ORIGINAL PAPER

On-line spectrophotometric determination of scandiumafter preconcentration on XAD-4 resin impregnatedwith nalidixic acid

Shabnam Shahida • Akbar Ali • Muhammad Haleem Khan

Received: 7 June 2012 / Accepted: 11 October 2012 / Published online: 22 November 2012

� Iranian Chemical Society 2012

Abstract An on-line scandium preconcentration and

determination method was developed with spectropho-

tometer associated with flow injection. Scandium from

aqueous sample solution of pH 4.5 was selectively retained

in the minicolumn containing XAD-4 resin impregnated

with nalidixic acid at a flow rate of 11.8 mL min-1 as

scandium–nalidixic acid complex. The scandium complex

was desorbed from the resin by 0.1 mol L-1 HCl at a flow

rate of 3.2 mL min-1 and mixed with arsenazo-III solution

(0.05 % solution in 0.1 mol L-1 HCl, 3.2 mL min-1) and

taken to the flow through cell of spectrophotometer where

its absorbance was measured at 640 nm. The preconcen-

tration factors obtained were 35 and 155; detection limits

of 1.4 and 0.32 lg L-1 and sample throughputs of 40 and

11 were obtained for preconcentration time of 60 and

300 s, respectively. The tolerance limits of many interfer-

ing cations like Th(IV), U (VI), rare-earths and anions like

tartrate, citrate, oxalate and fluoride were improved. The

method was successfully applied to the determination of

scandium from mock seawater samples and good recovery

was obtained. The method was also validated on certified

reference material IAEA-SL-1 (lake sediment) and the

result was in good agreement with the reported value.

Keywords Scandium � Nalidixic acid � XAD-4 resin �Flow injection � On-line preconcentration

Introduction

One of the great concerns in metallurgy is the determina-

tion of scandium [Sc(III)] in alloys and pure metals. In

addition, as toxicity of Sc(III) ions against giant algae has

been reported, the demand for measuring Sc(III) in envi-

ronmental samples has also been recognized [1].

Fluorimetry [2], inductively coupled plasma atomic

emission spectrometry (ICP-AES) [3, 4], inductively cou-

pled plasma optical emission spectrometry (ICP-OES) [5],

inductively coupled plasma mass spectrometry [6, 7],

electro thermal atomic absorption spectrometry (ETAAS)

[8] and neutron activation analysis (NAA) [9, 10] have

been used to determine Sc(III). Due to the economic con-

straints faced by the developing countries, these highly

expensive instruments cannot be purchased for all the

laboratories throughout the world. On the other hand,

spectrophotometry still enjoys wide popularity due to its

accuracy, inexpensive instrumentation, simple operation,

and wide availability in most laboratories [11]. A number

of chromogenic reagents were used for the spectrophoto-

metric determination of Sc(III) such as, alizarin red S [12],

8-quinolinol [12], tiron [13], chlorophosphonazo-III [14],

arsenazo-III [15], bromopyrogallol red [16], 5,7-dichloro-

8-quinolinol [17], xylenol orange [18], chromazurol S [19],

nile blue [20] and arsenazo [21]. But these spectrophoto-

metric methods show a lack of selectivity and sensitivity.

In order to resolve these limitations, some preliminary

operations such as separation and preconcentration are

required to be carried out before the determinations of

analyte. Solid phase extraction has become a very impor-

tant technique for the separation and preconcentration of

trace elements. A number of offline preconcentration pro-

cedures for Sc(III) have been developed by using various

supports including amberlite IRC 718 chelating resin [22],

S. Shahida � M. H. Khan

Department of Chemistry, University of Azad Jammu

and Kashmir, Muzaffarabad, AJK, Pakistan

A. Ali (&)

Chemistry Division, Pakistan Institute of Nuclear Science

and Technology, P.O. Nilore, Islamabad, Pakistan

e-mail: akbar@pinstech.org.pk; akbar223@gmail.com

123

J IRAN CHEM SOC (2013) 10:461–470

DOI 10.1007/s13738-012-0180-6

ammonium tetraphenylborate-naphthalene used to precon-

centrate Sc-1-(2-thiazolazo)-2-naphthol chelate [23] and

C18-silica gel used to preconcentrate Sc-diacyl-N,N-bis

(4-hydroxybenzoylhydrazone) chelate [24]. However, the

offline preconcentration procedures are often time con-

suming, involves the loss of reagent and faces the risk of

contamination.

In order to solve these problems, SPE has been com-

bined with flow injection analysis to obtain advantages

such as automation, high sensitivity and sampling fre-

quency, improvement of selectivity, precision, utilization

of small volumes of sample, reagent and minimal risk of

contamination [25]. But still only one study on the spec-

trophotometric determination of Sc(III) by FIA has been

performed by Kuzetsov [26]. In this study the reaction of

copper (II) displacement by Sc(III) from its chelate with

EDTA in the presence of 4-(2-pyridylazo)-resorcinol as a

photometric reagent was used for the determination of

Sc(III) in FIA. The interference from rare earth elements,

indium and gallium was eliminated by hydrogen peroxide

and Fe(III) by using ascorbic acid. But the indirect deter-

mination of Sc(III) using displacement reaction is com-

plicated. So there is a need of cheap, efficient, selective and

sensitive determination methods for scandium.

Styrene divinylbenzene copolymer represents an out-

standing solid phase having high surface area, uniform pore

size and good adsorbent properties, widely used to pre-

concentrate metal ions [27–30] or to develop chelating

resins via functionalization with selective organic reagents

[31–34] or by simple impregnation [35–37] for the pre-

concentration of metal ions. A good review on the use of

styrene divinylbenzene copolymer for the preconcentration

of metal ions was described by Soylak et al. [38]. The use

of impregnated resins is particularly convenient because it

is easy to prepare.

Active ingredients of drugs commonly available in the

market have got little attention for their applications as

metal extracting agents. Nalidixic acid (HNA) (1-ethyl-1,

4-dihydro-7-methyl-4-oxo-1, 8-naphthyridine-3-carboxylic

acid) is an active ingredient of a cheap drug Negram which

is commonly used for treating several bacterial diseases

[39]. HNA is a weak acid and its pka value is 5.9–6.35 [40–

42]. Analytical application of this reagent is limited to

spectrophotometric determination of iron(III) [43], fluoro-

metric determination of Eu(III), Tb(III), Dy(III) [44] and

luminescence determination of Eu (lll) using zirconium

phosphate as solid support [45]. In our earlier communi-

cation, HNA in dichloromethane is used for the solvent

extraction of Eu(III) and Nd(III) at pH 6.5 [46], Sc(III) at

pH 3 [47] and online determination of uranium (VI) [48].

The use of HNA for the modification of solid sorbent and

its use in online preconcentration of Sc(III) prior to their

determination have not been cited so far in the literature.

In continuation of our earlier work [48–50], a very

selective and sensitive method for the online spectropho-

tometric determination of Sc(III) after preconcentration in

a minicolumn packed with Amberlite XAD-4 resin

impregnated with HNA is presented. The retained metal is

eluted with hydrochloric acid and determined by spectro-

photometer using arsenazo-III as a chromogenic reagent

due to its fast complex formation kinetics with arsenazo-III

[15]. Various parameters affecting the on-line preconcen-

tration and determination of Sc(III) are optimized and their

detail is given below. The effect of various cations and

anions was also studied. The ability of the system to

function in the presence of high sample matrix concentra-

tion was ascertained using ground and sea water samples

spiked with Sc(III). The validity of the method was also

checked on standard reference material IAEA SL-1 (lake

sediment).

Experimental

Apparatus

The FIA system made by Beijing Vital Instruments CO.

Ltd., P.R. China, having two peristaltic pumps and one

eight channel multifunctional valve controlled by a built-in

computer was used. The detector was a UV–visible spec-

trophotometer from Biotech Engineering Management CO.

Ltd. UK, consisting of a flow through cell of 10 lL

capacity having 5 mm path length. Tygon tube of 2.56 mm

(i.d.) was used for the propulsion of sample, whereas

1.56 mm (i.d.) tubes were used for eluent and chromogenic

reagent solutions. All the connecting tubes were 0.5 mm

(i.d.) Teflon tubes. Minicolumn (5-cm long, 5-mm i. d.)

containing XAD-4 resin impregnated with HNA (0.5 g)

was made from a polyethylene tube and small pieces of

polyurethane foam washed with ethanol were used to plug

both the ends of the column. Sample and eluent were flo-

wed in the reverse direction to each other from the mini-

column in order to minimize the dispersion. A pH meter

model 605 from METROHM Ltd, Switzerland, was used

for the measurement of pH of aqueous solutions.

Reagents

Amberlite XAD-4 resin of surface area 750 m2 g-1 and bead

size 0.3–1.1 mm were purchased from Merck, Darmstadt,

Germany. All aqueous solutions were prepared with distilled

deionized water (DDW). Nalidixic acid (HNA) was purified

from Negram tablets, obtained from local pharmaceutical

company (Searle Pakistan Ltd.) according to the method

given elsewhere [46]. Dichloromethane was purchased from

Riedel-de-Haen, Seelze, Germany.

462 J IRAN CHEM SOC (2013) 10:461–470

123

The stock solution of Sc(III) ions (1,000 lg mL-1) was

prepared by heating the required amount of Sc2O3 (Johnson

Matthey, Royston, England) with 10 mL of conc. HNO3

(Merck, Darmstadt, Germany) in a beaker to near dryness,

then adding DDW, and making the volume to 100 mL in a

volumetric flask. The working standard solutions were

prepared daily by stepwise dilution of stock solution. The

pH adjustments were made with 0.01 mol L-1 NaOH or

HCl solution. A 0.1 mol L-1 HCl solution was used as an

eluent (E). Chromogenic reagent (CR) arsenazo-III (Fluka,

Vienna, Austria) solution was prepared by dissolving the

required amount in 0.1 mol L-1 HCl. The glassware used

were soaked in 10 % HNO3 overnight and cleaned

repeatedly with DDW before use.

The certified reference material (CRM) IAEA SL-1

(lake sediment) was obtained from spectroscopic group of

this institute. The mock sea water was prepared by dis-

solving the appropriate amounts of various salts to get the

sea water composition [51] and stored in clean polyethyl-

ene bottle. The tap and ground water samples were col-

lected from Nilore, Islamabad, Pakistan.

Purification of XAD-4 resin

A known weight (5.0 g) of XAD-4 resin was mixed with

50 mL of ethanol in a 100 mL Pyrex glass beaker and

stirred for 2 h at room temperature using an electrical

stirrer (China). The resin was filtered and dried in an oven

at 40 �C, then treated with 50 mL of 2.0 mol L-1 HCl for

30 min and repeatedly washed with DDW till the washing

was free of any traces of acid. The washed resin was dried

in an oven at 100 �C.

Impregnation of XAD-4 resin with HNA

Nalidixic acid impregnated resins were prepared at four

different impregnation ratios by mixing extractant and

resin in the following mass ratios (w/w); 1:1, 2:1, 3:1 and

4:1 in a 100 mL of dichloromethane. A 100 mL of 1 %

HNA solution in dichloromethane was mixed with washed

XAD-4 resin (1 g). Then the mixture was stirred for 2 h at

room temperature. The resin was filtered, washed with

DDW and dried overnight at 50 �C. Similar impregnation

method is reported in the literature for XAD-4 resin with

dibenzoylmethane [52]. The same procedure was repeated

with 2, 3 and 4 % HNA solution in dichloromethane. The

weight of complexing agent impregnated on XAD-4 resin

was determined by the weight difference of XAD-4 resin

before and after impregnation.

Desorption of HNA from XAD-4 resin

A 1.0 g of XAD-4 resin impregnated with HNA was taken

in a 100 mL beaker and added into 50 mL of fresh

dichloromethane and stirred for 15 min. Then, the resin

was filtered and the filtrate was collected in a 500 mL flask.

The resin was stirred with another 50 mL of fresh dichlo-

romethane. The process was continued until the filtrate

gave no absorbance at 259 nm, the characteristic absorp-

tion band of HNA [53]. The filtrate were collected and

diluted to the desired volume with dichloromethane. The

absorption bands of HNA desorbed from XAD-4 resin was

examined in the range of 200–400 nm with 10 mm capped

quartz cell. Dichloromethane was used as blank.

Preconcentration method

The complete cycle of determination of Sc(III) after online

preconcentration in the minicolumn containing XAD-4

resin loaded with HNA by flow injection-spectro-

photometry using arsenazo-III as a chromogenic reagent is

given in Table 1. It consists of three steps i.e. preconcen-

tration, elution and conditioning steps. The FI manifold

used for these steps is shown in Fig. 1.

In step 1 (Fig. 1a), the sample solution (pH 4.5) was

pumped at 11.8 mL min-1 through the minicolumn to

waste keeping the multifunctional valve at load position by

running peristaltic pump 1 (P1). After a suitable precon-

centration time (60 s), the P1 was stopped. In this step,

Sc(III) ions were retained in the minicolumn by forming

Sc(III)–HNA complex.

In step 2 (Fig. 1b), P1 was stopped and the multifunc-

tional valve was changed to inject position. P2 was used for

the propulsion of E (0.1 mol L-1 HCl) and CR (0.05 %

Table 1 Sequence of flow injection on-line preconcentration operations

Figure Steps Flow rate (mL min-1) Valve position Time (s) Medium pumped Operation stage

Pump 1 Pump 2

1a I 11.8 0 Load 60 Sample, pH 4.5 Column loading

1b II 0 3.2 Inject 20 Eluent (HCl, 0.1 mol L-1) and

CR (arsenazo-III 0.05 % in

0.1 mol L-1 HCl)

Column elution

1c III 0 5.9 Load 10 Solution of pH 4.5 Column conditioning

J IRAN CHEM SOC (2013) 10:461–470 463

123

arsenazo-III in 0.1 mol L-1 HCl) solutions at a flow rate of

3.2 mL min-1 for 20 s. The E solution percolated through

minicolumn desorbing the analyte from the solid phase,

mixed with CR and taken to the spectrophotometer, where

absorbance was continuously measured at 640 nm. The

peak height was used for data analysis.

In step 3 (Fig. 1c), the position of eight-channel valve

was changed to load position and the column was con-

ditioned to optimum pH suitable for complexation of

Sc(III) with HNA by passing aqueous solution of pH 4.5

for 10 s at a flow rate of 4.9 mL min-1 by running P2.

The E and CR solutions were recycled during this step

to minimize the wastage of solutions. After the condi-

tioning step the minicolumn is ready for a new precon-

centration cycle.

Pretreatment of water and lake sediment samples

Water

Water and mock sea water samples were stored in plastic

bottles with the addition of concentrated HCl (10 ml per

liter of water). Samples were filtered and adjusted the pH to

4.5. A known quantity of Sc(III) was spiked in it and the

added amount was measured by the proposed procedure.

Lake sediment SL-1 (Standard reference material)

A known amount (1.0 g) of sample was taken into a Teflon

beaker, moistened with water, and mixed with 10 mL of

concentrated HNO3 and 1–2 mL of HF. The mixture was

digested for 1 h on a hot plate, evaporated to near dryness

and then made the solution to 100 mL with pH adjustment

to 4.5. The lake sediment contained iron which was pre-

cipitated as Fe (OH) 3 and was removed by filtering the

solution. Then the appropriate dilution was made and

determined for Sc(III).

Results and discussion

Amount of HNA impregnated on XAD-4 resin

Preliminary studies suggested that there was no uptake of

Sc(III) by virgin XAD-4 and the uptake of Sc(III) by the

impregnated resin was only due to the presence of HNA in

it. The weight of HNA impregnated on XAD-4 resin was

determined by the difference of weight of XAD-4 resin

before and after impregnation. The maximum amount of

impregnated HNA was found at 1:3 resin and HNA mixing

mass ratio as shown in Table 2. The peak absorbance was

also found to be maximum for the column containing this

resin. Therefore, it was selected for further experiments.

Fig. 1 Flow injection manifold for the on-line preconcentration of

Sc(III) ions in a minicolumn containing XAD-4 loaded with HNA,

elution and determination with spectrophotometer using arsenazo-III

as a chromogenic reagent. P1 and P2 Peristaltic pumps, V multifunc-

tional valve, Column = minicolumn, chromogenic reagent solution

(CR) = arsenazo-III, 0.05 % in 0.1 mol L-1 HCl, E = HCl solution

(0.1 mol L-1)

464 J IRAN CHEM SOC (2013) 10:461–470

123

Confirmation of impregnated HNA by UV absorption

spectrum

HNA solution desorbed from XAD-4 resin was examined

in the range of 200–400 nm, and its absorption spectrum

was compared with that of HNA reported already in the

literature [53]. Both absorption spectra have identical

absorption peaks. This fact suggests that the reagent could

be retained without any loss.

Size of column

The effect of length and internal diameter of the column

were studied after preparing six columns i.d. of 0.25, 0.5

and 0.75 cm with the length 3 and 5.5 cm, respectively.

Column length [5.5 cm cannot be studied due to increase

in backpressure in the manifold which caused leakage. The

absorbance of 0.5 9 5.5 cm column shows higher sensi-

tivity than other columns due to limit of the amount of

resin for adsorption and/or sample volume passing through

the column [54]. Thus, the 0.5 9 5.5 cm column was

chosen for further experiments.

Optimization of parameters

The parameter optimization was carried out by using

100 lg L-1 Sc(III) solution at a flow rate of

11.8 mL min-1 for a period of 60 s, 0.1 mol L-1 HCl as E

and 0.05 % arsenazo-III as CR at a flow rate of

3.2 mL min-1 for a period of 20 s. The pH of the sample

was the most important variable to be studied, since the

complexing capacity of the chelating group contained by

the resin depends on the pH due to the presence of proton

acceptors. The influence of the sample pH on the analytical

signal was examined by varying the pH in the range of

1.0–6.0. As can be seen in Fig. 2, the peak absorbance

increased with the increase of pH and reached to a maxi-

mum at pH 4.5 and then decreased with further increase in

pH. The decrease in the absorbance signal at pH [ 4.5

might be due to the formation of Sc (OH)3. On the other

hand, at pH \ 4.5, the chelating capacity of the solid phase

decreased due to the protonation of HNA present in the

resin. Therefore, the sample pH was always adjusted to 4.5

in all the further experimental work.

In order to check the effect of residual Sc(III) (not bound

with HNA) in the column, a washing step was added

between the preconcentration and elution step. This was

done by running the preconditioning step in between step 1

and step 2 of manifold by passing aqueous solution of pH

4.5 as shown in Fig. 1c. The peak height (absorbance)

obtained by adding washing step was compared to the peak

absorbance obtained without washing the column and a

very negligible change in the peak absorbance was

observed. The reason may be the low concentration of

Sc(III) used for preconcentration and/or the negligible void

volume of minicolumn due to good packing of resin.

Therefore, due to negligible effect of washing step on the

peak absorbance, it was eliminated from the preconcen-

tration method. However, washing step can be added to

remove those metal ions from the void volume of column

which might interfere in the determination of Sc(III) ions

with CR solution.

As column condition became different from the one

required for the Sc-HNA complex formation after passing

acidic eluent, therefore to resume the optimum pH, the

effect of conditioning step was checked by passing aqueous

solution of pH 4.5 by running pump 2 at the flow rate of

4.9 ml min-1 after elution step. The conditioning step was

found to increase the peak absorbance considerably. The

reason may be the adjustment of the conditions of column

by aqueous solution of pH 4.5, suitable for the complexa-

tion of Sc(IIII) ions with HNA. Therefore, a conditioning

step was added after the elution step in the whole process.

Hydrochloric acid solution was chosen to displace

Sc(III) from the column due to its non-oxidizing and less

interfering nature. The analyte was desorbed due to the

lowering of the pH caused by the acid which was not

Table 2 Amount of HNA impregnated on Amberlite XAD-4 resin

Resin:extractant mixing

ratio (w/w g) in 100 mL

of dichloromethane

Amount of HNA

impregnated on XAD-4

resin (mg/g of resin)

1:1 271

1:2 284

1:3 290

1:4 287

Fig. 2 Effect of pH of Sc(III) sample solution (100 lg L-1) on the

peak absorbance. Sample flow rate (100 lg L-1 Sc(III)) = 11.8 mL -

min-1, preconcentration time = 60 s, E = HCl solution (0.1 mol

L-1), CR = arsenazo-III, 0.05 % in 0.1 mol L-1 HCl, E and CR flow

rate = 3.2 mL min-1

J IRAN CHEM SOC (2013) 10:461–470 465

123

favored for the formation of the Sc–HNA complex and the

metal returned to the aqueous phase. Since the absorbance

of the complex as well as CR changes with the change of

the pH, the same concentration of HCl was used for E and

CR solution preparation so that after mixing of E and CR

solution, any change in the pH of the final mixture and

hence Schlieren effect should be avoided. Thus, the con-

centration of HCl was studied from 0.005 to 0.2 mol L-1.

The absorbance increased with the increase of acid con-

centration up to 0.1 mol L-1 and after that a decrease in

the absorbance was observed. This behavior is shown in

Fig. 3. For acid concentrations less than 0.1 mol L-1, a

decrease in absorbance signal was observed because the

acid concentration was not sufficient to completely desorb

the analyte from the resin. The decrease in absorbance at

acid concentrations higher than 0.1 mol dm-3 is due to the

residual acidity present in the minicolumn, which causes a

loss of analyte in the early stage of preconcentration [55] as

10 s conditioning step is insufficient to remove the residual

acidity for acid concentration [0.1 mol L-1. In order to

ensure the maximum elution of Sc(III) ions from the mi-

nicolumn, an eluent solution of 0.1 mol L-1 HCl was

selected for further studies.

The sample flow rate is the variable that controls the

amount of material that passes through the minicolumn.

Therefore, the influence of the sample flow rate was inves-

tigated in order to allow the maximum mass transfer from the

liquid to solid phase without the loss of sampling frequency.

The effect of the sample flow rate was studied from 1.8 to

15.2 mL min-1 and the results are shown in Fig. 4. An

increase in the signal was observed at 11.8 mL min-1

sample flow rate and then the signal became constant. Thus, a

Fig. 3 Plot of peak absorbance versus concentration of HCl used as

eluent and CR medium. Sample flow rate (100 lg L-1 Sc(III), pH

4.5) = 11.8 mL min-1, preconcentration time = 60 s, E and CR

flow rate = 3.2 mL min-1

Fig. 4 Effect of sample flow rate on the peak absorbance. pH of

sample solution [Sc(III),100 lg L-1] = 4.5, preconcentration

time = 60 s, E = HCl solution (0.1 mol L-1), CR = arsenazo-III,

0.05 % in 0.1 mol L-1, E and CR flow rate = 3.2 mL min-1

Fig. 5 Peak absorbance as a function of E and CR flow rate. Sample

flow rate [100 lg L-1 Sc(III) pH 4.5] = 11.8 mL min-1, E = HCl

solution (0.1 mol L-1) CR = arsenazo-III, 0.05 % in 0.1 mol L-1

HCl

0.000

0.025

0.050

0.075

0.100

0.00 5.00 10.00 15.00 20.00

Time (sec.)

Abs

Fig. 6 Elution profile at the optimized conditions. Sample flow rate

[100 lg L-1 Sc(III), pH 4.5] = 11.8 mL min-1, preconcentration

time = 60 s, E = HCl solution (0.1 mol L-1), CR = arsenazo-III,

0.05 % in 0.1 mol L-1, E and CR flow rate = 3.2 mL min-1

466 J IRAN CHEM SOC (2013) 10:461–470

123

sample flow rate of 11.8 mL min-1 was selected for further

studies.

As the P2 was used for the flow of E and CR solutions

using the tygon tubes of the same internal diameter for both

the solutions, the effect of flow rate of both the solutions

was studied on the peak absorbance simultaneously.

Experiments were performed employing a 0.1 mol L-1

eluent solution at flow rates between 1.8 and 6.4 mL min-1

as shown in Fig. 5. The peak absorbance increased with the

increase of flow rate and the best results were found at

3.2 mL min-1 and after that the signal was decreased. This

decrease in signal at high flow rate might be due to the

dilution of metal ions in the eluent zone [37] while slower

flow rates cause higher dispersion and thus decrease the

peak absorbance [56]. So, 3.2 mL min-1 flow rate for E

and CR solution was selected for further studies. The elu-

tion profile was found to be better at a flow rate of

3.2 mL min-1 and only 20 s was found to be sufficient for

quantitative elution of metal ions as shown in Fig. 6.

In order to investigate the optimum time for the metal-

CR complex formation, the effect of the varying reaction

coil lengths (45–125 cm) after the confluence point to the

flow through cell of the spectrophotometer was studied.

The results showed that the peak absorbance gradually

decreased as the reaction coil length increased. This can be

attributed to the increased dispersion of the sample zone,

particularly when the reaction rate of complex formation is

fast [57]. Therefore, the minimum possible Teflon tube

length (45 cm) was used between the confluence point and

the flow cell of the spectrophotometer.

The preconcentration time has a remarkable influence on

the sensitivity of the system. Thus, the influence of the

varying preconcentration time on the analytical signal

yielded by 100 lg L-1 Sc(III) solution was studied from

10 to 150 s. The analytical signal increased with the

preconcentration time up to 140 s without increasing the

back pressure in the manifold as shown in Fig. 7. The

signal became constant at preconcentration time [140 s

that might be due to availability of less binding sites of

complexing agent because of the saturation of the mini-

column with the metal [43]. In the present case, 60 s pre-

concentration time was used for parameter optimization,

however, longer preconcentration times can be used for

samples having low metal concentration.

Analytical performance

The proposed methodology was able to produce analytical

fits with good linearity in the range 25–125 lg L-1 when

preconcentration time of 60 s was employed. The linear

equation with regression is as A = 0.0007C ? 0.0004 with

correlation coefficient 0.9996, for n = 15 (no. of readings),

where A is the peak absorbance and C is the concentration

of Sc(III) in lg L-1. All the statistical calculations were

based on average of triplicate readings for each standard

solution in the given range. The detection limit corre-

sponding to 3r of the blank was found to be 1.4 lg L-1. In

such condition a sampling frequency of 40 h-1 was

observed. The preconcentration factors were calculated by

comparing the analytical curve slope obtained from before

and after the preconcentration procedure [58]. Sample loop

of 250 ll was used and calibration curve without precon-

centration was drawn in the range of 1 9 103–

25 9 103 lg L-1 which resulted in the following equation:

Y¼0:00002Cþ0:0003ðR2¼0:9996Þnðnumberof readingsÞ¼18

where A is the peak absorbance and C is the concentration

of Sc(III) in lg L-1.The enrichment factor was calculated

to be 35. Ten replicate determinations of 100 lg L-1

Sc(III) solution gave a mean absorbance of 0.069 with a

relative standard deviation of 1.6 %.

Increasing the preconcentration time to 300 s, the ana-

lytical fit built up in the range 5–25 lg L-1 had the fol-

lowing equation: A = 0.0031C ? 0.0009, with a

correlation coefficient R2 = 0.9996 with n = 15. Follow-

ing the same calculations done in the former situation, the

detection limit was 0.32 lg L-1. In this case the sampling

frequency of 11 h-1 was observed with enrichment factor

of 155. Ten replicate determinations of 20 lg L-1 Sc(III)

solution gave a mean absorbance of 0.063 with a relative

standard deviation of 2.2 %.

The detection limit (0.32 lg L-1) obtained by the pro-

posed method is the lowest among all the spectrophoto-

metric methods e.g.; alizarin red S [12], 8-quinolinol [12],

tiron [13], chlorophosphonazo-III [14], arsenazo-III [15],

bromopyrogallol red [16], 5,7-dichloroquin-8-ol [17],

Fig. 7 Peak absorbance of Sc(III) (100 lg L-1) as a function of

sample preconcentration time

J IRAN CHEM SOC (2013) 10:461–470 467

123

xylenol orange [18], chromazurol S [19], nile blue [20] and

arsenazo [21] whose detection limits lie in the range

(1.8–9.3 lg L-1). Features of the proposed system under

the optimum conditions for the spectrophotometric deter-

mination of Sc(III) are given in Table 3.

Stability of minicolumn

To evaluate the HNA impregnated XAD-4 resin stability,

almost 1,000 loading, elution and preconditioning column

operations were carried out. The sorption capacity of the

resin was reproducible after so many preconcentration–

elution cycles. This showed no leakage of HNA from the

resin.

Interference

The effect of various cations as their chloride or nitrate salts

and anions as their sodium or potassium salts has been

studied on the preconcentration of Sc(III) (100 lg L-1)

using 60 s preconcentration time. The tolerance limits

(±5.0 % variation in the peak absorbance) are given in

Table 4. From the table, it is clear that most of the cations

do not interfere in the determination of Sc(III) by the pro-

posed method. Cations like Fe(III), Fe(II) Ni(II), Cd(II),

Co(II), Mn(II), Zn(II), Pb(II), Al(III) and Cu(II) can be

tolerated up to 1,000 times higher mass ratio of Sc(III).

These metals like Fe(III), Fe(II), Al(III) and Cu (II) interfere

at the same concentration of Sc(III) in most of the reported

spectrophotometric methods e.g. bromopyrogallol red [16],

chromazurol S [19] and arsenazo [21] methods. Metals like

Y (III), Th(IV) and rare earth elements which almost always

occur mixed with scandium [19] can be tolerated up to 20

times higher mass ratio of Sc(III), whereas these metals

interfere at the same mass ratio in the chromazurol S [19]

method and only three- to sevenfold higher mass ratio of

these metals can be tolerated in photometric methods such

as bromopyrogallol red [16], p-nitrochlorophosphonazo

[59] and p-acetylchlorophosphonazo [60]. So the proposed

method is more selective than other reported spectropho-

tometric methods.

It was observed that the anions like I-, Cl-, CO32-,

HCO3-, ClO4

-, ClO3-, SO4

2- and S2O32- can be tolerated

up to 1,000 times higher mass ratio of Sc(III), whereas the

anions like tartrate, citrate, oxalate and fluoride can be

tolerated up to 10 times higher mass ratio which interfered

at the same mass ratio of Sc(III) in most of the reported

spectrophotometric methods e.g.; bromopyrogallol red

[16], chromazurol S [19] and arsenazo [21] methods.

HPO42- interfered severely in the proposed method.

Therefore, the removal of HPO42- is required prior to

determination of Sc(III). Phosphate can be removed by

passing the solution through a bed of sorbent, polymeric

ligand exchanger (PLE). PLE removes phosphate selec-

tively from the solution [61].

Analysis of spiked water samples and certified

reference material (CRM)

In order to assess the applicability of the method to real

samples with different matrices containing varying

Table 3 Performance of the FI-

spectrophotometry system for

on-line preconcentration and

determination of scandium

S. No. Performance parameters Preconcentration time 60 s Preconcentration time 300 s

1 Enrichment factor 35 155

2 Detection limit (lg L-1) 1.4 0.32

3 Precision (n = 10, % RSD) 1.6 2.2

4 Sample throughput (f, h-1) 40 11

5 Sample consumption (mL) 11.8 59.0

6 Reagent consumption (mL) 1.06 1.06

7 Calibration equation (n = 15) A = 0.0007C ? 0.0004

R2 = 0.9994

A = 0.0031C ? 0.0009

R2 = 0.9996

Table 4 Tolerance level of various cations and anions for scandium

(100 lg L-1) recovery

Cations Tolerance

level

(lg mL-1)

Anions Tolerance

level

(lg mL-1)

Na(I), K(I), Ca(II),

Mg(II) Ni(II),

Cd(II), Co(II)

Mn(II), Ba(II),

Zn(II) Be(II), Fe(II),

Al(III) Pb(II)a,

Fe(III)a, Cu(II)a

100 I-, Cl-, CO32-,

HCO3-, ClO4

-

ClO3-, SO4

2-,

S2O32-

CN-

100

Th(IV)a, Y(III)a,

Eu(IV)a U(VI)b2 Br- 50

C4H4O62-,

C6H5O73-

C2O42-, EDTA,

F-

1

HPO42- \0.1

a After adding washing stepb After adding 50 lg mL-1 Na2CO3 as masking agent

468 J IRAN CHEM SOC (2013) 10:461–470

123

amounts of a variety of diverse ions, it was applied to the

separation and recovery of Sc(III) from three different

water samples that were spiked with known amount of

Sc(III) and CRM (IAEA Lake Sediment SL-1) using 300 s

preconcentration time and a washing step of 10 s in order

to eliminate the effect of matrix. Na2CO3 was added in the

Lake Sediment SL-1 to mask the effect of uranium (VI).

The analytical results are shown in Table 5. According to

table the Sc(III) was quantitatively recovered with good

precision.

Conclusion

The present work described a cheap and robust analytical

arrangement consisting of flow injection-spectro-

photometric system with a minicolumn containing XAD-4

resin impregnated with HNA for the preconcentration and

determination of Sc(III) in real samples with simple

matrices like tap water and ground water to complex matrix

of mock sea water and CRM lake sediment IAEA-SL-1.

The proposed system showed simplicity and rapidity

with a good sampling frequency of 40 and 11 h-1 for 60

and 300 s preconcentration times, respectively. The toler-

ance limits for most of the reported interfering elements

were improved in our method. Detection limits of 1.4 and

0.32 lg L-1 and enrichment factors of 35 and 155 were

obtained. These characteristics are very important in lab-

oratories for routine analysis, equipped only for metal

determination by spectrophotometer.

The present study has demonstrated that the active

ingredients of cheap pharmaceutical drugs can be suc-

cessfully used for the preconcentration of metals ions

prior to their determination by UV–visible spectropho-

tometry. This has opened a new class of organic reagents

that can be used as selective complexing agents for

various metal ions. Further research work is required to

explore more drugs to find more selective and specific

complexing reagents for metal ions.

Acknowledgments S. Shahida, one of the authors, is highly grateful

to Higher Education Commission (HEC), Pakistan, for awarding

fellowship for Ph. D studies.

References

1. R.J. Reid, Z. Rengel, F.A. Smith, J. Exp. Bot. 47, 1881 (1996)

2. B.D. Karcher, I.S. Krull, J. Chromatogr. Sci. 25, 472 (1987)

3. N. Daskalova, S. Velichkov, P. Slavova, Spectrochim. Acta Part

B 51, 733 (1996)

4. N. Lihareva, M. Delaloye, Fresenius J Anal. Chem. 375, 314

(1997)

5. S. Cerutti, J.A. Salonia, J.A. Gasquez, R.A. Olsina, L.D. Marti-

nez, J. Anal. At. Spec. 18, 1198 (2003)

6. A. Rivoldini, S. Fadda, J. Anal. At. Spectrom. 9, 519 (1994)

7. P. Robinson, A.T. Townsend, Z. Yu, C. Munker, Geostand

Newslett 23, 31 (1999)

8. D.R. Bryant, A.R. Hodges, Anal. Chem. 44, 405 (1972)

9. S.D. Jadhav, Z.R. Turel, J. Radioanal. Nucl. Chem. 176, 443

(1993)

10. M.Z. Iqbal, M.A. Qadir, J. Radioanal. Nucl. Chem. 145, 189

(1990)

11. P.D. Tzanavaras, D.G. Themelis, Anal. Chim. Acta 588, 1 (2007)

12. A.R. Eberle, M.W. Lerner, Anal. Chem. 27, 1551 (1955)

13. H. Hamaguchi, N. Onuma, R. Kuroda, R. Sugisita, Talanta 9, 563

(1962)

14. V.I. Fadeeva, I.P. Alimarin, Zh. Analit. Khim. 17, 1020 (1962)

15. S.B. Savvin, Talanta 8, 673 (1961)

16. T. Shimizu, Talanta 14, 473 (1967)

17. Y. Nishikawa, K. Hiraki, S. Aida, T. Shigematsu, J. Chem. Soc.

Japan, Pure Chem. Sect. 83, 1264 (1962)

18. S.S. Berman, G.R. Duval, D.S. Russell, Anal. Chem. 35, 1392

(1963)

19. R. Ishida, N. Hasegawa, Bull. Chem. Soc. Jpn. 40, 1153 (1967)

20. L. Zubi, W. Jialin, X. Qihieng, Anal. Sci. 12, 259 (1996)

21. H. Onishi, C.V. Banks, Anal. Chim. Acta 29, 240 (1963)

22. C.I. Park, K.W. Cha, Bull. Korean Chem. Soc. 20, 1409 (1999)

23. A. Bhalotra, B.K. Puri, Anal. Sci. 16, 507 (2000)

24. N. Uehara, T. Tanaka, Y. Shijo, Analyst 123, 2149 (1998)

25. P. B. Stockwell, J. Automat. Chem. 12, 95 (1990)

26. V. V. Kuznetsov, Z. D. Dong, J. Anal. Chem. (Transl. Zh. Anal.

Khim.) 50, 125 (1995)

27. M. Soylak, Y. Akkaya, J. Trace Microprobe Tech. 21, 455 (2003)

28. F.A. Aydin, M. Soylak, Talanta 72, 187 (2007)

29. M. Soylak, L. Elci, Int. J. Environ. Anal. Chem. 66, 51 (1997)

30. A. Uzun, M. Soylak, L. Elc, Talanta 54, 197 (2001)

31. P. Metilda, K. Sanghamitra, J. M. Gladis, G. R. K Naidu, T.

P. Rao, Talanta 65, 192 (2005)

Table 5 Analyses results of spiked water and CRM samples

Water samples Sc added (lg L-1) Sc found (lg L-1) n = 3 ±Deviation (%)

Tap water 10 10.2 ± 2.1 ?2.0

20 20.6 ± 1.5 ?3.0

Well water 10 10.3 ± 2.0 ?3.0

20 21.0 ± 1.4 ?5.0

Sea water 10 10.5 ± 2.2 ?5.0

20 19.1 ± 1.6 -4.5

CRM (Lake sediment) Certified value (lg g-1) Found value (lg g-1), n = 3

SL-1 17 16.7 ± 1.2 -1.76

J IRAN CHEM SOC (2013) 10:461–470 469

123

32. R. Pathak, G.N. Rao, Anal. Chim. Acta 335, 283 (1996)

33. V.K. Jain, A. Handa, S.S. Sait, P. Shrivastav, Y.K. Agrawal,

Anal. Chim. Acta 429, 237 (2001)

34. N. Demirel, M. Merdivan, N. Pirinccioglu, C. Hamamci, Anal.

Chim. Acta 485, 213 (2003)

35. K. Venkatesh, B. Maiti, Sep. Sci. Technol. 39, 1779 (2004)

36. S. Tokalioglu, V. Yilmaz, S. Kartal, Environ. Monit. Assess. 152,

369 (2009)

37. S. Ayata, I. Kaynak, M. Merdivan, Environ. Monit. Assess. 153,

333 (2009)

38. M. Soylak, L. Eici, M. Dogen, J. Trace Microprobe Tech. 19, 329

(2001)

39. A.E. Czeizel, H.T. Sorensen, M. Rockenbauer, J. Olsen, Int.

J. Gynaecol. Obstet. 73, 221 (2001)

40. E.J. Lozano, I. Marques, D. Barron, J.L. Beltran, J. Barbosa,

Anal. Chim. Acta 464, 37 (2002)

41. C.E. Lin, Y.J. Deng, W.S. Liao, S.W. Sun, W.Y. Lin, C.C. Chen,

J. Chromatogr. A 1051, 283 (2004)

42. J. Barbosa, R. Berges, I. Toro, V.S. Nebot, Talanta 44, 1271

(1997)

43. P.B. Issopoulos, Acta Pharm. Jugosl. 39, 267 (1989)

44. X.Q. Jia, L.Y. Li, H. Huang, Fenxi Huaxue 24, 1216 (1996)

45. S.B. Meshkova, Z.M. Topilova, N.A. Nazarenko, A.N. Lit-

vinenko, N.P. Efryushina, J. Anal. Chem. 59, 246 (2004)

46. A. Ali, Y.A. Abbasi, M.H. Khan, M.M. Saeed, Radiochim. Acta

98, 513 (2010)

47. Y. A. Abbasi, A. Ali, M. H. Khan, M. M. Saeed, J. Radioanal.

Nucl. Chem. 292, 277 (2011)

48. S. Shahida, A. Ali, M.H. Khan, M.M. Saeed, Environ. Monit.

Assess. (2012). doi:10.1007/s10661-012-2655-4

49. A. Ali, S. Shahida, M.H. Khan, M.M. Saeed, J. Radioanal. Nucl.

Chem. 288, 735 (2011)

50. S. Shahida, A. Ali, M.H. Khan, M.M. Saeed, J. Radioanal. Nucl.

Chem. 289, 929 (2011)

51. G. Lyman, R.H. Fleming, J. Mar. Res. 3, 134 (1940)

52. H.R. Park, O.H. Park, H.Y. Lee, J.J. Seo, K.M. Bark, Bull.

Korean Chem. Soc. 24, 1618 (2003)

53. E.F. Salim, I.S. Shupe, J. Pharm. Sci. 55, 1289 (1996)

54. J. Klamtet, S. Sanguthai, S. Sriprang, NU Sci. J. 4, 122 (2007)

55. V.A. Lemos, E.M. Gama, Envir. Monit. Assess. 171, 163 (2010)

56. K. Grudpan, S. Laiwraungrath, P. Sooksamiti, Analyst 120, 2107

(1995)

57. Y. Takeshi, I. Hiroya, T. Tatsuhiko, ISIJ Int. 44, 698 (2004)

58. A.S.D. Nezio, M.E. Palomeque, B.B.S. Fernandez, Talanta 63,

405 (2004)

59. C.G. Hsu, Q. Xu, J.M. Pan, Mikrochim. Acta 126, 83 (1997)

60. C.G. Hsu, S.C. Liu, J.M. Pan, Talanta 42, 1905 (1995)

61. D. Zhao, A.K. Sengupta, Water Sci. Technol. 33, 139 (1996)

470 J IRAN CHEM SOC (2013) 10:461–470

123