Journal of Saudi Chemical Society (2012) 16, 451–459

King Saud University

Journal of Saudi Chemical Society

www.ksu.edu.sawww.sciencedirect.com

ORIGINAL ARTICLE

Study of the solid phase extraction and spectrophotometric

determination of nickel using 5-(40-chlorophenylazo)-6-

hydroxypyrimidine-2,4-dione in environmental samples

Alaa S. Amina,*, Amirah S. AL-Attas

b

a Chemistry Department, Faculty of Science, Benha University, Benha, Egyptb Chemistry Department, King Abdul Aziz University, Girls College of Education, Saudi Arabia

Received 7 December 2010; accepted 21 February 2011

Available online 5 March 2011

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KEYWORDS

Pyrimidine azo dyes;

Nickel determination;

Spectrophotometry;

Solid phase extraction;

Environmental analysis

Corresponding author. Ad

ent of Medical Science, Umm

rabia. Tel.: +966 596269644

-mail address: asamin2005@

19-6103 ª 2011 King Saud

sevier B.V.

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dress: Fa

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; fax: +2

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BY-NC-N

Abstract A rapid, sensitive and selective method for the determination of nickel based on the rapid

reaction of nickel(II) with 5-(40-chlorophenylazo)-6-hydroxypyrimidine-2,4-dione (CPAHPD) and

the solid phase extraction of the Ni(II)–CPAHPD complex with C18 membrane disks has been

developed. In the presence of pH 6.8 buffer solution and cetylpyridinium bromide (CPB) medium,

CPAHPD reacts with nickel to form a red complex of a molar ratio of 1:1 (nickel to CPAHPD).

This complex was enriched by solid phase extraction (SPE) with C18 membrane disks. An enrich-

ment factor of 100 was obtained by elution of the complex from the disks with the minimal amount

of isopentyl alcohol. The molar absorptivity and Sandell sensitivity of the complex was

3.11 · 105 L mol�1 cm�1 and 0.0189 ng cm�2, respectively at 549 nm in the measured solution.

Beer’s law was obeyed in the range of 0.01–0.37 lg mL�1, while that obtained by Ringbom plot

was in the range of 0.025–0.35 lg mL�1. The detection and quantification limits were calculated

culty of Community, Depart-

a University, Makkah, Saudi

0 133222568.

com (A.S. Amin).

y. Production and hosting by

Saud University.

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D license.

452 A.S. Amin, A.S. AL-Attas

and found to be 0.003 and 0.01 lg mL�1. The proposed method was applied to the determination of

nickel in water, food, biological and soil samples with good results.

ª 2011 King Saud University. Production and hosting by Elsevier B.V.

Open access under CC BY-NC-ND license.

1. Introduction

The determination of heavy metals in environmental samplessuch as water and biological samples is a task for analyticalchemists frequently asked by environmentalists, for the evalu-

ation and phenomena interpretation of aquatic systems. In re-cent years, the toxicity and the effect of trace elements onhuman health and the environment are receiving increasing

attention in pollution and nutritional studies. Nickel was longthought to be essential to plants and some domestic animals(Wang, 1991), but not considered to be a metal of biological

importance until 1975, when Zerner discovered that ureasewas a nickel enzyme (Zerner, 1991; Thauer, 2001). It is knownthat inhalation of nickel and its compounds can lead to seriousproblems, including nasopharynx, lung and dermatological

diseases and malignant tumors (Kalyakina et al., 2003;Kristiansen et al., 2000). So, separation of toxic Ni(II) is of in-tense current interest in research and environmental cleanup.

The traditional preconcentration and separation methods formetal ions are liquid–liquid extraction, coprecipitation, andion-exchange, etc. These methods often require large amounts

of high purity organic solvents, some of which are harmful tohealth and cause environmental problems (Liu et al., 2004).Nowadays, the SPE is being widely utilized for preconcentra-tion or separation of metals due to the following advantages.

These include (Liu et al., 2005): (1) higher enrichment factors;(2) absence of emulsion; (3) safety with respect to hazardoussamples; (4) minimal costs due to low consumption of re-

agents; (5) flexibility; (6) ease of automation.Nickel is one of the essential micronutrients for plants, ani-

mals, and humans, but is toxic at elevated concentrations

(Krstic et al., 2007; Soylak, 2002). Compared with other tran-sition metals, nickel is a moderately toxic element (Soylak andDogan, 1996; Amini et al., 2009). For example, nickel can

cause a skin disorder known as nickel-eczema (Soylak andDogan, 1996; Amini et al., 2009; Saraji and Yousefi, 2009).Therefore, the accurate and sensitive determination of nickelin environmental samples is very important.

The biological monitoring of trace amounts of nickel hasreceived considerable attention (Akesson and Skervfing,1985; Easton et al., 1994), because excessive exposure to cer-

tain nickel compounds in biological tissues and fluids may re-sult in genotoxicity or carcinogenesis. Many analyticalmethods such as neutron activation analysis (Byrne and

Krasovec, 1988), inductively coupled plasma mass spectrome-try (Ponce de Leon et al., 2002), atomic absorption spectrom-etry (Wang and Hansen, 2001; Narin et al., 2000), atomic

emission spectrometry (Barnett, 1987), flame atomic absorp-tion spectrometry (Ghaedi et al., 2005, 2008a,b; Soylaket al., 1999, 2007, 2010; Soylak and Elci, 2000; Yebra et al.,2008; Mohammadi et al., 2010; Dadfarnia et al., 2010), modi-

fied activated carbons (Ghaedi et al., 2008a,b) and spectropho-tometry (Vicente et al., 2002) have been developed for thedetermination of nickel. The first two methods have disadvan-

tages in terms of cost and instruments in routine analysis.These methods generally require sample pretreatment and

infrastructure backup and are therefore, not very convenientfor routine analysis of large number of environmental samples.

However, the spectrophotometric method still has theadvantages of simplicity and of not requiring expensive orcomplicated test equipment. This has led to the development

of a wide variety of spectrophotometric methods for the deter-mination of nickel (Fan et al., 1998; Ma et al., 2001; Luciaet al., 1999; Fan and Zhu, 1998; Zhao et al., 1994; Ishizukiet al., 1993; Barreto et al., 2010; Sarma et al., 2008; Antunes

et al., 2009). Routine spectrophotometric methods are oftennot sensitive enough to determine low concentrations of nickelion in environmental samples, i.e. nickel concentrations less

than the lg L�1 level. Consequently, a preconcentration stepis usually required. SPE is an attractive technique because ofits notable advantages (Garg et al., 1999; Hu et al., 2002;

Haddad et al., 1999). The presented paper, based on the colorreaction of CPAHPD with nickel and the SPE of the coloredcomplex with C18 disks, describes the development of a highly

rapid, sensitive and selective method for the determination ofnickel in water, food, biological and soil samples.

2. Experimental

2.1. Apparatus

A Perkin–Elmer Lambda 12 UV–visible spectrophotometerwith a 10 mm quartz cell was used for all spectral measure-

ments. The extraction was performed on Waters SPE Device(that can prepare 20 samples simultaneously), and ZorbaxC18 membrane disks [47 mm (diameter), 0.5 mm (thickness),

8.0 lm, 50 mg] (Agilent Technologies, USA) were used. A Per-kin–Elmer atomic absorption spectrometry model A Analyst300 was used for all AAS measurements. An Orion research

model 601 A/digital ionalyzer pH meter was used for checkingthe pH of solutions.

2.2. Reagent

All chemicals used were of analytical grade unless otherwisestated. All the solutions were prepared with ultra-pure water

obtained from a Milli-Q50 SP Reagent Water System(Millipore Corporation, USA). High purity isopentyl alcohol(Fisher Corporation, USA) was used. 5-(40-Chloropheny-

lazo)-6-hydroxypyrimidine-2,4-dione used in the present inves-tigation was prepared according to the procedure describedpreviously (Amin and Mohammed, 2001). An accurate weightof CPAHPD was dissolved in 100 mL of absolute ethanol to

prepare 1 · 10�3 M solution.A stock standard solution of nickel 1 · 10�3 M, was pre-

pared from nickel sulphate hexahydrate (Aldrich product)

and standardized gravimetrically with dimethylglyoxime(Vogel, 1964). Working solutions were prepared by appropri-ate dilution with de-ionized distilled water. A hexamine–

hydrochloric acid buffer solution, 0.5 M with a pH 6.8 con-taining 0.1 M sodium thiosulfate and 0.2 M sodium fluoride,

Study of the solid phase extraction and spectrophotometric determination of nickel 453

was used. CPB (Fluka product) solution (2.0% (m/v)) was pre-

pared by dissolving CPB with water.

2.3. General procedure

To a standard or sample solution containing no more than1.85 lg of Ni(II) in a 250 mL measuring flask, 15 mL of0.5 M hexamine–hydrochloric acid buffer solution with pH

6.8, 5.0 mL of 1 · 10�3 M CPAHPD solution and 4.0 mL of2.0% CPB (m/v) solution were added. The mixture was dilutedto 250 mL with water and mixed well. After 5.0 min, the

solution was passed through the C18 disks at a flow rate of50 mL min�1. After the enrichment, the retained complexwas eluted from the disks with 5.0 mL of isopentyl alcohol

at a flow rate of 5.0 mL min�1. The absorbance of the eluentwas measured in a 10 mm cell at 549 nm against a reagentblank prepared in a similar way without nickel.

0

0.2

0.4

0.6

0.8

1

1.2

Abs

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2.4. Procedure for food samples

The analytical procedure was used for nickel determination in

several natural samples such as starch, sugar, black tea leaves,tobacco and rice flour. These samples were homogenized anddried overnight at 70 �C, and were kept in dry ambient. A

dry-ashing sample preparation was carried out for a samplemass of 1.0 g, which was decomposed at 500 �C for 60 min, fol-lowed by a treatment with 20 mL concentrated nitric acid anda second step of heating for 45 min. The solution was boiled

almost to dryness. This was cooled and then 10 mL of waterwas added to dissolve the salts. The solution was transferredto a 25 mL standard flask, 1.0 mL of 9.0% (w/v) thiourea solu-

tion and 2.0 mL of 2.0% (w/v) sodium fluoride solution wereadded to prevent the interference of Al3+, Fe3+ Co2+,Pd2+, Cu2+, and Zn2+. Then the experimental general proce-

dure was followed to complete the determination.

340 380 420 460 500 540 580 620 660 700

Wavelength (nm)

Figure 1 Absorption spectra for (A) 10�3 M CPAHPD (. . ...)

and (B) its complex with 0.2 lg mL�1 Ni(II) (___) at the optimum

reaction conditions.

0.8

1

1.2

e

2.5. Procedure for human hair sample

An accurately weighed 0.20 g of Human hair sample wasplaced in the Teflon high-pressure microwave acid digestionbomb (Fei Yue Analytical Instrument Factory, Shanghai,

China). 2.5 mL of concentrated nitric acid and 2.5 mL of30% (v/v) hydrogen peroxide were added. The bombs weresealed tightly and then positioned in the carousel of the micro-

wave oven. The system was operated at full power for 6.0 min.The digest was evaporated to near dryness. The residue wasdissolved with 1.0% of HCl (v/v), and the nickel contents were

analyzed according to general procedure described above.

0

0.2

0.4

0.6

2 3 4 5 6 7 8 9 10pH

Abs

orba

nc

Figure 2 Effect of pH on the absorbance of 0.2 lg mL�1 Ni(II)

complexed with 10�3 M CAPHPD under the optimum reaction

conditions.

2.6. Soil sample pretreatment

Homogenized soil sample 2.0 g was weighed accurately and ina 200 mL beaker was digested in the presence of an oxidizingagent, following the Jacson method (Jacson, 1965) then

10 mL concentrated HNO3 and 2.0 mL of 70% HClO4 (v/v)was added and heated for 1 h. The content of beaker wasfiltered through a Whatman No. 40 filter paper into a

250 mL calibrated flask and its pH was adjusted to desiredvalue and diluted to mark with de-ionized water. In all of realand synthetic sample amount of Ni(II) ion was found by stan-

dard addition method.

2.7. Procedure for water samples

The samples (5.0 L) were acidified with hydrochloric acid,filtered with a 0.45 lm filter, heated and evaporated to

250 mL. The nickel contents were analyzed according togeneral procedure described above. A standard method usingthe above general procedure and AAS has been used as a

reference method.

3. Results and discussion

3.1. Absorption spectra

The absorption spectra of CPAHPD and its Ni(II) complex inisopentyl alcohol medium are represented in Fig. 1. Theabsorption peaks of CPAHPD and its complex are located

at 423 nm and 549 nm, respectively.

454 A.S. Amin, A.S. AL-Attas

3.2. Effect of buffer

Different types of buffers were examined (borate, acetate, hex-amine, phosphate, thiel and universal buffers). Results show

that the optimal pH for the reaction of Ni(II) with CPAHPDwas slightly acidic medium. A hexamine–hydrochloric acidbuffer solution was found to be the optimal one. Moreover,

the optimum pH value for complexation was pH from 5.8 to7.8 (Fig. 2). The pH 6.8 is recommended to control pH, asthe use of 12–18 mL buffer solution per 250 mL of final solu-tion was found to give a maximum and constant absorbance.

The use of 15 mL of buffer solution is recommended. Theuse of basic medium, cause decomposition of the complexand formation of nickel hydroxide which has a high solubility

product prevent the complexation and preconcentration pro-cess. The buffer solution containing a 0.08–0.15 M of sodiumthiosulfate and 0.15–0.25 M of sodium fluoride can increase

the selectivity of this system [without sodium thiosulfate andsodium fluoride in the buffer solution, the tolerance limits offoreign ions were 0.7 mg for Cu(II), Zn(II); 0.85 mg for

Fe(III), Pd(II). However, the tolerance limits of foreign ionsreached 0.22 mg for Fe(III); 0.03 mg for Cu(II), Zn(II);0.035 mg for Pd(II), when sodium thiosulfate and sodium fluo-ride existed in the buffer solution]. So 0.1 mol L�1 of sodium

thiosulfate and 0.2 M of sodium fluoride in buffer are recom-mended. The influence of sodium thiosulfate and sodium fluo-ride on absorbance of nickel solution and its extracted complex

increase the stability constant of the complex with respect toligand.

3.3. Effect of surfactants

The Ni(II)–CPAHPD complex has a poor solubility in watersolution. It needs to add a suitable amount of surfactants to

enhance the solubility of the complex. Experiments showedthat all the non-ionic and anionic surfactants have no effectto enhance the solubility, whereas the cationic surfactants have

a good effect on the solubility of the complex formed, indicat-ing that the nickel complex has an ionic nature. In addition to

0

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1

1.2

0 1 2 3 4 5 6 7CPB volume (mL)

Abs

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Figure 3 Effect of 2.0% CPB on the complexation of

0.2 lg mL�1 Ni(II) using 10�3 M CPAHDP.

enhancing the solubility, in the cationic surfactants medium,

the sensitivity of the Ni(II)–CPAHPD complex has increasedmarkedly too. The effect of four nonionic {Triton X-100,Tween-80, Tween-20 and Emulsified–OP}, three anionic {so-dium lauryl sulphate (SLS), sodium dodecyl sulfonate (SDS)

and sodium dodecyl benzenesulfonate} and five cationic{tetradecyltrimethyl ammonium bromide (TDTAB), tricetylm-ethyllammonium bromide (CTAB), cetylpyridinium bromide

(CPB), benzyldimethyl tetradecylammonium chloride (zephir-amine), and cetylpyridinium chloride (CPC)} were studied tochoose the most favorable one which gave higher solubility

and sensitivity. CPB and CTAB surfactants improve the solu-bility and sensitivity. The results showed that CPB was the bestand a most probable additive and the use of 3.0–5.0 mL of

2.0% CPB gives a constant and maximum absorbance valuefor the studied complex (Fig. 3). Accordingly, 4.0 mL CPBsolution was recommended.

3.4. Effect of CPAHPD concentration

For up to 1.85 lg of Ni(II), different volumes of 1 · 10�3 M

CPAHPD were used to choose the optimum reagent concen-tration for complexation process. The use of about 4.0–6.0 mL of 1 · 10�3 M CPAHPD solution has been found to

be sufficient for a complete reaction. Accordingly, 5.0 mL of1 · 10�3 M CPAHPD solution was added in all further mea-surements (Fig. 4), for complete complex formation. Higherconcentrations of CPAHPD decrease the complexation due

to dissociation of the formed complex.

3.5. Stability of the chromogenic system

After mixing the components, the absorbance reached its max-imum within 5.0 min at room temperature and remained stable

for 9.0 h in aqueous solution. The complex was stable at least24 h, after it was extracted into the isopentyl alcohol medium.

3.6. Solid phase extraction

Both the enrichment and the elution were carried out on aWaters SPE device (Amin, 2009; Liu et al., 2005). The flow rate

0

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0.4

0.6

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1

1.2

0 2 4 6 8 10 12CPAHPD volume (mL)

Abs

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Figure 4 Effect of 10�3 M CPAHPD concentration on the

absorbance of 0.2 lg mL�1 Ni(II) at the optimum conditions.

Table 1 Analytical characteristics of the proposed methods.

Parameter Before

preconcentration

After

preconcentration

pH 6.8 6.8

kmax (nm) 543 549

Study of the solid phase extraction and spectrophotometric determination of nickel 455

was set to 50 mL min�1 for enrichment and 5.0 mL min�1 for

elution. Some experiments were carried out to investigate theretention of CPAHPD and its Ni(II) complex on the disks.The CPAHPD and its Ni(II) complex can be retained on thedisks quantitatively when they pass the disks as aqueous solu-

tion. The capacity of the disks for CPAHPD was 32 mg andfor its Ni(II)-complex 19 mg in a 250 mL of solution usingboth of the batch and column methods. The disks have ade-

quate capacity to enrich the Ni(II)–CPAHPD complex andthe excessive CPAHPD.

In choosing the proper eluent to retained CPAHPD and

its Ni(II) complex, various organic solvents were studied.The effect of various organic solvents was in the followingsequence: isopentyl alcohol > acetonitrile > dioxane > ace-

tone > ethanol > methanol. So isopentyl alcohol was selectedas the eluent. The experiment shows that it is easier to elute theretained CPAHPD and its Ni(II) complex in reverse directionthan in forward direction, so it is necessary to upturn the disks

for the elution. 5.0 mL of isopentyl alcohol was a sufficientamount to elute the CPAHPD and its Ni(II) complex fromdisks at a flow rate of 5 mL min�1. The volume of 5.0 mL elu-

ent was selected.

3.7. Nature of the complex

The stoichiometry of the complex was established at the opti-mum conditions described above using the molar ratio andcontinuous variation methods. The plot of absorbance versus

the molar ratio of CPAHPD to Ni(II), obtained by varyingthe CPAHPD concentration, showed inflection at molar ratio1.0, indicating the presence of one CPAHPD molecule in the

complex formed (Fig. 5). Moreover, Jobs method (Job, 1936)showed a ratio of CPAHPD to Ni(II) = 1.0. Consequently,the results indicated that the stoichiometric ratio was (1:1)

[Ni(II):CPAHPD]. The shape of the resulting curves indicatesthat the complex is labile. Consequently, a large excess ofreagent must be always used (upto the optimum concentration

estimated above under Section 3.4) to enhance the formationof the complex. The conditional formation constant (log K),calculated using Harvey and Manning equation (Harvey andManning, 1950):

0

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1.2

1.6

2

2.4

0 0.4 0.8 1.2 1.6 2 2.4 2.8 3.2 3.6 4Molar ratio

Abs

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nce

Figure 5 Molar ratio for Ni(II) complexed with CPAHPD.

Kn ¼ ðA=AmÞ=ð1� A=AmÞnþ1CRn2

where Kn is the formation constat, CR is the reagent concentra-tion, A is the absorbance of CR, Am is the maximum absor-bance, and n is the stoichiometric ratio applying the data

obtained from the above two methods, was found to be 7.14,whereas the true constant (Amin et al., 1997) was 7.20. Theformation constant for CPAHPD was found to be 4.37 at

the same experimental conditions indicating that the highcomplexing ability to nickel.

3.8. Calibration curve and sensitivity

The calibration curve shows that Beer’s law is obeyed in theconcentration range of 0.01–0.37 lg mL�1. For more accurate

analysis, Ringbom optimum concentration ranges (Ringbom,1938) were calculated and found to be 0.025–0.35 lg mL�1.The linear regression equation obtained was:

A ¼ 5:28Cðlg mL�1Þ � 0:022; ðr ¼ 0:9995Þ:

Characteristics performance of method is presented inTable 1, The molar absorptivity was calculated to be3.11 · 105 L mol�1 cm�1 at 549 nm. The detection and quanti-

fication limits were also calculated as the standard deviationsof the absorbance measurements of 13 blank solution. The lim-its of detection (K= 3) and of quantification (K = 10) of the

method (IUPAC, 1978) were found to be 0.003 and0.01 lg mL�1, according to the IUPAC definitions (C1 =KSo/s), where C1 is the limit of detection, So is the standard er-

ror of blank, s is the slope of the standard curve and K is theconstant related to the confidence interval. The relative stan-dard deviation at a concentration level of 0.2 lg Ni(II) per mil-liliter (11 repeat determination) was 1.32%.

Stability (h) 9.0 24

Beer’s conc. range (lg mL�1) 0.1–36.8 0.01–0.37

Ringbom optimum

range (lg mL�1)

0.3–33.4 0.025–0.035

Detection limits (lg mL�1) 0.029 0.003

Quantification limits (lg mL�1) 0.1 0.01

Molar absorptivity

(L mol�1 cm�1)

3.06 · 104 3.11 · 105

Sandell sensitivity (ng cm�2) 1.85 0.0189

Regression equationa

Slope 0.259 5.28

RSD % of slope 0.0075 0.0067

Intercept +0.07 �0.022Correlation coefficient 0.9985 0.9995

RSD (%) 1.95 1. 23

Range of error (%) ±1.35 ±0.78

Calculated t-values (2.57)b 1.28 0.78

Calculated F-test (5.05)b 2.74 2.05

a A= a+ bC, where C is the concentration in lg mL�1.b Values in parentheses are the theoretical values for t- and

F-values at 95% confidence limits and five degrees of freedom.

Table 2 Comparison of the sensitivity for spectrophotometric determination of Ni(II).

Reagent kmax

(nm)

e · 10�4 L

(mol�1 cm�1)

Medium References

5-(6-Methoxy-2-benzothiazoleazo)-8-aminoquinoline 623 12.80 0.5% CTAB Zhao et al. (1999)

2-[2-(5-Methylbenzothiazolyl)azo]-5-dimethyl aminobenzoic acid 640 13.20 0.48% SDS Fan et al. (1998)

1-(2-Pyridylazo)-2-naphthol-6-sulfonic acid 570 5.60 Extr. CHCl3 Ohshita et al. (1982)

Dimethyl glyoxime 445 1.50 Bromine water Marczenko (1976)

3-(4-Methoxyphenyl)-2-mercaptopropenoic acid 415 1.95 Isoamyl alcohol Izquierdo and Carrasco (1984)

2-(2-Benzothiazolylazo)-5-dimethyl aminobenzoic acid 640 12.00 28% Methanol Furukawa (1982)

N,N-Bis(3-methylsalicylidene)-o-phenylenediamine 430 9.50 2.0% Methanol Fakharia et al. (2005)

p-Acetylarsenazo 630 6.50 Aqueous Zhao et al. (1994)

Benzothiaxolyldiazaoaminoazobenzene 550 19.60 0.8% OP Zhao et al. (1997)

5,17-Bis(quinolyl-8-azo)-25,26,27,28-tetrahydroxy 580 12.80 2.0% DMF Hu et al. (2004)

2-[2-(5-Methylbenzothiazolyl)azo]-5-dimethylaminobenzoic acid 640 13.20 Aqueous pH 6.5, SDS Ma et al. (2001)

2-[2-(6-Methylbenzothiazolyl)azo]-5-

(N-ethyl-N-sulfomethyl)aminobenzoic acid;

620 8.22 Aqueous pH 5.6, SDS Hu et al., (2003)

2-(2-Quinolylazo)-5-diethylaminoaniline 590 13.80 pH 6.0, SDS Lee and Choi (2000)

2-[2-(4-Methylquinolyl)azo]-5-diethylaminophenol 574 12.40 pH 9.0, CHCl3 Fan et al., (1998)

1-(2-Pyridylazo)-2-naphtol-6-sulfonic acid 570 5.60 pH 5–10, CHCl3 Zhao et al. (1994)

Ammonium pyrolydinedithiocarbamate 340 – Tween 80 Macit et al. (2000)

4-Benzyl-1-piperazineglyoxime 267 2.25 CCl4, pH 6–9 Kumar et al. (2004a,b)

Salicylaldehyde 3-oxobutanoylhydrazone 405 30.25 Aqueous, pH 6 Li et al. (2002)

o-Carboxylbenzenediazo-aminoazobenzene 540 33.00 Aqueous, pH 10 Kumar et al. (2004a,b)

Dibromo-p-methyl-carboxyazo 625 1.04 Aqueous Singh et al. (1979)

Benzyl dioxime 562 6.86 SDS Ghaedi (2007)

4-Methyl-8-quinolinol 450 8.09 Chloroform Suresh et al. (2008)

2-(2-Quinolinylazo)-5-dimethylaminoaniline 590 13.20 Isopentyl alcohol Hu et al. (2004)

5-(40-Chlorophenylazo)-6-hydroxypyrimidine-2,4-dione 549 31.10 pH 6.8, CPC This work

Table 3 Tolerance limits in the determination of 0.2 lg of

Ni(II) with CPAHPD (relative error ± 5.0%).

Foreign ions Tolerance limit

(lg mL�1)

Na+, K+, Li+, Cl�, ClO�4 , CH3COO� 21,000

Cetrate, thiourea, PO3�4 ;SO2�

4 ; SiO2�3 17,500

Ca2+, Mg2+, Sr2+, Ba2+, NO�3 , tartrate 14,000

Mn2+, Ce4+, SnO2�3 , Ti4+, Bi3+, F� 11,500

WO2�4 ;MoO2�

4 ;CrO24 9000

Cr3+, Ru3+, Br� 7500

Ir4+, Rh3+, I� 6000

OsO2�5 ; SeO2�

3 ;TeO2�3 4500

Hg2+, Sb3+,CN�, SCN� 3500

Be2+, Fe2+, Cd2+ 2250

Pb2+, , Ru3+, Bi3+ 1500

Gd3+, Sc3+ 1000

Al3+, La3+, Sm3+ 750

Th4+, UO42� 500

Fe3+ 220

Co2+, Pd2+ 35

Cu2+, Zn2+ 30

456 A.S. Amin, A.S. AL-Attas

The sensitivity expressed as molar absorptivity of theproposed method is compared with those of publishedspectrophotometric methods (Table 2). Although the spectro-

photometric method depending on the complexation with achromogenic reagent o-carboxylbenzenediazoaminoazoben-zene gave a higher sensitivity (3.3 · 105 L mol�1 cm�1) (Kumaret al., 2004a,b) compared with the proposed method, it suf-

fered from positive interferences of Cu(II), Fe(II), Co(II) and

Zn(II) at all concentration levels. The higher sensitivity ofthe proposed method is notable, greater even than that ofthe SPE (Hu et al., 2004) that used 2-(2-quinolinylazo)-5-dim-

ethylaminoaniline. Also, the proposed method is more sensi-tive than other methods that based on spectrophotometry(Table 2).

3.9. Interferences

A systematic study of the effect of potentially interfering spe-

cies on the nickel determination was undertaken. This studywas carried out by adding a known amount of foreign speciesto nickel solution of 0.2 lg mL�1. The tolerance limit was ta-

ken as ±5.0% change in absorbance. The results are listedin Table 3, showing that most common ions do not interferewith the determination suggesting the highly selectivity of theproposed method. Only some elements, Al3+, Fe3+ Co2+,

Pd2+, Cu2+, and Zn2+ interfered, which can be eliminatedby masking with sodium thiosulfate and sodium fluoridesolution.

3.10. Analytical applications

The proposed method has been successfully applied to thedetermination of nickel in food, plants, soil, biological andwater samples. The analytical results for the examined food,

plant and biological samples were compared with those foundby the atomic absorption spectrometry (AAS) method (Wangand Hansen, 2001), and the results shown in Table 4 were inagreement with AAS results. For the analysis of natural water

Table 5 Analytical results for the determination of trace nickel in natural water samples (5.0 L) with the proposed and AAS methods.

Samples Added (lg L�1) Founda (lg L�1)

Proposed ± SD t-Testb F-Valueb AAS ± SD

Benha lake water 0.00 1.750 ± 0.03 1.31 2.68 1.74 ± 0.05

0.50 2.242 ± 0.06 1.65 3.29 2.23 ± 0.07

1.00 2.760 ± 0.04 1.08 2.46 2.74 ± 0.06

5.00 6.745 ± 0.05 1.22 2.53 6.75 ± 0.07

River Nile water 0.00 1.335 ± 0.05 1.34 2.74 1.34 ± 0.08

0.50 1.840 ± 0.04 1.87 3.47 1.84 ± 0.06

1.00 2.345 ± 0.06 1.44 2.79 2.35 ± 0.08

5.00 6.320 ± 0.05 1.11 2.51 6.34 ± 0.06

Tap water 0.00 0.47 ± 0.03 0.98 2.31 0.46 ± 0.05

0.50 0.96 ± 0.05 1.32 2.71 0.97 ± 0.07

1.00 1.48 ± 0.02 1.15 2.59 1.47 ± 0.03

5.00 5.46 ± 0.04 1.45 2.83 5.47 ± 0.07

Makkah well water 0.00 1.82 ± 0.05 1.47 2.85 1.83 ± 0.07

0.5 2.33 ± 0.05 1.32 2.70 2.34 ±0.08

1.0 2.82 ± 0.03 1.56 3.08 2.83 ±0.05

5.0 6.52 ± 0.04 1.20 2.66 6.84 ± 0.06

Soil sample (lg g�1) Added (lg g�1)0.0 0.41 ± 0.04 0.95 2.05 0.41 ± 0.05

0.5 0.91 ± 0.06 1.14 2.37 0.92 ± 0.08

1.0 1.41 ± 0.03 1.22 2.49 1.41 ± 0.04

5.0 5.41 ± 0.02 1.48 2.89 5.41 ± 0.04

a Average of six determinations.b Theoretical values for t- and F-values at 95% confidence level for five degrees of freedom are 2.57 and 5.05, respectively.

Table 4 Analytical results of Ni(II) in plant, food and biological samples (lg g�1).

Samples Founda (lg g�1)

Proposed method t-Testb F-Valueb AAS method

Balsam pear leaves 0.51 ± 0.02 1.41 2.77 0.52 ± 0.03

Celery leaves 0.47 ± 0.03 1.25 2.49 0.48 ± 0.04

Spinach leaves 0.62 ± 0.03 1.08 2.14 0.63 ± 0.05

Black tea leaves 0.34 ± 0.02 1.22 2.38 0.34 ± 0.04

Rice flour 0.65 ± 0.02 1.11 2.15 0.64 ± 0.05

Tobacco 0.40 ± 0.04 1.38 2.61 0.39 ± 0.06

Sugar 0.61 ± 0.03 1.57 2.96 0.61 ± 0.05

Starch 0.43 ± 0.01 1.34 2.49 0.43 ± 0.03

Human hair 0.82 ± 0.04 1.61 3.13 0.81 ± 0.06

The value following ‘‘±’’ is the standard deviation.a The value following ‘‘±’’ is the standard deviation.b Theoretical values for t- and F- values at 95% confidence level for five degrees of freedom are 2.57 and 5.05, respectively.

Study of the solid phase extraction and spectrophotometric determination of nickel 457

(5.0 L) and soil samples, the standard addition method wasused, as recorded in Table 5.

In all cases, the results were compared with the AAS meth-od (Wang and Hansen, 2001). The performance of the pro-

posed method was assessed by calculation of the t-value (foraccuracy) and F-test (for precision) compared with AAS meth-od. The mean values were obtained in a Student’s t- and F-tests

at 95% confidence limits for five degrees of freedom (Millerand Miller, 2005). The results showed that the calculated val-ues (Tables 4 and 5) did not exceed the theoretical values.

Therefore, there is no significant difference between the pro-posed and the reference method, indicating that the developedmethod is as accurate and precise as the reference method(Wang and Hansen, 2001).

4. Conclusion

In this study, a highly sensitive reagent CPAHPD for nickel

determination was used. By SPE with C18 disks, an enrich-ment factor of 100 was achieved (Amin, 2009). The experi-ments showed that the molar absorptivity after SPE of

the Ni(II)–CPAHPD–CPB complex reaches 3.11 · 105 Lmol�1 cm�1 in the measured solution. The detection and quan-tification limits reached 0.003 and 0.01 lg mL�1 in the original

samples, and low concentrations of nickel in samples can bedetermined with good results. The consumption of organicsolvents in this method is much lower than that in the

liquid–liquid extraction method. By using a Waters SPEdevice, 20 samples can be prepared simultaneously. This

458 A.S. Amin, A.S. AL-Attas

method is a rapid means of simultaneously preparing large

amounts of sample.

References

Akesson, B., Skervfing, S., 1985. Exposure in welding of high nickel

alloy. Inter. Arch. Occup. Environ. Health 56, 111–117.

Amin, A.S., 2009. Utilization of solid phase spectrophotometry for the

determination of trace amounts of copper using 5-(2-benzothiaz-

olylazo)-8-hydroxyquinoline. Chem. Pap. 63, 625–634.

Amin, A.S., Mohammed, T.Y., 2001. Simultaneous spectrophotomet-

ric determination of thorium and rare earth metals with pyrimidine

azo dyes and cetylpyridinium chloride. Talanta 54, 611–620.

Amin, A.S., Moustafa, M.M., Issa, R.M., 1997. A rapid, selective

spectrophotometric method for the determination of Ce(III)

using some bisazophenyl-b-diketone derivatives. Talanta 44, 311–

316.

Amini, M., Younesi, H., Bahramifar, N., 2009. Biosorption of

nickel(II) from aqueous solution by Aspergillus niger: response

surface methodology and isotherm study. Chemosphere 75, 1483–

1491.

Antunes, P.A., Bannach, G., Chierice, G.O., Cavalheiro, E.T.G., 2009.

Direct and simultaneous spectrophotometric determination of

Ni(II) and Co(II) using diethanoldithiocarbamate as complexing

agent. Ecl. Quım. 34, 7–13.

Barnett, N.W., 1987. Determination of lead and nickel in animal bone

by microwave-induced plasma atomic emission spectrometry with

sample introduction by electrothermal vaporization. Anal. Chim.

Acta 198, 309–314.

Barreto, W.J., Barreto, S.R.G., Scarminio, I.S., Ishikawa, D.N.,

Proenca, M.F.S.M.V.B., 2010. Determination of Ni(II) in metal

alloys by spectrophotometry UV–vis using dopasemiquinone.

Quim. Nova 33, 109–113.

Byrne, A.R., Krasovec, I., 1988. Trace determination of nickel (and

cobalt) in biological reference materials by radiochemical neutron

activation analysis. Fresenius’ Z. Anal. Chem. 332, 666–668.

Dadfarnia, S., Shabani, A.M.H., Bidabadi, M.S., Jafari, A.A., 2010. A

novel ionic liquid/micro-volume back extraction procedure com-

bined with flame atomic absorption spectrometry for determination

of trace nickel in samples of nutritional interest. J. Hazard. Mater.

173, 534–538.

Easton, D., Peto, J., Morgan, L.G., 1994. Respiratory cancer mortality

in Welsh nickel refiners: which nickel compounds are responsible.

In: Nieboer, E., Nriagu, J.O. (Eds.), Nickel and human health.

John Wiley and Sons, Inc., New York, p. 603.

Fakharia, A.R., Khorramia, A.R., Naeimib, H., 2005. Synthesis and

analytical application of a novel tetradentate N2O2 Schiff base as a

chromogenic reagent for determination of nickel in some natural

food samples. Talanta 66, 813–817.

Fan, X.Z., Zhu, C.H., Zhang, G.F., 1998. Synthesis of 2-[2-(5-

methylbenzo-thiazolyl)azo]-5-dimethylaminobenzoic acid and its

application to the spectrophotometric determination of nickel.

Analyst 123, 109–112.

Fan, X.Z., Zhu, C.H., 1998. Syntheses of three new benzoic acid-type

thiazolylazo reagents and their application to spectrophotometric

determination of microamounts of nickel. Microchem. J. 59, 284–

293.

Furukawa, M., 1982. Syntheses and spectrophotometric studies of 2-

(2-thiazolylazo)- and 2-(2-benzothiazolylazo)-5-dimethylaminoben-

zoic acids as analytical reagents: determination of nickel. Anal.

Chim. Acta 140, 281–289.

Garg, B.S., Sharma, R.K., Bhojak, N., Mittal, S., 1999. Chelating

resins and their applications in the analysis of trace metal ions.

Microchem. J. 61, 94–114.

Ghaedi, M., 2007. Selective and sensitized spectrophotometric deter-

mination of trace amounts of Ni(II) ion using a-benzyl dioxime in

surfactant media. Spectrochim. Acta A 66, 295–301.

Ghaedi, M., Shokrollahi, A., Kianfar, A.H., Mirsadeghi, A.S.,

Pourfarokhi, A., Soylak, M., 2008a. The determination of some

heavy metals in food samples by flame atomic absorption

spectrometry after their separation-preconcentration on bis salicyl

aldehyde, 1,3 propan diimine (BSPDI) loaded on activated carbon.

J. Hazard. Mater. 154, 128–134.

Ghaedi, M., Fathi, M.R., Marahel, F., Ahmadi, F., 2005. Simulta-

neous preconcentration and determination of copper, nickel, cobalt

and lead ions content by flame atomic absorption spectrometry.

Fresenius Environ. Bull. 14, 1158–1163.

Ghaedi, M., Ahmadi, F., Tavakoli, Z., Montazerozohori, M., Khan-

mohammadi, A., Soylak, M., 2008b. Three modified activated

carbons by different ligands for the solid phase extraction of copper

and lead. J. Hazard. Mater. 152, 1248–1255.

Haddad, P.R., Doble, P., Macka, M., 1999. Developments in sample

preparation and separation techniques for the determination of

inorganic ions by ion chromatography and capillary electrophore-

sis. J. Chromatogr. A 856, 145–153.

Harvey, A.E., Manning, D.L., 1950. J. Am. Chem. Soc. 71, 4450–

4488.

Hu, Q., Yang, G., Huang, Z., Yin, A., 2004. Study on solid phase

extraction and spectrophotometric determination of nickel in

waters and biological samples. Bull. Kor. Chem. Soc. 25, 545–

548.

Hu, Q.F., Yang, G.Y., Huang, Z.J., Yin, J.Y., 2003. Determination of

nickel with 2-(2-quinolylazo)-5-diethylaminoaniline as a chromo-

genic reagent. Anal. Sci. 19, 1449–1452.

Hu, Q.F., Yang, G.Y., Yin, J.Y., 2002. Determination of trace lead,

cadmium and mercury by on-line column enrichment followed by

RP-HPLC as metal-tetra-(4-bromophenyl)-porphyrin chelates.

Talanta 57, 751–756.

Ishizuki, T., Tsuzuki, M., Yuchi, A., Ozawa, T., Wada, H., Nakagawa,

G., 1993. Synthesis of 2-[2-(4-methylquinolyl)azo]-5-diethylamino-

phenol and its use for the spectrophotometric determination of

nickel. Anal. Chim. Acta 272, 161–167.

IUPAC, 1978. Nomenclature, symbols, units and their usage in

spectrochemical analysis–II. Data interpretation analytical chem-

istry division. Spectrochim. Acta B, 33, 241–245.

Izquierdo, A., Carrasco, J., 1984. Selective spectrophotometric deter-

mination of nickel in hydrogenated greases, steels and solders by

solvent extraction with 3-(4-methoxyphenyl)-2-mercaptopropenoic

acid. Analyst 109, 605–609.

Jacson, M.L., 1965. Soil chemical analysis. Prentice Hall, Englowed

Cliffs, NJ, 326.

Job, P., 1936. In Advanced Physicochemical Experiments, Ann.

Chem., vol. 16, second ed., Oliner and Boyd, Edinburgh, UK, p.

54, 1964.

Kalyakina, O.P., Kononova, O.N., Kachin, S.V., Kholmogorov, A.G.,

2003. Sorption preconcentration and determination of nickel in

wastes of heat power industry by diffuse reflection spectroscopy.

Bull. Kor. Chem. Soc. 24, 173–178.

Kristiansen, J., Christensen, J.M., Henriksen, T., Nielsen, N.H.,

Menne, T., 2000. Determination of nickel in fingernails and

forearm skin (stratum corneum). Anal. Chim. Acta 403, 265–

272.

Krstic, B., Stankovic, D., Igic, R., Nikolic, N., 2007. The potential of

different plant species for nickel accumulation. Biotechnol. Equip.

21, 431–436.

Kumar, S.K., Rao, P.S., Krishnaiah, L., Jayaraj, B., Chiranjeevi, P.,

2004a. Determination of nickel in alloys and plant leaves with

salicylaldehyde 3-oxobutanoylhydrazone by spectrophotometry.

Anal. Sci. 20, 951–953.

Kumar, S.K., Swaroop, L.B., Rao, P.S., Chiranjeevi, P., 2004b.

Spectrophotometric determination of nickel using a new chromo-

genic reagent in plant leaves. Inter. J. Environ. Stud. 61, 719–726.

Lee, S.K., Choi, H.S., 2000. DFT studies for the substituent effect on

the diels-alder reaction of 1,4-diaza-1,3-butadienes. J. Kor. Chem.

Soc. 44, 207–212.

Study of the solid phase extraction and spectrophotometric determination of nickel 459

Li, Z., Pan, J., Tang, J., 2002. Determination of nickel in food by

spectrophotometry with o-carboxylbenzenediazo-aminoazoben-

zene. Anal. Lett. 35, 167–183.

Liu, Y., Chang, X., Wang, S., 2004. Solid-phase extraction and

preconcentration of cadmium(II) in aqueous solution with Cd(II)-

imprinted resin (poly-Cd(II)-DAAB-VP) packed columns. Anal.

Chim. Acta 519, 173–179.

Liu, Y., Chang, X., Yang, D., Guo, Y., Meng, S., 2005. Highly

selective determination of inorganic mercury(II) after preconcen-

tration with Hg(II)-imprinted diazoaminobenzene–vinylpyridine

copolymers. Anal. Chim. Acta 538, 85–91.

Lucia, H.S., Avila, T.M.C., Cunha, A.I., 1999. Solvent extraction-

spectrophotometric determination of nickel(II) in natural waters

using di-2-pyridyl ketone benzoylhydrazone. Spect. Lett. 32, 257–

271.

Macit, M., Bati, H., Bati, B., 2000. Synthesis of 4-benzyl-1-piper-

azineglyoxime and its use in the spectrophotometric determination

of nickel. Turk. J. Chem. 24, 81–89.

Marczenko, Z., 1976. Spectrophotometric determination of elements.

Horwood, Chichester, pp. 370.

Ma, Q.L., Su, M.H., Wang, Z.H., Nie, L.H., Liang, S.C., Ma, H.M.,

2001. Determination of nickel by a new chromogenic azoca-

lix[4]arene. Anal. Chim. Acta 439, 73–79.

Miller, J.N., Miller, J.C., 2005. Statistics and Chemometrics for

Analytical Chemistry, fifth ed. Prentice Hall, England.

Mohammadi, S.Z., Afzali, D., Baghelani, Y.M., 2010. Flame atomic

absorption spectrometry determination of trace amounts of nickel

ions in water samples after ligandless ultrasound-assisted emulsi-

fication microextraction. Anal. Sci. 26, 973–977.

Narin, I., Soylak, M., Elci, L., Dogan, M., 2000. Determination of

trace metal ions by AAS in natural water samples after precon-

centration of pyrocatechol violet complexes on an activated carbon

column. Talanta 52, 1041–1046.

Ohshita, K., Wada, H., Nakagawa, G., 1982. Sulfonated 1-(2-

pyridylazo)-2-naphthols and 2-(2-pyridylazo)-1-naphthols as spec-

trophotometric reagents: determination of nickel. Anal. Chim.

Acta 140, 291–300.

Ponce de Leon, C.A., Montes Bayon, M., Caruso, J.A., 2002. Trace

element determination in vitamin E using ICP-MS. Anal. Bioanal.

Chem. 374, 230–234.

Ringbom, A., 1938. ¨Uber die Genauigkeit der colorimetrischen

Analysenmethoden I.Fresenius’. J. Anal. Chem. 115, 332–343.

Saraji, M., Yousefi, H., 2009. Solid-phase extraction of Ni(II) by an

ion imprinted polymer from water samples. J. Hazard. Mater. 167,

1152–1157.

Sarma, L.S., Kumar, J.R., Reddy, K.J., Thriveni, T., Reddy, A.V.,

2008. Development of highly sensitive extractive spectrophotomet-

ric determination of nickel(II) in medicinal leaves, soil, industrial

effluents and standard alloy samples using pyridoxal-4-phenyl-3-

thiosemicarbazone. J. Trace Elem. Med. Biol. 22, 285–295.

Singh, R.B., Garg, B.S., Singh, R.P., 1979. Oximes as spectrophoto-

metric reagents – a review. Talanta 26, 425–444.

Soylak, M., 2002. Nickel determination in samples with high salt

content by atomic absorption spectrometry after enrichment/

separation on diaion HP-20. Quim. Anal. 20, 175–179.

Soylak, M., Dogan, M., 1996. Separation and enrichment of zinc,

iron, copper, cadmium, cobalt and nickel from urine with

amberlite XAD-16 resin, Trace Elem. Trace Elem. Electrol. 13,

130–132.

Soylak, M., Elci, L., 2000. Solid phase extraction of trace metal ions in

drinking water samples from kayseri-turkey. J. Trace Microprobe

Tech. 18, 397–403.

Soylak, M., Elci, L., Dogan, M., 1999. Flame atomic absorption

spectrometric determination of cadmium, cobalt, copper, lead

and nickel in chemical grade potassium salts after an enrichment

and separation procedure. J. Trace Microprobe Tech. 17, 149–

156.

Soylak, M., Tuzen, M., Souza, A.S., Korn, M.G.A., Ferreira, S.L.C.,

2007. Optimization of microwave assisted digestion procedure for

the determination of zinc, copper and nickel in tea samples

employing flame atomic absorption spectrometry. J. Hazard.

Mater. 149, 264–268.

Soylak, M., Unsal, Y.E., Aydin, A., Kizil, N., 2010. Membrane

filtration of nickel(II) on cellulose acetate filters for its preconcen-

tration, separation, and flame atomic absorption spectrometric

determination. Clean 38, 91–95.

Suresh, T., Kumar, S.S., Kottureshawara, N.M., Revanasidappa, M.,

Suresh, S.K., 2008. Spectrophotometric study of nitrogen base

adducts of nickel(II)-4-methyl-8-quinolinate. Eur. J. Chem. 5, 404–

408.

Thauer, R.K., 2001. Enzymology. Nickel to the fore. Science 293,

1264–1265.

Vicente, S., Maniasso, N., Queiroz, Z.F., Zagatto, E.A.G., 2002.

Spectrophotometric flow-injection determination of nickel in bio-

logical materials. Talanta 57, 475–480.

Vogel, A.I. 1964. A Text book of Quantitative Inorganic Analysis’’,

third ed. Longmans, London. p. 526.

Wang, J., Hansen, E.H., 2001. Coupling sequential injection on-line

preconcentration by means of a renewable microcolumn with

ion-exchange beads with detection by electrothermal atomic

absorption spectrometry: comparing the performance of eluting

the loaded beads with transporting them directly into the

graphite tube, as demonstrated for the determination of nickel

in environmental and biological samples. Anal. Chim. Acta 435,

331–342.

Wang, K., 1991. Nickel Trace Elements in Life Science. Chinese

Measurement Press, Peking, China, pp. 278–280.

Yebra, M.C., Cancela, S., Cespon, R.M., 2008. Automatic determi-

nation of nickel in foods by flame atomic absorption spectrometry.

Food Chem. 108, 774–778.

Zerner, B., 1991. Recent advances in the chemistry of an old enzyme,

urease. Bioorg. Chem. 19, 116–131.

Zhao, S.L., Xia, X.Q., Hu, Q., 1999. Complex formation of the new

reagent 5-(6-methoxy-2-benzothiazoleazo)-8-aminoquinoline with

cobalt and nickel for their sensitive spectrophotometric detection.

Anal. Chim. Acta 391, 365–371.

Zhao, S.L., Xia, X.Q., Kong, X., Liu, T., 1997. Highly sensitive

colour-reaction of nickel with a new chromogenic reagent ben-

zothiaxolyldiazoaminoazo-benzene and its application. Talanta 45,

13–17.

Zhao, S.L., Xia, X.Q., Ma, H.R., Xi, H.J., 1994. Spectrophotometric

determination of nickel with p-acetylarsenazo. Talanta 41, 1353–

1356.