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Polietilenterftalat (PET) malzemelerden içme suyuna geçen antimon miktarının tespiti ve bu geçişi etkileyen faktörlerin incelenmesi

İlknur Durukan Temuge

Hacettepe Üniversitesi

Çevre Mühendisliği Bölümü,

Ankara

lknurt@hacettepe.edu.tr

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Aim: To suggest a new simple, fast, cost-effective method to separate and determine trace amount of antimony leaching from PET bottles into drinking water.

*To apply this new and simple method to other heavy metal ions, polymeric structures, and water samples.

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Plastic bottles are typically used to store liquids such as water, soft drinks, cooking oil, medicine, shampoo and milk.

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What is PET?



PET is polyethylene terephthalate. It's a plastic resin and the most common type of polyester. Two monomers—modified ethylene glycol and purified terephthalic acid—are combined to form the polymer called polyethylene terephthalate. PET was discovered and patented in England in 1941.

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PET is the plastic labeled with the #1 code. Many beverages, food items and other consumer products are delivered in bottles or packages made from PET. The #1 code is usually found on or near the bottom of the container.

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PET makes good packages for food and non-food items. Manufacturers like it because it's safe, strong, transparent and versatile. Customers choose it for its safety, light weight, reseal ability, shatter-resistance and recyclability.



UP TO 100% OF A PET PACKAGE CAN BE MADE FROM RECYCLED PET, AND THE MATERIAL CAN BE RECYCLED AGAIN AND AGAIN.

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PET Production

Polyethylene terephthalate (PET) is a general-purpose plastic made through polycondensation of purified terephthalic acid (PTA) with ethylene glycol (EG).

Mn, Zn, Ti, Sn, Pb, Ge, Sb are used as catalysts.

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Antimony ???

Antimony (Sb) is a metalloid element that is used as a catalyst in the form of compounds such as antimony trioxide (Sb₂O₃) or antimony triacetate in the production of PET.

High catalytic activity
Low tendency to catalyze side reactions
No unwanted color changes during the reaction
Not to damage the carboxyl end groups such as other catalysts

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After manufacturing, a detectable amount of antimony can be found on the surface of the product.
This residue can be removed with washing.
Antimony also remains in the material itself and can, thus, migrate out into food and drinks.
Many commercial PET materials contain 190-300 mg / kg Sb.

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Toxicity of Antimony

Experimental and clinical experience with compounds containing antimony have shown that the trivalent compounds are generally more toxic than the pentavalent ones.
Antimony toxicity occurs either due to occupational exposure or during therapy. Occupational exposure may cause respiratory irritation, pneumoconiosis, antimony spots on the skin and gastrointestinal symptoms.
In addition antimony trioxide is a possible carcinogenic to humans.

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Maximum Contamination Levels for Antimony (MCL)

	MCL (µg/L)
The United States Environmental Protection Agency (USEPA)	6
The Canadian Public Health Association (CPHA)	6
Federal Ministry of Environment (Germany)	5
European Union	5
Japan	2
World Health Organization (WHO)	20
Turkish Ministry of Health TS 266 “Sular – İnsani Tüketim Amaçlı Sular»	5

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*TS 266 “Sular – İnsani Tüketim Amaçlı Sular” standardında maksimum müsaade edilen değer antimon için 5 µg/L olarak verilmiştir (Sağlık Bakanlığı, 2014). Sınırlardan tehlikeli atıkların geçirilmesindeki sınırlamalarla ilgili yapılan *Basel Toplantısı’nda, belirtilen tehlikeli maddeler listesinde antimona da yer verilmiştir (Montserrat vd., 2002).

*Ülkemizde antimonun gıdalarda bulunabileceği maksimum kirletici seviyesi ile ilgili ulaşılabilir tek bilgi Türk gıda kodeksi yönetmeliğinde , “Gıda Maddeleri ile Temasta Bulunan Plastik Madde ve Malzemeler Tebliği” başlığı altında, Ek 3, Bölüm A’da yer alan tabloda antimon tiroksit için spesifik migrasyon limiti (SML) (SML: Madde veya malzemeden gıdaya veya gıda benzerine geçen belirli bir maddenin izin verilen maksimum miktarını) 0,02 mg/kg şeklindedir (Türk Gıda Kodeksi, 2017).

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WHO has published a risk assessment for antimony in drinking water.
Fruit juice concentrates (for which no guidelines are established), however, that were produced and bottled in PET in the UK were found to contain up to 44.7 µg/L of antimony, well above the EU limits for tap water of 5 µg/L.

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The direct determination of metal ions at trace levels by atomic absorption spectrometry (AAS) is limited not only due to insufficent sensitivity, but also by matrix interference.

Despite the selectivity and sensitivity of analytical techniques, there is a crucial need for the preconcentration and/or separation of trace elements before their analysis.

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A very novel technique to effectively enhance atomic absorption spectrometry’s sensitivity and selectivity is

solidified floating organic drop microextraction (SFODME).

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SOLIDIFIED FLOTING ORGANIC DROP MICROEXTRACTION (SFODME)

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Procedure

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Solidified Floating Organic Drop Microextraction (SFODME)

100 mL Sb(III) solution + 5% (w/v) KI

1:1 H₂SO₄ solution

8% (v/v) didecyl dimethyl ammonium chloride (DDAC) solution

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Solidified Floating Organic Drop Microextraction (SFODME)

40^oC

500 rpm

15 min later

45 min later

1-dodecanol

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�Solidified Floating Organic Drop Microextraction (SFODME)

Solidified floating organic drop

Floating organic drop

Cooling in fridge

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�Solidified Floating Organic Drop Microextraction (SFODME)

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�Solidified Floating Organic Drop Microextraction (SFODME)

Atomic absorption spectrometer

Methyl alcohol solution

V_final =300 µL

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Sb2O3

[SbI₄]^-

Cationic surface active material

Hydrophobic compund (ion association complex) (ion complex)

Book reference: Separation and Spectrophotometric Determination of Elements

Zygmunt Marczenko

Article Reference:Talanta,Volume 41, Issue 2, February 1994, Pages 171–178, Separation of antimony(III) with iodide and dithizone by sorption on polyurethane foam from sulphuric acid medium

for its spectrophotometric determination in glasses, Alakananda Raychaudhuri, S.K. Roy

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The optimum parameters were obtained

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Optimum conditions for SFODME of Sb	Value
Extraction solvent	1-dodecanol
Diluent	methanol
pH (sulphuric acid)	~1.5
DDAC concentration (mmol/L) (Cationic surface active agent)	6.6
KI concentration (%, w/v)	5
Extraction time (min)	45
Stirring rate (rpm)	500
Sample volume, mL	100
Extracted phase volume, mL	0.300
Extraction temperature (^oC)	~40

Table 1. Optimum conditions for SFODME of antimony ion

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Ion	[Sb(III)]/[interfering ion]	Ion	[Sb(III)]/[interfering ion]
Na⁺	>1/1000	Mn²⁺	1/1000
K⁺	>1/1000	Cd²⁺	1/25
Ca²⁺	>1/1000	As³⁺	1/250
Ba²⁺	>1/1000	Fe³⁺	1/250
Mg²⁺	1/1000	Br^-	1/1000
Zn²⁺	1/750	SCN^-	1/1000
Co²⁺	1/1000	Cl^-	1/750
Pb²⁺	1/50	F^-	1/1000
Cu²⁺	1/50	H₂PO₄^-	>1/2000
Hg²⁺	1/50	CO₃^2-	1/750
Ni²⁺	1/1000	PO₄^3-	>1/2000

Effect of interfering ions on determination of 100 µg/L Sb(III).

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ANALYTICAL PERFORMANCE

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Calibration curve obtained by Graphite Furnace AAS without preconcentration

Calibration curve obtained by Graphite Furnace AAS with preconcentration

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Table 2. Analytical characteristic of the method

Parameter	Analytical feature
Enrichment factor	570
Limit of detection, ng mL^-1 (3s)	0.018
Limit of quantification, ng mL^-1 (10s)	0.060
Precision (1.25 ng mL^-1, n = 10) RSD (%)	4.5
Linear range, ng mL^-1	0.1 – 1.7

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Analysis of Sb(III) by proposed method in drinking water kept in PET bottles

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In this section, leached antimony content from different brand of PET bottles into water was detected and compared. Also, the effects of environmental factors on antimony transfer were investigated.
Preconcentrated samples were analyzed by graphite furnace AAS.

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Parameters affecting the antimony transfer

Temperature
Exposing to UV light
Deposition time
Kind of plastic

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1. Comparision of antimony content of water samples held in different brands of PET bottles

Sb content in water samples held 5 months in PET bottles.

Highest Sb concentration was detected in brand with number 7.

At the end of 5 months → 0.66 µg/L

All samples were under the limit values at room temperature 22°C.

Antimony content of water samples held in different brand of PET bottles at room temperature (22 ºC) for 5 months

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2. Effect of Deposition Time

Effect of deposition time on antimony transfer (brand with number 7) for different duration period

At room temp. for PET bottles;

7 days later → 80 ng/L antimony,

150 days later → 630 ng/L antimony transfer.

Increasing deposition time causes an increase in transfered antimony amount.

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3. Effect of UV Light

Brand	Model	Electrical parameter	The distance of UV Lamp to PET bottle (cm)	Temperature of water sample (ºC)
Philips	G8T5	8W-56V	15	35

UV Lamp properties and applied parameters

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Effect of UV Light

Although the time of exposing to UV light was increased, the temperature of samples was stabilized to 35 ºC.

Increasing time of exposing to UV light causes an increase in transferred amount of antimony.

12 hours later → 53 ng/L,

72 hours later → 850 ng/L antimony transfer occurred.

Effect of UV Light on the transferred amount of antimony to water samples held in PET bottles.

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4. Effect of temperature

It is important to test the effect of temperature because especially in summer time high weather temperature values can be detected in Turkey.
In summer months, the weather temperature can be over 40 - 45 ºC and PET bottles which are held in closed areas, depots, garages, cars, containers without cooling system are exposed to high level of temperature.
Since, it was crucial to test the effect of temperature. Bottled water samples were held for 24 hours in different temperatures in the range of 22 - 70 ºC.

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Effect of temperature

Increasing temperature – increases leached amount of antimony into water.

The transferred amount of Sb was close to each other for water samples held at 22 ºC and 40 ºC.

When temperature was increased to 70 ºC

antimony content was increased to 1.23 µg/L.

Effect of temperature on transferring amount of antimony to water samples held in PET bottles

(exposing time: 24 hours)

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5. Effect of temperature and deposition time

Water samples were stored in the range of 12 - 72 hours and 22 - 70 ºC .

With the increasing of temperature, antimony leaching was increased.

When both temperature and deposition time increased together;

At 60°C for 48 hours →

1.21 µg/L

At 70°C for 24 hours → 1.23µg/L
At 70°C for 72 hours → 2.57µg/L

Effect of temperature and deposition time on leached amount of antimony into PET bottled water

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6. Effect of kind of plastic on antimony transfer

In bottles made by High Density Polyethylene (HDPE) antimony transfer to water is very small, insignificant.

In Transparent PET,

antimony transfer to water was nearly 3 times higher than the Blue PET.

Blue PET

72 hours → 0.57 µg/L

Transparent PET

72 hours → 1.74 µg/L

Effect of kind of plastic on antimony transfer (temperature: 60°C)

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�

Summary

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Parameters affecting the leaching of antimony from PET bottles to water change as follows;

Temperature > Exposing to UV light > Deposition time

Due to high levels of temperature in summer time in Turkey, it is important to investigate the effect of temperature on the transfer of antimony to drinking water. It is observed that above 50 °C and for a long period of deposition, a fast increase was detected in transferred amount of antimony.

Leaching of Sb is temperature dependent process.

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As the results show, the most safest kind of plastic for drinking water bottles was High Density Polyethylene (HDPE).

It is observed that, for all tests, the level of antimony was below the maximum contamination level for ‘Human daily intake water samples’ TS 266 (5 µg/L) proposed by Turkish Ministry of Health.

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Metodun Doğruluğu

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Örnek	Sertifika değeri (µg/L)	Bulunan değer (µg/L)	% Geri Kazanım
TMDA-61.2	33.6 ± 2.8	33.1 ± 0.5	98.4

SFODME metodu kullanılarak önderiştirilmiş sertifikalı referans su maddesinde Sb(III) tayin sonuçları

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Gerçek Örneklerin Analizi

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Musluk suyunda ve Körfez Suyunda Sb(III) tayin sonuçları

Örnek	Eklenen (µg L^-1)	Bulunan (µg L^-1)	% Geri kazanım
Musluk suyu	0	T.E.	-
	10	9.8 ± 0.7	98.0
	25	25.3 ± 0.3	101.2
	50	49.4 ± 0.5	98.8
Deniz suyu	0	T.E.	-
	10	9.1 ± 0.4	91.0
	25	23.4 ± 0.9	93.6
	50	46.2 ± 0.3	92.4

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Musluk suyunda ve Körfez Suyunda Sb(III) tayin sonuçları

Örnek	Eklenen (µg L^-1)	Bulunan (µg L^-1)	% Geri kazanım
Göl suyu	0	1.3	-
	10	11.2 ± 0.4	99.5
	15	16.6 ± 0.5	101.8
	20	20.9 ± 0.5	98.1
Körfez suyu	0	1.8	-
	10	11.1 ± 0.3	94.0
	20	22.0 ± 0.7	100.9
	30	31.6 ± 0.2	99.4

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Sonuç olarak

SFODME yönteminin F-AAS ile kombinasyonunun antimon ağır metal iyonunun sulu çevresel örneklerde

basitliği,
düşük maliyeti,
iyi doğruluk ve kesinlik değerleri,
basit gereçlerin kullanımı
minimum organik çözelti kullanımı
yüksek önderiştirme ve zenginleştirme faktörleri eldesi

gibi özellikleri bakımından uygun bir tayinine olanak sağladığı söylenebilir.

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