**3.3. Validation and application**

**Figure 4.** Response surfaces obtained for (A) benzophenone and (B) sulisobenzone after extraction and preconcentration

The effect of pH on the extraction and preconcentration of UV filters can be seen from **Tables 2** and **3**. Acidic pH resulted in lower recoveries. This is because benzophenone and sulisobenzone have pKa values of 7.5 and 7.6, respectively, meaning that in acidic pH they are more likely to

more alkaline conditions (pH 10), the analytes are easily displaced on the adsorbent, resulting in

The central pH (7) showed the highest recoveries for both UV-filters. This is a result of the interaction of the analytes' negative charge with the positive charges of the adsorbent prior to

The optimum conditions obtained by the multivariate approach were confirmed experimentally. Under these conditions (7.5, 3.5, 2 mL min−1 for sample pH, sample and eluent flow rates, respectively), quantitative recoveries ranging from 96 to 98.6% were obtained. These recoveries were compared with the predicted recoveries values (95.6 and 98.1% for benzophenone and sulisobenzone) obtained using the RSM model. It was then concluded that the results obtained by RSM model were valid since there was no significant difference at a 95%

Under the determined optimum experimental conditions, the analytical performances of the developed method for preconcentration and determination of UV-filters were investigated. The calibration curves were obtained after a set of standard solutions (0 to 350 μg L−1) was processed using the described SPE procedure. The concentrations of the analytes in the eluent solutions were quantified with the aid of a UV spectrophotometer. The limits of detection and quantification were calculated using the expressions: LOD = 3*Sd* ⁄ *<sup>b</sup>* and LOQ= 10*Sd* ⁄ *<sup>b</sup>*, where *Sd* is the standard deviation of 10 replicate measurements at lower concentrations of calibration curves and *b* is the slope of each calibration curves. Dynamic

benzophenone were determined to be LOQ-250 μg L−1, 0.9990, 50, 0.28 μg L−1 and 0.93 μg L−1,

), enrichment factor (EF), LOD and LOQ for

confidence level between the experimental and predicted values.

52 Emerging Pollutants - Some Strategies for the Quality Preservation of Our Environment

ions resulting in lower recoveries as they end up with an overall positive charge. In

by SPE.

accept H<sup>+</sup>

little or no adsorption.

elution with methanol.

**3.2. Analytical performance**

linear ranges (DLR), correlation coefficient (R2

The accuracy of the SPE/UV procedure was evaluated using a sunscreen lotion with a sulisobenzone content of 1.75% (w/w). The recovered sulisobenzone was 1.69 ± 0.07% (w/w) meaning that the percentage recovery was 96.6%. Therefore, the determined values by SPE/UV were in the acceptable range. In addition, the accuracy and matrix effects were investigated by analysing spiked real waste water samples and the results are shown in **Table 5**. From the recoveries shown in **Table 4**, it can be seen that the SPE/UV procedure described was not affected by the matrix effects as the recoveries for both benzophenone and sulisobenzone ranged from 99.3 to 100.7%.

As seen on **Tables 5** and **6**, there was a significant amount of both UV filters on the influent. This can be explained by the fact that the Daspoort waste water treatment plant treats domestic waste water. Therefore as explained by [37], personal care products are usually applied to


MEPS = microextraction in packed syringe, CE-ESI = capillary electrophoresis-electro spray ionisation, SBSE-LC-MS/ MS = stirbar sorptive extraction-liquid chromatography tandem mass spectroscopy, DLLME-UPLC = dispersive liquidliquid microextraction-ultra pressure liquid chromatography, GC-MS = gas chromatography-mass spectroscopy, SPE = solid phase extraction, DDA-IL =double dispersant assisted-ionic liquid, UV/vis = ultraviolet-visible spectrophotometry.

**Table 4.** Comparison of the analytical figures of merit of the current method and those reported in the literature.

#### 54 Emerging Pollutants - Some Strategies for the Quality Preservation of Our Environment


forms the backbone of sulisobenzone, this means that when the sulisobenzone losses the methoxy and sulfonic acid side chains, traces of the benzophenone can remain in the water. The described SPE/UV procedure was compared with a reference method, SPE/HPLC method using the same extraction conditions. The obtained results from the SPE/UV methods were comparable with the SPE coupled with HPLC method. According to the paired student t-test, there was no significant difference between the two methods at 95% confidence level. Therefore, the SPE/UV procedure can be utilised as a rapid, cheap and effective method for

Multivariate-Assisted Solid Phase Extraction Procedure for Simultaneous Preconcentration…

http://dx.doi.org/10.5772/intechopen.75641

55

The combination of SPE and UV-Vis spectrophotometry offers a simple, inexpensive and selective procedure for the assessment of UV-filters in wastewater samples. With the aid of multivariate optimisation of key parameters in the solid phase extraction procedure, it was possible to achieve satisfactory analytical performance. Real sample analysis showed that as explained by [27], wastewater treatment plant processes are not exhaustive enough to completely remove emerging organic pollutants. There were still some traces of benzophenone and sulisobenzone found in the effluent which is released into the nearby river. This means that the flora and fauna in the river is exposed to these potentially toxic compounds. Thus, the next step would be to study the distribution of these UV-filters in the river where the effluent is released into.

The authors wish to thank National Research Foundation (NRF, South Africa, Grant No.

[1] Nieto A, Borrull F, Marcé RM, Pocurull E. Determination of personal care products in sewage sludge by pressurized liquid extraction and ultra high performance liquid chromatography–tandem mass spectrometry. Journal of Chromatography A. 2009;

the determination of UV-filters in water samples.

**4. Conclusions**

**Acknowledgements**

**Author details**

**References**

99270) for financial assistance.

**1216**(30):5619-5625

Anele Mpupa and Philiswa N. Nomngongo\*

\*Address all correspondence to: pnnomngongo@uj.ac.za

Department of Applied Chemistry, University of Johannesburg, South Africa

**Table 5.** Analysis of wastewater samples (influent and effluent) spiked and unspiked from Daspoort (Pretoria, Gauteng, South Africa) wastewater treatment plant.


**Table 6.** Analysis of influent and effluent over from Daspoort (Pretoria, Gauteng, South Africa) wastewater treatment plant a period of 3 months.

the skin and later washed off into drains which are connected to wastewater treatment plants. From wastewater treatment plants, the water is discharged into rivers [3]. This has resulted in the occurrence of UV-filters in surface waters [22], sediments [38, 39], drinking water and even fish [4, 12, 40].

The presence of UV-filter in different water bodies does not only have an effect in humans as suspected endocrine disrupters [18]. Their effects spans into aquatic life, as reported by [3], benzophenone can cause cell membrane impairments in fresh water protozoa. Benzophenone was also found in other fresh water species in percentages ranging from 50 to 80% by [41].

The described method was applied in the analysis of real water samples collected over a period of three months as expressed in **Table 6**. The influent and effluent samples were collected over two seasons, namely winter (one month) and spring (two months). From **Table 6**, it was observed that between the three months, October showed the highest concentrations for both the influent and effluent. This was because it was significantly warmer during spring when compared to August. It is also worthy to note that the concentrations of benzophenone were higher than those of sulisobenzone. This could be the consequence of the degradation of sulisobenzone during the water treatment process. This is possible because benzophenone forms the backbone of sulisobenzone, this means that when the sulisobenzone losses the methoxy and sulfonic acid side chains, traces of the benzophenone can remain in the water.

The described SPE/UV procedure was compared with a reference method, SPE/HPLC method using the same extraction conditions. The obtained results from the SPE/UV methods were comparable with the SPE coupled with HPLC method. According to the paired student t-test, there was no significant difference between the two methods at 95% confidence level. Therefore, the SPE/UV procedure can be utilised as a rapid, cheap and effective method for the determination of UV-filters in water samples.
