Home Archive Vol 36, No.3, 2010 Original Papers Lead Determination In Meat Products By Atomic Absorption Spectrometry

Lead Determination In Meat Products By Atomic Absorption Spectrometry

Mariana - Luminiţa Neacşu(1), L. Chirigiu(2), Maria – Viorica Bubulică(2)

 (1) Technology Department, Constantin Brâncoveanu University, (2) Faculty of Pharmacy, University of Medicine and Pharmacy of Craiova

Abstract: The presence of heavy metals in food is the consequence of soil and atmosphere contamination (vegetable products); feeding animals with contaminated feed with heavy metals (animal products); acquisition of polluted waters (fish and other aquatic creatures); due to other sources (technological water, utensils, pots, etc.). The lead content along with other elements in food is of major interest for protection because of cumulative toxicity and animal and human health risks [1, 2]. The presence of lead traces production in many flows of production is also undesirable, because it can possibly go into food and thus be consumed by humans [3].               The presence of lead in technological flows is undesirable in particular due to possible food migration or other products used or consumed by humans [4]. Spectrophotometric methods [5] and atomic absorption spectrometry [6, 7] are the most common methods for determining lead in solution.

Keywords: atomic absorption spectrometry, lead, meat products


Introduction

In this study we determined the content of lead in: hot smoked products / pasteurized /cold smoked (Summer sausage); hot smoked products / pasteurized without structure (parizer, frankfurters); hot smoked products / pasteurized with heterogeneous structure (salami, sausage) from six companies in Braila producing and marketing these products over three years: 2008, 2009, 2010.

Sample preparation for determining lead is made by dry mineralization.

Principle of the method Organic substance in the sample is destroyed by carbonization and then ignited in the electric furnace at 450 – 500°C and the resulting ash is passed into solution by dissolving in dilute hydrochloric acid.

Meat samples taken according standards and technical regulations are chopped twice through the mincer with 2 to 3 mm sieve, and the ones of cans and meat products are chopped into homogenizer or mortar, until it is obtain a very homogenous mass. Samples thus prepared are stored in refrigerator in sealed jars.

Material and Methods

Experimental Part

Of homogenized sample are weigh 10 g with 0,01 g precision into a quartz or porcelain capsule. The amount taken for mineralization is treated with 3 cm3 magnesium nitrate solution (10 % solution purified of metals by shaking with dithizone, 0.005 % solution in chloroform) and stir with a glass rod. Wipe glass rod with a small piece of filter paper without ash witch passes in the capsule. On sample surface is then applied quantitative filter paper rondel, perforated, so the sample to be completely covered. The sample is placed in an electric furance and is dried for one hour at 100 – 120°C, after which the temperature is raised gradually with 50 – 100oC every half hour, until it reaches 300 – 350°C and is maintained at this temperature until complete carbonization (no longer smoke is liberate) taking care not to burn. The sample can be dried and char in niche on an electrical sand bath or on flame on a asbestos sieve (with care not to burn) until no longer smoke is liberate then the sample is inserted into the electric furnace and is carbonized. The sample can be dried in the oven too at 105 – 110°C for one hour then another hour at 150 – 160°C then is inserted into the electric furnace and is carbonized. After complete carbonization of the sample, electric oven temperature is raised to 500°C and sample is ashed for 4 hours until the ash is white with a few points of coal. Ash capsule is removed from oven and is let to cool on an asbestos sieve. After cooling, the ash is treated with 5 cm3 HCl and a drop of hydrogen peroxide and then is evaporated to dryness on a boiling water bath. Another 5 cm3 of HCl are added and the capsule is covered with a watch glass and is heated 5 minutes in a water bath under niche. The sample is then diluted with 5 cm3 water and is quantitatively passed, through filter paper with high or medium porosity, in a 100 cm3 volumetric flask. The capsule and the filter are washed three or four times with small quantities of hot water, (80 – 100°C) poured in thin stream, until the balloon is filled with ¾ of the volume. The solution should be colorless or slightly greenish no brown color due to unburnt organic matter. Filter paper with the remaining coal is introduced again in the same capsule, is dried and carbonized in the electrical furnace, raising the temperature to 300 – 350°C, followed by one hour at 500°C calcination. Over the remaining ash is added 1 cm3 HCl (d = 1,19 g/cm3, diluted 1 + 1 : at 100 cm3 is added 1 cm3 glacial acetic acid), the capsule is covered with a watch glass then is heated on the water bath about 5 minutes, after witch is quantitatively passed with hot water (80 – 100°C) in the volumetric flask and the capsule is washed with water. After cooling, is brought the content of the flask at sign with water and mix. Two mineralization are performed of the same sample for analysis. In parallel, blank solution is prepared with mineralization reagents thus: into a capsule is introduced a rondel and a piece of filter paper without ash, both identical in size and quality to those used in determinations, 3 cm3 of magnesium nitrate solution are added, are evaporated and mineralized. From mineralized sample solution can be determined: Cu, Zn, Fe, Pb. If only one element is determined, 5 g sample is mineralized reducing the amount of magnesium nitrate and HCl at half. The resulting solution is made up to 50 cm3.

Reagents

Direct determination of the analyzed sample by flameless atomic absorption spectrometry is made with an atomic absorption spectrometer, equipped with graphite furnace [4], with correction for nonspecific absorbance and multi-potentiometric recorder (spectrophotometer GBC Avanta Australia). The required materials are lead hollow cathode lamp; 5 ml micropipette provided with special tips for atomic absorption measurements. As reagents are used:

- phosphoric acid solution, obtained by dilution, as follows: into a 100 mL volumetric flask 8 mL of phosphoric acid are introduced, 85 % solution (d = 1.71 g/mL) and is brought the content of the flask at sign with water;

- nitric acid (d = 1,38 g/mL);

- lead standard solution, with the lead content of 1 mg / mL. The standard solution used is Pb(NO3)2 in HNO3 0.5 mol / L from CERT PLUS MERCK Germany, analytical putity.

Procedure

The sample is diluted according to the presumed content of lead, with phosphoric acid solution. standard solution is prepared containing 0.5, 1, 3, 5 mg Pb / L of stock solution. Working conditions for lead determination are drying at 1000oC for 30 seconds; mineralization at 9000°C for 30 seconds; atomization at 2250°C for 2 – 3 seconds; nitrogen flow 6 liters per minute. At the end of determination, the temperature is set at 277°C to purge the oven.

Is chosen the wavelength of 217 nm. Is adjusted the zero point with water, 5 mL of working standard solutions and of sample solution for analysis are injected into the programmed furnace using a micropipette for three times. Measured absorbances are measured and from the relative results of the three injections is calculated the average absorbance.

Results and Discussion

Results calculation

The curve of absorbance variation is plotted depending on the lead content of the working standard solutions (linear variation). The lead content is read from the calibration curve, corresponding to the sample absorbance. Lead content, expressed in micrograms per liter of product, is given by relationship:

 

Lead (Pb) = C · F     [μg/L]                (1)

where:

C = lead content on the calibration curve in micrograms;

F = dilution applied to the sample.

In this study we determined the content of lead in: hot smoked products/ pasteurized /cold smoked (Summer sausage); hot smoked products / pasteurized without structure (parizer, frankfurters); hot smoked products / pasteurized with heterogeneous structure (salami, sausage) from six companies in Braila producing and marketing these products over three years: 2008, 2009, 2010.

For reasons of confidentiality required by companies who have provided analyzed products, Company names will not be used, they will be replaced with fictitious names.

Average content of Pb in mg / kg at hot smoked products / pasteurized without structure is given in Table 1.

Analyzing the data from Table 1 it shows that in 2009 the average lead content was significantly higher than in 2008 instead, in 2010, the content is significantly lower than that of 2008 and from that of 2009.

The average lead content in mg/kg at hot smoked products / pasteurized with structure is given in Table 2.


Table 1 – Average content of Pb in mg / kg at hot smoked products /pasteurized without structure

Society

Year

 

2008

2009

2010

 

Average

Di1

Di2

Average

Di1

Di2

Average

Di1

Di2

S.C. Basta . SRL

0,34

-0,04

+0,05

0,34

-0,26

+0,04

nd

nd

nd

S.C. Solaris SA

0,39

+0,01

+0,10

0,5

-0,11

+0,19

nd

nd

nd

S.C. Tara SRL

0,32

-0,06

+0,03

0,63

+0,02

+0,33

nd

nd

nd

S.C. Drog SRL

0,31

-0,07

+0,02

0,53

-0,07

+0,24

0,64

+0,02

+0,32

S.C. Panta SA

0,38

+0,002

+0,09

0,71

+0,10

+0,41

0,56

-0,05

+0,24

S.C. Troia . SRL

0,49

+0,11

+0,20

0,65

+0,04

+0,36

nd

nd

nd

S.C. Oros SRL

0,31

-0,07

+0,02

0,48

-0,13

+0,18

nd

nd

nd

                       

Di1 – deviation from the county average

Di2 – deviation from the country average

* Nd. - unspecified limit

Table 2 – The average lead content in mg/kg at hot smoked products / pasteurized with structure

Society

Year

2008

2009

2010

 

Average

Di1

Di2

Average

Di1

Di2

Average

Di1

Di2

 

S.C. Basta . SRL

0,5

+0,13

+0,22

0,70

+0,09

+0,40

nd

nd

nd

 

S.C. Solaris SA

0,46

-0,08

+0,17

0,52

-0,08

+0,22

0,78

+0,16

+0,46

 

S.C.  Tara SRL

0,42

+0,04

+0,13

0,82

+0,21

+0,52

0,69

+0,08

+0,37

 

S.C. Drog SRL

0,47

+0,09

+0,18

0,74

-0,13

+0,44

0,58

-0,03

+0,26

 

S.C. Panta SA

0,36

+0,015

+0,07

0,81

+0,2

+0,51

0,71

+0,09

+0,39

 

S.C. Troia . SRL

0,5

+0,13

+0,22

0,70

+0,09

+0,40

nd

nd

nd

 

S.C. Oros SRL

0,46

-0,08

+0,17

0,52

-0,08

+0,22

0,78

+0,16

+0,46

 

                         

Di1 – deviation from the county average

Di2 – deviation from the country average

Nd. – unspecified limit

Table 3 – The average lead content in mg/kg at hot smoked products / pasteurized with heterogeneous structure

Society

Year

 

2008

2009

2010

 

Average

Di1

Di2

Average

Di1

Di2

Average

Di1

Di2

S.C. Basta . SRL

0,34

-0,03

+0,05

0,56

-0,04

+0,26

nd

nd

nd

S.C. Solaris SA

0,31

-0,06

+0,02

0,63

+0,02

+0,34

nd

nd

nd

S.C. Tara SRL

0,48

+0,10

+0,19

0,43

-0,17

+0,14

nd

nd

nd

S.C. Drog SRL

0,45

+0,07

+0,16

nd

nd

nd

nd

nd

nd

S.C. Panta SA

0,48

+0,10

+0,19

0,66

+0,05

+0,37

nd

nd

nd

S.C. Troia . SRL

0,25

-0,12

-0,03

0,60

-0,01

+0,30

0,66

+0,05

+0,35

S.C. Oros SRL

nd

nd

nd

0,65

+0,04

+0,35

0,45

-0,15

+0,13

                         

Di1 – deviation from the county average

Di2 – deviation from the country average

* Nd. – unspecified limit


Analyzing the data of Table 2 it shows that in 2009 the average lead content was significantly higher than in 2008, however, in 2010, this content is much higher than that of 2008, but in some cases is smaller than that of 2009.

The average lead content in mg/kg at hot smoked products / pasteurized with heterogeneous structure is given in Table 3.

Analyzing the data of Table 2 it shows that in 2009 the average lead content was significantly higher than in 2008, however, in 2010, this content except two companies is so small that could not be determined.

Conclusions

In 2008 the average content of lead in meat products from Braila county ranged between 0.17 mg / kg and 0.50 mg / kg and was framed in the maximum content permissible by the legislation (1 mg/kg), with an average of 0.38 mg / kg, value witch is closed to the average lead content in meat products from Romania in 2008.

At national level, the average lead content in meat products in 2008 ranged between 0,07 mg/kg and 0,65 mg/kg.

In 2009, the average lead content in meat products from Braila county ranged between 0,38 mg/kg and 0,84 mg/kg, and was framed within the maximum content permissible by the legislation (1 mg/kg), with an average of 0,61 mg/kg, value witch is significantly increased compared to the average content of lead in meat products in Romania in 2009.

At national level, the average lead content in meat products in 2009 ranged between 0,013 mg/kg and 0,45 mg/kg.

In 2010, the average lead content in meat products from Braila county ranged between 0,36 mg/kg and 0,78 mg/kg, and was framed within the maximum content permissible by the legislation (1 mg/kg), with an average of 0,61 mg/kg value witch is closed compared to the average content of lead in meat products in Romania in 2009.

At national level, the average lead content in meat products in 2010 ranged between 0,01 mg/kg and 0,25 mg/kg.

References

1.     Berman T.E - (1980) Toxic metals and their analysis, Heyden & Sons, London, 106-118.

2.     Klassen C.D, Amdur M.D, Dull J - (1986) Casarett and Dulls toxicology 3rd ed. Mac Millan, New York, 214.

3.     Yin Z.Z., Khopkar S.M - (1991) Anal. Lett., 23, 635.

4.     Izatt R.M., Bradshaw J.S., Tarbat B.J., Bruening R.L - (1995) Pure Appl. Chem., 67, 1069.

5.     Marczenko Z - (1986) Separation and Spectrophometric Determination of Elements, Elis Harwood, London, 97-122.

6.     Welz B - (1985) Atomic Absorption Spectrometry, VCH, Amsterdam,314.

7.     Sekerka I., Lechner I - (1991) Anal. Chim. Acta, 254, 49.

 

 

Correspondence Adress: Mariana Luminiţa Neacșu MD, Technology Department, Constantin Brâncoveanu University, 16 - 18, Rubinelor Street, 200349 Brăila, Romania; Phone 0239613308, Fax 0239612539, E-mail ucb.braila@bytenet.ro, Tel. 0239-613 308, Fax 0239-612 539


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