AOAC ZA

8/13/2019 AOAC ZA

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Background

High nitrogen containing fertilizers may containmore than one source of nitrogen:

Urea N

Ammonium nitrate

Ammonia in any combination

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Methods

ISO 5315:19!

"he metho# consists in re#ucing of nitrate to ammonia bychromium $o%#er in aci# me#ium& con'erting of organican# urea nitrogen into ammonium sulfate by #igestion %ithconcentrate# sulfuric aci# in the $resence of a catalyst&#istilling of the ammonia from an al(aline solution an#absorbing in an e)cess of stan#ar# 'olumetric so#ium

hy#ro)i#e solution* "he metho# is not recommen#e# formaterials containing more than + , of organic matter*

METHODS

• BS EN 15750:2009 Fertilizers. Determination oftotal nitrogen in fertilizers containingnitrogen only as nitric, ammoniacal an!rea nitrogen "y t#o ifferent met$os

• BS EN 15750 specifies two different methods(Methods A and B) for the determination ofthe total nitrogen content in fertilizersMethod A specifies the titrimetric methodafter distillation according to BS !S"5#15$1%&' Method B specifies a method red*ction of nitrate with iron and tin(!!)+chloride

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Methods

Cyanamid & Nitrate Mixtures-Davisson-Parsons

The sample is placed in 800 cc Kjeldhalflask, 100-200 cc D-water , 0! "a#$eno%&h to make the sol%tion 10th

normal and s%fficient Devarda's allo()*%-0, +l-, n-. is added to red%ce

all the nitrate nitro&en

Methods in Agricultural Chemical

Analysis: a practical handbook-N.T. Faithfull

Determination of total nitrogen in presence of nitrate andorganic N

eagents: !alicylic acid

!e po"der

#$% sulfuric acid

&n dust

Apparatus:

'(eldhal

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AOAC Methods

-et .hemistry

Principle: Destruction & reduction hydrolysis,digestion step followed by titration of theammoniacal N

AOAC Wet Methods

AOAC 2!"#$2!"% 'ra(il)

*aney Ni

AOAC 2!+$2!"!, 2!"-$2!"2

Cr Powder

AOAC ++!%

.gO, /n granules, /n dust

0mpro1ed method for Nitrate free sample AOAC #3, +" -++), .go, /n powder

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• AOA. 9+*/0

Copper sulfate pentahydrate

• AOA. 9+/*/3

*aney catalyst powder

• AOA. 90/*/3

4gO

• AOA. 90/*/5

5ormaldehyde titration for ammonium nitrate 2 sulfate

AOAC 920.05

Fe sulfate-Zn Soda

AOAC 892.01

Devarda’s alloy

AOAC 930.01

Hg

AOAC 930.02

Hg

AOAC 935.01

Hg

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T') A*AC M*D+F+CAT+*N!%$e moifications are for &'&( #et met$os

• )e !se )et *+el$al- et$o

• )e analyses /5 samles er mont$ on t$e aerage

• )e analyze mostly !reaformale$ye conensatero!cts, 3&N, &mmoni!m %$ios!lfate,4 &m S!lfate

• Fertilizer samles are li!i *e6cet &m S!lfate-

N N

N

O

H H

N

H

O

N H2

TKI AOAC MODIFIED METHOD

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TKI AOAC Modified Method

The Goals

Kjeldhal Catalyst – Eliminating catalyst inTotal Kjeldhal Digestion Procedure: AOAC

(1th edition! O""icial #ethod $%%&')itrogen (Total! in *ertili+ers,

#a-ing the method more sa"e .yeliminating the ha+ardous metal salts

(/gO0 inc granules0 inc dust!,

#a-ing the method sa"er and moreeconomical&

of Samles &nalyze(!ric S!lfate &e

Samle 8es No

15&mmoni!m S!lfate

*eference St.- *21.1; N-21.15 <0.0= 21.12 <0.09

> %?SE%+@ *5.0; N- 5.25 < 0.1 5.2> < 0.20

2 %?SE%+S *15.0; N- 1/.91 < 0.00 1/.92 < 0.01

19 NS3E *2; N- 2.0> < 0.15 2.0/ < 0.1/

2 %?SE%(B *2=.0; N- 25.= < 0.0/ 25.90 < 0.0

1 %?SE%NB *2=.0; N- 2=.1> < 0.1= 2=.11 < 0.19

5 F''AENEA3S *29.5; N- >0.00 < 0.0 29.97 < 0 .1/

1 (9 *29.5; N- 29.>7 29.>/

10 3ran>2 *22 2/; N- 22.5

1 &mmoni!m t$ios!lfate *12.0; N- 11.9/

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"he results sho% that using the %et metho# %ith theaforementione# $ro#ucts #oes not nee# the metalsalts use*

"his com$arison sho%e# be e)ten#e# to other

fertilizers to establishe# a generality*

"his stu#y is only for -et .hemistry 4el#halmetho# recommen#e# by I6A 7as %ell .ombustion

8etho# AOA. 993*13 recommen#e# by I6A*

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AOAC ZA