Monitoring of Pesticides Residues in Italian Mineral Waters by Solid Phase Extraction and Gas Chromatography Mass Spectrometry

doi:10.4236/jwarp.2012.410097

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Journal of Water Resource and Protection, 2012, 4, 842-846

http://dx.doi.org/10.4236/jwarp.2012.410097 Published Online October 2012 (http://www.SciRP.org/journal/jwarp)

Monitoring of Pesticides Residues in

Italian Mineral Waters by Solid Phase Extraction and

Gas Chromatography Mass Spectrometry

Anna Maria Tarola, Raffaella Preti

Department Management and Technologies, “Sapienza” University of Rome, Roma, Italy

Email: [email protected]

Received March 2, 2012; revised May 8, 2012; accepted July 9, 2012

ABSTRACT

Twenty-two pesticides and metabolites, selected on the basis of regional priority lists, were surveyed in thirty Italian

mineral waters springs for three years by a procedure based on solid phase extraction in combination with gas chroma-

tography coupled with mass spectrometry detection. The procedure proved to be simple, sensitive and reliable, the lim-

its of detection and relative standard deviations were respectively in the range of 0.002 - 0.04 µg/L and 3% - 7%, re-

coveries ranged from 86% to 105% at the European Union Maximum Acceptable Concentration (MAC). Pesticide

residues were detected in just one of the ninety water samples analyzed but no one exceeding the MAC. These results

demonstrate the good quality of Italian mineral waters, not forgetting the need of constant revision and update of the

priority list of pollutants.

Keywords: Mineral Water, Pesticides, SPE, GC-MS

1. Introduction

The packaged waters sector is growing steadily over the

last few years. The worldwide consumption of packaged

waters can be estimated to be around 200 billion L in

2008, which means that the rate was 25 - 26 L/per capita/

year. Data in Table 1 show the world market of bottled

water in 2008 compared to 2003, with Italy being the

highest consumption (each citizen consumes 200 L/year).

Italian production of bottled water has increased by of

30% over the last 5 years. In Italy there are more than

three hundred brands of Italian bottled waters recognized

by the European Community, with 46% of bottled waters

being in Northern Italy while only 15% in the South [1].

In Italy pesticides consumption for agricultural use for

the 2008 was about 150 thousand tons, being the fungi-

cide class the most used (63.4%) followed by insecticide

and acaricide (10.5%). Almost half of the pesticides are

used in the Northern regions, the 12 percent in the central

the remaining in the Southern [2]. Several studies have

provided evidence that pesticides can be transferred rap-

idly at high concentrations beyond the root zone, there-

fore leaching of pesticides from agricultural soils may

threaten the quality of drinking water resources [3,4].

Generally, pesticide residue analysis is carried out fol-

lowing several steps, e.g. extraction from sample matrix,

clean up and final chromatographic separation and deter-

mination. Thus, environmental water samples cannot be

analysed without some preliminary sample preparation.

In this sense, liquid-liquid extraction (LLE) has been

employed for many years as the routine technique for the

extraction of pesticides from environmental water sam-

ples. However, LLE presents some disadvantages such as

being time-consuming and requiring consumption of

large amounts of organic solvents, so this technique has

been replaced by other methodologies such as SPE, solid

phase microextraction (SPME), stir bar sorptive extrac-

tion (SBSE) or liquid phase microextraction (LPME).

Despite the advantages of these microextraction tech-

niques, SPE is still widely accepted as the best technique

for isolating pesticide residues in water samples, because

it is fast, accurate, precise, consumes small volume of

organic solvent, does not involve costly material and a

wide range of selective sorbent materials are available.

The most widely used sorbents are C8 and C18 chemi-

cally bonded to silica, carbon black and polymeric resins.

The sensitivity of this technique can be increased in mi-

cropollutants from water and has now become the

method of choice in order to carry out simultaneously the

extraction and concentration of many pesticides and me-

tabolites in aqueous samples [5-7].

The most widely used methods for the analysis of pes-

ticides in water are based on GC and LC. Although con-

ventional detectors such as electron capture detection and

UV absorbance detection can be used, identification based

A. M. TAROLA, R. PRETI 843

Table 1. List of the pesticides studied.

Pesticide Type logKow* Chemical class Rt min MS ion LOD** μg/L Max. Limit*** μg/L

1-Molinate H 2.88 Thiocarbamate 11.14 1,265,583 0.005 0.05

2-Desethylatrazine H 1.49 Triazine 13.86 172,174,1870.005 0.05

3-Trifluralin H 5.27 Dinitroaniline 14.19 306,264,3070.002 0.05

4-Benfluralin H 5.29 Dinitroaniline 14.29 29,226,445 0.002 0.05

5-Desethyl-terbutilazine H 2.3 Triazine 14.3 186,188,201 0.002 0.05

6-Atrazine H 2.50 Triazine 16.06 200,202,2150.003 0.05

7-Propazine H 2.94 Triazine 16.27 214,216,2290.005 0.05

8-Lindane I-R 3.69 Organochlorine 16.47 181,183,2170.01 0.05

9-Terbuthylazine A-H-M 3.04 Triazine 16.78 214,216,1730.005 0.05

10-Diazinone I-A 3.30 Organophosphorus 17.42 179,137,1520.02 0.05

11-Chlorthalonil F 3.05 Substitued benzene 17.99 264,266,2680.003 0.05

12-Metil parathion I 2.86 Organophosphorus 19.88 109,125,2630.005 0.05

13-Alaclor H 2.63 Chloroacetoanilide 20.29 160,188,1460.002 0.05

14-Linuron H 3.00 Urea 21.56 61,248,250 0.005 0.05

15-Malathion I-A 2.75 Organophosphorus 22.10 127,125,1730.03 0.05

16-Pendimetalin H 5.18 Dinitroaniline 24.44 252,162,1920.002 0.05

17-Meditathion I-A 2.20 Organophosphorus 25.91 145,85,93 0.005 0.05

18-Oxadiazon H 4.80 Unclassified 27.90 175,177,2580.002 0.05

19-Oxadixyl F 1.40 Aniline 29.50 163,132,2330.002 0.05

20-Phosalone I-A 4.30 Organophosphorus 33.15 182,184,1210.005 0.05

21-Azinphos methyl I-A 2.96 Organophosphorus 33.18 77,160,132 0.04 0.05

22-Azinphos ethyl I-A 3.18 Organophosphorus 34.11 132,160,77 0.02 0.05

H = herbicide, I = insecticide, A = acaricide, M = microbiocide, R = rodenticide; *Values from Royal Society of Chemistry 1994; **LOD: limit of detection for

a signal-to-noise ratio S/N = 3; ***Maximum Acceptable Concentration (Dir. 2003/40/EC).

only on chromatographic analysis (retention time) with-

out the use of spectrometric detection is not suitable as

confirmatory method so MS detection has found to be

indispensable for high sensitivity and unambiguous de-

tection, confirmation and determination of such residues

in different matrices.

The main objective of this study is to determine the

occurrence of 22 selected pesticides in 90 mineral water

samples coming from three Italian regions, during a three

year period (2006-2008) in order to assess the actual im-

pact of the applied practices on the groundwater quality.

2. Materials and Methods

2.1. Sampling

Mineral water samples were collected in a three year

period from 2006 to 2008 in Pyrex borosilicate amber

glass (1L) capped with Teflon lined screw caps and

stored at 4˚C. The three sampling sites were in the fol-

lowing Italian regions: Emilia (North Italy) the first re-

gion for pesticides use in the country, with about 22

thousands tons and 40 springs of bottled mineral waters;

Toscana (Centre Italy) with more than 6.6 thousands tons

of pesticides used and 37 springs and Campania (South

Italy) where in 2008 were used nearly 10 thousands tons

of pesticides and has in its territory 18 springs.

Each year, during the summer season, in each region

ten wells were sampled, for a total of 90 samples col-

lected. Mineral water samples from Emilia and Toscana

had a TDS concentration < 500 mg/l, while those from

Campania had a TDS concentration > 500 mg/l and two

of them were naturally carbonated with an average CO2

content of 1900 mg/l.

2.2. Chemicals and Materials

Pesticide standards of analytical grade were purchased

from Riedel de Haen (Seelze, Germany), with a purity

>99%. Individual stock standard solution, containing 0.1

µg/ml of each pesticide were prepared in acetone and

stored at –20˚C. Working standard mixture solutions were

prepared by appropriate dilution with n-hexane and stor-

ed under refrigeration (4˚C).

Pesticide-quality solvents (n-hexane, acetone, metha-

nol, ethyl acetate) were supplied from J.T. Baker (De-

venter, The Netherlands). SPE extraction columns LC18

A. M. TAROLA, R. PRETI

844

(500 mg, 6 ml) were purchased from Sigma Aldrich. Ul-

trapure water was obtained from a Milli-Q water system

(Millipore, Bedford, MA, USA). An extraction manifold

from Alltech (Alltech Associates, Deerfield, USA) was

used for the SPE analysis.

2.3. Instrumentation

GC-MS Separation and Determination

All analysis were performed with Finnigan Trace GC

ultra gas chromatograph coupled to a Finnigan Polaris Q

mass spectrometer (Thermo Electron Co., Austin, Texas).

Separations were conducted on a DB-5 ms fused-silica

column, 30 m × 0.25 mm × 0.25 µm film thickness

(J&W Scientific, Folsom, CA), with helium as carrier gas,

at a flow of 1.0 ml/min.

The column was held at 70˚C ramped 15˚C/min to

150˚C, then up to 200˚C at 3˚C/min and finally ramped at

8˚C/min to 300˚C and held for 5 minutes. A volume of 2

µl of sample extract was injected manually on a PTV

injector operating in splitless mode. The injector tem-

perature was set at 60˚C. The mass spectrometer operated

in the EI mode. The parameters were set at the following

values: an electron energy of 70 eV and a filament emis-

sion current of 200 µA. The interface and ion source tem-

peratures were maintained at 250˚C and 200˚C, respec-

tively. The scan mode was used between m/z 40 and 350.

2.4. Procedure

Samples of mineral water naturally carbonated were de-

gassed in an ultrasonic bath for 5 min.

Spe Procedure

The procedure followed the guidelines EPA Method n

525 [8]. SPE C18 cartridges were conditioned with 5 ml

of ethyl acetate, followed by 5 ml of methanol and 10 ml

of bidistillated water, without allowing the cartridge to

dry out. Then, 2.5 ml of methanol were added to 500 ml

of water sample that was passed through the conditioned

cartridges at a flow rate of approximately 8 ml/min under

vacuum. The cartridges were dried for 10 min under

vacuum and afterwards the analytes were eluted from the

solid phase with 5 ml of ethyl acetate, traces of water

were removed with anhydrous sodium sulphate. The elu-

ate was evaporated to dryness under a stream of nitrogen

and the residue was dissolved in 0.5 ml of n-hexane.

3. Results

The quality of water for human consumption has always

been and still is one of the most serious challenges. Since

the late decades, concern about the contamination of wa-

ter sources has risen due to the increasing number of pes-

ticides detected. Regulations for drinking water are re-

quired in order to limit human risks and environmental

pollution. These regulations are well defined in Europe,

setting at 0.05 µg/l of each pesticide concentration limit

in mineral water samples. Consequently, it becomes nec-

essary to provide control laboratories with analytical

methods allowing the monitoring of pesticide residues at

this trace level, with basic performance data in agreement

with the drinking water EC Directives 98/83 and 2003/40

requirements [9,10].

Pesticides used in agricultural practices are several,

therefore to ensure an effective quality control it is nec-

essary to develop a list of priority substances to be mon-

itored by the producers themselves who are obliged to

carry out annual controls by Italian law. The methodol-

ogy developed to generate the list of priority substances

is based on relevant factors, including for example sale

data, the target, their degradation, the environmental dis-

tribution, which results from many chemical characteris-

tics such as molecular weight, vapour pressure, solubility

in water and octanol/water partition coefficient (Kow).

The priority list, that includes the pesticides considered

in this study, is developed by the Italian Environmental

Protection Agency.

In this study a multiresidue method based on SPE and

GC separation with MS detection were utilised to assess

the presence of 22 selected pesticides residues in 30 Ital-

ian mineral water wells for three years. The method sho-

wed to be suitable to the analysis of these compounds

since they were detected at low concentrations, according

to European Union maximum admissible concentration

(Table 2). The LODs were calculated multiplying by

three the average value of the noise sampled at the reten-

tion time of each analyte. Repeatability and reproducibil-

ity studies yielded Relative Standard Deviations (RSDs)

lower than 7% in all the cases, with recoveries ranging

from 86% to 105% evaluated at 0.05 µg/l spiked level.

All measurements were performed in triplicate. The ty-

pical chromatogram is showed in Figure 1. During the

screening only in 2007 one sample belonging to an Emilia

well had a level of meditathion of 0.01 mg/l which is

over our detection limit but under the European Union

Maximum Acceptable Concentration (MAC) (Table 2).

4. Discussion

Italy is the nation with highest production and consump-

tion of mineral waters in the world. The results of this

three-year study on pesticide residues in 90 mineral wa-

ter samples coming from three regions with intensive use

of pesticides, are reassuring for the quality of Italian

mineral waters, being residues detected in just one sam-

ple and at a concentration lower than the European Union

Maximum Acceptable Concentration (MAC).

The multiresidue analytical method used has proved to

be sensitive and reliable. The method does fulfill the de-

tection limits required by the EC Directive, with LOD

A. M. TAROLA, R. PRETI

845

Table 2. Results of the pesticides determination in mineral waters (µg/l).

Pesticides Emilia Toscana Campania

2006 2007 2008 2006 2007 2008 2006 2007 2008

1-Molinate <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005

2-Desethylatrazine <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005

3-Trifluralin <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002

4-Benfluralin <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002

5-Desethyl-terbutilazine <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002

6-Atrazine <0.003 <0.003 <0.003 <0.003 <0.003 <0.003 <0.003 <0.003 <0.003

7-Propazine <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005

8-Lindane <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01

9-Terbutilazine <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005

10-Diazinone <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02

11-Chlorthalonil <0.003 <0.003 <0.003 <0.003 <0.003 <0.003 <0.003 <0.003 <0.003

12-Metil parathion <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005

13-Alaclor <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002

14-Linuron <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005

15-Malathion <0.03 <0.03 <0.03 <0.03 <0.03 <0.03 <0.03 <0.03 <0.03

16-Pendimetalin <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002

17-Meditathion <0.005 <0.005 <0.005 <0.005 0.01 <0.005 <0.005 <0.005 <0.005

18-Oxadiazon <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002

19-Oxadixyl <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002

20-Phosalone <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005

21-Azinphos methyl <0.04 <0.04 <0.04 <0.04 <0.04 <0.04 <0.04 <0.04 <0.04

22-Azinphos ethyl <0.04 <0.04 <0.04 <0.04 <0.04 <0.04 <0.04 <0.04 <0.04

Figure 1. Total ion GC/MS chromatogram of a 22 pesticides standard mixture. Peaks are listed in Table 1.

ranging from 0.002 to 0.04 μg/L, and therefore is useful

to verify occurrence and frequency of pesticides belong-

ing to a priority list in mineral waters.

Considering the costs and the social relevance that are

related to such monitoring activities, appears to be essen-

tial that the priority list of pesticides is regularly re-

viewed and developed on a regional basis.

5. Conclusion

The aim of this study was to evaluate the risk to water

resources of 22 priority pesticides. It is a significant

example of a three year monitoring of a sector with great

relevance for economy and public health, involving 90

samples from three sampling sites at high risk of water

resources contamination for massive use of pesticides.

To our knowledge, this the first example in literature of a

such long screening of pesticides in mineral waters com-

ing from areas with intensive agricultural practices. The

simple, reliable and sensitive multiresidue analytical

method, optimized to assess the presence of these conta-

minants, has proved to be suitable for routine analysis of

pesticides residues in both environmental and drinking

waters monitoring.

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