ELECTROCHEMICAL ANALYSIS OF BUTYLATED HYDROXYTOLUENE

: Electrochemical analysis has carried out butylated hydroxytoluene (BHT) measurements. Cyclic voltammetry is used in this research as a qualitative-quantitative analysis of oxidation and reduction reaction processes, adsorption processes on electrode surfaces, and chemical electron transfer mechanisms. This research aims to determine the optimum deposition time and scan rate in cyclic voltammetry, the BHT standard equation, the limit of detection, and the recovery percentage. In this research, a deposition time of 25 seconds produces the highest current response of 3.89672 x 10 -4 Ampere. The scan rate is 150 mV/second, producing the highest and optimum current response of 4.24561 x 10 -4 Ampere. BHT standard equation y = (4.92784 x 10 - 6 ) x + (1.25207 x 10 -4 ) is obtained with R 2 = 0.99933. The limit of detection value is 2.69683 ppm, and the recovery percentage is 101.314%. Therefore, this cyclic voltammetry method is suitable for analyzing BHT because it has high sensitivity.


INTRODUCTION
Butylated hydroxytoluene (BHT) is a chemical substance widely used as an antioxidant in packaged foods [1].BHT is classified as a synthetic phenolic antioxidant compound [2].BHT is incompatible with hydrochloric acid, anhydrous acid, copper steel, bases, and oxidizing agents [3].BHT can damage the autooxidation reaction chain by donating hydrogen atoms to fat radicals, producing stable and radical-free products [4].Adding BHT reduces free radicals so that product quality is maintained regarding texture, taste, colour, and smell.However, the use of BHT in large quantities can cause toxicity effects on the lungs and have the potential to induce tumour effects.High levels of BHT have been reported to be responsible for liver damage and are carcinogenic in animals [6].In clinical trials, 100% BHT could cause mild irritation and sensitive skin [4].Apart from that, applying BHT to the skin can also cause problems with dermatitis and urticaria [7].
Determination of BHT levels is often carried out using the high-performance liquid chromatography (HPLC) method.This method is popularly used in determining BHT levels because of its detection sensitivity, good separation ability, precision, and reproducibility for quantitative analysis [8].Sometimes, analyzing BHT levels using the HPLC method requires a long time because separating compounds in the sample depends on the type of mobile phase, flow rate, pressure, and column temperature.Besides that, an alternative method can be used to determine BHT levels in lotion, namely the voltammetry method.Voltammetry is a kind of electrochemistry method.Voltammetry methods are essential in inorganic chemistry, physical chemistry, and biology.One type of voltammetry method is cyclic voltammetry.This cyclic voltammetry method can be used as a qualitative-quantitative analysis of oxidation and reduction reaction processes, adsorption processes on electrode surfaces, and chemical electron transfer mechanisms [9].This research is essential because it has advantages in good detection sensitivity, which can be seen from its low limit detection value [9].This research aims to determine the optimum deposition time and scan rate in cyclic voltammetry, the BHT standard equation, the limit of detection, and the recovery percentage.Therefore, BHT content analysis was carried out using the cyclic voltammetry method.

RESEARCH METHODS
In this research, the following materials and instruments were used.There are BHT p.a. ethanol 96% for analysis, aquadest, voltammetry type 797 computrace program, working electrode, auxiliary electrode (Pt), reference electrode (Ag/AgCl), analytical balance, measuring pipette, and measuring flask.

Preparation of Main Solution
0.25 grams of BHT was weighed and dissolved in a 250 mL volumetric flask with 96% ethanol solvent.Homogenized and stored in a dark bottle to avoid sunlight.

Preparation of BHT Standard Solution
Standard solutions are prepared by graded dilution from high to low concentration.A total of 10 mL of 1000 ppm BHT solution was pipetted into a 100 mL flask and diluted with 96% ethanol to the limit mark.Next, homogenize by shaking gently.The following is the volume obtained for BHT when dilution is carried out in stages.

The optimum Deposition Time Determination
The optimum deposition time was determined using cyclic voltammetry in 60 ppm BHT with a volume of 20 mL at a voltage of -2 to +2 V, a scan rate of 50 mV/s, and various deposition times of 5, 10, 15, 20, and 25 seconds.The highest peak deposition time determines the optimum scan rate measurement.

The optimum Scan Rate Determination
The optimum scan rate was determined using cyclic voltammetry in 60 ppm BHT with a volume of 20 mL at a voltage of -2 to +2 V, using optimum deposition time, and various scan rates of 50, 75, 100, 125, 150 mV/s seconds.The highest peak of the scan rate is used to determine the BHT standard concentration measurement to make a standard curve.

BHT Standard Equation
The standard equation is obtained from the linearity relationship between standard solutions.This research uses standard solutions for 20, 40, 60, 80, and 100 ppm BHT.

Limit of Detection Determination
The limit of detection is the smallest concentration of BHT that the instrument can analyze.LOD =

Recovery Percentage Determination
The recovery percentage is one of the parameters to determine data accuracy.% recovery =

RESULTS AND DISCUSSION Optimum Deposition Time Determination
Deposition time is when the electrode is immersed in the voltammetry cell so ions depose on the electrode surface.This step aims to determine the optimum deposition time that can be used to characterize BHT in terms of the highest current response.
A voltammogram indicates the BHT solution at 5, 10, 15, 20, and 25 seconds deposition times.Based on the voltammogram above, it is found that a deposition time of 25 seconds produces the highest current response of 3.89672 x 10 -4 Ampere.The higher the deposition time applied, the higher the current read [10].The longer the deposition time, the greater the deposition of ions on the electrode surface so that more BHT ions are deposited.
Besides that, it is known that the voltammogram shows one upward peak, which is called the oxidation peak.The BHT oxidation reaction occurs when the electrode surface is negatively charged at a negative potential, releasing + in the phenolic group to form positively charged BHT ions accompanied by the transfer of 2 electrons [11].

Optimum Scan Rate Determination
The electrode scan rate is a measure of how fast and slow the electrode scans are for analyte ions within a specific potential range.This step aims to determine the optimum scan rate that can characterize BHT regarding the highest current response.A voltammogram indicates the BHT solution at scan rates of 50, 75, 100, 125, and 150 mV/s.At a 50 scan rate, the most negligible current response was 3.89672 x 10 -4 Ampere with -0.124259 as potential voltage.A scan rate that is too small makes the diffusion area wider so that the diffusion rate is slower than the reaction rate.A low scan rate requires a long scanning time.As a result, the oxidation reaction of the BHT compound is almost complete, and charge transfer is not optimal.Therefore, the resulting current response is also small.
Based on the voltammogram above, the resulting current also increases as the scan rate increases.A scan rate of 150 mV/second produces the highest current response of 4.24561 x 10 -4 Ampere with potential voltage (Epa) value relative at the same points, indicating that the measurement is of good precision.A high scan rate narrows the analyte diffusion layer so that the diffusion rate is faster than the reaction rate.The rapid diffusion rate causes the accumulation of analyte ions on the electrode surface [12][13].Therefore, the resulting current response becomes higher.So, the scan rate of 150 mV/s is used as the standard solution measurement to make the BHT standard curve.ISSN 1907-1744 (Print) DOI: 10.29303/jpm.v18i6.5858ISSN 2460-1500 (Online)

BHT Standard Equation
Standard solution measurements were carried out under optimal conditions: optimum deposition time and scan rate.Based on research that has been carried out, the optimal state of BHT in the voltammetry cell is using a deposition time of 25 seconds and a scan rate of 150 mV/second.The standard solution concentrations used in this research include 20, 40, 60, 80, and 100 ppm, so the standard equation y = ax + b and the R 2 value are obtained.Below is a voltammogram of the BHT standard curve.Based on the data above, the standard BHT equation y = (4.92784x 10 -6 ) x + (1.25207 x 10 -4 ) is obtained with R 2 = 0.99933.The results of this standard equation can be used to determine the BHT concentration using the cyclic voltammetry method.

Limit of Detection Determination
The standard deviation of the residual current is required to be determined before calculating the LOD.It is known that the standard deviation of the residual current in this study is 4.02714 x 10 -6 with a slope of 4.92784 x 10 -6 .Therefore, it can be determined that the LOD in this measurement is 2.69683 ppm.

Recovery Percentage Determination
Recovery percentage is a value that expresses the accuracy of the data if the method is said to have good accuracy if the percent recovery range is in the field of 90 -100% [14].Based on the data above, a recovery percentage above 100% indicates that the measured value for the matrix is higher than the spike value [20].It's because of uncertainty during the calibration process, either when using or reading the instrument [21].Also, recovery is more than 100% because the sample contains compounds that, in solution, can produce electrochemistry current that interferes with the measurement working electrode [22][23].However, the recovery percentage of 101.314% is still said to be excellent and accurate.

CONCLUSION
A deposition time of 25 seconds produces the highest current response, 3.89672 x 10 -4 Ampere.The scan rate is 150 mV/second, producing the highest and optimum current response of 4.24561 x 10 -4 Ampere.BHT standard equation y = (4.92784x 10 -6 ) x + (1.25207 x 10 -4 ) is obtained with R 2 = 0.99933.The limit of detection value is 2.69683 ppm, and there is a recovery percentage of 101.314%.Therefore, this cyclic voltammetry method is suitable for analyzing BHT because it has high sensitivity.

Figure 5 .
Figure 5. Voltammogram of BHT standard solution at optimum deposition time and optimum scan rate

Table 1 .
BHT standard solution calculation

Table 2 .
Ipa and Epa of various deposition time

Table 3 .
Ipa and Epa of various scan rates

Table 6 .
Recovery percentage calculation