a new coprecipitation methodology with lutetium hydroxide for preconcentration of heavy metal ions...

Soylak amp Murat Journal of aoaC InternatIonal Vol 97 no 4 2014 1189

A New Coprecipitation Methodology with Lutetium Hydroxide for Preconcentration of Heavy Metal Ions in Herbal Plant SamplesMustafa soylak and Ipek MuratErciyes University Faculty of Science Department of Chemistry 38039 Kayseri Turkey

Received August 26 2012 Accepted by AK October 10 2012Corresponding authorrsquos e-mail msoylakgmailcomDOI 105740jaoacint12-331

RESIDUES AND TRACE ELEMENTS

A new coprecipitation methodology that used lutetium hydroxide as a precipitant for Cu(II) Pb(II) Mn(II) Co(II) Cd(II) Fe(III) and Ni(II) ions in herbal plant and water samples for analysis by atomic absorption spectrometry has been investigated The parameters such as pH amount of lutetium and volume of aqueous sample were optimized for the recovery of these seven metals The effects of concomitant ions on the separation-preconcentration of analytes were also checked The validation of the procedure was checked with addition recovery tests and analysis of Standard Reference Material 1570a-Trace Elements in Spinach Leaves and TMDA-70 fortified lake water Certified Reference Material The LODs for analyte ions were in the range of 17ndash72 microgL The application of the present procedure was successfully performed for the analysis of analyte contents of herbal plant samples from Turkey

The analysis of trace metal contents of food environmental and biological samples is an important area in the analytical chemistry field (1ndash3) because certain trace

metals are generally problematic for the environment (4ndash6) Separation and preconcentration is generally a necessary step for the determination of trace metals in highly saline samples by flame atomic absorption spectrometry (7ndash10) due to their low levels and negative or positive effects of the components of real samples Solvent extraction membrane filtration ion exchange SPE cloud-point extraction and electrodeposition have been used for this purpose (11ndash15)

One of the important separation-preconcentration techniques is coprecipitation It is a simple rapid green technique Accurate and precise results can be obtained with coprecipitation (16ndash20) Organic and inorganic precipitants can be used in the coprecipitation studies for trace metal ions (18 19 21ndash23) Metal hydroxides are most popular for the coprecipitation of metal ions at trace levels due to good trace recoveries and separation of analyte elements

Our working group has also been focused on the use of various metal hydroxides including samarium cerium erbium europium holmium aluminum magnesium dysprosium and praseodymium (21 22 24ndash28) for the enrichment-separation of some transition metals prior to their flame atomic absorption

spectrometric determinations Until now lutetium (Lu) hydroxide was not used for the preconcentration and separation of transition metals The solubility product constant of Lu hydroxide is 1 times 10ndash26 (29) thus it could easily be dissolved by acidic media like other metal hydroxides This is an advantage for the use of metal hydroxides for coprecipitation procedures for preconcentration methods

A new coprecipitation method using Lu hydroxide for the separationenrichment and determination of Cu(II) Pb(II) Mn(II) Co(II) Cd(II) Fe(III) and Ni(II) ions in herbal plant samples from Turkey has been established The analytical parameters for quantitative coprecipitation of metal ions like pH Lu(III) amount and sample volume have been optimized

Experimental

Apparatus

A Perkin-Elmer Model 3110 (Norwalk CT) atomic absorption spectrometer equipped with single-element hollow cathode lamps and a 10 cm air-acetylene burner was used for the determination of analyte metals under the conditions recommended by the manufacturer with an air-acetylene flame A pH meter (pH-900 Model Nel Nel AS Ankara Turkey) was used to measure the pH of the aqueous phase

A Sartorius pH meter (Model PT-10 Sartorius AG Gottingen Germany) was used to measure pH values in the aqueous phase and a centrifuge (ALC PK 120 ALC International Srl Monzese Italy) was also used The reverse osmosis water was obtained from a Human Model RO 180 (Human Corp Seoul Korea) with a conductivity of 1 microS cmndash1

Reagents and Solutions

All chemicals were reagent-grade and all solutions were prepared in distilled-deionized water Stock solutions of analyte elements were prepared from appropriate amounts of nitrate salts of analyte elements as 1000 mgL solutions in 001 M HNO3 and further diluted daily for obtaining reference and working solutions prior to use The standard solutions of analytes used for the calibration procedures were prepared before use by dilution of the stock solution with 1 M HNO3

A 01 solution of Lu2O3 was prepared fresh by dissolving

Lu(III) oxide (Aldrich Milwaukee WI) in small amounts of nitric acid and diluting to 50 mL with water Nitric acid (65) used for preparing of diluted acid solution was supra-pure grade (Merck Darmstadt Germany)

Certified Reference Materials (CRM) such as Standard Reference Material 1570a-Trace Elements in Spinach Leaves

1190 Soylak amp Murat Journal of aoaC InternatIonal Vol 97 no 4 2014

and TMDA-70 fortified lake water were from the National Institute of Standard Technology (NIST Gaithersburg MD) and from the National Water Research Institute Environment Canada (Burlington ON Canada) respectively

Sampling

Herbal plant samples were obtained from local markets in Kayseri Turkey The samples were dried at 110degC for 6 h The dried samples were homogenized using an agate homogenizer and were stored at room temperature in plastic bottles until analysis

Working Model

Lu(III) (10 mg) was added to 15 mL of solution containing 5ndash20 microg of analyte metal ions Then the pH was adjusted with dilute NaOH After 5 min the solution was centrifuged at 3000 rpm for 20 min and the supernatant was removed The precipitate was dissolved with 1 mL of 1 M HNO3 The final volume was made up to 50 mL with reverse osmosis water The levels of analyte metals were determined by flame atomic absorption spectrometry (FAAS)

Applications

An aliquot of 25 mL TMDA-70 fortified lake water CRM or 250 mL of water sample was placed in a beaker The pH was adjusted to 110 by the addition of dilute NaOH to obtain Lu

hydroxide Then the procedure given above was performed The concentration of analytes was determined by flame AAS

NIST 1570a spinach leaves CRM (05 g) and 10 g of herbal plant sample were digested with the mixture of HNO3 and H2O2 according to the literature (28) Then the procedure given in the working model section was applied The analytes were determined with FAAS

Results and Discussion

Effects of pH on the Recoveries

In light of our previous studies on coprecipitation of the trace metals with metal hydroxides quantitative recoveries were generally obtained at pH values higher than 70 (21 22 24ndash26) Lu hydroxide was precipitated at different pH values from model solutions containing 1 mg Lu and a fixed trace amount of other elements between the pH range of 70ndash120 The pH values were adjusted with 0 1 M NaOH solution The results are shown in Figure 1 All analyte ions were quantitatively (gt95) recovered at pH 110 For all further work a pH of 110 was selected

Influences of Amounts of Lu Ion

The amount of Lu ion needed for quantitative recoveries of the analyte on the present coprecipitations was examined experimentally (Figure 2) The influence of the amounts of Lu(III) was investigated between the range of 0ndash18 mg The recovery values of Cu(II) Pb(II) Mn(II) Co(II) Cd(II) Fe(III)

Table 1 Effects of centrifugation speed on the recovery values of analyte ions (n = 3)

Centrifugation speed rpm

Recovery

Cu Co Ni Fe Cd Pb Mn

1000 87 plusmn 3 92 plusmn 1 81 plusmn 1 85 plusmn 2 87 plusmn 3 66 plusmn 0 89 plusmn 1







2

0

20

40

60

80

100

0 04 08 12 16

Amount of Lutetium mg

Reco

very

Cu

Pb

Mn

Co

Cd

Fe

Ni

Figure 2

Figure 2 Influences of amount of Lu on the recoveries of analyte elements by using present coprecipitation system

1

0

20

40

60

80

100

7 8 9 10 11 12

pH

Reco

very

Cu

Pb

Mn

Co

Cd

Fe

Ni

Figure 1

Figure 1 Relations between pH and recoveries of analyte ions (n = 3)


and Ni(II) ions without Lu(III) were not quantitative (lt95) The recoveries of analyte ions were quantitative after 08 mg of Lu was used The optimum amount of Lu(III) was taken as 1 mg in further experiments

Effects of Centrifugation

The effect of centrifugation speed on the analyte recoveries was investigated keeping the other parameters constant (Table 1) The recoveries were quantitative for all analyte ions above a speed of 3000 rpm therefore 3000 rpm was selected as the optimal centrifugation speed

The influence of centrifugation time on the recoveries of Cu(II) Pb(II) Mn(II) Co(II) Cd(II) Fe(III) and Ni(II) ions was investigated in the range between 5ndash30 min The results are given in Table 2 Quantitative recoveries were obtained after 20 min of centrifugation time All further work was carried out at 20 min of centrifugation time

Incubation Time

The influence of incubation time on the formation of the Lu hydroxide precipitate and its influence on the recoveries of analyte ions were also examined under optimal conditions The results are given in Table 3 The analyte ions were quantitatively recovered between a range of 0ndash20 min of incubation time Five minutes was selected as the optimum incubation time in this coprecipitation work

Effect of Sample Volume

The sample volume is one of the important points for obtaining a high preconcentration factor in the enrichmentndashseparation steps (25 26 30ndash39) The effect of the sample volume on the analyte recoveries was investigated in the range of 10ndash1000 mL

under optimal conditions The investigations of the sample volume higher than 50 mL were performed by using a cellulose nitrate membrane filter For that purpose after 5 min the precipitate was collected on a cellulose nitrate membrane filter and then washed with a small volume of the blank solution The membrane loaded with the precipitate was dissolved with 10 mL of concentrated HNO3 and the final volume was made up to 50 mL with reverse osmosis water The results are depicted in Figure 3 The analyte ions were quantitatively (95) recovered in the sample volume range of 10ndash500 mL After 500 mL of sample volume the recoveries of manganese and cobalt ions were not quantitative A preconcentration factor of 100 can be achieved when the final volume is 50 mL

Effect of Concomitant Ions

The possible interferences of alkaline earth alkaline and transition metal ions and a few anions on the recovery of the analyte ions utilizing the present coprecipitation system were

Table 3 Relations between incubation time for Lu hydroxide precipitate and recoveries of analyte ions (n = 3)

Time min

Recovery







Table 2 Effects of centrifugation time (n = 3)

Centrifugation time min

Recovery






25 98 plusmn1 98 plusmn 1 100 plusmn 1 98 plusmn 2 97 plusmn 2 100 plusmn 2 97 plusmn 2


3

0

20

40

60

80

100

0 200 400 600 800 1000Sample volume mL

Reco

very

Cu

Pb

Mn

Co

Cd

Fe

Ni

Figure 3

Figure 3 Relationship between sample volume and recovery (n = 3)


investigated (Table 4) A relative error of less than 5 was considered to be within the range of experimental error

Detection Limits

The LOD defined as the concentration equivalent to three times the SD of the reagent blank (n = 10) and calculated by dividing by the preconcentration factor (100) is shown in Table 5 (40ndash42)

Method Validation

The validation of the present procedure was performed by the analysis of two CRMs (NIST 1570a spinach leaves and TMDA-70 fortified lake water) for analytes The certified and observed values for the CRMs are given in Table 6 for NIST 1570a spinach leaves and in Table 7 for TMDA-70 fortified lake water The results were in good agreement with the certified values of CRMs When the accuracy of the present method is considered together it can be concluded that the proposed method is free from interferences of the various constituents

The validation of the proposed method was evaluated by a standard addition method in a tap water and Urtica dioica herbal plant sample by spiking a known amount of all analytes in three concentration stages The satisfactory results were obtained as shown in Table 8 Good agreement was obtained between the added and recovered content The recovery values calculated for the standard additions were always higher than 95 thus confirming the accuracy of the procedure and the absence of matrix effects

Analysis of the Herbal Plant Samples

The coprecipitation procedure was applied to the determination of analyte ions in some herbal plant samples The results are summarized in Table 9 The concentration of copper in all samples was below the LOD The results obtained

Table 4 The influences of concomitant ions on the recovery of the analyte ions (n = 3)

Ion Concn mgL Added as

Recovery

Fe Cu Ni Mn Pb Cd Co

Na+ 25000 NaCl 100 plusmn 1 97 plusmn 1 99 plusmn 1 100 plusmn 1 101 plusmn 1 96 plusmn 2 95 plusmn 2

Ca2+ 2000 Ca(NO3)24H2O 99 plusmn 2 100 plusmn 1 100 plusmn 1 98 plusmn 1 100 plusmn 1 97 plusmn 2 98 plusmn 1

K+ 5000 KCl 99 plusmn 1 98 plusmn 1 101 plusmn 1 101 plusmn 2 97 plusmn 1 98 plusmn 1 96 plusmn 1

Cl- 25000 NaCl 100 plusmn 1 96 plusmn 1 98 plusmn 1 101 plusmn 2 98 plusmn 1 98 plusmn 2 100 plusmn 2

SO42ndash 3000 Na2SO4 98 plusmn 1 100 plusmn 0 97 plusmn 2 100 plusmn 1 100 plusmn 0 98 plusmn 1 97 plusmn 1

Cr3+ 20 Cr(NO3)39H2O 100 plusmn 1 97 plusmn 1 100 plusmn 0 98 plusmn 1 98 plusmn 1 99 plusmn 1 95 plusmn 1

Mg2+ 1000 Mg(NO3)26H2O 97 plusmn 1 97 plusmn 1 99 plusmn 1 100 plusmn 2 101 plusmn 2 97 plusmn 1 96 plusmn 2

Fe3+ 20 Fe(NO3)39H2O mdash 102 plusmn 1 98 plusmn 1 96 plusmn 0 100 plusmn 2 98 plusmn 1 95 plusmn 1

Cu2+ 20 Cu(NO3)23H2O 98 plusmn 2 mdash 99 plusmn 1 100 plusmn 0 94 plusmn 2 98 plusmn 1 98 plusmn 1

Ni2+ 10 Ni(NO3)26H2O 100 plusmn 1 99 plusmn 1 mdash 97 plusmn 2 95 plusmn 2 100 plusmn 1 103 plusmn 2

Mn2+ 10 Mn(NO3)24H2O 99 plusmn 0 98 plusmn 2 100 plusmn 0 mdash 101 plusmn 1 100 plusmn 0 100 plusmn 0

Pb2+ 20 Pb(NO3)2 96 plusmn 1 98 plusmn 2 100 plusmn 1 98 plusmn 1 mdash 98 plusmn 2 98 plusmn 0

Cd2+ 15 Cd(NO3)24H2O 96 plusmn 1 100 plusmn 0 100 plusmn 1 99 plusmn 1 95 plusmn 1 mdash 96 plusmn 2

Co2+ 10 Co(NO3)26H2O 99 plusmn 1 98 plusmn 0 102 plusmn 1 97 plusmn 1 100 plusmn 0 97 plusmn 2 mdash

Table 7 Levels of analytes in TMDA-70 fortified lake water CRM (n = 3)Analyte Certified value μgL Determined value μgL

Cd 145 142 plusmn 3

Co 285 270 plusmn 26

Cu 399 390 plusmn 15

Fe 368 351 plusmn 19

Pb 443 450 plusmn 23

Mn 302 289 plusmn 2

Ni 328 335 plusmn 33

Table 6 Analysis of NIST 1570a spinach leaves CRM by using the present procedure (n = 3)

Analyte Certified value μgL Determined value μgL

Cd 289 28 plusmn 01

Co 039 BDLa


Mn 759 719 plusmn 04

Ni 214 BDLa BDL = Below the LOD

Table 5 LOD values for analyte elements in the presented coprecipitation system

Analyte Detection limit microgL

Mn 25

Ni 72

Cu 17

Co 16

Pb 45

Fe 72

Cd 19


Table 8 Analysis of real sampled after standard addition method (n = 3)

Analyte Added microg

Tap water from Kayseri Urtica dioica

Found microg Recovery Found microg Recovery

Co 0 BDLa mdash 35 plusmn 08 mdash

10 99 plusmn 09 99 plusmn 2 132 plusmn 07 97 plusmn 1



Cd 0 BDL mdash BDL mdash




Fe 0 38 plusmn 07 mdash 238 plusmn 05 mdash




Ni 0 BDL mdash 68 plusmn 21 mdash




Cu 0 BDL mdash BDL mdash



40 386 plusmn 04 97 plusmn 2 382 plusmn 02 96plusmn1

Mn 0 BDL mdash 164 plusmn 03 mdash




Pb 0 BDL mdash BDL mdash


20 192 plusmn2 1 96 plusmn 2 192 plusmn 00 96 plusmn 0

40 392 plusmn 06 98 plusmn 1 392plusmn 20 98 plusmn 2a BDL = Below the LOD

Table 9 The levels of analyte elements in herbal plant samples from Kayseri Turkey as an application of presented procedure (n = 3)

Sample

Concentration microgga

Co Ni Fe Cu Pb Cd Mn

Coriandrum sativum BDLb BDL 92 plusmn 17 BDL BDL BDL 59 plusmn 02

Pimenta racemosa BDL BDL BDL BDL BDL BDL BDL

Nigella BDL BDL 208 plusmn 04 BDL BDL BDL 94 plusmn 03

Cynara scolymus 44 plusmn 05 57 plusmn 00 711 plusmn 54 BDL 57 plusmn 00 BDL 174 plusmn 01

Ocimum basilicum 39 plusmn 03 49 plusmn 11 1102 plusmn 45 BDL 48 plusmn 00 BDL 237 plusmn 03

Alchemilla BDL BDL 62 plusmn 07 BDL BDL BDL 101 plusmn 02

Malva sylvestris 44 plusmn 03 71 plusmn 14 1162 plusmn 142 BDL 57 plusmn 05 20 plusmn 01 276 plusmn 02a Mean plusmn SDb BDL = Below the LOD


for trace elements in analyzed food samples were acceptable for human consumption

Conclusions

The present work describes a simple economic fast and accurate procedure for the determination of trace amounts of metal ions in herbal plant and water samples from Turkey It combines FAAS with separationndashenrichment of Cu(II) Pb(II) Mn(II) Co(II) Cd(II) Fe(III) and Ni(II) ions by coprecipitation using Lu hydroxide The method could be successfully used for the analysis of other foods agricultural products and geological matrixes after successful method validation

Acknowledgments

Mustafa Soylak thanks King Saud University for their Visiting Professor Program

References

(1) Wang Q Chang X Li D Hu R Li Z amp He Q (2011) J Hazard Mater 186 1076ndash1081 httpdxdoiorg101016jjhazmat201011107

(2) Soylak M Elci L amp Dogan M (1995) Fresen J Anal Chem 351 308ndash310 httpdxdoiorg101007BF00321654

(3) Karak D Banerjee A Sahana A Guha S Lohar S Adhikary SS amp Das D (2011) J Hazard Mater 188 274ndash280 httpdxdoiorg101016jjhazmat201101110

(4) Soylak M amp Turkoglu O (1999) J Trace Microprobe Tech 17 209ndash217

(5) Gasparik J Venglarcik J Slamecka J Kropil R Smehyl P amp Kopecky J (2012) J Environ Sci Health A Tox Hazard Subst Environ Eng 47 1267ndash1271 httpdxdoiorg101080109345292012672127

(6) Narin I Soylak M Kayakirilmaz K Elci L amp Dogan M (2002) Anal Lett 35 1437ndash1452 httpdxdoiorg101081AL-120006679

(7) Soylak M amp Tuzen M (2006) J Hazard Mater 137 1496ndash1501 httpdxdoiorg101016jjhazmat200604027

(8) El-Shahawi MS Al-Saidi HM Bashammakh AS Al-Sibaai AA amp Abdelfadeel MA (2011) Talanta 84 175ndash179 httpdxdoiorg101016jtalanta201012039

(9) Duran C Gundogdu A Bulut VN Soylak M Elci L Senturk HB amp Tufekci M (2007) J HazardMater 146 347ndash355 httpdxdoiorg101016jjhazmat200612029

(10) Zhou Y Jin Q Zhu T amp Akama Y (2011) J Hazard Mater 187 303ndash310 httpdxdoiorg101016jjhazmat201101025

(11) Ghaedi M Shokrollahi A Niknam K Niknam E Najibi A amp Soylak M (2009) J Hazard Mater 168 1022ndash1027 httpdxdoiorg101016jjhazmat200902130

(12) Soylak M Akkaya Y amp Elci L (2003) Trace Elem Electrolytes 20 16ndash22 httpdxdoiorg105414TEP20016

(13) Fan C-H Zhang Y Zhang Y-C Li J amp Chefetz B (2010) Spectrosc Spect Anal 30 2345ndash2349

(14) Chang QY Zhang JW Du X Ma JJ amp Li JC (2010) Front Environ Sci Eng China 4 187ndash195 httpdxdoiorg101007s11783-010-0030-7

(15) Minhas FT Solangi IB Memon S amp Bhanger MI (2010) Separ Sci Technol 45 1448ndash1455 httpdxdoiorg10108001496391003652791

(16) Saracoglu S Soylak M amp Elci L (2011) Trace Elem Electroly 18 129ndash133

(17) Aydin FA amp Soylak M (2007) Talanta 73 134ndash141 httpdxdoiorg101016jtalanta200703007

(18) Soylak M Ozcan B amp Elci L (2004) Kuwait J Sci Eng 31 47ndash59

(19) Jiang J Liang D amp Zhong Q (2011) Hydrometallurgy 106 165ndash169 httpdxdoiorg101016jhydromet201012009

(20) Araki Y Kagaya S Sakai K Matano Y Yamamoto K Okubo T amp Tohda K (2008) J Health Sci 54 682ndash685 httpdxdoiorg101248jhs54682

(21) Saracoglu S Soylak M amp Elci L (2003) Talanta 59 287ndash293 httpdxdoiorg101016S0039-9140(02)00501-5

(22) Soylak M Saracoglu S Divrikli U amp Elci L (2005) Talanta 66 1098ndash1102 httpdxdoiorg101016jtalanta200501030

(23) Saracoglu S Soylak M Peker DSK Elci L dos Santos WNL Lemos VA amp Ferreira SLC (2006) Anal Chim Acta 575 133ndash137 httpdxdoiorg101016jaca200605055

(24) Soylak M amp Aydin A (2012) J Iranian Chem Soc 9 263ndash267 httpdxdoiorg101007s13738-011-0020-0

(25) Peker DSK Turkoglu O amp Soylak M (2007) J Hazard Mater 143 555ndash560 httpdxdoiorg101016jjhazmat200609075

(26) Tuzen M Citak D Mendil D amp Soylak M (2009) Talanta 78 52ndash56 httpdxdoiorg101016jtalanta200810035

(27) Saracoglu S Soylak M Cabuk D Topalak Z amp Karagozlu Y (2012) J AOAC Int 95 892ndash896 httpdxdoiorg105740jaoacint11-304

(28) Soylak M amp Unsal YE (2011) Environ Monit Assess 181 577ndash586 httpdxdoiorg101007s10661-010-1852-2

(29) httpwwwnoveduruanotesreferctprhtm (accessed August 10 2012)

(30) Dobrowolski R amp Otto M (2010) Adsorption 16 279ndash286 httpdxdoiorg101007s10450-010-9240-3

(31) Soylak M Narin I Elci L amp Dogan M (2002) Fresen Environ Bull 11 132ndash136

(32) Li Z Tang Q Katsumi T Tang X Inui T amp Imaizumi S (2010) Desalination 264 70ndash77 httpdxdoiorg101016jdesal201007006

(33) Soylak M Divrikli U Elci L amp Dogan M (1998) Kuwait J Sci Eng 25 389ndash396

(34) Karaoglu MH Zor S amp Ugurlu M (2010) Chem Eng J 158 98ndash106 httpdxdoiorg101016jcej201002047

(35) Li Y Yue Q-Y amp Gao B-Y (2010) Applied Clay Sci 48 481ndash484 httpdxdoiorg101016jclay201002010

(36) Rao RAK amp Rehman F (2010) J Hazard Mater 181 405ndash412 httpdxdoiorg101016jjhazmat201005025

(37) Baig A Kazi TG Shah AQ Kandhro GA Afridi HI Khan S Kolachi NF Wadhwa SK amp Shah F (2011) J AOAC Int 94 293ndash299

(38) Baig JA Kazi TG Shah AQ Arain MB Afridi HI Khan S Kandhro GA Naeemullah K amp Soomro AS (2010) Food Chem Toxicol 48 3051ndash3057 httpdxdoiorg101016jfct201007043

(39) Soylak M Sahin U amp Elci L (1996) Anal Chim Acta 322 111ndash115 httpdxdoiorg1010160003-2670(95)00603-6

(40) Baytak S Kenduzler E Turker AR amp Nuray G (2008) J Hazard Mater 153 975ndash983 httpdxdoiorg101016jjhazmat200709049

(41) Akl MAA Kenawy IMM amp Lasheen RR (2004) Microchem J 78 143ndash156 httpdxdoiorg101016jmicroc200403019

(42) Song J Oh H Kong H amp Jang J (2011) J Hazard Mater 187 311ndash317 httpdxdoiorg101016jjhazmat201101026


and TMDA-70 fortified lake water were from the National Institute of Standard Technology (NIST Gaithersburg MD) and from the National Water Research Institute Environment Canada (Burlington ON Canada) respectively

Sampling

Herbal plant samples were obtained from local markets in Kayseri Turkey The samples were dried at 110degC for 6 h The dried samples were homogenized using an agate homogenizer and were stored at room temperature in plastic bottles until analysis

Working Model

Lu(III) (10 mg) was added to 15 mL of solution containing 5ndash20 microg of analyte metal ions Then the pH was adjusted with dilute NaOH After 5 min the solution was centrifuged at 3000 rpm for 20 min and the supernatant was removed The precipitate was dissolved with 1 mL of 1 M HNO3 The final volume was made up to 50 mL with reverse osmosis water The levels of analyte metals were determined by flame atomic absorption spectrometry (FAAS)

Applications

An aliquot of 25 mL TMDA-70 fortified lake water CRM or 250 mL of water sample was placed in a beaker The pH was adjusted to 110 by the addition of dilute NaOH to obtain Lu

hydroxide Then the procedure given above was performed The concentration of analytes was determined by flame AAS

NIST 1570a spinach leaves CRM (05 g) and 10 g of herbal plant sample were digested with the mixture of HNO3 and H2O2 according to the literature (28) Then the procedure given in the working model section was applied The analytes were determined with FAAS

Results and Discussion

Effects of pH on the Recoveries

In light of our previous studies on coprecipitation of the trace metals with metal hydroxides quantitative recoveries were generally obtained at pH values higher than 70 (21 22 24ndash26) Lu hydroxide was precipitated at different pH values from model solutions containing 1 mg Lu and a fixed trace amount of other elements between the pH range of 70ndash120 The pH values were adjusted with 0 1 M NaOH solution The results are shown in Figure 1 All analyte ions were quantitatively (gt95) recovered at pH 110 For all further work a pH of 110 was selected

Influences of Amounts of Lu Ion

The amount of Lu ion needed for quantitative recoveries of the analyte on the present coprecipitations was examined experimentally (Figure 2) The influence of the amounts of Lu(III) was investigated between the range of 0ndash18 mg The recovery values of Cu(II) Pb(II) Mn(II) Co(II) Cd(II) Fe(III)

Table 1 Effects of centrifugation speed on the recovery values of analyte ions (n = 3)

Centrifugation speed rpm

Recovery









2

0

20

40

60

80

100

0 04 08 12 16

Amount of Lutetium mg

Reco

very

Cu

Pb

Mn

Co

Cd

Fe

Ni

Figure 2

Figure 2 Influences of amount of Lu on the recoveries of analyte elements by using present coprecipitation system

1

0

20

40

60

80

100

7 8 9 10 11 12

pH

Reco

very

Cu

Pb

Mn

Co

Cd

Fe

Ni

Figure 1

Figure 1 Relations between pH and recoveries of analyte ions (n = 3)






Incubation Time








Time min

Recovery









Recovery








3

0

20

40

60

80

100

0 200 400 600 800 1000Sample volume mL

Reco

very

Cu

Pb

Mn

Co

Cd

Fe

Ni

Figure 3




Detection Limits


Method Validation







Recovery

















Cd 145 142 plusmn 3





Mn 302 289 plusmn 2




Cd 289 28 plusmn 01

Co 039 BDLa






Mn 25

Ni 72

Cu 17

Co 16

Pb 45

Fe 72

Cd 19



































Sample












Conclusions


Acknowledgments


References
















































Incubation Time








Time min

Recovery









Recovery








3

0

20

40

60

80

100

0 200 400 600 800 1000Sample volume mL

Reco

very

Cu

Pb

Mn

Co

Cd

Fe

Ni

Figure 3




Detection Limits


Method Validation







Recovery

















Cd 145 142 plusmn 3





Mn 302 289 plusmn 2




Cd 289 28 plusmn 01

Co 039 BDLa






Mn 25

Ni 72

Cu 17

Co 16

Pb 45

Fe 72

Cd 19



































Sample












Conclusions


Acknowledgments


References













































Detection Limits


Method Validation







Recovery

















Cd 145 142 plusmn 3





Mn 302 289 plusmn 2




Cd 289 28 plusmn 01

Co 039 BDLa






Mn 25

Ni 72

Cu 17

Co 16

Pb 45

Fe 72

Cd 19



































Sample












Conclusions


Acknowledgments


References













































































Sample












Conclusions


Acknowledgments


References













































Conclusions


Acknowledgments


References











































a new coprecipitation methodology with lutetium hydroxide for preconcentration of heavy metal ions...

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