of the specific pesticide, as well as the timing between precipitation and pesticide application [10–13]. A recent study by Muskus et al. showed that temperature, pH, and total organic carbon

**122**

adjuvants.

regulation [8].

**2. Glyphosate residues in soil**

*2.1.1 Glyphosate in the soil*

of glyphosate in the soil [9].

**2.1 Environmental fate of glyphosate**

(TOC) variations influenced the mineralization kinetics of glyphosate as well as the amount of extractable glyphosate and the extent of bio-NER formation over time in a German soil [14].

Glyphosate degrades at a relatively rapid rate in most soils, with a half-life estimated to be between 7 and 60 days. The relatively rapid degradation of glyphosate has the advantage of limiting its role in polluting the environment, especially soil and water resources. However, its degradation could increase the pollution risk by its metabolites: aminomethylphosphonic acid (AMPA) and/or sarcosine. The degradation of the herbicide molecule as described in the literature (**Figure 1**) can follow two paths: the first is based on the breakdown of the carbon-nitrogen bond and leads to the formation of AMPA (main metabolite of glyphosate) via glyphosate oxidoreductase which is further degraded to carbon dioxide, while the second way is based on the splitting of the carbon-phosphorus (C-P) bond that is mediated by C-P lyase enzyme and results in the formation of sarcosine and glycine [15–20]. However, AMPA also exists in the environment as a photodegradation product of aminopolyphosphonates in water [21].

Glyphosate is a small, amphoteric molecule characterized by three polar functional groups. These are the phosphonomethyl, amine, and carboxymethyl groups arranged in a linear manner. As a result of the presence of those groups in its structure, glyphosate is an ionic compound (log KOW = −3.20), highly polar and soluble in water (10.5 g L<sup>−</sup><sup>1</sup> at 20°C). GPS is a polyprotic acid with four pKa values, 0.7, 2.2, 5.9, and 10.6, 8 meaning that the speciation of the molecule is dependent upon the pH value of the solution. Three pKa values, 0.9, 5.6, and 10.2, characterize AMPA. Over the pH values commonly found in soils, mono- and divalent anions are the predominant species present [6, 22].

Glyphosate is soluble in water, but it also binds onto soil particles under certain conditions, particularly in clays. Numerous laboratory studies have shown that the absorption constant of the molecule in the soil varies between 8 and 377 dm3 /kg. This coefficient value indicates a high absorption in the soil. Glyphosate adsorption to soil, and later release from soil, varies depending on the characteristics and

**Figure 1.** *Main glyphosate biodegradation pathways in the environment [5].*

composition of the soil (clay, sand, or gravel), temperature, and soil moisture. So it may quickly wash out of sandy soils or last for more than a year in soils with a high clay content. Even when bound to soil particles, it may dissolve back into soil water later on, for example, in the presence of phosphates. Glyphosate can also form complexes with metal ions, potentially affecting the availability of nutrients in the soil.

The mechanism of glyphosate sorption to soil is similar to that of phosphate fertilizers, the presence of which can reduce glyphosate sorption [23]. Glyphosate compared to most other pesticides strongly absorbs to soil and is not expected to move vertically below the six-inch soil layer, exception made of a colloid-facilitated transport. Its soluble residues are expected to be poorly mobile in the free pore water of soils. The mobility of glyphosate in soil is very low because, as a strong chelating agent through the carboxyl, phosphonate, and amino groups, it creates the complexes that immobilize the mineral micronutrients of the soil (calcium, iron, magnesium, manganese, nickel, zinc, etc.) making them unavailable to plants [11, 24]. Similar to glyphosate, AMPA accumulates in soil and adsorbs in soils with high mineralization rates. Where strong sorption is demonstrated, glyphosate accumulation in soils can be expected. The interaction of pesticide-soil and the diffusion process lead to the formation of non-extractable residues trapped in areas not accessible to water flowing through the soil. The contamination of the environment is therefore considered to be relatively limited.

Nevertheless, this adsorption is not permanent because glyphosate can also be found in lower soil layers. Many studies suggest the possibility of a slow remobilization of these residues, which could explain the low pollution level of groundwater by some pesticides at a long term. Glyphosate does have the potential to contaminate surface waters through erosion, as it adsorbs to soil particles suspended in runoff. Rain events can trigger dissolved glyphosate loss in transport-prone soils [25, 26].

#### **2.2 Glyphosate occurrence in soil**

The increase of glyphosate-based herbicides has raised concerns about the occurrence of GLY and AMPA in the environment. Reports of GLY presence in the environment from other parts of the world are numerous. A considerable attention has been given to Argentina [27–30], Canada [31], across the United States [32], Mexico [33], and Portugal [34] as well to Spain [35], New Zealand [36], Austria [37], and French [38].

However, although GLY is the most sold herbicide in Europe, a combined approach on the occurrence and levels of glyphosate residues in European soils and air, in conjunction with analytical methods used for this scope, is still scarce, compared to the magnitude of its use though some research articles and reviews (not only focusing on soil) started to appear (indicatively see [39–41]).

The first large-scale assessment of distribution of GLY and AMPA in soils from agricultural topsoils of the European Union was recently published by Silva, where glyphosate and its metabolite AMPA were tested in 317 EU agricultural topsoils; 21% of the tested EU topsoils contained glyphosate and 42% contained AMPA, while both glyphosate and AMPA displayed a maximum concentration in soil of 2 mg kg<sup>−</sup><sup>1</sup> . Both compounds were present at higher frequencies in northern soils, while eastern and southern regions generally had the most glyphosate- and AMPA-free soils (<0.05 mg kg<sup>−</sup><sup>1</sup> ), respectively. In addition, some contaminated soils were observed in areas highly susceptible to water and wind erosion [42]. Therefore, residue threshold values in soils are urgently needed to define potential risks for soil health and off-site effects related to export by wind and water erosion.

**125**

*Glyphosate Residues in Soil and Air: An Integrated Review*

**2.3 Analytical methods for quantification of GLY and AMPA**

hard to detect GLY without a pretreatment method [47].

weak acids such as 10% phosphoric acid buffers [13, 61].

In order to detect the presence and quantity of GLY dispersed in the environ-

One of the key problems for obtaining reliable results from field samples is the use of the best suitable extraction solution, since sorption and desorption of glyphosate in soils are extremely pH dependent. Some reports showed that humic substances (substances and heterogenic mixtures dispersed and abundant in soils and sediments) adsorb glyphosate strongly due to the hydrogen bonding interactions between the two matrices. Another important aspect is that GLY is a highly polar herbicide, very soluble in water and insoluble in most organic solvents, which does not allow extraction with organic solvents and makes the extraction difficult and the preconcentration step quite lengthy. However, due to the amphoteric character of GLY and AMPA, both anionic and cationic resins have been used for preconcentration and cleanup purposes (commented in the below sections).

As already mentioned, GLY has been shown to bind strongly to soils, especially to soils with high amounts of organic matter, iron, and aluminum [43, 44]. There is also evidence that glyphosate binds to clay minerals in a manner similar to inorganic phosphate [44–46]. The strength of the interactions of the phosphonate, carboxyl, and amino groups with iron oxides, silica, alumina, and organic matter depends on factors such as pH, metal cations, phosphate from fertilizers, etc. Therefore, it is

The choice of the best suitable extraction solution remains a problem that must

Moreover, it is vital to adjust the concentration of the extraction media in such a way that high recovery rates can be obtained while avoiding matrix problems provoked by excessively aggressive alkaline media, which may enrich the dissolved humic substances in the extraction solution [49]. Humic acids interfere, for example, with the derivatization and suppress the ionization in ESI-MS/MS detectors.

Although GLY is the most widely used agrochemical in the world, it is also the most cumbersome in its determination in analytical methods, a fact known as the "glyphosate paradox." The challenge to detect GLY using a simple analytical method is an outcome of its ionic character, low volatility and low mass, high polarity and solubility in water, poor solubility in common organic solvents, high boiling points,

Several authors in the past reported different extraction methods of these compounds from soil, mainly using alkaline solutions with different recovery rates [48–51] and most times applicable for one type of soil. In 1980 the FDA's "Pesticide Analytical Manual" (PAM) including a procedure for the analysis of glyphosate residues in soil is published. However low and irreproducible recoveries in soil samples have been reported using this method. Later, Glass in 1983–1984 analyzed soils by alkaline extraction, followed by cleanup using flocculation with CaCl2 and anion exchange [52–54]. Yet, recoveries were still remained poor and ranged from 19 to 55%. Many extractants for soil have been tested in the years that followed with the most commonly used being aqueous bases KOH or NaOH, aqueous NH4OH or NH3, or triethylamine. Other extractants include NaHCO3, KH2PO4, mixed solutions of KH2PO4 and NH3 or NH4OH and HPO4, sodium borate buffers [55–60], or even

ment, various laboratory analyses are performed on samples taken in situ.

*DOI: http://dx.doi.org/10.5772/intechopen.93066*

*2.3.1 Extraction procedure*

be addressed accordingly.

*2.3.2 Analytical methods*

#### **2.3 Analytical methods for quantification of GLY and AMPA**

In order to detect the presence and quantity of GLY dispersed in the environment, various laboratory analyses are performed on samples taken in situ.

One of the key problems for obtaining reliable results from field samples is the use of the best suitable extraction solution, since sorption and desorption of glyphosate in soils are extremely pH dependent. Some reports showed that humic substances (substances and heterogenic mixtures dispersed and abundant in soils and sediments) adsorb glyphosate strongly due to the hydrogen bonding interactions between the two matrices. Another important aspect is that GLY is a highly polar herbicide, very soluble in water and insoluble in most organic solvents, which does not allow extraction with organic solvents and makes the extraction difficult and the preconcentration step quite lengthy. However, due to the amphoteric character of GLY and AMPA, both anionic and cationic resins have been used for preconcentration and cleanup purposes (commented in the below sections).

#### *2.3.1 Extraction procedure*

*Pests, Weeds and Diseases in Agricultural Crop and Animal Husbandry Production*

ment is therefore considered to be relatively limited.

**2.2 Glyphosate occurrence in soil**

concentration in soil of 2 mg kg<sup>−</sup><sup>1</sup>

export by wind and water erosion.

[37], and French [38].

composition of the soil (clay, sand, or gravel), temperature, and soil moisture. So it may quickly wash out of sandy soils or last for more than a year in soils with a high clay content. Even when bound to soil particles, it may dissolve back into soil water later on, for example, in the presence of phosphates. Glyphosate can also form complexes with metal ions, potentially affecting the availability of nutrients in the soil. The mechanism of glyphosate sorption to soil is similar to that of phosphate fertilizers, the presence of which can reduce glyphosate sorption [23]. Glyphosate compared to most other pesticides strongly absorbs to soil and is not expected to move vertically below the six-inch soil layer, exception made of a colloid-facilitated transport. Its soluble residues are expected to be poorly mobile in the free pore water of soils. The mobility of glyphosate in soil is very low because, as a strong chelating agent through the carboxyl, phosphonate, and amino groups, it creates the complexes that immobilize the mineral micronutrients of the soil (calcium, iron, magnesium, manganese, nickel, zinc, etc.) making them unavailable to plants [11, 24]. Similar to glyphosate, AMPA accumulates in soil and adsorbs in soils with high mineralization rates. Where strong sorption is demonstrated, glyphosate accumulation in soils can be expected. The interaction of pesticide-soil and the diffusion process lead to the formation of non-extractable residues trapped in areas not accessible to water flowing through the soil. The contamination of the environ-

Nevertheless, this adsorption is not permanent because glyphosate can also be found in lower soil layers. Many studies suggest the possibility of a slow remobilization of these residues, which could explain the low pollution level of groundwater by some pesticides at a long term. Glyphosate does have the potential to contaminate surface waters through erosion, as it adsorbs to soil particles suspended in runoff. Rain events can trigger dissolved glyphosate loss in transport-prone soils

The increase of glyphosate-based herbicides has raised concerns about the occurrence of GLY and AMPA in the environment. Reports of GLY presence in the environment from other parts of the world are numerous. A considerable attention has been given to Argentina [27–30], Canada [31], across the United States [32], Mexico [33], and Portugal [34] as well to Spain [35], New Zealand [36], Austria

However, although GLY is the most sold herbicide in Europe, a combined approach on the occurrence and levels of glyphosate residues in European soils and air, in conjunction with analytical methods used for this scope, is still scarce, compared to the magnitude of its use though some research articles and reviews

The first large-scale assessment of distribution of GLY and AMPA in soils from agricultural topsoils of the European Union was recently published by Silva, where glyphosate and its metabolite AMPA were tested in 317 EU agricultural topsoils; 21% of the tested EU topsoils contained glyphosate and 42% contained AMPA, while both glyphosate and AMPA displayed a maximum

frequencies in northern soils, while eastern and southern regions generally had

tion, some contaminated soils were observed in areas highly susceptible to water and wind erosion [42]. Therefore, residue threshold values in soils are urgently needed to define potential risks for soil health and off-site effects related to

. Both compounds were present at higher

), respectively. In addi-

(not only focusing on soil) started to appear (indicatively see [39–41]).

the most glyphosate- and AMPA-free soils (<0.05 mg kg<sup>−</sup><sup>1</sup>

**124**

[25, 26].

As already mentioned, GLY has been shown to bind strongly to soils, especially to soils with high amounts of organic matter, iron, and aluminum [43, 44]. There is also evidence that glyphosate binds to clay minerals in a manner similar to inorganic phosphate [44–46]. The strength of the interactions of the phosphonate, carboxyl, and amino groups with iron oxides, silica, alumina, and organic matter depends on factors such as pH, metal cations, phosphate from fertilizers, etc. Therefore, it is hard to detect GLY without a pretreatment method [47].

The choice of the best suitable extraction solution remains a problem that must be addressed accordingly.

Several authors in the past reported different extraction methods of these compounds from soil, mainly using alkaline solutions with different recovery rates [48–51] and most times applicable for one type of soil. In 1980 the FDA's "Pesticide Analytical Manual" (PAM) including a procedure for the analysis of glyphosate residues in soil is published. However low and irreproducible recoveries in soil samples have been reported using this method. Later, Glass in 1983–1984 analyzed soils by alkaline extraction, followed by cleanup using flocculation with CaCl2 and anion exchange [52–54]. Yet, recoveries were still remained poor and ranged from 19 to 55%. Many extractants for soil have been tested in the years that followed with the most commonly used being aqueous bases KOH or NaOH, aqueous NH4OH or NH3, or triethylamine. Other extractants include NaHCO3, KH2PO4, mixed solutions of KH2PO4 and NH3 or NH4OH and HPO4, sodium borate buffers [55–60], or even weak acids such as 10% phosphoric acid buffers [13, 61].

Moreover, it is vital to adjust the concentration of the extraction media in such a way that high recovery rates can be obtained while avoiding matrix problems provoked by excessively aggressive alkaline media, which may enrich the dissolved humic substances in the extraction solution [49]. Humic acids interfere, for example, with the derivatization and suppress the ionization in ESI-MS/MS detectors.

#### *2.3.2 Analytical methods*

Although GLY is the most widely used agrochemical in the world, it is also the most cumbersome in its determination in analytical methods, a fact known as the "glyphosate paradox." The challenge to detect GLY using a simple analytical method is an outcome of its ionic character, low volatility and low mass, high polarity and solubility in water, poor solubility in common organic solvents, high boiling points,

difficult evaporation, and poor retention on traditional analysis columns. The quantitative and qualitative analyses of GLY (and AMPA) are extremely difficult due to the absence of fluorophores or chromophores in their structure. Furthermore, its determination at the low concentration levels required for residue analysis in different matrices is very difficult. In soil its determination is even more difficult due to the complexity of this matrix and subsequent matrix effects. The derivatization process using different derivatization reagents has been extensively used to overcome some of the above problems [62].

Prior to any attempt, it is important that all analysts to work with a glass that is not silanized to avoid the typical pitfall of GLY analysis. GLY has a profound affinity to glass, and any analytical solution prepared by this way will deviate substantially from its nominal concentration.

Chromatography is the most used and powerful method for the determination of GLY and its main metabolite AMPA, utilizing gas chromatography (GC) and liquid chromatography (LC) after derivatization or directly and capillary electrophoresis (CE). Conventional detectors are difficult to be used (especially for a straightforward analysis) due to the lack of chromophore and fluorophore groups in GLY. Usually, the limits of detection for GLY in soil vary between 0.01 and 0.3 mg/kg.

In all cases, the analytical methodology is practically exclusive for this analyte, since the working conditions cannot be applied to the determination of pesticides different from glyphosate, except for some organophosphorus, such as glufosinate and other polar compounds, and this chemical is difficult to incorporate in the vast majority of multiresidue methods. However, many of the methods published for the determination of GLY are also suitable and report results for the determination of AMPA. The majority of developed analytical methods concerned a single matrix (most often water) and may not be suitable for other matrices. Therefore, the last decade, numerous revised methods have been published on the analysis of glyphosate and AMPA in different matrices such as water, plants, or soils. Many of them just modify several parameters of previously published methods, as the pH of the water in the extraction, cleanup procedure, and derivatization step (volume and/or concentration of the samples or reagents). Other modifications include the use of different separation techniques or detection systems or even new matrices. Fewer new methods have been reported in the past 5 years for more complex matrices such as soil. Very few articles have been published on multimatrix methods.

In **Table 1** numerous analytical methods that have been used for the determination of GLY and AMPA in soil matrices are summarized. Based on the given information, at present LC is the most used method since it is considered the most suitable technique for the detection of phosphonic and amino acid-type herbicides at low concentrations. Hence, the lack of chromophore or fluorophore groups makes it difficult to use conventional detection methods such as ultraviolet (UV) absorption or fluorimetry. LC–MS/MS is currently the method of choice for polar analytes due to its high selectivity and sensitivity.

#### *2.3.3 Gas chromatography - Derivatization*

Gas chromatography methods are used after derivatization by simultaneous acylation, esterification, or trialkylsilylation reactions to convert the analytes into volatile compounds [69, 91, 92]. Typically used derivatization reagents are the mixture of trifluoroacetic anhydride (TFAA) and trifluoroethanol (TFE) or N-methyl-N-(tert-butyldimethylsilyl)-trifluoroacetamide (MTBSTFA) containing 1% tertbutyldimethylchlorosilane (TBDMCS) in excess producing sufficiently

**127**

**Year**

**Sample preparation (extraction/**

**Derivatization (pre- or post-column)**

**Analytical method**

**LOD/LOQ μg/g**

**Other information**

**Reference**

> **cleanup)**

> > 1986

1988 1989 1991,

1999

1994

0.25 M

HFB/TFAA (1:2)

NH

OH and 4

0.1 M KH2PO4

1996 1996 2000 2002 2005 2007

0.1 N NaOH/

FMOC-CI

HPLC-ESI-MS/MS

SAX-SPE

0.6 M KOH

FMOC-CI

1 M NaOH

TFAA/TFE (2:1)

GC–MS (EI) Cyan sensor LC-ESI-MS/MS

NaOH 0.2 M

iso-PCF

GC-FPD

0.8/8.0 GLY

1.2/12 AMPA

0.003/0.006 GLY

0.003/0.006 AMPA

0.45 GLY 0.005/0.05 GLY

0.005/0.05 AMPA

0.02/0.035 GLY

0.03/0.05 AMPA

0.6 M KOH

FMOC-CI

LC–LC/FLD (263 nm

0.01/0.05 GLY

Concerning soil organic matter and clay contents, the LOQ can

[68]

reach 0.01 μg/g for both analytes for sandy samples, and for

soil samples with a high organic matter and clay contents, LOQ

is of 0.04 μg/g for glyphosate and 0.1 μg/g for AMPA

Recoveries 91–106%

Recoveries 75–78%

Phosphonomethyl glycine Inhibits amino acid biosynthesis

Recoveries 88–92%

Mean recovery values were 70%

(7%) for GLU and 63% (3%) for AMPA

[70]

[49]

[71]

[69]

[48]

0.01/0.05 AMPA

λex = excitation,

λem = 317 nm)

0.1 M KH2PO4

TFAA-TFE

TsCl

0.1 M KH2PO4 or

FMOC-CI

HPLC-FLD

(λex = 270 nm,

λem = 315 nm)

GC-NPD HPLC-UV (240 nm or

280 nm)

GC–MS (EI-SIM)

0.01/0.05 8 mg/L GLY

10 mg/L AMPA

0.01/0.05 GLU,

Recoveries 84–97%

0.01/0.05 AMPA

0.2 M KOH

0.1 M (C

H2 5)3 N/

FDNB

HPLC-UV (405 nm)

0.05 GLY

0.1 AMPA

0.5–1.0 GLY

Minutes till some days of analysis time

0.1 M KH2PO4 (sandy soils)/0.2 M KOH (high clay soils)

Recoveries 66–75%

SAX cleanup

*Glyphosate Residues in Soil and Air: An Integrated Review*

[64]

[64–66]

[67]

*DOI: http://dx.doi.org/10.5772/intechopen.93066*

[50]

[63]

#### *Glyphosate Residues in Soil and Air: An Integrated Review DOI: http://dx.doi.org/10.5772/intechopen.93066*

*Pests, Weeds and Diseases in Agricultural Crop and Animal Husbandry Production*

overcome some of the above problems [62].

tially from its nominal concentration.

0.3 mg/kg.

trix methods.

difficult evaporation, and poor retention on traditional analysis columns. The quantitative and qualitative analyses of GLY (and AMPA) are extremely difficult due to the absence of fluorophores or chromophores in their structure. Furthermore, its determination at the low concentration levels required for residue analysis in different matrices is very difficult. In soil its determination is even more difficult due to the complexity of this matrix and subsequent matrix effects. The derivatization process using different derivatization reagents has been extensively used to

Prior to any attempt, it is important that all analysts to work with a glass that is not silanized to avoid the typical pitfall of GLY analysis. GLY has a profound affinity to glass, and any analytical solution prepared by this way will deviate substan-

Chromatography is the most used and powerful method for the determination of GLY and its main metabolite AMPA, utilizing gas chromatography (GC) and liquid chromatography (LC) after derivatization or directly and capillary electrophoresis (CE). Conventional detectors are difficult to be used (especially for a straightforward analysis) due to the lack of chromophore and fluorophore groups in GLY. Usually, the limits of detection for GLY in soil vary between 0.01 and

In all cases, the analytical methodology is practically exclusive for this analyte, since the working conditions cannot be applied to the determination of pesticides different from glyphosate, except for some organophosphorus, such as glufosinate and other polar compounds, and this chemical is difficult to incorporate in the vast majority of multiresidue methods. However, many of the methods published for the determination of GLY are also suitable and report results for the determination of AMPA. The majority of developed analytical methods concerned a single matrix (most often water) and may not be suitable for other matrices. Therefore, the last decade, numerous revised methods have been published on the analysis of glyphosate and AMPA in different matrices such as water, plants, or soils. Many of them just modify several parameters of previously published methods, as the pH of the water in the extraction, cleanup procedure, and derivatization step (volume and/or concentration of the samples or reagents). Other modifications include the use of different separation techniques or detection systems or even new matrices. Fewer new methods have been reported in the past 5 years for more complex matrices such as soil. Very few articles have been published on multima-

In **Table 1** numerous analytical methods that have been used for the determination of GLY and AMPA in soil matrices are summarized. Based on the given information, at present LC is the most used method since it is considered the most suitable technique for the detection of phosphonic and amino acid-type herbicides at low concentrations. Hence, the lack of chromophore or fluorophore groups makes it difficult to use conventional detection methods such as ultraviolet (UV) absorption or fluorimetry. LC–MS/MS is currently the method of choice for polar

Gas chromatography methods are used after derivatization by simultaneous acylation, esterification, or trialkylsilylation reactions to convert the analytes into volatile compounds [69, 91, 92]. Typically used derivatization reagents are the mixture of trifluoroacetic anhydride (TFAA) and trifluoroethanol (TFE) or N-methyl-N-(tert-butyldimethylsilyl)-trifluoroacetamide (MTBSTFA) containing 1% tertbutyldimethylchlorosilane (TBDMCS) in excess producing sufficiently

analytes due to its high selectivity and sensitivity.

*2.3.3 Gas chromatography - Derivatization*

**126**


**129**

**Year**

**Sample preparation (extraction/**

**Derivatization (pre- or post-column)**

**Analytical method**

**LOD/LOQ μg/g**

**Other information**

**Reference**

> **cleanup)**

> > 2014

2016 2015 2015 2015,

0.6 M KOH

2016,

2018

2016 2018 2018 2018 2018 2019 2019

Water

HFBA/FBA

0.6 M KOH

40 mM Na2B O4 7

2% succinic

anhydride IN

DMSO

FMOC-CI

LC-ESI-MS/MS using

GLY

0.01 AMPA

0.10/0.37 ng/mL

GLY

0.22/0.81 ng/mL

AMPA

reversed-phase C18

SPE-GC-FPD

or NaHCO3 0.5 M

0.1 M K2PO4

FMOC-CI

HPLC-MS (negative

0.002 GLY

0.005 AMPA

0.8 10–3/0.1 GLY

ionization)

L'ELISA (via microtiter

plate reader at 450 nm)

KOH

NH4Cl

FMOC-CI FMOC-CI

UV–Vis (264 nm)

SPE-HPLC–MS

NaOH

FMOC-CI

SPE-HPLC–MS

0.02 mg/L GLY

0.05 mg/L AMPA

20 GLY

NaOH

FMOC-Cl FMOC-CI

HPLC-UV (254 nm)

HPLCMS/MS/using

reversed-phase C18

—

0.02/0.05 GLY

Recoveries 77–87%

0.03/0.05 AMPA

1 M Na2B O4 7

FMOC-Cl

Water

Water

HCl/NaNO2

DIPN-GNPs-PGE

IS-FLD using lgG-CDs

HPLC-PDA (206 nm)

0.35 ng/mL GLY

0.01/0.1 GLY 0.01/0.1 AMPA

0.35 ng/mL GLY

1.0 g soil was suspended in a 30 mL water

Recoveries 98.6–102.8%

Recoveries 87.4–105.5%

Recoveries 70–76%

Confirmation with QTOF MS

[79]

*Glyphosate Residues in Soil and Air: An Integrated Review*

[3]

[81–83]

[84]

[85]

[86]

[27]

[87]

0.001 GLY

0.001 AMPA

Recovery 80% Recoveries 87.4–97.2% (0.1–10 μg/g) confirmed with HPLC-FLD (by Ibanez)

Recoveries from 89.6 to 118.8% for GLY and from 68 to 94.6%

[88]

[89]

for AMPA

Recoveries 94–110%

*DOI: http://dx.doi.org/10.5772/intechopen.93066*

[16]

[80]

*Pests, Weeds and Diseases in Agricultural Crop and Animal Husbandry Production*
