Chromate in different matrices

Transcription

1 Chromate in different matrices Applica 2014 Dr. Katinka Ruth Product Specialist Competence Center Ion Chromatography Metrohm International Headquarters 1

2 Chromium an ubiquitous pollutant and health concern Cr VI = toxic, allergen, cancerogen Cr VI better water soluble than Cr III Easily passes cell membranes But sensibilization caused by Cr III Arises from Cr VI reduction inside cells Forms complexes with proteins er99_news/chrom_fig1.htm 2

3 Different matrices Hexavalent chromium - Cr VI Ground water, potable water, waste water Toys Leather extracts Ore leaches 3

4 Water & environmental Cr VI in drinking water, waste water, 1 Metrosep A Supp Cr VI 5.16 Reagent water fortified with 5 ppb ppb 540 nm 10 mm LiOH mm Li 2 SO 4 ; PCR 0.8 g Diphenylcarbazide + 10 % MeOH + 1N H 2 SO 4 ; 0.8 ml/min; 2 ml loop size US EPA method Drinking and Waste Water SW846 method 7199 Soil Analysis mv s s s s s s s min 4

5 Method: UV/VIS system with PCR Instrument configuration 5

6 Water & environmental Method parameters Column Metrosep A Supp 5-100/4.0 eluent 12.8 mmol/l Na 2 CO mmol/l NaHCO 3 PCR reagent 2 mmol/l1,5-diphenylcarbazide Flow rate column 0.4 ml/min Flow rate PCR 0.2 ml/min Inj. Volume 1000 µl Temperature column 45 C Temperature PCR 45 C Light source VIS (W) Measuring duration 1000 ms Wavelength 538 ± 21 nm Reference 650 ± 21 nm 0.6 ppb chromate Recovery 98% 6

7 Sample preparation is crucial Water samples work well Sediments, colours, textiles Strong influence of sample prep. on peak shape Optimize for each sample type! ph > mm Na 2 CO mm NaOH ph mm NaOH ph mm Na 2 CO mm NaOH ph > mm Na 2 CO mm NaOH UV/Vis generation 886/887 7

8 Cr VI in leather extracts with Inline Dialysis Dilution 1:10 Dialysis Eluent NaHCO 3 /Na 2 CO 3 ; 4/12.8 mmol/l Flow rate 0.7 ml/min Injection volume 50 µl PCR with diphenylcarbazide VIS 540 nm Chromate 19 µg/l 8

9 CrVI in leather extracts with Inline Dialysis Removal of particles, oils, proteins from emulsions Stopped-flow dialysis Installed in sample pathway (in front of injection valve) Suitable for leather, cutting oils, dairy products, body liquids, fermenter solutions, waste waters, fruit and vegetable juices 9

10 Cr VI in leather extracts with Inline Dialysis 10

11 Chromium - Cr VI Norms and regulations norm limit sample DIN EN ISO LFGB B RoHS; ELV (End of Life Vehicles Directive); DIN EN Verpackungsverordnung 94/62/EG REACH EU-Guideline 2009/48/EG 3 mg/kg Leather utensils max. 0,1% (w/w) kumulativ max. 100 mg/kg (Pb/ Cd / Hg & Cr VI ) SVHC (Substance of Very High Concern) Metals, non-metals, electronics packaging various Migration >0.02/0.005/0.2 mg/kg toys Dry, brittle, dusty liquid Threadbare Crayons, colored pencils, Inks, finger paints, Dyes, coatings, 11

12 Toy safety regulation Sample treatment Add 0.07 mol/l HCl (50x mass of sample) Extraction: Mix 1 h at (37±2) C (in the dark) Dwell time: 1 h at (37±2) C (in the dark) Filtration: pore size 0.45 µm or 0.22 µm Neutralization with buffer Analytical methods Photometry IC-ICP/MS IC-PCR/UVVIS Problems with colored samples High purchase costs & operating expenses 12

13 Standard Application Cr VI with post-column reaction (PCR) and VIS detection Standard setup Metrosep A Supp 5 Eluent 12.8 mmol/l Na 2 CO mmol/l NaHCO 3 Loop 1 ml PCR with diphenylcarbazide Detection at nm Only Cr VI detected 13

14 Chromate in toys New regulations - New challenges Lower detection limits Complicated matrices Finger paints, crayons, inks, opaque white, water colors, lacquers, High calcium content, organics, salts, Extraction with 0.25% HCl to imitate stomach ~3000 mg/l chloride Neutralization & dilution required due to matrix µg/l range necessary (!) 14

15 Chromate in toys Cr VI with pre-concentration & matrix elimination Metrosep A PCC 1 VHC/4.0 Metrosep A Supp 5-250/4.0 PCR with Dosino 50% acetone 20% methanol 15

16 Variable preconcentration Sample aspiration (exact volume) Aspiration of the required (exact) preconcentration volume 16

17 Variable preconcentration Sample aspiration Transfer capillary Transfer of the sample volume into the Transfer Tubing with ultrapure water of the Rinsing Station Total aspirated volume: large enough to move the complete sample segment into the Transfer Tubing (inclusive diffusion zone!) 17

18 Variable preconcentration Sample loading Preconcentration column Injector to fill > START loading < 18

19 Variable preconcentration Sample loading Preconcentration column Transfer of the sample volume into the Preconcentration Column Rinsing of the Eluent with ultra pure water 19

20 Variable preconcentration Sample loading Preconcentration column Transfer of the sample onto the preconcentration column 20

21 Variable preconcentration Sample parking Matrix Elimination Transfer of 50% acetone to complete sample transfer / matrix elimination Injection to inject > start analysis < 21

22 Chromate in toys Typical result for acidic dye sample Sample neutralized & diluted (factor 13.3) End concentration 0.04 µg/l Cr VI in 6.25 mmol/l HCl, 5.78 mmol/l, Na 2 CO 3, 0.47 mmol/l NaHCO 3, 0.91 mmol/l (NH 4 ) 2 SO 4 ) Calibration µg/l Cr VI RSD 0.9% Correl. Coef

23 Chromate in toys Preconcentration vs. Direct Injection Is chromate retained on the PCC? yes but some samples need dilution first Direct injection Disturbance from matrix Column life time Or: manual sample preparation with SPE cartridges 1 µg/l Cr VI 2 ml sample volume Metrosep A PCC 1 VHC/4.0 Direct 23

24 Chromate in toys Sample dilution factor Typical sample: 2 µg/l Cr VI in HCl (0.25%) neutralized & diluted recovery [%] dilution factor Dilution too small c(ions) too high not retained on PCC Dilution factor

25 Chromate in toys Preconcentration volume 2 µg/l Cr VI in 6.25 mmol/l HCl, 5.78 mmol/l Na 2 CO 3, 0.47 mmol/l NaHCO 3, 0.91 mmol/l (NH 4 ) 2 SO 4 ; (similar to sample matrix after neutralization & dilution) 4 ml injected 2 ml injected 4 ml sample volume can be loaded on the PCC (Sufficient capacity) 25

26 Chromate in toys Optimal rinse volume for matrix elimination (50% acetone) Too fast or too much risk of eluting Cr VI from PCC ml/min 5 1 ml/min 10 1 ml/min No Cr VI elution Up to 10 ml = ok Up to 10 ml/min = ok Depends on sample 26

27 Chromate with IC-ICP/MS Metrohm IC & Agilent 8800 ICP-QQQ Calibration ng/l Check blank! 27

28 Cr VI in ore leaches, ph MiPCT-ME setup Matrix elimination with water Removal of cationic components e.g. Al, Si Linear calibration µg/l Sample volumes µl RSD 2% Corr. Coef Ore leach ph µl injected β(cr VI ) = 54 µg/l 28

29 Cr(VI) in ore leaches, ph MiPCT-ME setup method check Control 150 µg/l Cr VI injection volumes between 50 µl µl Correct result Recovery % 29

30 Chromate in ore leaches Cr VI with pre-concentration & matrix elimination water 30

31 Chromate Separation Cr III /Cr VI Speciation Metrosep A Supp 1 250/4.6 Eluent: dipicolinic acid (2 mm), Na 2 HPO 4 (2mM), NaI (10 mm), CH 3 COONa (50 mm), LiOH (2.8 mm), ph 6.8, 1.3 ml/min PCR: diphenylcarbazide (0.5 g/l), methanol (10%), H 2 SO 4 (0.3 M), 0.4 ml/min Injection vol. 250 µl Detection 365 nm (Cr III ) nm (Cr VI ) Sample must be ph 6 Cr III Cr VI Cr III 20 mg/l & Cr VI 0,40 mg/l 31

32 Chromate in different matrices Any questions? 32