The absorbance measurements and absorption spectra were obtained using a Shimadzu UV-visible 160 double-beam spectrometer equipped with glass cells measuring 1.0 centimeters. A professional benchtop pH meter, model number BP3001, was used to measure the pH of the solutions.

The materials used in this method were obtained in high purity from Fluka, BDH, and Merck.

Using 0.0100 g of pure ESM powder from the State Company for Drug Industries and Medical Appliances (S.D.I.), Samara-Iraq, 100 μg/mL (2.9 × 10^-4 M) was made immediately by dissolving it in 10 mL of ethanol and diluting it to 100 mL with distilled water in a volumetric flask.

Three injection vials were mixed together for each company separately, and then the average weight was taken of one injection, and the entire contents of the injection (Nexium Esoblok) containing 40 mg of the active substance ESM were dissolved in distilled water; then the volume was completed to 100 mL using a volumetric flask, after which the concentration was diluted to the equivalent of 100 μg/mL with distilled water.

The general principle of the proposed method involved the decomposition of ESM by adding 1 mL of dilute hydrochloric acid (1 M) to 1 mL of 100 μg of ESM in a final volume of 10 mL in a volumetric flask. It was observed that when the acid was added, the reaction gave the highest absorption at the maximum wavelength of 352 nm, while ESM gave its highest absorption at the maximum wavelength of 300 nm, so there was a shift of the maximum wavelength, as was clear in the following equation.

A 10 mL volumetric flask contained 1 mL of ESM standard stock solution (100 µg/mL), which was then diluted with distilled water to a mark. A UV (200–400 nm) scan was performed on the resultant solution. ESM displayed the highest absorption at 300 nm in the spectrum.

Several trials were carried out using this technique, utilizing 100 µg of ESM in a final volume of 10 mL to investigate and select the ideal parameters for the reaction that produces the highest absorbency.

Several acid solutions, including hydrochloric acid, sulfuric acid, nitric acid, acetic acid, and phosphoric acid, at a concentration of 1M for each, were studied by adding 2 mL of each acid and recording the absorbance value of the resulting solution. The results shown in Table 1 showed that 1M HCl gave the best absorbance value (0.226), so it was adopted.

In order to obtain the best absorption value, the effect of several different volumes of hydrochloric acid (0.25–3 mL) at 1M on the absorption value of the final product was studied. It was observed that by adding 2 mL of acid, the highest absorbance value was obtained, as shown in Fig. 2, which was adopted in subsequent experiments.

Figure 2. 

Effect of HCl volume.

The influence of time on the stability of the resultant at 352 nm was examined at room temperature and under pre-established experimental conditions using two different concentrations of 100 and 200 μg of ESM. The data in Fig. 3 demonstrate that the absorbance values of the resulting remained almost consistent for sixty minutes.

Figure 3. 

Effect of time on absorbance.

The final absorption spectra of the product were obtained under the optimum procedure conditions by applying the proposed method to 100 μg of ESM in a 10 mL volumetric flask. Fig. 4 shows the final spectrum of the method, where the resulting spectrum gave the highest absorbance value (0.221) at 352 nm.

Figure 4. 

Absorption spectra of (A) 10 μg ESM/mL vs. D.W. and (B) ESM vs. blank (D.W.+HCl).

In a series of 10 mL volumetric increasing volumes of 100 µg/mL ESM working solution ranging from 0.1 to 4 mL were added, followed by 2 mL of 1 M hydrochloric acid solution, with well shaking of the contents, and then the flasks were filled up to the mark with distilled water. The absorbance values of the products formed were taken against their blank solutions at 352 nm and recorded. A standard curve of the procedure was plotted depending on the curve; the linearity between the absorbance values and the ESM concentration was in the range of 1–40 μg of ESM/mL, as shown in Fig. 5. The apparent molar absorbance was 7.737 × 10³ L/mol.cm, and Sandall sensitivity was 0.0446 µg/cm².

Figure 5. 

The calibration curve for ESM determination.

The ESM was determined using three quantities of its working solution (50, 100, and 250 µg/10 mL) and repeating the process five times for each concentration in order to identify the accuracy and precision of the proposed procedure. The results of this study recorded in Table 2 confirmed that the proposed method had acceptable accuracy and precision.

ESM was successfully analyzed in pharmaceuticals (injectable) using the present method. The results summarized in Table 3 showed acceptable accuracy of the proposed.

Table 3 results show that the experimental “t-test” values are less than the theoretical “t-test” value in table (3.18) at a (95)% confidence level for four measured samples. The value indicated that there are no significant differences between the two values (calculated and theoretical) (Christian et al. 2014).

The analytical values оbtained using this method are included in this study’s Table 4, and based on the information given in this table, the proposed method is considered to have good sensitivity and accuracy.

The standard addition method was successfully performed (Harris 2016) using two different concentrations (5 & 8) of working solution for each pharmaceutical preparation (Nexium injection and Esoblok injection), and the results shown in Fig. 6 and Table 5 demonstrated that the proposed method had good selectivity for the determination of ESM in pharmaceutical preparations.

Figure 6. 

Standard addition curves for estimation of ESM in pharmaceutical preparations.

Green analytical chemistry aimed to make analytical processes safer for people and the environment. Many factors were considered when evaluating the greenness of an analytical approach, including the quantity and toxicity of reagents, waste produced, energy requirements, the number of procedural steps, downsizing, and automation. Using greenness evaluation criteria calls for certain instruments. The Analytical Greenness calculator was presented, a thorough, adaptable, and uncomplicated evaluation method that yielded an understandable and instructive outcome. The evaluation criteria were converted into a single 0–1 scale using the 12 principles of green analytical chemistry (SIGNIFICANCE). The SIGNIFICANCE principles were used to compute the final score. The outcome was a pictogram that showed the analytical procedure’s performance and final score. According to the data of the proposed method, no organic reagent or any toxic chemicals were used, so this proposed method could be considered one of the environmentally friendly methods. Therefore, using the Analytical Greenness-AGREE (Pereira et al. 2020).

The method was evaluated by entering the information that was deduced from the research into 12 variables in the AGREE system. The result obtained was 0.86, and this result indicates that the method can be described as environmentally friendly (Fig. 7).

Figure 7. 

Analytical Greenness report sheet.

The values of the spectroscopic analytical variables of the proposed method for the determination of ESM were compared with the same variables of spectroscopic methods from previous literature, and the results were recorded in Table 6.

The results in the above table showed that our results were equally significant to the outcomes of the two methods used for comparison, and the present method was considered a friend to the environment according to Analytical Greenness-AGREE.