lab 1

7/17/2019 lab 1

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Title: Laboratory 1 Quantification of Sodium Benzoate in Food

Objective:

i. To detect the quantities of sodium benzoate found in food.

Introduction:

Sodium benzoate is a type of salt that may occur naturally in some foods but it is

more likely to be chemically produced and added as a preservative to foods. hen used as

a preservative! sodium benzoate is typically added to foods in small amounts only. "f too

much is added! food may have a very bitter taste. #http$%%&&&.&ise'eek.com%&hat(is(sodium(

benzoate.html)

Sodium benzoate used as the in'redients of foods as it &orks very &ell at killin'

bacteria! yeast and fun'i. "t commonly used as a preservative in foods &ith a hi'h acid

content! since sodium benzoate &ill only &ork &hen the p* balance of foods is less than +.,.

"t is therefore effective in most sodas! vine'ar! fruit -uice! and in mied in'redients like salad

dressin'. "t is additionally used to stop the fermentation process in &ines.

#http$%%&&&.&ise'eek.com%&hat(is(sodium(benzoate.html)

Sodium benzoate is &idely used in carbonated and still bevera'es! syrups! cider!

salted mar'arine! olives! sauces! relishes! -ellies! -ams! preserves! pastry and pie fillin's! lo&fat salad dressin'! fruit salads! prepared salads! and in stora'e of ve'etables. "t has been

incorporated in those foods as an antimicrobial a'ent at concentrations of /./0 to /.1

#Sivasankar! 2//3).

There have been some health concerns about the combination

of sodium benzoate and ascorbic acid or vitamin 4. hen the t&o are mied! they can form

the chemical benzene! &hich is carcino'enic. *o&ever! sodium benzoate on its o&n is not

considered a carcino'en and consumption of a hu'e amount of it in order to have toic

levels in body. #http$%%&&&.&ise'eek.com%&hat(is(sodium(benzoate.html)

Materials:

5eionized &ater! micropipette! nylon syrin'e filter #/.607m)! 413 column! sodium acetate!

acetic acid 'lacial! *8L4 'rade methanol! micropipette tips! small beaker! *8L4 'rade

Sodium benzoate and sample #Sprite soft drink).

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i. 0mL of sample #Sprite soft drink) &astransferred into a small beaker by usin'

a syrin'e.

ii. 9pproimately 2/mL of deionized&as then &ater added into the beaker.

iii. The miture then &as mied &ith

+0mL of methanol.

iv. The miture then transferred intovolumetric flask. The volume &as

topped up to 1//mL &ith deionized&ater.

v. Samples then &ere filtered throu'h/.607m syrin'e filter prior to in-ection.

i. The chromato'raphicseparation &as achieved &ith a

413 column.

iii. The in-ection volume &as2/7L! mobile phase &as ,0$+0!

acetate buffer #p* 6.:6) andmethanol &ith flo& rate of

/.3mL%min for 10 minutes at&avelen'th of 2+0nm.

Methods:

a) Sample Preparation

b) HPLC conditions

c) Preparation of standard curve

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i. The eternal standard plot method&as used.

ii. 5uplicate in-ections of 2/7L sodiumbenzoate standard solutions &ere used

to construct linear re'ression lines#peak area versus concentration).

iii.The peaks &ere identified based onthe retention time.

iv.The standard curves &ere obtained&ith five points #0! 1/! 2/! 6/ and

3/m'%L) for sodium benzoate.

esult:

From the instrumental result$

Instrument Conditions !t start !t stop

Column Temp" #left) 6/./ 6/./o 4

Column Temp" #ri$ht) 6/./ 6/./o 4

Pressure ;1.+ ;2./ bar

%lo& /.3// /.3// ml% min

<sin' Beer=s La&$

!'ebc

9 > absorbance of the sodium benzoate #proportional to the peak hei'ht of the sodium

benzoate on the chromato'ram.)

e > constant particular to sodium benzoate

b > path len'th of the cell in the instrument #&hich remains unchan'ed)

c > concentration of sodium benzoate

Since eb is a constant! it can be represented as k! and the equation can be simplified to$

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! ' (c

?earran'in' this equation 'ives us$

( ' !

c

( > :.:cm

:.,,++: m'%L

( > 1./6:3

So! the concentration of sodium benzoate! c ' !

(

@pandin' c &e 'et > Aass of sodium benzoate #mL)

olume of solution #mL)

4oncentration of sodium benzoate! c *Mass of sodium ben+oate #mL), ' !

-olume of solution #mL) (

c #0mL) > :.: cm

1//mL 1./6:3 cm per m'%L

c > :.+63:m'%L

/./0 mL

c > 16,.;:m'%L

c >."/0123 m$4 mL

5iscussion

Buffer solution is an aqueous solution consistin' of a miture of a &eak acid and its

con-u'ate base or a &eak base and it=s a con-u'ate acid. Buffer solutions are functionin' to

keep p* at a nearly constant value in a &ide variety of chemical applications. 8lus! buffer

solutions are necessary to keep the correct p* for enzymes in many or'anisms to &ork.

"ndustrially! buffer solutions are used in fermentation processes and in settin' the correct

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conditions for dyes used in colourin' fabrics. They are also used in chemical analysis and

calibration of p* meters.

The buffer used in this eperiment is acetate buffer. 9cetate is a salt or ester of acetic

acid. Salts of acetic acid contain a metal attached to the acetic acid radical 4* +4CC. The

esters contain another radical! such as ethyl! attached to the acetic acid radical. "n this

eperiment! the p* of the acetate buffer used is 0"30. This buffer can be made usin' an

equal volume of ."/. M acetic acid! *42*+C2! and ."/. M sodium acetate! Da42*+C2.

Typically the p* can be set to one p* unit above or one p* unit belo& the pE a for the acid.

The p* used is 0"30 because the pEa of acetic acid is 0"3! &hich can be fi'ured out usin'

*enderson(*asselbalch equation! p* > pEa lo' G91(H% G*9H. 5espite! a buffer solution

resists chan'e of p*! &ater does not. That is the reason &hy acetate buffer solution is used

instead of usin' &ater.

9ccordin' to the result obtained from the *8L4 instrumentation! the pressure used is

2/"6 bar at start and 27". bar at stop. hile the flo& is ."8.. mL4 min both at start and stop.

The amount of sodium benzoate can be determined by usin' the equation belo&$

!'ebc

&here 9 is the measured absorbance. The absorbance &ill be proportional to the peak

hei'ht of the sodium benzoate on the chromato'ramI e is the constant particular to the

sampleI b is the path len'th of the cell in the instrument! &hich remains unchan'ed and last

but not least! c is the concentration of the sample. The Beer(Lambert La& is useful for

characterizin' many compounds but does not hold as a universal relationship for the

concentration and absorption of all substances. The Beer(Lambert la& has implicit

assumptions that must be met eperimentally for it to apply. For instance! the chemical

makeup and physical environment of the sample can alter its etinction coefficient. The

chemical and physical conditions of a test sample therefore must match reference

measurements for conclusions to be valid.

Conclusion:

9t the end of the eperiments! the quantity of sodium benzoate in food #Sprite soft

drink) &as able to be detected. The amount of sodium benzoate obtained from the

instrument is 3"11 m$4L. The eact amount of sodium benzoate calculated is ."/0123

m$4mL.

eferences:

Sivasankar! B. #2//3). Food Processing and Preservation !0th ed.! 8rentice *all of "ndia

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8rivate Limited! De& 5elhi.

@llis(4hristensen. T.! 2/11. What Is Sodium Benzoate? 5ate of retrieved 3th Dovember 2/11

http$%%&&&.&ise'eek.com%&hat(is( sodium (benzoate .html.

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lab 1