General description and determination of 1-Naphthylacetic acid

General description

1-Naphthaleneacetic acid (NAA) is naphthalene derivative used as a synthetic plant growth stimulator (auxin type) utilized for various crops commonly in mixture with naturally occurring auxins like indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA) or more often with synthetically prepared agents like naphthylacetamide (NAD). It is applied as a spray with concentration between 20 and 100 mg·L^-1 depending on the targeted plant. Therefore, its residua have been found in fruits, like apples or pears, and in the soil and water samples as well. Considering the toxicity, NAA is qualified as unlikely hazardous by the WHO and highly toxic by U.S. EPA. The European Union has set a maximum residua limit (MRL) for sum of NAD and NAA (expressed as amount of NAA) between 0.6 and 0.15 mg·kg^-1 for various fruits, vegetable, legumes, seeds, and others and MRL for NAA of 0.05 mg·kg^-1 for citrus fruits and nuts [1]. 

Figure 1. Chemical structure formula and three-dimensional structure of 1-Naphthylacetic acid

Application

1-Naphthylacetic acid is used as a plant growth regulator and for plant tissue culture. It is used for the vegetative propagation of plants from stem and leaf cutting, abscission promoter and substrate for auxin inducers of specific plant enzymes[2]. Further, it stimulates root formation in cuttings of woody and herbaceous plants. It is also used to prevent premature flower and fruit drop. It is also employed to control regrowth of tree sprouts after trimminguse. In addition to this, it is used in ornaments and serves as an ingredient in many commercial plant rooting horticultural products[3].

Determination

1. Electrochemical behavior of a plant growth stimulator 1-naphthaleneacetic acid (NAA) was studied using a boron doped diamond electrode. It was found that NAA provided two irreversible anodic signals about the potential values of +1450 and +1630 mV, respectively, in an acidic medium. Products of the observed electrode reaction were identified using gas chromatography-mass spectrometry (GC-MS) and nuclear magnetic resonance (¹H NMR) techniques. Based on the obtained results, the oxidation mechanism of studied compound was proposed. Subsequently, voltammetric method for NAA determination was developed with the following statistical parameters: LOD = 0.09 μg·mL^-1 and RSD₁₁ = 2.1% (10.8 μg·mL^-1). Moreover, The proposed method allows the determination of NAA, IBA, and IAA in mixed formulations without application of any sophisticated separation techniques. This new method was finally applied for NAA determination in commercially available herbicide preparation[1].

2. A spectrofluorimetric method for the determination of 1-naphthylacetic acid (NAA) was developed. The sample solution was equilibrated with Sephadex QAE A-25 gel by agitation. The relative fluorescence intensity of NAA fixed on Sephadex QAE A-25 gel was measured directly after packing the gel beads in a 1-mm silica cell, using a solid-phase attachment. The wavelengths of excitation and emission chosen for the determination of NAA were 280 and 336 nm, respectively. The applicable concentration range was 12-60 ng·mL^-1 for NAA. The detection limit was 3 ng·mL^-1 for NAA. The method was applied satisfactorily to the determination of NAA in commercial formulations of phytohormones and soil samples[4].

3. A convenient method for the determination of 1-naphthaleneacetic acid (NAA) plant growth regulator in spiked canned pineapple samples by micellar-stabilized room temperature phosphorescence with sodium dodecyl sulfate as a micellar medium, thallium nitrate as an external heavy atom, and sodium sulfite as an oxygen scavenger. A multivariate optimization approach using the type of central composite blocked cube-star design was carried out. The analytical curve of NAA gives a linear dynamic range of 70−500 ng·mL^-1 with a detection limit of 21 ng·mL^-1 and precision of 2.37% (n=7). A mean recovery value of 98.6% was obtained for 250 ng·mL^-1 NAA in the pineapple samples[5].

References

1.Janíková L, Chylková J, ?ele?ovská R, et al. Electrochemical behavior of plant growth stimulator 1-naphthaleneacetic acid and its voltammetric determination using boron doped diamond electrode[J]. Journal of Electroanalytical Chemistry, 2020, 859: 113855.

2.Canepa, Alicia, S, et al. Intramolecular sulfonylamidomethylation of 2-(2-naphthyl) and 2-(1-naphthyl)ethanesulfonamides: synthesis of new class of naphthosultams. Tetrahedron Lett. 2015, 56 (16), 2054-2058.

3.Li G, Liu S, Sun Z, et al. A simple and sensitive HPLC method based on pre-column fluorescence labelling for multiple classes of plant growth regulator determination in food samples[J]. Food Chemistry, 2015, 170: 123-130.

4.Vilchez J L, Blanc R, Navalón A. Simultaneous spectrofluorimetric determination of 1-naphthylacetic acid and 1-naphthalenacetamide in commercial formulations and soil samples[J]. Talanta, 1997, 45(1): 105-111.

5.Segura Carretero A, Cruces Blanco C, Ales Barrero F, et al. Method for the quantitative determination of 1-naphthaleneacetic acid in spiked canned pineapple samples by micelle-stabilized room temperature phosphorescence[J]. Journal of Agricultural and Food Chemistry, 1998, 46(2): 561-565.