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QUANTITATIVE ANALYSIS OFGOLD CONCENTRATE USING FIRE
ASSAY BY GRAVIMETRY ANDSPECTROPHOTOMETRY METHOD
Bayu Wiyantoko∗a, SantosobbProfessional Program of Chemical
Analysis,
Islamic University of Indonesia*Corresponding author Email:
*[email protected]
April 2, 2018
Abstract
The analysis of gold content in concentrate sample us-ing fire
assay by gravimetric and sample basis cupel lossby Atomic
Absorption Spectrophotometry (AAS) have beendone. Certification
standard used was ISO 10378: 2005 -Cooper, Lead, and Zinc Sulphide
Concentrates-Determinationof Gold and Silver-Fire Assay Gravimetric
and Atomic Ab-sorption Spectrophotometry (AAS). The gold content
ob-tained by gravimetric was 14.41 mg/g, and by spectropho-tometry
was 0.12 mg/g. The results of both tests wereadded together in
order to get the gold content that was14.53 mg/g in the ratio of
standard concentrate that hasbeen certified which was 14.89 mg/g.
The resulted of goldcontent by fire assay using gravimetric method
based hada precision value (% RSD) was 3.3850%, while the valueof
CV Horwitz was 10.7078%, and accuracy with truenessvalue of 99.06%.
The AAS test results with precision of %RSD value was 41.1290% and
the value of CV Horwitz was34.3292%. Meanwhile the accuracy test
expressed the valueof % recovery around 99.88%, and for LOD and LOQ
valuesrespectively were 0.6146 mg/L and 2, 0488 mg/L.
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International Journal of Pure and Applied MathematicsVolume 118
No. 24 2018ISSN: 1314-3395 (on-line version)url:
http://www.acadpubl.eu/hub/Special Issue
http://www.acadpubl.eu/hub/
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Key Words:Gold; Gravimetric; Atomic Absorption
Spec-trophotometry; Fire Assay; Cupel Loss; Concentrate
1 Introduction
Gold is a chemical element in the periodic table that has the
sym-bol Au (aurum) with an atomic number of 79, and gold includinga
transition metal (trivalent and univalent) is shiny and yellow.Gold
does not react with other chemicals and melt at temperatures1000◦C
(1). Gold occurs in association with ores of lead, iron sul-fide,
copper, in quartz veins in the gravel of stream beds. Goldhave four
basic colors which are obtain by the use of two or morevaried
quantities of base metals including silver, copper, zinc andnickel.
Some precipitate formed because of metasomatism process,while
mechanically concentrating produce sediment placer which isdivided
into two categories namely primary sludge and sedimentplacer (2).
Gold ore containing silver (10-15%), less copper, iron,metals Bi,
Pb, Sn, Zn, and platinum in small quantities (2). Thegold is
separated from other metal elements to obtain pure gold.In the
geological samples, the concentration of gold is very low to-gether
with the high concentration of matrix components that
ofteninterferes the separation.
Gold separation and preconcentration contained in the
geolog-ical samples have been developed using fire assay,
coprecipitation,solvent and solid phase extraction besides possible
used anotherways including amalgamation, sluice box, and cyanide
leach. Theselection of suitable sample preparation is highly
depends on thegold concentration and the further method to final
determination.Basically there are three methods used for
determining of gold likelygravimetry, titrimetry and instrumental.
The last method for golddetermination including atomic absorption
spectroscopy(3), neu-tron activation analysis (4) and inductively
coupled plasma spec-troscopy (5). The gold separation in this
research is done usingfire assay due to this is the most important
method used for thepreconcentration of gold and for separation from
their base met-als and silicates. The fire assay has known as
classical method ofgold collection which currently used two kinds
of collectors namelylead and nickel sulfide (6). The usage of the
fire assay method was
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performed for purification methods including gold content of
thecheapest and most accurate to date compared to another
methodeven the ability of this method can equal gold content
testing usingX-ray machines. The fire assay using NiS collector has
been usedfor quantitative recovery of gold from geological samples
althoughmajor precautions to lower the level of contaminants from
the fluxcomponents are necessary(7). The level of accuracy of the
methodof separation by fire assay methods can achieve 0:04% (8).
The finalresults of the analysis using fire assay method is then
conducted theweighing of metal or measured with instrumentation
such as atomicabsorption spectroscopy(8).
The analysis of gold grades in this research using two
samplesare concentrates and cupel loss. The concentrate is the
result ofthe concentrated of the ore containing high grade gold and
silver,and determined using a gravimetric method. The cupel loss is
acontainer that is used to process gold cupellation process, so
whengold be merged on the cupel so the container named as cupel
lossand analyzed using AAS. The determination of gold by fire
assaymethod is necessary to acquire the precision, accuracy, LOD
andLOQ values in order to figure out the measurements that have
beendone has fulfilled the quality assurance of the test. The
precisiondetermination was important to know whether the
measurementbased on the proximity of the measurement results with
measure-ment repeatability. The accuracy is the closest of the
measurementresults with actual levels, so that the accuracy needs
to be deter-mined to find out the accuracy of test results (9).
Limit of detection(LOD) is the concentration or amount of the
smallest / lowest ofthe analyte in the sample can be detected, and
limit of quantita-tion (LOQ) is defined as the lowest analyte
concentration in thesample can be determined with precision and
accuracy that can beaccepted on the condition operational methods
used (10). Basedon this background, the problem in this test
includes quantitativeanalysis of gold content in the samples of
concentrate and cupel lossusing fire assay by gravimetric and
atomic absorption spectropho-tometry (AAS) as well as quality
assurance testing results in termsof precision, accuracy, limit
detection and the limit of quantitation.
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2 Literature Review
2.1 Concentrate
Concentrate is a product which is the result of concentration of
theore/seed, in this case is meant copper containing
approximately30% copper, but also contains high grade gold and
silver. The goldcontent varies between 20 - 70 ppm, while silver is
about 60 - 100ppm. Preparation of concentrate sample is drilling
and blasting tobe obtained by ore, then crushed with the size of 75
um - 150 umand separation of Cu, Pb, Zn, Au, Ag, Pt, and Si by
floating untilthe metal floats above and the precipitate is silica
(tailings/waste).Concentrates sample that still contain lots of
water is collectedand dried in the dewatering plan (DWP). The dried
samples withmoisture content under 9% were loaded with bulk to the
vessel, andsampling each time span and composed into one sample in
each lot(± 2000 tons) (11).
2.2 Fire Assay
Fire assay is a quantitative method in analytical chemistry to
de-termine the levels of precious metals such as gold, silver which
aredetermined by extraction by fusion and by using a dry
chemicalreagent (flux). This method is still believed to be the
cheapest andmost accurate method of testing the gold content to
date even theability of this method can match the testing of gold
content usingx-ray machines. The accuracy of the fire assay method
can reach0.04%, and is ideal if done on objects with gold content
between33%-92%. Fire assay method is more emphasis on the
propertiesof metals in certain conditions of temperature and
chemical prop-erties. Broadly speaking the fire assay method is
divided into 6major processes namely (12):
2.2.1 Sample Preparation
The concentrated sample is of the crystal form so that in the
prepa-ration there is only a milling stage to ensure that the
sample is 200mesh.
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2.2.2 Fluxing (Flux Addition)
Flux can be defined as a reaction / reagent added to a substance
ormaterial that cannot or is difficult to melt to form a mixture
thatcan be easily melted. The melting mixture is called slag (ore
slag).Reagents in the flux contain various chemical compositions
such asNa2CO3, P bO, SiO2, Na2B4O7, and CaF2.
2.2.3 Fusion (Consolidation)
Fusion of flux mixed sample, potassium nitrate and silver are
meltedat 1050◦C in a fusion furnace. The required time ranges from
45to 60 minutes. Temperature must be maintained because if
thetemperature is too low it can lead to imperfect gold and
silveraccumulated in the lead liquor and will also produce small
leadbutton. After the process of melting the lead liquor is poured
intoa lead-button cone mortar and the slag will be separated, after
thecold lead button is removed by hammering the slag of the
mold.
2.2.4 Cupellation (Separation of Pb)
The separation of gold and silver from the lead button in the
cupel iscarried out by means of a warming where the lead will be
absorbedby the cupel and the remaining granules of gold and silver.
Theheating temperature is 900-950 ◦C for 1 hour. The oxidized
leadbutton to Pb metal is 98.5% absorbed into the cupel and
1.5%would be evaporates.
2.2.5 Bulking
Before the process of adding acid, the seeds prill flatted until
mea-suring ±0.2 mm. This process aims to obtain perfect gold
whendiluted with acid
2.3 Digestion (Dissolution)
Separation of gold and silver is done by adding nitric acid to
silverdissolve. After the silver is completely dissolved and then
addedwith 65% hydrochloric acid to dissolve the minerals still
containedin gold by heating.
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The fire assay is the most employed method for determining
goldin geological material. This method enables a high
pre-concentrationbefore quantification and allows precise as well
as accurate deter-mination of gold. The research have been
conducted such as com-paring three analytical methods based on the
atomic absorptiondetermination of gold following classical fire
assay, the aqua regialeach and the sodium cyanide leach (13).
3 Methodology/Materials
3.1 Materials and Tools
The tools used in this test include fusion furnace, muffle
furnace,multipour set (loader + mould + unloader), test tubes 10
mL, hotplate with a water bath, analytical balances d = 1 mg,
crucible,cupel 8A & 6A and Atomic Absorption Spectrophotometer.
Thematerials used in this test include sample concentration,
sampleSTD G. 905 6, Flux (Na2CO3, P bO, SiO2, Na2B4O7, CaF2,
flour,KNO3 and NaCl), concentrated hydrochloric acid, potassium
ni-trate, nails, silver, concentrated nitric acid and distilled
water.
3.2 Analysis of concentrate by gravimetric
A total of 15 grams of sample is inserted in a plastic bag
with0.5 gram weight is then added 200 grams of flux and 18 grams
ofKNO3 then inserted into crucible which contains 2 mg of
silver.The sample is melted in a furnace at a temperature 1050◦C
for45 minutes. The resulted molten iron poured into a mold,
allowedcooling to form two phases which leads button (below), slag
(above)which are then separated from the slag layer button lead.
Slag willbe washing while lead button moved into cupel 8A.
3.3 Washing process
The slag put into crucible then added 25 grams of flux washing
and10 grams of wheat flour and then merged back with 1050◦C
temper-ature for 45 minutes, the result of molten iron is poured
into a mold.The re-melting test samples left at room temperature to
form twophases which leads button (below), slag (top) and separated
lead
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button of slag. Lead button moved into cupel 8A which
alreadycontain lead button of the first smelting process and slag
(impuri-ties) disposed of in the waste. Furthermore, the separation
of goldand silver from lead button with cupellation process with
950◦Ctemperature for 60 minutes until the process is perfect
complete.The prill seeds flattened until the size of± 0.2 mm then
resultedproduct put into crucible.
The prill seeds added 65% nitric acid solution (1: 5) 10 mL,then
heated to a temperature 90-100 ◦C for 20-30 minutes. Furthersamples
were rinsed 3 times with distilled water, and added 65%nitric acid
solution (1: 1) 10 mL. The prill seed reheated for 30-45minutes
then rinsed four times with distilled water and added 1-2mL of 65%
hydrochloric acid solution for 3-5 minutes. The prillseeds rinsed
again 4 times with distilled water, then re-heated anddried for 10
minutes. After the addition of acid, the prill seedsincluded in
muffle furnace with 900◦C for 10 minutes, then cooled,dried and
weighed using the analytical balance.
3.4 Analysis of cupel loss by spectrophotomet-ric
The cupel loss sample reduced to 200 mesh with ship loading
toolauto sampler, then cupel loss sample weighed as much as 15
grams(duplo). The samples added 2.5 g sample STD G. 905 6 then
in-serted into a plastic bag and added 150 g of flux. The samples
weremixed until homogeneous and then put into crucible and
addedspikes. The cupel loss sample inserted into the furnace to a
tem-perature suitable melting process steps, namely 830, 880, 950,
980and 1050 ◦ C and then the sample poured into a mold of iron.
Fur-thermore, the sample cooled into ambient temperature until
formedtwo phases which leads button (below), slag (above).
Lead button included into cupel 6A for cupellation process,which
is heated to a temperature of 950 C for 60 minutes, untilthe prill
seed formed. Furthermore prill seeds were transferred toa test tube
and then added 10 mL of 65% nitric acid solution, anddo warming to
a temperature of 100 ◦C to dissolve prill. Cupelloss added 1 mL of
concentrated hydrochloric acid and heated toa temperature of 100 ◦C
until the yellow color vapor disappearedthen added distilled water
muted and to mark boundaries and ho-
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mogenized. The cupel loss samples were analyzed using
atomicabsorption spectrophotometry (AAS) at a wavelength of 242
nm.
4 Results and Findings
4.1 Gold separation by fire assay
Fire Assay is a quantitative analysis method to determine the
metalcontent in rock and metallurgical products such as gold,
silver andplatinum group metals. Fire assay method involves the dry
chem-ical reagents or flux and the assay done by gravimetric based
onthe heavy metals mass in a pure state (8). The stages of fire
assaymethod includes sample preparation, the addition of flux,
smelting,cupellation, the separation of gold and silver, partings
and weigh-ing. Smelting process coupled with flux, which is a
substance thatbinds impurities and to form a substance that is easy
to melt, calledslag.
Figure 1. The smelting process
Sample preparation includes crushing the samples, milling
ma-chines, and stirring. Samples were crushed until smooth reaches
±200 mesh size to obtain representative results. The addition of
fluxwhich has a composition include Na2CO3, P bO, SiO2, Na2B4O7,
CaF2,and flour aims to make the process of fusion by binding to
sub-stances which are not desirable as a metal oxide (SiO2 and
TiO2)and sulfur, such as pyrite (FeS2) and chalcopyrite (CuFeS2)
con-tained in the minera (12). The addition of potassium nitrate
(KNO3)having an oxygen content, which oxygen is used to oxidize
sulfides
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in the ore is high grade sulfide. The reactions that occur as
shownbelow (12):
2KNO3(s) −→ 2KNO2(s) + O2(g)4CuFeS2(s) + 9O2(g) −→ 2Cu2S(s) +
2Fe2O3(s) + 6SO2(g)FeS2(s) + O2(g) −→ Fe2O3(s) + SO2(g)
Figure 2. Lead botton on cupel
Each of flux composition has function when smelting namelysodium
carbonate (Na2CO3) strongly alkaline material, reacts withthe
sample to form alkali sulfide, aluminate and quartz. The oxi-dizer
and sulfur removal is the next properties of sodium carbon-ate. The
alkaline properties of lead (II) oxide (PbO) is weaker thansodium
carbonate, but still good as oxidizing sulfur, when PbO isreduced
in the melt to produce Pb which acts as a collector of pre-cious
metals. Silicon dioxide (SiO2)is a very common substancefound in
rocks, strongly acidic which will form quartz with metaloxides.
Silicon dioxide is added when low levels of ore to producethe
molten quartz more fluid and protect the cup from PbO at-tacks.
Meanwhile borax (Na2B4O7)is also a strong acid, capableof
dissolving all of a metal oxide. The ability to lower the melt-ing
point to the fire assay process is another advantage of
borax.Calcium fluoride (CaF2) serves to increase the fluidity of
the melt,is used when the sample has Al content of more than 1%.
Flour(flour) serves as a carbon source to reduce PbO into Pb
importantin collecting precious metals(14).
Samples included in the concentrate to smelting furnace at
atemperature of 1050 ◦ C to melt the metals, concentrates
includedin the iron mold and cooled. In the process of fusion
reaction wouldlead oxide oxidizing sulfur in the iron sulfide that
the iron sulfideundergoes desulfurization to form metals oxide.
While the sodiumcarbonate reacts with sulfur into sodium sulfate.
The addition
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of sodium carbonate to prevent sulfur binds lead into lead
sulfide(PbS) in the form of black sediment, so that the metal
impuritiesare not oxidized. Borax hydrolyzed due to heating
resulting borontrioxide. Metal oxides along with other impurities
tied with borontrioxide formed a green colored glass called slag.
The reaction ofthe melting process with the addition of flux as
follows (8):
FeS2(s)+7PbO(s)+2Na2CO3(aq) −→
FeO(s)+7Pb(s)+2Na2SO4(aq)+2CO2(g)Na2B4O7(aq) −→ Na2B2O4(l) +
B2O3(s)FeO(s) + B2O3(s) −→ FeB2O4(s)
Fire assay smelting process generates a metal precipitate,
whichconsists of a variety of heavy metals that are not oxidized by
PbO.Therefore it is necessary to separate more specifically with
cupel-lation process which results into prill consisting of gold
and silver.
In the process of washing gold analysis performed on a slag
(im-purities) and put it back in crucible then added 25 grams of
fluxwashing, and 10 grams of wheat flour samples of the
concentrateback later merged with 1050 ◦C temperature for 45
minutes. Sam-ple concentrates washing iron is poured into molds and
then cooled.Samples were cold separation slag and lead button by
means solvedusing a spoon and lead button was added cupel 8A which
alreadycontain lead button. Heavy metals will be under as a result
ofdifferences in specific gravity is called the button. The
precipitatealloy or lead is cleared physically is hit with a hammer
on a bed ofiron. Lead button which has been separated from
impurities wouldthen be analyzed the content of the gold in the
sample. Slag (impu-rity) obtained in the melting process conducted
advanced processcalled washing by adding a flux and flour to melted
to obtain leadsbutton. The phase of lead button then had
cupellation process toobtain prill seed which will be combined with
the seed prill fromthe initial melting process.
4.2 Analysis of concentrate by gravimetric
The cupellation process was conducted after the lead has been
cleanof impurities, at a temperature of 800-900◦C. The
temperature,which is below the melting point of gold and silver,
but above themelting point so that the Pb melts and is absorbed in
the cupel,while precious metal will be deposited on the surface of
the cupel
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which is often called prills. The resulted prill cooled and
flattenedwith a hammer until the thickness of ± 0.2 mm. Gold and
silver areseparated with the help of nitric acid 65% 1: 5 by 10 mL
and thenheated in a fume hood with a temperature of 100◦C for 30
minutesfor the process to dissolve the silver. The prill seed after
heating andthen washed with distilled water 3 times and added
concentratedhydrochloric acid (1:1) for 1-2 mL and reheated for 15
minutes.The process of flushing the testing was conducted after
addition ofnitric acid and hydrochloric acid prior to addition.
This is doneto prevent any reaction between nitric acid with
hydrochloric acid,because if nitric acid reacts with hydrochloric
acid will be formedsolution aqua regia, where these solution are
compounds that candissolve gold, so as to dissolve the silver
without dissolving the goldto be tested, the rinsing process is
done to prevent leaching of goldby aqua regia(15).
3Ag(s) + 4HNO3(l) −→ 3AgNO3(aq) + NO(g) + 2H2O(l)Ag(s) + HCl(l)
−→ AgCl(s) + H+(aq)
The addition of nitric acid used to dissolve silver in prill
seedand separating the resulting silver ions to precipitate
chloride afterthe addition of hydrochloric acid. The seed prill
rinsed again withdistilled water 3 times, put in a furnace with a
temperature of 900◦C for 15 minutes to evaporate the silver
chloride and silver nitrateleft over from rinsing with distilled
water, because silver chloridehas a melting point at a temperature
of 455 ◦C and silver nitratehas a melting point with temperature of
212 ◦C, so that the heating900 ◦C silver chloride and silver
nitrate will be lost and the onlyremaining pure gold. Pure gold is
weighed using the analyticalbalance d = 0.1 mg, in order to more
accurate results. The resultsof analysis of samples of concentrate
using gravimetric fire assaycan be shown in Table 1 and the
resulted product in Fig. 3
Figure 3. The gold from concentrate sample
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Table 1. Concentration of Concentrate Samples Using
Gravimetric
Based on Table 1 gravimetric testing obtained an average
goldweight on a sample of 0.216 g of concentrate. The
concentrationof gold in the concentrate sample is obtained using
the followingequation 1.
goldconcentration(mgg
) =goldweight(g)× 1000(mg
g)
weightofsample(g)(1)
4.3 Analysis of cupel loss by spectrophotomet-ric
The cupel loss used to be reanalyzed to view the gold content
thatstill settles in cupel using fire assay by atomic absorption
spec-trophotometry (AAS). The stages of fire assay methods
includesample preparation, the addition of 2.5 g sample STD G. 905
6,the addition of flux, smelting, cupellation, the separation of
goldand silver, and is measured using AAS. Smelting process
coupledwith flux, which is a substance that binds impurities and to
forma substance that is easy to melt, called slag. The addition of
thegold standard in the sample cupel loss for gold content on a
cupelloss is so small that when analyzed by AAS is not too good
becauseoutside of the range of the standard curve calibration
sequence thatshould be added to the standard.
Samples cupel loss in the form of prill seeds, added
concentratednitric acid and heated to a temperature of 100 ◦C to
dissolve prillseeds. Furthermore, concentrated hydrochloric acid
was added in 1mL and heated to steam yellow disappears. The test
sample is thencooled and added to mark boundaries distilled water
volume of 10mL, then homogenized and measured using AAS with a
wavelengthof 242 nm. Gold is resistant to nitric acid or
hydrochloric acid, only
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aqua regia (hydrochloric acid: nitric acid, 1: 1) to dissolve it
byforming anion tetrachloroaurate (III), and gain of hydrogen
fromnitric acid that producing yellow gas nitrous oxide. The
reactionof the addition of nitric acid and hydrochloric acid in the
samplecupel loss is as follows(15).
Au(s) + 4HCl(l) −→ [AuCl4]−(aq) + 4H+(aq)
[AuCl4]−(aq) + 4H
+(aq) −→ HAuCl4(aq) + NO(g) + 2H2O(1)
Table 2. Concentration Gold In Cupel Loss Using AtomicAbsorption
Spectrophotometer (AAS)
Gold assays on samples cupel loss using standard addition
methodfor gold content contained in cupel loss is so small that
needs to beadded to the gold standard as much as 5 g. The gold
standard isadded to the testing cupel loss can be determined by the
followingequation 2.
goldstandardconcentration =weightofgoldstandard
weightofsample + weightofgoldstandard)×
5.96mg/L(2) Description: 5.96 mg/L = certified of samples STD
Gcontent The results of the equation obtained by concentration
ofgold is added by 0.85 mg/L. Gold concentrations in samples
ob-tained from the measured cupel loss reduction from gold
concen-trations and the concentration of the gold standard. Based
on datashowed in Table 2, the average gold concentration in the
cupel losswas 6.26×10−6 mg/g. The results of the analysis of the
concentra-tion of gold in concentrate sample was added to the gold
concentra-tion results in cupel loss to determine the total gold
concentrationin the test sample. The result of the total gold
content is shown inTable 3.
Table 3. Total Concentration of Gold
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Based on Table 3 obtained the average level of total gold
was14.41 mg/g. The results of the analysis will be compared withthe
concentration of gold standard samples which have been cer-tified.
The average concentration of gold in concentrate standardwas shown
in Table 4. The result suggested that the value of thegold content
of the test sample included in the standard with amaximum of 14.86
mg/g.
Table 4. Gold Concentration on Concentrate Standard
4.4 Determination of precision and accuracy
Precision is the degree of similarity measurements proximity to
oneanother. The precision is important to know whether or not a
mea-surement based on the proximity of the measurement results
withmeasurement repeatability. Meanwhile accuracy is the closeness
ofthe measurement results with actual levels, so that the
accuracyneeds to be determined to find out the accuracy of test
results(9).The precision value of gold assay using a gravimetric
can be shownin Table 5.
Table 5. Precision and accuracy values of gravimetric method
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The test is said to be precise if the value of RSD
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The value of RSD obtained is 41.13 % which is greater than 2%,
sothe CV Horwitz is further determined and resulted 34.329%,
whichindicates that the gold assay in cupel loss with
spectrophotometricusing fire assay is precise based on the value of
RSD ¡CV Hor-witz. Meanwhile the accuracy in the spectrophotometric
methodmeasured using % recovery. The test results said to be
accurate ifthe% recovery value approaching 100%. Value% recovery
obtainedin the determination of gold by AAS amounted to 99.88%, so
theresult is said to be accurate because the value % recovery
obtainedapproaching 80-110%.
4.5 Determination of LOD and LOQ
The gold assays on cupel loss using fire assay by Atomic
AbsorptionSpectrophotometry (AAS), needs to be conducted to
determine thelimit of detection (LOD) is the concentration or
amount of thesmallest/lowest of the analyte in the sample can be
detected, andthe limit of quantitation (LOQ) is quantification
limit is defined asthe lowest concentration of the analyte in the
sample, which can bedetermined with precision and accuracy that can
be accepted onthe condition of operational methods used(10). The
determinationof LOD and LOQ value aim to figure out the sensitivity
of AASinstrument and resulted data can be seen in Table 8.
Table 8. The LOD and LOQ Value
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The LOD value for the measurement of concentration of gold
isequal to 0.6146 mg/L, and the concentration LOQ value of goldis
equal to 2.0488 mg/L, whereas the concentration of gold in thecupel
loss before the addition of the gold standard that is equalto 0.121
mg/L. Gold concentrations in samples cupel loss is toosmall to meet
the minimum limits on the concentration of LOD andLOQ, therefore
the sample cupel loss should be added to the goldstandard addition
with a concentration of 0.85 mg/L so cupel losscan be detected by
AAS. The test resulted cupel loss concentrationafter the addition
of gold standard was 0.97 mg/L.
5 Conclusion
Based on test results, it can be summed up as follows:1. The
average gold content of the concentrate and cupel loss
prepared using fire assay respectively by gravimetric and
spec-trophotometric were 14.41 mg/g and 6.27 ×10-6 mg/g.
2. The result of gold content analysis with gravimetric
methodgave the precision value (% RSD) around 3.385, while the CV
Hor-witz value was 10.708, and the accuracy with trueness value
of99.06%. Meanwhile the spectrophotometric obtain the
precisionvalue (% RSD) was 41.129 and the CV Horwitz around
34.329,while the value of accuracy (% recovery) of 99.88%, and the
LODand LOQ values respectively were 0.6146 and LOQ 2.049.
Acknowledgement The authors are grateful to PT.
Sucofindo(Persero) Timika Branch for fully supporting the materials
and lab-oratory facilities also the permission to publish this
work.
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