Forensic Science International 251 (2015) 50–55
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Determination of cocaine in Real banknotes circulating at the State of Rio de Janeiro, Brazil V.G.K. Almeida, R.J. Cassella, W.F. Pacheco * UFF—Universidade Federal Fluminense, Analytical Chemistry Department, Outeiro Sa˜o Joa˜o Batista s/n, Nitero´i, RJ, Brasil
A R T I C L E I N F O
A B S T R A C T
Article history: Received 25 August 2014 Received in revised form 9 February 2015 Accepted 11 February 2015 Available online 19 February 2015
This paper shows the result of a study on the extent of cocaine contamination in Real banknotes in circulation in the state of Rio de Janeiro (Brazil). A study of the percentage of contaminated banknotes was made, as well as a study on the contamination of banknotes based on different values, and a study of contamination depending on the region where the banknote was collected. The idea of this last study was to verify if the peculiar characteristics of the region of study (in particular, the city of Rio de Janeiro) influence the amount of cocaine in the banknotes. Some regions have higher consumption/drug trafficking of cocaine than others. Also, some contaminated banknotes confiscated directly from drug dealers and users were analyzed. Also, is showed in this paper all the optimization of the available analytical techniques for making the measurements possible. ß 2015 Elsevier Ireland Ltd. All rights reserved.
Keywords: Cocaine Fluroescence Rio de Janeiro
1. Introduction Nowadays, drug use is considered not only a health problem but also a problem of urban violence. The three main reasons for this violence are: drug violence, which occurs as a change of behavior for either short or long period of certain drugs, such as cocaine [1]; the economic motivation of addicts because there is the execution of the crime to acquire funds to purchase illicit drugs [2,3] and; the territorial dispute between drug dealers [4]. In some regions this dispute is fierce, which creates even more violence. In the specific case of Rio de Janeiro, the drug trafficking began in the 70s and was intensified in the following decade, with the city of Rio becoming a strategic bridge of drug trafficking from South America to Europe [5] and today maintains the territorial dispute between various armed groups that submit communities of the slums to their political and economic interests through violence. Although many actions have been taken by the government (both at state and federal level) to suppress the drug trade and reduce violence (as most recently, the occupation of some slums in Rio de Janeiro by the police), these actions still have not achieved the desired effect.
* Corresponding author at: UFF—Universidade Federal Fluminense, Analytical Chemistry Department, Outeiro Sa˜o Joa˜o Batista s/n, 24020-141 Nitero´i, Rio de Janeiro, Brazil. Tel.: +55 21 26292140; fax: +55 21 26292143. E-mail address: [email protected] (W.F. Pacheco). http://dx.doi.org/10.1016/j.forsciint.2015.02.014 0379-0738/ß 2015 Elsevier Ireland Ltd. All rights reserved.
A reflection of this can be noticed on the world drug report of 2009, released by the United Nations Office on Drugs and Crimes (UNODC) [6], in which the growth of drug trafficking in Brazil is in the opposite direction of the rest of the world. While consumption in the rest of the world decreased, the consumption in Brazil has nearly doubled. The UNODC attributed to the coordinated effort of different countries the main reason for the fall in production of drugs in the world. According to this agency, greater international cooperation is the main reason of the increased efficiency in combating the drug trafficking. Just as there was an increase in cooperation between different countries in combating the drug trafficking, there was also an improvement in efficiency within each country to combat this drug trafficking. One of these improvements can be attributed to criminology techniques. The development and application of analytical methodologies to investigative techniques is an important tool to aid in the elucidation of various crimes, providing scientific data that can be used reliably and being accepted in courts as physical evidence to support the conviction. Among the tools that have been developed in different countries, the identification of drug residues in banknotes can be noted. Several laws were enacted in order to relate the amount of drug in banknotes used in the drug trafficking and those can be used as forensic evidence to make a request for search warrants and seizure or even arrest order [7].
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In the United States and Europe, the presence of drug residues in samples of banknote is not enough to say that the person who carried the banknote was a drug dealer or user, since several studies [8–10] showed that a large number of banknotes is contaminated with detectable drug residues. This does not come as a surprise, especially in the case of the United States where there is a high number of users. The residue of the drug can reach the banknote by direct handling of the drug user or dealer when this one is with contaminated hands, or the residue can move on to the banknote when the user rolls the money and uses it to inhale the narcotic. The residue can also be spread from a banknote to another within the ATMs or machines that count money [11,12]. Since the banknote is always circulating, people who never had any contact with any kind of drug can carry the contaminated banknote. Otherwise, the city of Rio de Janeiro has its particularity with other cities, with some regions under the control of drug dealers. It would be interesting to study if the distribution of the residue of the drug in the bank note in this region is equal or different other regions. And as the material of the real bank note is similar to Dollar and Euro (paper, not plastic), it is plausible to think that the same factors that allowed the banknote to retain the drug residue would be applied here. In Brazil, there are two studies in the literature about the determination of cocaine in real banknotes. In the study of Di Donato [13], the determination of residues of cocaine is realized by gas chromatography–mass spectrometry, and the banknotes used in this study were collected in nine different cities (including Rio de Janeiro). In the study of Roberts [14], the determination of cocaine in banknotes circulating in the city of Belo Horizonte (MG), using liquid chromatography with UV–vis, was realized. In this present work, the determination of residues of cocaine in real banknotes collected at different points of the city of Rio de Janeiro, and in some nearby counties was realized. Also, the concentration of cocaine in the banknotes seized directly with users was determined. The quantification of the cocaine was realized fluorimetrically and the influence of the pH and the solvent used was studied to obtain better analytical signal. The best condition chosen was composed by sodium acetate buffer solution with pH 3.9. To ensure accuracy of the results, the quantification was also realized by HPLC-UV and a great concordance of the results was achieved. The extraction of the cocaine residue from banknote was realized by liquid–solid extraction. The influence of the solvent of extraction was studied and the best solvent in this situation was also the sodium acetate buffer solution with pH 3.9.
51
an ultrasound Unique, Ultracleaner 1600 with a frequency of 40 kHz was used. The 1000 mg L 1 standard solutions of cocaine were provided by Cerillant. Acetonitrile, methanol, ethanol and acetone were obtained from Tedia (HPLC grade) and glacial acetic acid was obtained from Vetec. 2.2. Preparation of standard solutions The analytical solutions of cocaine used in the spectrofluorimetric method were prepared in 5.0 ml volumetric flasks, by the dilution of 1000 mg L 1 standard solution. Each solution (for each concentration) were prepared by taking appropriate volume of the standard solution and the volume was made up to the mark of 5.0 ml using an acetate buffer solution, with pH 3.9, 0.01% v/v. The solutions of cocaine used in the HPLC were prepared in volumetric flasks of 1.0 mL by diluting the same standard solution, and the volume for each solution prepared was made up to the mark with acetonitrile. The sodium acetate solution was prepared by dissolving an adequate mass of sodium acetate in a volumetric flask of 1000 mL, the desired pH as achieved by addition of HCl 1.0 mol L 1, and then, the final volume was obtained by adding ultra-purified water. 2.3. Sampling To collect the banknotes, a small purchase using 100 and/or 50 real bills was realized at some premises (like market, bar, newsstand, etc.). Three banknote (change) obtained in each establishment were stored in a sealed plastic bag until the extraction was made. 2.4. Notes confiscated directly from drug dealers/users The notes were seized by the civil police of the state of Rio de Janeiro, and were held by the Institute of Criminology Carlos Eboli (ICCE). In this study, one of the banknotes was used by a user to inhale the drugs, and the other three banknotes were seized along with the cocaine. 2.5. Preparation of samples
2. Methods
The extraction of cocaine from the banknotes was realized by placing a crumpled banknote in a polyethylene plastic tube of 50 ml, followed by addition of 15 mL of sodium acetate buffer solution with pH 4.0. Each tube was placed in table roller mixer for 30 min. After that time, the banknote was removed and dried at room temperature. This banknote was replaced with no damage to the market. The extraction solution was used for the measurement.
2.1. Equipments and reagents
2.6. Conditions of measurements in the spectrofluorimeter
For fluorimetric measurements, a spectrofluorometer Varian, Cary Eclipse. Using a quartz cuvette of 10 mm path length was used. The chromatographic separations were performed on a high performance liquid chromatography using ultraviolet detector (HPLC-UV), Dionex, Ultimate 3000, using a Zorbax C-18 column with 5 mm particle size, 2.1 mm of internal diameter and 150 mm length, provided by Agilent, model 300SB. All solutions were prepared with ultra-purified water obtained from a system of ultrapurification Purellab Classic, with resistivity of 18 mV and before being injected into the chromatographic system, the solutions were filtered through a nylon membrane UNIFIL of 47 mm diameter and 0.45 mm pore. To the stirring of solutions, a table roller mixer, model MR-II was used. For removal of air bubbles from the prepared solutions,
The spectrofluorometric measurements were realized at 315 and 230 nm for excitation and emission, respectively, with nominal pass band of 5 nm. 2.7. Conditions of HPLC-UV measurements The measurements were realized at 230 nm and the mobile phase consisted of: (A) acetonitrile and (B) acetic acid 0.01% w/v. The elution was realized in a gradient mode, starting with 10% of A, changing linearly up to 50% during 20 min. The retention time of the cocaine was 12 min and the detector response was recorded using the peak area. The column was at room temperature (25 1 8C) and volume of injection was 20 mL. The flow rate of mobile phase was kept at 1 mL min 1.
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Table 2 Recovery of cocaine added in clean notes in different extraction times.
3. Results and discussion 3.1. Preliminary studies of the fluorimetric characteristics of the cocaine
Time of extraction (min)
Mass of cocaine (mg) Added
Recovered
10 15 30 60 120 180
25.0 25.0 25.0 25.0 25.0 25.0
21.7 25.9 25.1 25.6 25.6 27.1
Recovery (%)
87.0 1.6 103.6 1.2 100.3 0.8 102.3 1.3 102.6 1.4 108.4 2.1
Cocaine has a native fluorescence at 230/315 nm [15], however, few studies were realized to reach a condition of maximum sensitivity. The first of these studies was the influence of the solvent, where the influence of water, acetonitrile, methanol, ethanol, acetone and the Britton Robinson buffer solution adjusted to pH 7 on the fluorescence signal of a standard solution of cocaine was realized. Among these solvents, the best signal to noise ratio was observed for the Britton Robinson buffer solution at pH 7. Based on this study, the influence of the pH on the analytical signal of the standard solution of cocaine was evaluated and the higher signal to noise ratio was observed at pH 4. These conditions allowed the achievement of a linear relationship of the fluorescence signal of cocaine from 0.30 to 6.0 mg L 1.
put to stir during different periods of time. At the end of this time, the amount of cocaine in the extraction solution was determined spectrofluorimetrically. Table 2 shows the result of this study. Although total extraction of cocaine could be accomplish in just 15 min, for the next experiments the time of 30 min was chosen, leaving a safety margin.
3.2. Extraction of the cocaine banknotes
3.3. Analytical figures of merit for the fluorescence method
In the beginning of this study, some banknotes of high value (R$ 100,00 and R$ 50,00) were washed with water, HCl, water, NaOH and then, rinsed with water (subsequently), so the banknote could be totally free of any residues of cocaine or other compounds. To do so, some scramble notes (individually) were put inside a polyethylene tube (50.0 mL) with 15.0 mL of the desired solvent, each tube was mixed on a table roller mixer during 1 h, and after this sequence of solvents, each note was left to dry for 24 h. The use of different solvents to extract the cocaine from the banknotes proved to be effective in several publications [16–21]. In this present work, various solvents were tested to determine which one showed better efficiency in extracting the cocaine from the banknotes. The solvents tested were acetonitrile, methanol, water and the Britton Robinson pH 7.0. This experiment was carried out with banknotes spiked with 25 mL of the 1000 mg L 1 standard solution of cocaine. These banknotes were kept at room temperature for 1 day, so they could dry. After this time, each banknote was placed in a polyethylene tube of 50 mL, followed by addition of 15.0 mL of the solvent in question and placed to stir for 10 min in the roller mixer table. After the required time, the banknote was removed and the solvent was used to quantify the recovery spectrofluorimetrically. Table 1 shows the extraction efficiency obtained for each solvent. The highest extraction efficiency of cocaine was obtained using the Britton Robinson buffer solution at pH 4. Combining the highest extraction efficiency and the fact that the solvent was used to construct the calibration curves, this solvent was chosen as extraction solvent of cocaine from the banknotes. The next step of this present work was the evaluation of the time of extraction. In this study, different banknotes were previously cleaned, enriched with 25 mL of the 1000 mg L 1 standard solution of cocaine. These banknotes were kept at room temperature for 1 day, so they could dry. After this, each banknote was placed in a polyethylene tube of 50 ml followed by addition of 15 mL of the Britton Robinson buffer solution, and each tube was
Some figures of merit for the method were studied in order to establish its analytical performance: linearity, limit of detection, limit of quantification, precision and recovery. The calibration curve was prepared in seven different concentration levels, (real triplicate for each level) with the fluorescence analytical science recorded for each aliquot of a solution. The equation of the curve was calculated by the method of least squares (linear regression) with subsequent evaluation of the coefficient of determination (r2). Tests for normality, independence, homoscedasticity of the residue and deviation of linearity showed to be adequate (Table 3). This implies that residues of the calculated regression followed a normal distribution and that they were homoscedastics (the variance of the deviations were not different), independent (no autocorrelation between the residues) and the regression was significant, with no deviation from the linearity [22]. The equation obtained by linear regression [22] was y = 34.786x + 26.439 and the coefficient of determination (r2)
Table 1 Recovery of cocaine from clean notes using different solvents. Solvent
Acetonitrile Methanol Water Buffer solution
Mass of cocaı´na (mg) Added
Recovered
25.0 25.0 25.0 25.0
18.7 11.2 17.7 21.7
Recovery (%)
74.6 44.6 70.7 87.0
Table 3 Parameters for statistical evaluation of the linear regression. Statistic
Values
N
15
Normality r2 P
0.9960 P > 0.10
Homoscedasticity tL P
0.17 0.85
Independence D P
1.89 P > 0.05
Significance of regression gl (regression) gl (residue) SQ regression SQ residue MQ regression MQ residue F F critical
1 5 35840 150.0 35840 30.0 1195.9 3.80 10
2
7
n, number of data; r , coefficient of determination; tL, Levene’s test; P, significance; D, Durbin–Watson statistic.
Residues
V.G.K. Almeida et al. / Forensic Science International 251 (2015) 50–55
10 8 6 4 2 0 -2 0 -4 -6 -8 -10 -12
1
2
3
4
5
6
53
7
[cocaine] mg L-1 Fig. 1. Residue of the analytical curve.
equal to 0.9960. A test F was made to evaluate the significance of the regression, and as the F calculated was higher than the F critical, it was evidence that the regression was achieved. A plot of residue was made and no bias for the residue was observed (Fig. 1). The detection limit found in method was 0.11 mg L 1 (1.7 mg/ note) and the limit of quantification was 0.27 mg L 1 (4.1 mg/note). The study of analytical precision was performed by determining the coefficients of variation intra-assay and inter-assay for the standard solutions at concentrations of 0.5, 2.0 and 5.0 mg L 1, and the averages found were 4.8% (intra-assay) and 5.5% (inter-assay), both for an n of 4 replicates (Table 4). To estimate the recovery, a set of 6 banknotes was taken, subjected to the extraction process (described in Section 3.2) and put to dry at room temperature. At this point, a defined volume of standard of cocaine was added to the banknote (mass of 25 mg), left for 24 h to dry, and then the note was again subjected to the extraction process. This extract was analyzed (3 aliquots of each note) to estimate the recovery of cocaine added, and as the banknote went through a previous extraction procedure, it can be considered that the banknotes were previously cleaned. The result of this study is described in Table 5. There was an average recovery at the three studied concentrations of 101.4 + 3.0%, considered to be satisfactory, implying that
Table 4 Intra and inter-assay precision obtained for the fluorescent method. Concentration (mg L 1)
0.5 2.0 5.0 Average
Coefficient of variation (%) Intra-assay (n = 4)
Inter-assay (n = 4)
10 2.5 1.9
8.3 4.1 4.0
4.8
5.5
Fig. 2. Comparison, note by note, of the HPLC and fluorescence techniques.
the extraction procedure was efficient to extract the cocaine residue from the banknotes (Table 5). 3.4. Results of the determination of cocaine in banknotes As there was no certified material for this case, and due the possible interferences inherent to a fluorimetric method, the results obtained fluorimetrically were compared with the results obtained with another method, in this case, a high performance liquid chromatographic. Fig. 2 shows a comparison, note by note, of the results obtained by both techniques. In this figure, it can be observed a good correlation between the two techniques discussed expressed by the correlation coefficient (r2), whilst the value of the slope of the straight line equation suggests that these results are equal, once the value is close to the unity. A paired t-test was realized and a value of t = 0.189 for 144 observations (P = 0.05) was found. As t critic is 1.96, that indicates that there is no statistical difference between the two means (probably, the extraction method has minimized the potential interferences for the fluorescence method). The variance between the results obtained for both methods was tested using the F test. The F value was 1.30, for an F critical of 1.40 (a = 0:05, 144 observations). From these observations, the analysis of results was only realized with the results obtained by the spectrofluorimetric method. 3.5. Distribution of cocaine by value of the banknotes Table 6 shows the percentage of banknotes contaminated with cocaine residue depending on their value, regardless of the location where they were collected. It was found residue of cocaine in 85% of the banknotes.
Table 5 Recovery of the extraction method used for the determination of different concentrations of cocaine in banknotes. Banknote
Recovery (%)
CV (%) (n = 3)
1 2 3 4 5
97.2 96.3 136 88.4 89.0
6.1 5.6 13 9.2 11.1
Average
101.4
9.0
Table 6 Percentage of banknotes found with residue of cocaine according to their value. Value (R$)
n
% of banknotes with cocaine
2 5 10 20 50 100
98 29 3 4 4 4
83.0 86.2 66.7 25.0 0.0 0.0
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V.G.K. Almeida et al. / Forensic Science International 251 (2015) 50–55
Fig. 3. Location of collection of the banknote used in this work.
Another important factor to be discussed is that, in addition to the direct contamination (the aspiration of the drug from the surface of the banknote) the contamination spreads from one banknote to another within the ATM is a parameter that should be mentioned. As the banknotes are stored on these machines grouped by the same value, a contaminated banknote propagates the residue of cocaine to the other banknotes of the same value. 3.6. Distribution of the amount of cocaine as function of the region where the banknotes were collected The first study realized was the distribution of cocaine depending on the region where the banknote was collected. In this study, only banknote of 2 and 5 Reais were used. Fig. 3 shows most of the collection regions. All locations are shown in Table 7 as well as the average amount of cocaine found in each of these locations. To determine whether there is statistical difference between the concentrations of cocaine found in each region or not, an analysis of variance (ANOVA) of the results was realized by grouping the values by location. An analysis of variance of these results was made. A statistic F value of 0.9844 was found, a value lower than the critical F value of 1.65, what means that the null hypothesis cannot be excluded, i.e., there is no statistical difference between the results. The explanation for this is quite simple, since the banknote is always in movement, it does not make difference where the banknote was collected (whether it is a region of high consumption/drug trafficking, or not). As the dispersion of the results is large (the average yield 133.7 + 119.7 mg banknote 1), even in the regions where the banknotes had amount of cocaine below the limit of detection (as in the international airport of the Galleon, or Gavea), statistically, these results are equal to those results found in the regions where the highest amount of cocaine was found on the banknotes. A conclusion similar to this was achieved by other group in the United Kingdom [23].
Table 7 Location of collection and amount of cocaine found in the banknotes. Location of collection
Amount of cocaine (mg)
Standard deviation
Alto da Boa Vista Anil Aperibe´ Bangu Barra Bom Jesus do Itabapoana Borel Botafogo Campos dos Goitacazes Caxias Centro- Nitero´i Cidade de Deus Copacabana Engenha˜o Formiga Freguesia Galea˜o Ga´vea Iguaba Ipanema Itaguaı´ Jacare´ Jardim Botaˆnico Leblon Mangueira Marica´ Paraty Penha Petro´polis Rio das Ostras Sa˜o Cristo´va˜o Serope´dica Terreira˜o Tijuca Urca Vila Mimosa Vila Isabel
90.8 185.3 76.5 119.3 67.5 231.0 87.2 9.0 121.2 79.5 253.5 142.5 160.5 333.8 225.0 33.8 0.0 0.0 38.4 90.0 63.0 282.8 37.5 52.5 294.1 258.0 308.5 107.0 207.3 58.0 48.6 65.0 180.8 57.0 55.0 496.5 31.0
39.1 155.9 40.3 26.5 84.9 218.5 123.2 12.7 105.6 50.9 297.0 127.3 227.0 111.4 57.3 47.7 0.0 0.0 54.3 59.4 67.9 300.2 53.0 48.8 254.7 224.9 377.4 52.8 212.9 12.2 43.2 21.3 73.2 80.6 57.9 549.4 53.7
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Even selecting the results of determination only for the city of Rio de Janeiro and grouping them by region (south, central, north and west), no statistical difference was found between the mean (again, employing the analysis of variance).
where the banknote (location) was found, but there is a significant difference if the banknote was in circulation or directly in contact with the drug (either inside a bag of drugs, or was recently used for inhale drug).
3.7. Comparison between the average amount of cocaine found in the banknotes in circulation and the banknotes seized by the police
Acknowledgement
A total of 3 banknotes were provided by the Civil Police of the state of Rio de Janeiro to realize this work. The banknotes were seized with traffickers and were in plastic bags containing about 5 kg of cocaine. The residual amount of cocaine in these notes was 3425 mg banknote 1, with a standard deviation of 156.1 mg banknote 1. This value is about 30 times higher than the average value found in the banknotes in circulation. The only note seized straight from a drug dealer showed a concentration of 4725 mg banknote 1, also, a value much higher than the average value found in the banknotes in circulation. 4. Conclusion In this present work, banknotes of real collected in various regions of the city of Rio de Janeiro and some municipalities in the same state (Caxias, Petropolis and Marica) were analyzed. Practically every (around 86% of the banknotes) showed detectable amount of cocaine. Separating the banknotes by value (2, 5, 10, 20, 50 and 100 Reais), it was observed that on the banknote of higher values (50 and 100 Reais), the percentage of drugs is negligible. Knowing that the problem of drug trafficking is common throughout the state of Rio de Janeiro, however, more pronounced in some regions, one of the premises of this present work was to identify whether there is a statistical difference in the amount of residue of cocaine found on the banknotes collected at different points city. The fact that no differences were observed on the banknotes is probably caused by the high rate of movement of the banknotes. Another objective of this work was to evaluate whether the developed methodology can be used as a forensic test to judge if an individual had direct contact with the drug or not. The amount of cocaine found in the 3 samples of real banknotes seized directly with dealers showed a very large difference of value (3425 + 156 mg banknote 1), as well as banknotes collected immediately after a drug user inhale the cocaine (4725 mg banknote 1), which indicates that there is no difference
The authors would like to thanks FAPERJ for sponsoring this work.
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Determination of cocaine in Real banknotes circulating at the State of Rio de Janeiro, Brazil V.G.K. Almeida, R.J. Cassella, W.F. Pacheco * UFF—Universidade Federal Fluminense, Analytical Chemistry Department, Outeiro Sa˜o Joa˜o Batista s/n, Nitero´i, RJ, Brasil
A R T I C L E I N F O
A B S T R A C T
Article history: Received 25 August 2014 Received in revised form 9 February 2015 Accepted 11 February 2015 Available online 19 February 2015
This paper shows the result of a study on the extent of cocaine contamination in Real banknotes in circulation in the state of Rio de Janeiro (Brazil). A study of the percentage of contaminated banknotes was made, as well as a study on the contamination of banknotes based on different values, and a study of contamination depending on the region where the banknote was collected. The idea of this last study was to verify if the peculiar characteristics of the region of study (in particular, the city of Rio de Janeiro) influence the amount of cocaine in the banknotes. Some regions have higher consumption/drug trafficking of cocaine than others. Also, some contaminated banknotes confiscated directly from drug dealers and users were analyzed. Also, is showed in this paper all the optimization of the available analytical techniques for making the measurements possible. ß 2015 Elsevier Ireland Ltd. All rights reserved.
Keywords: Cocaine Fluroescence Rio de Janeiro
1. Introduction Nowadays, drug use is considered not only a health problem but also a problem of urban violence. The three main reasons for this violence are: drug violence, which occurs as a change of behavior for either short or long period of certain drugs, such as cocaine [1]; the economic motivation of addicts because there is the execution of the crime to acquire funds to purchase illicit drugs [2,3] and; the territorial dispute between drug dealers [4]. In some regions this dispute is fierce, which creates even more violence. In the specific case of Rio de Janeiro, the drug trafficking began in the 70s and was intensified in the following decade, with the city of Rio becoming a strategic bridge of drug trafficking from South America to Europe [5] and today maintains the territorial dispute between various armed groups that submit communities of the slums to their political and economic interests through violence. Although many actions have been taken by the government (both at state and federal level) to suppress the drug trade and reduce violence (as most recently, the occupation of some slums in Rio de Janeiro by the police), these actions still have not achieved the desired effect.
* Corresponding author at: UFF—Universidade Federal Fluminense, Analytical Chemistry Department, Outeiro Sa˜o Joa˜o Batista s/n, 24020-141 Nitero´i, Rio de Janeiro, Brazil. Tel.: +55 21 26292140; fax: +55 21 26292143. E-mail address: [email protected] (W.F. Pacheco). http://dx.doi.org/10.1016/j.forsciint.2015.02.014 0379-0738/ß 2015 Elsevier Ireland Ltd. All rights reserved.
A reflection of this can be noticed on the world drug report of 2009, released by the United Nations Office on Drugs and Crimes (UNODC) [6], in which the growth of drug trafficking in Brazil is in the opposite direction of the rest of the world. While consumption in the rest of the world decreased, the consumption in Brazil has nearly doubled. The UNODC attributed to the coordinated effort of different countries the main reason for the fall in production of drugs in the world. According to this agency, greater international cooperation is the main reason of the increased efficiency in combating the drug trafficking. Just as there was an increase in cooperation between different countries in combating the drug trafficking, there was also an improvement in efficiency within each country to combat this drug trafficking. One of these improvements can be attributed to criminology techniques. The development and application of analytical methodologies to investigative techniques is an important tool to aid in the elucidation of various crimes, providing scientific data that can be used reliably and being accepted in courts as physical evidence to support the conviction. Among the tools that have been developed in different countries, the identification of drug residues in banknotes can be noted. Several laws were enacted in order to relate the amount of drug in banknotes used in the drug trafficking and those can be used as forensic evidence to make a request for search warrants and seizure or even arrest order [7].
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In the United States and Europe, the presence of drug residues in samples of banknote is not enough to say that the person who carried the banknote was a drug dealer or user, since several studies [8–10] showed that a large number of banknotes is contaminated with detectable drug residues. This does not come as a surprise, especially in the case of the United States where there is a high number of users. The residue of the drug can reach the banknote by direct handling of the drug user or dealer when this one is with contaminated hands, or the residue can move on to the banknote when the user rolls the money and uses it to inhale the narcotic. The residue can also be spread from a banknote to another within the ATMs or machines that count money [11,12]. Since the banknote is always circulating, people who never had any contact with any kind of drug can carry the contaminated banknote. Otherwise, the city of Rio de Janeiro has its particularity with other cities, with some regions under the control of drug dealers. It would be interesting to study if the distribution of the residue of the drug in the bank note in this region is equal or different other regions. And as the material of the real bank note is similar to Dollar and Euro (paper, not plastic), it is plausible to think that the same factors that allowed the banknote to retain the drug residue would be applied here. In Brazil, there are two studies in the literature about the determination of cocaine in real banknotes. In the study of Di Donato [13], the determination of residues of cocaine is realized by gas chromatography–mass spectrometry, and the banknotes used in this study were collected in nine different cities (including Rio de Janeiro). In the study of Roberts [14], the determination of cocaine in banknotes circulating in the city of Belo Horizonte (MG), using liquid chromatography with UV–vis, was realized. In this present work, the determination of residues of cocaine in real banknotes collected at different points of the city of Rio de Janeiro, and in some nearby counties was realized. Also, the concentration of cocaine in the banknotes seized directly with users was determined. The quantification of the cocaine was realized fluorimetrically and the influence of the pH and the solvent used was studied to obtain better analytical signal. The best condition chosen was composed by sodium acetate buffer solution with pH 3.9. To ensure accuracy of the results, the quantification was also realized by HPLC-UV and a great concordance of the results was achieved. The extraction of the cocaine residue from banknote was realized by liquid–solid extraction. The influence of the solvent of extraction was studied and the best solvent in this situation was also the sodium acetate buffer solution with pH 3.9.
51
an ultrasound Unique, Ultracleaner 1600 with a frequency of 40 kHz was used. The 1000 mg L 1 standard solutions of cocaine were provided by Cerillant. Acetonitrile, methanol, ethanol and acetone were obtained from Tedia (HPLC grade) and glacial acetic acid was obtained from Vetec. 2.2. Preparation of standard solutions The analytical solutions of cocaine used in the spectrofluorimetric method were prepared in 5.0 ml volumetric flasks, by the dilution of 1000 mg L 1 standard solution. Each solution (for each concentration) were prepared by taking appropriate volume of the standard solution and the volume was made up to the mark of 5.0 ml using an acetate buffer solution, with pH 3.9, 0.01% v/v. The solutions of cocaine used in the HPLC were prepared in volumetric flasks of 1.0 mL by diluting the same standard solution, and the volume for each solution prepared was made up to the mark with acetonitrile. The sodium acetate solution was prepared by dissolving an adequate mass of sodium acetate in a volumetric flask of 1000 mL, the desired pH as achieved by addition of HCl 1.0 mol L 1, and then, the final volume was obtained by adding ultra-purified water. 2.3. Sampling To collect the banknotes, a small purchase using 100 and/or 50 real bills was realized at some premises (like market, bar, newsstand, etc.). Three banknote (change) obtained in each establishment were stored in a sealed plastic bag until the extraction was made. 2.4. Notes confiscated directly from drug dealers/users The notes were seized by the civil police of the state of Rio de Janeiro, and were held by the Institute of Criminology Carlos Eboli (ICCE). In this study, one of the banknotes was used by a user to inhale the drugs, and the other three banknotes were seized along with the cocaine. 2.5. Preparation of samples
2. Methods
The extraction of cocaine from the banknotes was realized by placing a crumpled banknote in a polyethylene plastic tube of 50 ml, followed by addition of 15 mL of sodium acetate buffer solution with pH 4.0. Each tube was placed in table roller mixer for 30 min. After that time, the banknote was removed and dried at room temperature. This banknote was replaced with no damage to the market. The extraction solution was used for the measurement.
2.1. Equipments and reagents
2.6. Conditions of measurements in the spectrofluorimeter
For fluorimetric measurements, a spectrofluorometer Varian, Cary Eclipse. Using a quartz cuvette of 10 mm path length was used. The chromatographic separations were performed on a high performance liquid chromatography using ultraviolet detector (HPLC-UV), Dionex, Ultimate 3000, using a Zorbax C-18 column with 5 mm particle size, 2.1 mm of internal diameter and 150 mm length, provided by Agilent, model 300SB. All solutions were prepared with ultra-purified water obtained from a system of ultrapurification Purellab Classic, with resistivity of 18 mV and before being injected into the chromatographic system, the solutions were filtered through a nylon membrane UNIFIL of 47 mm diameter and 0.45 mm pore. To the stirring of solutions, a table roller mixer, model MR-II was used. For removal of air bubbles from the prepared solutions,
The spectrofluorometric measurements were realized at 315 and 230 nm for excitation and emission, respectively, with nominal pass band of 5 nm. 2.7. Conditions of HPLC-UV measurements The measurements were realized at 230 nm and the mobile phase consisted of: (A) acetonitrile and (B) acetic acid 0.01% w/v. The elution was realized in a gradient mode, starting with 10% of A, changing linearly up to 50% during 20 min. The retention time of the cocaine was 12 min and the detector response was recorded using the peak area. The column was at room temperature (25 1 8C) and volume of injection was 20 mL. The flow rate of mobile phase was kept at 1 mL min 1.
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Table 2 Recovery of cocaine added in clean notes in different extraction times.
3. Results and discussion 3.1. Preliminary studies of the fluorimetric characteristics of the cocaine
Time of extraction (min)
Mass of cocaine (mg) Added
Recovered
10 15 30 60 120 180
25.0 25.0 25.0 25.0 25.0 25.0
21.7 25.9 25.1 25.6 25.6 27.1
Recovery (%)
87.0 1.6 103.6 1.2 100.3 0.8 102.3 1.3 102.6 1.4 108.4 2.1
Cocaine has a native fluorescence at 230/315 nm [15], however, few studies were realized to reach a condition of maximum sensitivity. The first of these studies was the influence of the solvent, where the influence of water, acetonitrile, methanol, ethanol, acetone and the Britton Robinson buffer solution adjusted to pH 7 on the fluorescence signal of a standard solution of cocaine was realized. Among these solvents, the best signal to noise ratio was observed for the Britton Robinson buffer solution at pH 7. Based on this study, the influence of the pH on the analytical signal of the standard solution of cocaine was evaluated and the higher signal to noise ratio was observed at pH 4. These conditions allowed the achievement of a linear relationship of the fluorescence signal of cocaine from 0.30 to 6.0 mg L 1.
put to stir during different periods of time. At the end of this time, the amount of cocaine in the extraction solution was determined spectrofluorimetrically. Table 2 shows the result of this study. Although total extraction of cocaine could be accomplish in just 15 min, for the next experiments the time of 30 min was chosen, leaving a safety margin.
3.2. Extraction of the cocaine banknotes
3.3. Analytical figures of merit for the fluorescence method
In the beginning of this study, some banknotes of high value (R$ 100,00 and R$ 50,00) were washed with water, HCl, water, NaOH and then, rinsed with water (subsequently), so the banknote could be totally free of any residues of cocaine or other compounds. To do so, some scramble notes (individually) were put inside a polyethylene tube (50.0 mL) with 15.0 mL of the desired solvent, each tube was mixed on a table roller mixer during 1 h, and after this sequence of solvents, each note was left to dry for 24 h. The use of different solvents to extract the cocaine from the banknotes proved to be effective in several publications [16–21]. In this present work, various solvents were tested to determine which one showed better efficiency in extracting the cocaine from the banknotes. The solvents tested were acetonitrile, methanol, water and the Britton Robinson pH 7.0. This experiment was carried out with banknotes spiked with 25 mL of the 1000 mg L 1 standard solution of cocaine. These banknotes were kept at room temperature for 1 day, so they could dry. After this time, each banknote was placed in a polyethylene tube of 50 mL, followed by addition of 15.0 mL of the solvent in question and placed to stir for 10 min in the roller mixer table. After the required time, the banknote was removed and the solvent was used to quantify the recovery spectrofluorimetrically. Table 1 shows the extraction efficiency obtained for each solvent. The highest extraction efficiency of cocaine was obtained using the Britton Robinson buffer solution at pH 4. Combining the highest extraction efficiency and the fact that the solvent was used to construct the calibration curves, this solvent was chosen as extraction solvent of cocaine from the banknotes. The next step of this present work was the evaluation of the time of extraction. In this study, different banknotes were previously cleaned, enriched with 25 mL of the 1000 mg L 1 standard solution of cocaine. These banknotes were kept at room temperature for 1 day, so they could dry. After this, each banknote was placed in a polyethylene tube of 50 ml followed by addition of 15 mL of the Britton Robinson buffer solution, and each tube was
Some figures of merit for the method were studied in order to establish its analytical performance: linearity, limit of detection, limit of quantification, precision and recovery. The calibration curve was prepared in seven different concentration levels, (real triplicate for each level) with the fluorescence analytical science recorded for each aliquot of a solution. The equation of the curve was calculated by the method of least squares (linear regression) with subsequent evaluation of the coefficient of determination (r2). Tests for normality, independence, homoscedasticity of the residue and deviation of linearity showed to be adequate (Table 3). This implies that residues of the calculated regression followed a normal distribution and that they were homoscedastics (the variance of the deviations were not different), independent (no autocorrelation between the residues) and the regression was significant, with no deviation from the linearity [22]. The equation obtained by linear regression [22] was y = 34.786x + 26.439 and the coefficient of determination (r2)
Table 1 Recovery of cocaine from clean notes using different solvents. Solvent
Acetonitrile Methanol Water Buffer solution
Mass of cocaı´na (mg) Added
Recovered
25.0 25.0 25.0 25.0
18.7 11.2 17.7 21.7
Recovery (%)
74.6 44.6 70.7 87.0
Table 3 Parameters for statistical evaluation of the linear regression. Statistic
Values
N
15
Normality r2 P
0.9960 P > 0.10
Homoscedasticity tL P
0.17 0.85
Independence D P
1.89 P > 0.05
Significance of regression gl (regression) gl (residue) SQ regression SQ residue MQ regression MQ residue F F critical
1 5 35840 150.0 35840 30.0 1195.9 3.80 10
2
7
n, number of data; r , coefficient of determination; tL, Levene’s test; P, significance; D, Durbin–Watson statistic.
Residues
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10 8 6 4 2 0 -2 0 -4 -6 -8 -10 -12
1
2
3
4
5
6
53
7
[cocaine] mg L-1 Fig. 1. Residue of the analytical curve.
equal to 0.9960. A test F was made to evaluate the significance of the regression, and as the F calculated was higher than the F critical, it was evidence that the regression was achieved. A plot of residue was made and no bias for the residue was observed (Fig. 1). The detection limit found in method was 0.11 mg L 1 (1.7 mg/ note) and the limit of quantification was 0.27 mg L 1 (4.1 mg/note). The study of analytical precision was performed by determining the coefficients of variation intra-assay and inter-assay for the standard solutions at concentrations of 0.5, 2.0 and 5.0 mg L 1, and the averages found were 4.8% (intra-assay) and 5.5% (inter-assay), both for an n of 4 replicates (Table 4). To estimate the recovery, a set of 6 banknotes was taken, subjected to the extraction process (described in Section 3.2) and put to dry at room temperature. At this point, a defined volume of standard of cocaine was added to the banknote (mass of 25 mg), left for 24 h to dry, and then the note was again subjected to the extraction process. This extract was analyzed (3 aliquots of each note) to estimate the recovery of cocaine added, and as the banknote went through a previous extraction procedure, it can be considered that the banknotes were previously cleaned. The result of this study is described in Table 5. There was an average recovery at the three studied concentrations of 101.4 + 3.0%, considered to be satisfactory, implying that
Table 4 Intra and inter-assay precision obtained for the fluorescent method. Concentration (mg L 1)
0.5 2.0 5.0 Average
Coefficient of variation (%) Intra-assay (n = 4)
Inter-assay (n = 4)
10 2.5 1.9
8.3 4.1 4.0
4.8
5.5
Fig. 2. Comparison, note by note, of the HPLC and fluorescence techniques.
the extraction procedure was efficient to extract the cocaine residue from the banknotes (Table 5). 3.4. Results of the determination of cocaine in banknotes As there was no certified material for this case, and due the possible interferences inherent to a fluorimetric method, the results obtained fluorimetrically were compared with the results obtained with another method, in this case, a high performance liquid chromatographic. Fig. 2 shows a comparison, note by note, of the results obtained by both techniques. In this figure, it can be observed a good correlation between the two techniques discussed expressed by the correlation coefficient (r2), whilst the value of the slope of the straight line equation suggests that these results are equal, once the value is close to the unity. A paired t-test was realized and a value of t = 0.189 for 144 observations (P = 0.05) was found. As t critic is 1.96, that indicates that there is no statistical difference between the two means (probably, the extraction method has minimized the potential interferences for the fluorescence method). The variance between the results obtained for both methods was tested using the F test. The F value was 1.30, for an F critical of 1.40 (a = 0:05, 144 observations). From these observations, the analysis of results was only realized with the results obtained by the spectrofluorimetric method. 3.5. Distribution of cocaine by value of the banknotes Table 6 shows the percentage of banknotes contaminated with cocaine residue depending on their value, regardless of the location where they were collected. It was found residue of cocaine in 85% of the banknotes.
Table 5 Recovery of the extraction method used for the determination of different concentrations of cocaine in banknotes. Banknote
Recovery (%)
CV (%) (n = 3)
1 2 3 4 5
97.2 96.3 136 88.4 89.0
6.1 5.6 13 9.2 11.1
Average
101.4
9.0
Table 6 Percentage of banknotes found with residue of cocaine according to their value. Value (R$)
n
% of banknotes with cocaine
2 5 10 20 50 100
98 29 3 4 4 4
83.0 86.2 66.7 25.0 0.0 0.0
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Fig. 3. Location of collection of the banknote used in this work.
Another important factor to be discussed is that, in addition to the direct contamination (the aspiration of the drug from the surface of the banknote) the contamination spreads from one banknote to another within the ATM is a parameter that should be mentioned. As the banknotes are stored on these machines grouped by the same value, a contaminated banknote propagates the residue of cocaine to the other banknotes of the same value. 3.6. Distribution of the amount of cocaine as function of the region where the banknotes were collected The first study realized was the distribution of cocaine depending on the region where the banknote was collected. In this study, only banknote of 2 and 5 Reais were used. Fig. 3 shows most of the collection regions. All locations are shown in Table 7 as well as the average amount of cocaine found in each of these locations. To determine whether there is statistical difference between the concentrations of cocaine found in each region or not, an analysis of variance (ANOVA) of the results was realized by grouping the values by location. An analysis of variance of these results was made. A statistic F value of 0.9844 was found, a value lower than the critical F value of 1.65, what means that the null hypothesis cannot be excluded, i.e., there is no statistical difference between the results. The explanation for this is quite simple, since the banknote is always in movement, it does not make difference where the banknote was collected (whether it is a region of high consumption/drug trafficking, or not). As the dispersion of the results is large (the average yield 133.7 + 119.7 mg banknote 1), even in the regions where the banknotes had amount of cocaine below the limit of detection (as in the international airport of the Galleon, or Gavea), statistically, these results are equal to those results found in the regions where the highest amount of cocaine was found on the banknotes. A conclusion similar to this was achieved by other group in the United Kingdom [23].
Table 7 Location of collection and amount of cocaine found in the banknotes. Location of collection
Amount of cocaine (mg)
Standard deviation
Alto da Boa Vista Anil Aperibe´ Bangu Barra Bom Jesus do Itabapoana Borel Botafogo Campos dos Goitacazes Caxias Centro- Nitero´i Cidade de Deus Copacabana Engenha˜o Formiga Freguesia Galea˜o Ga´vea Iguaba Ipanema Itaguaı´ Jacare´ Jardim Botaˆnico Leblon Mangueira Marica´ Paraty Penha Petro´polis Rio das Ostras Sa˜o Cristo´va˜o Serope´dica Terreira˜o Tijuca Urca Vila Mimosa Vila Isabel
90.8 185.3 76.5 119.3 67.5 231.0 87.2 9.0 121.2 79.5 253.5 142.5 160.5 333.8 225.0 33.8 0.0 0.0 38.4 90.0 63.0 282.8 37.5 52.5 294.1 258.0 308.5 107.0 207.3 58.0 48.6 65.0 180.8 57.0 55.0 496.5 31.0
39.1 155.9 40.3 26.5 84.9 218.5 123.2 12.7 105.6 50.9 297.0 127.3 227.0 111.4 57.3 47.7 0.0 0.0 54.3 59.4 67.9 300.2 53.0 48.8 254.7 224.9 377.4 52.8 212.9 12.2 43.2 21.3 73.2 80.6 57.9 549.4 53.7
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Even selecting the results of determination only for the city of Rio de Janeiro and grouping them by region (south, central, north and west), no statistical difference was found between the mean (again, employing the analysis of variance).
where the banknote (location) was found, but there is a significant difference if the banknote was in circulation or directly in contact with the drug (either inside a bag of drugs, or was recently used for inhale drug).
3.7. Comparison between the average amount of cocaine found in the banknotes in circulation and the banknotes seized by the police
Acknowledgement
A total of 3 banknotes were provided by the Civil Police of the state of Rio de Janeiro to realize this work. The banknotes were seized with traffickers and were in plastic bags containing about 5 kg of cocaine. The residual amount of cocaine in these notes was 3425 mg banknote 1, with a standard deviation of 156.1 mg banknote 1. This value is about 30 times higher than the average value found in the banknotes in circulation. The only note seized straight from a drug dealer showed a concentration of 4725 mg banknote 1, also, a value much higher than the average value found in the banknotes in circulation. 4. Conclusion In this present work, banknotes of real collected in various regions of the city of Rio de Janeiro and some municipalities in the same state (Caxias, Petropolis and Marica) were analyzed. Practically every (around 86% of the banknotes) showed detectable amount of cocaine. Separating the banknotes by value (2, 5, 10, 20, 50 and 100 Reais), it was observed that on the banknote of higher values (50 and 100 Reais), the percentage of drugs is negligible. Knowing that the problem of drug trafficking is common throughout the state of Rio de Janeiro, however, more pronounced in some regions, one of the premises of this present work was to identify whether there is a statistical difference in the amount of residue of cocaine found on the banknotes collected at different points city. The fact that no differences were observed on the banknotes is probably caused by the high rate of movement of the banknotes. Another objective of this work was to evaluate whether the developed methodology can be used as a forensic test to judge if an individual had direct contact with the drug or not. The amount of cocaine found in the 3 samples of real banknotes seized directly with dealers showed a very large difference of value (3425 + 156 mg banknote 1), as well as banknotes collected immediately after a drug user inhale the cocaine (4725 mg banknote 1), which indicates that there is no difference
The authors would like to thanks FAPERJ for sponsoring this work.
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