Table 2.
List of the sample preparation methods used in the CE-MS analysis of solid food
| Sample Type | Target Compounds |
Extraction Method |
Extraction Protocol | CE-MS Conditions | Ref |
|---|---|---|---|---|---|
| Almond Skin | Phenolic compounds | LLE | 10 g dry almond skin mixed with 150 mL hexane, stirred (40 min), and gravity filtered (Whatman #4). Solids refluxed with 100 mL of 70% MeOH (60 °C, 40 min), filtered, and dried (vacuum rotary evaporator 40 °C). Residue dissolved (2 mL of 50:50 (v/v) MeOH/H2O) and analyzed. | CZE: Uncoated capillaries 95 cm long and 50 μm inner diameter (360 μm outer diameter). BGE: 200 mM (NH4)3BO3 (pH 10). Injection and voltage: 50 mbar, 15s, +30 kV. SL: 0.1% (v/v) TEA in 60:40 IPA/H2O; 0.2 mL/min. ESI-MS: Negative, −4.5 kV. SC: DGF: 4 L/min, DGT: 190 °C, NP: 0.4 bar | 104 |
| Algae | Microcystins | SPE | Algae sample centrifuged to remove extra water and mixed with 50 mL of HOAc: H2O (5:95, v/v), ultrasonicated (10 min) and centrifuged (10 min @ 4000 RPM). Supernatant loaded on SPE cartridge (C-18 phase), pre-conditioned with 10 mL MeOH and 15 mL H2O. Sample washed with 15 mL MeOH: H2O (20: 80), eluted with 10 mL (100% MeOH), evaporated to dryness and reconstituted in 1 mL MeOH. | CZE: A 90 cm length of 50 μmi.d., 360 μm o.d. uncoated fused-silica capillary. BGE: 40 mM NH4OAc (pH 9.86). Injection: 20 kV, 20s. Separation voltage: +20 kV. SL: 7.5 mM HOAc in 50:50 IPA/H2O; 3 μL/min. ESI-MS: +5 kV, SC: DGF: 6 L/min, DGT: 150 °C, NP: 10 psi. | 59 |
| Edamame | Charged metabolites | SLE | Edamame beans homogenized without solvent (60s @2000 rpm), mixed with 2.5 mL MeOH (containing 200 μM IS), 2.5 mL CHCl3 and 1.0 mL H2O and centrifuged (20 min @ 3000 rpm). 250 μL aq. solution filtered (3 min @ 10 000 rpm through 5 kDa cutoff filter). 100 μL filtrate centrifugally concentrated and dissolved in 50 μL H2O. | Cationic analyte. BGE: 1 M formic acid, SL: MeOH/H2O (50% v/v) and 0.1 M hexakis; 10 μL/min. Anionic analyte BGE: 50 mM NH4OAc (pH 8.5) SL: 5 mM NH4OAc in 50% (v/v) MeOH/H2O and 0.1 μM Hexakis; SC: ESI 3500 V, DGF: 10 μL/min, DGT: 300 °C, NP: 10 psi | 72 |
| Melon, watermelon, apricot, and peach | Pesticides Simazine, Haloxyfop, Acifluorfen, Picloram Ioxynil, Dinoseb, Flutolanil |
PLE, SPE | PLE: preheat (2 min), heating cell (5 min), solvent in contact with the sample (5 min, static time), pressure 1500 psi, temperature 60 °C, N2 purging (60 s), solvent volume flushing respect the cell size (60%) and one times cycled. H2O used as extraction solvent. H2O extracts pumped (2 mL/min) through Strata TM cartridge (pre-conditioned with 5 mL MeOH, 5 mL H2O). Retained pesticides eluted with 4 mL MeOH (1 mL/min) followed by 0.5 mL air. Eluate dried (10 min with N2 @ 40 °C), redissolved in1 mL BGE and injected | CZE: Uncoated fused-silica capillary with 50 cm total length, 75 μm ID, and 375 μm OD. BGE: 35 mM NH4HCOO/formic acid (90:10 v/v), pH 9.7. Injection and voltage: 0.5 psi, 5s, 23 kV. SL: 35 mM NH4HCOO/-FA (90:10 v/v), pH 9.7; 5 μL/min ESI-MS: Positive, + 4kV; SC: ESI , DGF: 7 L/min, DGT: 200 °C, NP: 13 psi | 58 |
| Soybean | Peptides | SLE | 150 mg grounded beans + 1.5 mL extraction buffers (ACN/H2O (80:20 v/v), vortexed 10 min, sonicated 3 min, and centrifuged 5 min @ 9000 g). 50 μL supernatant boiled (10 min), and 50 μL bovine pancreas trypsin solution (50mM NH4HCO3, pH 8.0) + (1:50, 1:25 and 1:5 w/w) enzyme:substrate incubated overnight at 37 °C, shaking @ 600 rpm). Reaction stopped by heating (90 °C) for 5 min, suspension centrifuged (5 min @ 14 000 g), supernatant fraction collected and stored at 20°C prior to analysis. | CZE: Uncoated fused-silica capillary (50 μm id, 90 cm total length). BGE: 0.5 M formic acid. Injsction and voltage: 34.5 mbar, 20 s, +25 kV. SL: 50:50 (v/v) IPA/H2O; 3 μL/min. ESI-MS: positive ion mode, SC: DGF: 4 L/min, DGT: 200 °C, NP: 0.4 bar | 86 |
| Infant milk formula | Bioactive peptides | SPE | 4.7 g IF dissolved in 30mL H2O,0.5 mL of the resultant emulsions diluted with 2.5 mL of reduction buffer (73 mg of trisodium citrate dihydrate, 38mg of DTT in 37.5 mL of 8 M urea; pH 8 adjusted with NaOH),incubated (1 h at RT). Incubation samples centrifuged (30 min @ 4600 rpm), fat layer removed, clear solution filtered (0.22 μm nylon filters) before SPE. Sep-Pack® C18 cartridge conditioned (2 mL MeOH, and 2 mL H2O), 2mL of sample loaded, retained compounds eluted with 200 μL solution (80:20 (v/v) MeOH:H2O and 0.1% (v/v) of FA) at 1 mL/min. Eluate dried (air at RT) and reconstituted with 200 μL H2O before CE–MS. | CZE: Uncoated 57 cm× 50 μm I.D. fused silica capillary. BGE: 1 M HOAc. Injection and voltage, 33.5 mbar, 15s, +15 kV. SL: 0.05% (v/v) FA in 60:40 (v/v) IPA/H2O; 3.3 μL/min. ESI-MS: Positive +4 kV; SC: DGF: 4 L/min, DGT: 200 °C, NP: 7 psi. | 60 |
| Feces | Oligosaccharides | SPE | Fecal slurries (50 mg/mL) kept overnight at 4 °C, centrifuged (15 min, 3500 x g) and filtered (0.22 μm membrane). Fecal enzymes inactivated by heat (5 min, 100 °C). Carbohydrates extracts purified by SPE on graphitized carbon column cartridges (150 mg bed weight, 4 mL tube size; Cartridges washed with 0.1% (v/v) TFA in 80/20 (v/v) ACN/H2O followed by H2O. Extracts loaded onto cartridge; monomers/lactose removed using aq. 2% (v/v) ACN, and carbohydrates eluted with 0.05% (v/v) TFA in 40/ 60 (v/v) ACN/H2O. Dried and rehydrated with H2O. | CZE: Bare fused-silica capillary (50 μm ID x 85 cm L) BGE: 0.3% (v/v) formic acid (pH 2.4). Injection and voltage: 10 psi, 2s, −20 kV. SL: 50:50 IPA/H2O; 2 μL/min. ESI-MS: Negative, −1.9 kV SC: ESI −1.9 kV, DGF: μL/min, MS capillary T: 190 °C. | 68 |
| Milk powder | Melamine and its analogs (Melamine, Ammeline, Ammelide, Cyanuric Acid) | SPE | Delipidated milk powder reconstituted (instructions on package). Protocol (A): 1 mL sample + 100 μL of 0.2 M HCl + 33 mL ACN (vortex, centrifuge 10 min @ 6000 rpm). Supernatant loaded onto Strata cartridge (preconditioned 3 mL MeOH and 3 mL H2O (1 mL/min); washed (1 mL ACN/H2O (50:50, v/v), 500 μL MeOH/ H2O (50:50, v/v)); dried (2 min, 10 psi); eluted (500 μL MeOH and 1 mL MeOH-NH4OH (95:5, v/v)); dried (N2); reconstituted in 1 mL ACN/20 mM NH4OAc (95:5, v/v); injected into CE/MS. Protocol (B): 10 mL (0.12 M) HCl + 5 g sample (vortexed 45 s, centri-fuged 5 min @ 4000 rpm); supernatant loaded onto MCX cartridge (preconditioned 5 mL MeOH, 5 mL H2O (1 mL/min)); washed (5 mL (0.1 M HCl), 2 mL MeOH); eluted (5 mL ACN-NH4OH (95:5, v/v); injected into CE/MS | CZE: Bare fused-silica capillary (total length of 80 cm and an internal diameter of 50 μm). BGE: 25 mM NH4OAc (pH 5.2). Injection and voltage: 50 mbar, 25 s, +30 kV. SL: 25 mM HOAc in 50:50:2 (v/v/v) IPA/H2O/NH4OH; 3 μL/min. ESI-MS: Positive, +4.3 kV and negative, −3.4 kV; SC: DGF: 4 mL/min, DGT: 250 °C, NP: 4 psi. | 65 |
| Rice | Selenium monitored isotope (m/z): 78Se, 80Se | EAE | 0.5 g rice (crushed)+ 40 mg protease + 5 mL H2O (incubated 16 h @ 37 °C) centrifuged (10 min @ 5000 rpm); supernatant filtered (0.22 μm); diluted with H2O and analyzed by CE-ICP-MS. | CZE: Bare fused silica capillary i.d. 75 μm; o.d. 365 μm; 80 cm long. BGE: 20 mM NaH2PO4 + 10 mM Na2B4O7 + 0.2 mM CTAB (pH 8.6). Injection and voltage:10 s,−16 kV. ICP-MS: velocity: 12 μL/min (pump 1), 200 μL/min (pump 2); RF power: 1300 W; plasma gas: 15 L/min (outer), 0.9 L/min (intermediate); carrier gas: 0.7 L/min; makeup gas: 0.3 L/min; DRC reaction gas: H2 (3 mL/min); nebulizer: MCN (50-200 μL/min) | 39 |
| Milk powder | melamine | SLE | 0.5 g sample + 1 mL NH4OH (0.1 M) + 3.5 mL ACN (vortexed 20s, sonicated 30 min, and centrifuged 20 min @ 6000 rpm) and clear liquid dried (oven @ 70 °C), mixed with 1 mL NH4OH (0.1 M), and analyzed by CEC-MS | CEC: (100 μm i.d., 60 cm L). a polymerization solution (divinyl benzene and alkene (1-octene, 1-dodecene or 1-octadecene), porogenic solvents water, cyclohexanol and N,N-dimethylacetamide charged monomer (vinyl-benzyltrimethylammonium and initiator (AIBN) was used toprepare the monolithic columns. BGE: 80:20 (v/v) 5 mM NH4OAc/ACN (pH 8). Injection and voltage: −5 kV (3s), 0 kV. SL: 2.5 mM NH4OAc in 80:20 IPA/H2O; 220 μL/h. ESI-MS: Positive, +4 kV , SC: DGF: 4 L/min, DGT: 180 °C, NP: 5.8 psi | 20 |
| Tea leaves | Metabolites | SLE | 100 mg powdered leaf + 1 mL MeOH (containing 50 μM IS) + 1 mL CHCl3 + 400 μL H2O (vortexed 20s, sonicated 30 min, centrifuged 20 min @ 6000 rpm); aqueous layer recovered; ultrafiltered (5 kDa-cutoff filter by centrifugation 120 min @ 9,100 g, 4 °C); dried and dissolved in 50 μL H2O (containing 100 μM IS). | CZE: Bare fused-silica capillary (50 μm X 80 cm). BGE: 1 M formic acid (pH 1.8) (cationic analytes); 50 mM NH4OAc (pH 8.5) (anionic analytes). SL: 5 mM NH4OAc in 50% (v/v) MeOH/H2O; 10 μL/min. ESI-MS: Positive (+4 kV) and Negative (−3.5 kV) ion modes. SC: DGF: 10 L/min, DGT: 300 °C. | 83 |
| Fermented soybean | Metabolites | SLE | 5 mg sample + 5 mg/mL MeOH centrifuged (10 min @ 5000 rpm, 25 °C), extracts filtered (0.22 μm), and analyzed by CE-MS | CZE: Bare fused-silica capillary (50 μm i.d. × 100 cm total length). BGE: 1 M formic acid (cation analysis); 20 mM NH4HCOO, pH 10 (anion analysis). Injection and voltage: I5 mbar,5s, +30 kV, SL: 0.5 M reserpine in 1:1 (v/v) MeOH/H2O; 10 μL/min ESI-MS: + 4 kV (cation) −4kV (anion), SC: DGF: 10 psig, DGT: 300 °C. | 75 |
| Flour, pasta, bread | Furosine | Acid hydrolysis | 100 mg samples hydrolyzed with 5 mL (8 N) HCl (23 h @ 110 °C), filtered (0.45 μm PTFE); dried (N2), resuspended (2.5 mL BGE), and re-filtered (0.20 μm PTFE). Aliquot diluted with 14 μL (25 mg/L) quinine to obtain conc. 0.5 mg/L in 700 μL final volume. | CZE: Bare fused-silica capillary 50 μm id and effective length of 90 cm and 60 cm. (BGE: 50 mM formic acid (pH 2.7 adjust with 0.5 M NH4OH) Injection and voltage: 50mbar, 5s, +25 kV. SL: 0.1% FA in 50:50 (v/v) MeOH/H2O; 3 μL/min ESI-MS: Positive, +3.5 kV, SC: DGF: 5 L/min, DGT: 200 °C, NP: 10 psi. | 90 |
| Dietary polyphenols Treated with HT29 colon cancer cells | Metabolites | Cell-disruption | Cells (equal volume) washed (PBS solution) and centrifuged. Pellets suspended with homogenization buffer and protease inhibitor cocktail. Cells disrupted (Polytron homogenizer), centrifuged (14 min @14 000 × g, 4 °C), pellet (nuclear and mitochondrial fractions) discarded, supernatants centrifuged (1 h @ 100,000 × g, 4 °C), 400 μL of cytosolic fraction ultra-filtrated (40 min @14,000 × g, 20 °C). | CZE: Uncoated fused-silica capillary (50 μm id, 363 μm od and 80 cm total length). BGE: 1 M formic. Injection: 34.5 mbar, 80s, +25 kV. SL: 50:50 (v/v) IPA/H2O; 0.2 mL/min ESI-MS: Positive ion mode, −4.0 kV. SC: DGF: 4 L/min, DGT: 250 °C, NP: 0.4 bar. | 41 |
| K562 leukemia cells | Metabolites | Cell-disruption | Cells (equal volume) washed (PBS solution) and centrifuged. Pellets suspended with homogenization buffer and protease inhibitor cocktail. Cells disrupted (Polytron homogenizer), centrifuged (14 min @14 000 × g, 4 °C), supernatants centrifuged (1 h @ 100,000 × g, 4 °C) (cytoplasmic fraction). 400 μL of cytoplasmic fraction ultra-filtrated (40 min @14,000 × g, 20 °C). Fractions with molecular weight <3 kDa aliquoted and stored at −80m°C until CE-MS analysis. | CZE: Uncoated fused-silica capillary (50 μm id, 363 μm od and 80 cm total length). BGE: 1 M formic acid. Injection and voltage: 0.5 psi, 60s, +25 kV. SL: 50:50 (v/v) IPA/H2O; 0.2 mL/min ESI-MS: Positive, +4.0 kV , SC: DGF: 4 L/min, DGT: 250 °C, NP: 0.4 bar. | 46 |
| Milk powder | β-lactoglobulin and α-lactalbumin | Protein purification | 20 mg/mL milk powder solution centrifuged (5 min @15 000 × g). 2 mL of defatted milk pH adjusted to 4.5 with 1M HCl and centrifuged (5 min @15 000 × g), precipitated casein removed. supernatant diluted 50 x with sample BGE before analysis. | CZE: Uncoated fused silica capillaries (50 μm id, 375 μm od, 50 cm total length. BGE: 10% HOAc (pH 1.5); Sample BGE: 10 mM PBS + 0.1% Tween 20. Injection and voltage: 39 mbar, 600s, +24 kV. MALDI : positive, matrix: sample collected on MALDI plate, buffer droplets dried, 2 μL of matrix (2 mg/mL SA in 70% ACN, 0.1% TFA) spotted above each sample droplet, dried at RT. | 8 |
| Fish | Hg(II), MeHg, and EtHg (monitored isotope (m/z): 199Hg, 201Hg, 202Hg); | MSLE | 0.5 g dried fish + 20.0 mL of 1 M HCl solution in 100 mL Teflon beaker/screw covered placed in microwave digester (5 min @ 70 °C, 400 W). Sample cooled (RT), extracts separated by filtering (0.22 μm membrane filter), and dried (pressured N2 blowing concentrator). Residue diluted to the appropriate volume with BGE and used for the CE–ICP–MS analysis with continuous sample-introduction mode. | CZE: i.d. 75 μm; o.d. 365 μm; 85cm long. BGE: 50 mM H3BO3 + 12.5 mM Na2B4O7 (pH 9.2). Inject: 10s, +18 kV; sep voltage: +18 kV. ICP-MS: velocity: 11 μL/min (pump 1), 6 μL/min (pump 2); RF power: 1300 W; plasma gas: 15 L/min (outer), 0.9 L/min (intermediate); carrier gas: 0.75 L/min; makeup gas: 0.3 L/min; DRC reaction gas: H2 (3 mL/min); nebulizer: ACN (20-35 μL/min) | 42 |
| Chili powder | Sudan dyes | SLE | 1.0 g chilli powder diluted (10 mL 3:2:1, (v/v/v), acetone/DCM/MeOH), vortexed (2 min), sonicated (5 min), and centrifuged (5 min @ 10,000 rpm). supernatant dried, suspended (5 mL acetone) and diluted (50:50 v/v) with BGE (60mM NH4HCO3, 50mM SDS, and 30% ACN). | MEKC: Bare fused silica capillary (a total length of 80 cm and 50 μm id, 375 μm od). BGE: 40mM NH4HCO3, 32.5% ACN partially filled 25mM SDS (20 psi, 13.2s). Injection and voltage: 0.5 psi, 6s, +25 kV. SL: o.1% FA in 50:50 (v/v) IPA/H2O; 4 μL/min. ESI-MS: Positive, +4.5 kV, SC: DGF: 4 L/min, DGT: 200 °C, NP: 4 psi. | 88 |
| Infant milk formula | Peptides | SPE | 4.7 g of IF + 30 mL H2O (warm) water (45 °C). Resultant emulsion (0.5 mL) diluted with 2.5 mL reduction buffer (73 mg of trisodium citrate + 38 mg DTT in 37.5 mL (8 M) urea; pH 8 adjusted with dil. NaOH; make up to 50 mL with H2O); incubated (1 h at RT); centrifuged (30 min @ 2500 × g); fat layer removed; clear solutions filtered (0.22 μm nylon filter. 2 mL solution loaded onto SPE cartridge (preconditioned with 2 mL MeOH, 2 mL H2O); compounds eluted with 200 μL of 80:20 (v/v) MeOH/-H2O and 0.1% (v/v) FA at 1 mL/min. Eluate dried with air (RT) and reconstituted with 200 μL H2O before CE-MS analysis. | CZE: A 57 cm × 50 μm id × 365 μm od fused silica capillary. BGE: 1 M HOAc (pH 2.3). Injection and voltage: 33.5 mbar, 15 s, +15 kV. SL: 0.05% HF in 60:40 (v/v) IPA/H2O; 3.3 μL/min ESI-MS: Positive, + 4 kV, SC: DGF: 4 L/min, DGT: 200 °C, NP: 7 psi. | 61 |
| Egg | Benzimidazoles | QuEChERS | 3 g egg yolk + 10 g H2O + 10 mL ACN (mix 1 min in centrifuge tube). 4.0 g MgSO4, 1.0 g of NaCl and 1.0 mL NH4HCOO solution (2.5 mM, pH 7.5) added to tube (shake 1 min) and centrifuged (5 min @ 1500 × g). DSPE cleanup: 1 mL supernatant + 0.025 g PSA + 0.150 g MgSO4, centrifuged (2 min @ 1500 x g), dried (N2) and dry residue vortex-shaken in 1 mL of an ACN/formic acid (99:1, vol.) solution. | CZE: A 75 μm I.D. with a total length of 57 cm and 50cm to the UV detector. BGE: 6 M formic acid in 70:30 H2O/IPA. Injection and voltage: 50 mbar, 30 s, +22 kV. SL: 50:50 IPA/H2O; 10 μL/min ESI-MS: Positive, +4 kV , SC: DGF: 7 L/min, DGT: 350 °C, NP: 4 psi. | 72 |
| Soy biscuit | Peptides | QuEChERS | 2.5 g of grounded biscuit extracted (10.0 mL hexane), organic layer discarded and solid portion mixed with 10 mL 50:50 (v/v) ACN:H2O (shaken 5 min, RT) followed by addition of mixture (4 g MgSO4 + 1 g NaCl + 1 g Na3Cit.2H2O + 0.5 g Na2HCit. 1.5H2O), tube shaken vigorously (1 min to prevent MgSO4 conglomerates), and centrifuged (5 min @ 5000 rpm). 1.0 mL ACN fraction subjected to DSPE using a mixture of 150 mg MgSO4, 150 mg of silica sorbent, 25 mg of PSA and 25 mg of C18 sorbent, shaking vigorously (1 min), and centrifuging (5 min @ 5000 rpm). Extracts filtered (0.22 μm PVDF syringe filter) and 100 μL filtered extract diluted (H2O) to a volume of 1.0 mL before analysis. | CZE: Uncoated fused silica capillary 87.5-cm total-length, 21 cm to the UV detector. BGE: 15 mM NH4OAc (pH 11), Injection and voltage: 50 mbar, 50 s, +25 kV. SL: 90:10 (v/v) IPA/H2O; 1 μL/min. ESI-MS: Positive, 3.5 kV, DGF: 6 L/min, DGT: 350 °C, NP: 4 psi. | 71 |
| Royal jelly products | AAs | SLE | Tablets were grounded, capsules opened to release the contents. 1.0 g aliquot mixed with 9 mL of 75% (v/v) EtOH, ultrasonicated (5 min, RT) and centrifuged (5 min @3000 rpm/1200 x g). 0.9 mL supernatant mixed with 0.1 mL of 1 M HCl, and 0.1 mL portion of the IS (1 mg/mL Cys) added prior to CE-MS/MS analysis. | CZE: Uncoated fused-silica capillary (50 μm, I.D., 100 cm in length). BGE: 1 M formic acid (pH 1.8). Injection and voltage: 50 mbar, 5s, +30 kV. SL: 50:50 (v/v) MeOH/H2O; 8 μL/min. ESI-MS: +4 kV. SC: DGF: 10 L/min, DGT: 300 °C, NP: 10 psi. | 91 |
| Avocado fruits | 10 Metabolites | SLE | 4 g freeze-dried (and homogenized) sample mixed with 40 mL MeOH and shaken (vortex 30). Supernatants centrifuged (10 min @ 3000 rpm), resulting supernatants dried and redissolved in 1 mL of 50/50 (v/v) MeOH/H2O. | CZE: Bare fused-silica capillaries with 50 μm id and a total length of 85 cm. BGE: 40 mM NH4OAc (pH 9.5). Injection and voltage: 0.5 psi, 5s, +30 kV. SL: 60:40 (v/v) IPA/H2O; 0.24 mL/h ESI-MS: Negative, −3.5 kV , DGF: 5 L/min, DGT: 250 °C, NP: 5 psi. | 76 |
| Milk powder | Allergens (IgE) | SLE | Milk powder dissolved in H2O at 20 mg/ mL and 2 mL of solution mixed with 50 mM NH4OAc buffer (pH 4.5), centrifuged (2 min @ 12,000g), and supernatant with whey proteins removed from the casein precipitate. Casein precipitate washed (NH4OAc buffer) and dissolved in 2 mL of 25 mM NH4HCO3 buffer (pH 8.5). UHT treated milk defatted by centrifugation (5 min @12 000g). Whey and casein fraction solutions diluted 20x with the sample buffer prior to IACE analysis. | CZE: Capillary (50 μm i.d., 41.5 cm effective length, 50 cm total length) coated with 5% hydroxypropylcellulose (HPC) solution, BGE: 10% HOAc (pH 2); sample buffer: 10 mM PBS + Tween 20 (pH 7.4). Injection and voltage: 40 mbar, 300s, +24 kV. MALDI matrix: 2 mg/ml SA in 70% ACN, 29.9%H2O, 0.1% TFA) | 38 |
| Tea leaves | Caffeine | SLE | 2 g of Chinese white tea leaves + 10 mL MeOH/H2O (95/5, v/v) ultrasonicated (20 min), filtered and injected for online CZE-DART-MS analysis. | CZE: 80 cm fused silica capillary with 75 μm i.d. and 360 μm o.d.. BGE: 15 mM sodium borate, 15 mM SDS, 18% acetonitrile. Injection and voltage: 50 mbar, 10s,+25 kV. SL: 25:25:50 (v/v/v) MeOH/acetone/H2O; 10 μL/min. DART-MS: −3.5 kV, SC: DGF: 0.12 L/h, DGT: 300 °C, NP: 2 psi. | 5 |
| Infant formula | Five Riboucleotides (AMP, GMP, CMP, IMP, UMP) | SLE, CUF | 0.5 g of infant milk mixed with H2O up to 15 g, stored at 5°C (15 min) followed by centrifugation (15 min @ 2800 × g). 10 mL supernatant collected (avoid collecting top fat layer) and passed through the CUF device (30min, 2800×g), pre-conditioned with 5 mL H2O (15 min, 2800 × g). | CZE: Uncoated fused-silica capillaries (50 and 100 μm id) with total lengths of 87.5 (MS) and 20 cm to the UV. BGE: 30 mM NH4HCOO/NH4OH (pH 9.6). Injection and voltage: 50 mbar, 30s, +25 kV. SL: 50:50 (v/v) IPA/H2O; 10 μL/min. ESI-MS: −4.0 k V, DGF: 7 L/min, DGT: 350 °C, NP: 10 psi. | 94 |
| Mussel | Paralytic shellfish toxins | SPE | 3 mL 1% HOAc solution + 5.0 g homogenized raw meat vortexed (1 min), boiled (100°C, 5 min); revortexed, cooled (5°C, 5 min), and centrifuged (10 min @ 4500 rpm). Supernatant stored at −20°C. Prior to analysis, 0.5 mL extract cleaned using a C18 cartridge (Waters). Effluent containing toxins collected and column rinsed with 2 mL H2O to remove residual PSTs from the column. A 0.5 μL 1 M NaOH added to extract. | CZE: Bare fused silica capillaries (57 cm-long 50 μm id). BGE: 35 mM morpholine (pH 5 adjust with formic acid). Separation and voltage: 5 kV for 10s, +20 kV. SL: 0.1% formic acid in 80:20 (v/v) IPA/H2O; 4 μL/min. ESI-MS: Positive, 4.2 kV, SC: DGF: 2 L/min, DGT: 250 °C, NP: 10 psi. | 63 |
| Cheese | Lysozyme | SLE | 2 g cheese sample and 70 mL of 1 M HOAc (in H2O) added into a 100 mL volumetric flask and placed in thermal bath (40 °C). Sample homogenized (1 h @ 25,000 rpm), H2O added to the flask to 100 mL mark. Extracted samples filtered (0.45 μm) prior to analysis. | CZE: Polyacrylamide coated fused silica capillary, BGE: 100 mM formic acid. Injection and voltage: 100 mbar, 5s, +20 kV. SL: 50:49.5:0.5 (v/v/v) MeOH/H2O/FA; 4 μL/min. ESI-MS: Positive, +4 kV SC: DGF: 10 L/min, DGT: 200 °C, NP: 10 psi. | 93 |
| Cereals, barley | 5-hydroxymethylfurfural | SLE | 300 mg sample dissolved in 6 mL of 1% TCA solution, vortexed (2 min), ultrasonicated (10 min), vortexed (2 min), and centrifuged (10 min @ 9000 rpm, 4 °C). Extracts filtered (0.20 μm nylon filter) and mixed with 6 mL of 500 mg/L FMK solution to obtain a concentration of 5 mg/L to a final volume of 600 μL. | CZE: Untreated fused-silica capillaries of 50 μm i.d. total length 60 cm. BGE:50 mM formic acid (pH adjust with 0.5 M NH4OH). Injection and voltage: 50 mbar (10s), +25 kV. SL: 0.1% formic acid in 50% MeOH, 3 μL/min. ESI-MS: Positive, +3.5 kV. SC: DGF: 2 L/min; DGT: 200 °C; NP: 10 psi | 92 |
| Soybean | Cationic and anionic metabolites | LLE | 70 mg dry sample + 20 volumes of MeOH containing 8 μM reference compounds (methionine sulfone for cation and camphor 10-sulfonic acid for anion analyses) mixed (Retsch mixer mill MM310 @ 27 Hz for 1 min). Extracts centrifuged (3 min @15,000 × g, 4 °C), 500 μL supernatant mixed (500 μL of CHCl3 + 200 μL H2O), upper layer removed and evaporated (30 min @ 45°C) by centrifugal concentrator to obtain two layers. High-molecular-weight compounds (oligosugars) removed by centrifugal filtration (5-kDa cutoff filter @ 9,100 g and 4°C for 120 min) of upper layer and filtrate dried (120 min) by centrifugal concentrator | CZE: Bare fused silica capillary (50 μm i.d. × 100 cm total length). BGE: 1 M formic acid (cation analysis); 20 mM NH4HCOO, pH 10 (anion analysis). Separation and voltage: 50 mbar, 50 s, +30 kV. SL: 0.5 μM reserpine in 50:50 (v/v) MeOH/H2O; 10 μL/min. ESI-MS: +4 kV for cation and −4 kV for anions, SC: DGF: 10 psi, DGT: 300 °C | 99 |
| Algae | Harmala alkaloids | SLE | 0.1 g sieved powder extracted (500 μL MeOH and 500 μL of 3.5 M HCl), mixture incubated (6 h at 80 °C) in a shaker. Sample vortexed (30 s), centrifuged (15 min @10,000g, 25 °C), supernatant ultrafiltered (3 kDa cut-off,15 min @16,000g, 25 °C),washed with 50 μL H2O (centrifuged,10 min @12,000g). H2O added to a final volume of 250 μL | CZE: A 60 cm total length, 75 μm (i.d), and 360 μm o.d bare silica capillary. BGE: 25 mM NH4OAc + 10 (v/v) MeOH (pH 7.8). Injection and voltage: 35 mbar, 3s, +20 kV. SL: 0.05% formic acid in 60:40 (v/v) IPA/H2O; 3.3 μL/min. ESI-MS: Positive, +4 kV and −4 kV (cation and anion); SC: DGF: 5 mL/min, DGT: 250 °C | 95 |
| Yoghurt | Estrogenic compounds | DLLME | Yoghurt sample (centrifuged, protein extracted, and defatted) diluted to a final volume of 7.5 mL (with H2O and NaCl added to final concentration of 30% w/v) and filtered (0.45 μm PTFE filter). Mixture of 500 μL ACN (as dispersion solvent) and 110 μL CHCl3 (as extraction solvent) mixed with aqueous extract (vortex 2 min). Resulting dispersion centrifuged (4000 rpm/2500×g, 5 min) observing later a droplet of CHCl3 in the bottom layer. Upper aqueous phase partially removed (about 4 mL), droplet transferred to a vial, dried (N2), reconstituted (75 μL BGE), and injected. | MEKC: Fused-silica capillaries of 60 cm (50 μm id × 363 μmid). BGE: 45 mM ammonium perfluorooctanoic acid (pH 9.0) + 10% (v/v) MeOH. Injection and voltage: 0.5 psi (25 s), +25 kV. SL: 96:4 (v/v) IPA/H2O, 1.7 μL/min. ESI-MS: Negative, −4.6 kV; SC: DGF: 3 L/min; DGT: 200 °C; NP: 3 psi | 12 |
| Yeast tablet | Cr(III), Cr(VI), Cr picolinate | SLE | 0.1 g sample + 4 mL (1:3, v/v) MeOH/H2O, ultrasonicated (20 min, 200 W). whole solution cooled (RT), extract separated by filtering (0.22 μm membrane filter), residue diluted (H2O) and used for CE-ICP-MS analysis. | CZE: BGE: 25 mM Na2HPO4 + 6.26 mM Na2B4O7 + 0.6 mM CTAB (pH 7.8) ICP-MS: velocity: 20 μL/min (pump 1), 280 μL/min (pump 2); RF power: 1400 W; plasma gas: 15 L/min (outer), 0.9 L/min (intermediate); carrier gas: 0.8 L/min; makeup gas: 0.2 L/min; DRC reaction gas: H2 (2 mL/min); monitored isotope (m/z): Cr52; nebulizer: MCN (100-400 μL/min) | 84 |
| Rice | Arsenic species monitored isotope (m/z): 75 (As+); 77 (ArCl+) | EWPMD | Rice and rice cereal ground with an 8000 M mixer/mill, sieved (0.1 mm mesh), oven-dried (2 h @ 90 °C). 0.2 g of rice powder + 0.1 g of 0.5% (w/w) α- amylase mixed (15 mL glass tube) and diluted to final weight (2 g with H2O). Tube capped and placed in a microwave digestion system (1 h @ 80 °C and 2 h @ 90 °C with stirring). Centrifuge to remove remaining solids and 30 μL of o-ASA (50 ng/g) added to the 270 μL rice extract. | CZE: A 60 cm long coated fused silica capillary, 100 μm i.d., 360 μm o.d. BGE: 8 mM Na2CO3 (pH 11). Injection and voltage: 15 mbar (8s), + 20 kV. ICP-MS: velocity: 20 μL/min (pump 1), 280 μL/min (pump 2); RF power: 1500 W; plasma gas: 15 L/min; carrier gas: 0.9 L/min; makeup gas: 0.45 L/min; DRC reaction gas: H2 (2 mL/min); nebulizer: Mira Mist CE. | 40 |
| Cheese | Lysozyme | SLE | 2 g of grounded cheese mixed with 20 mL NaCl 1M (10 min at 30 Hz). pH of mixer raised to 6.0 with 1M NaOH, and temp. maintained (40°C for 30 min). pH decreased 4.3 with 1M HCl and mixture filtered ( filter paper and 0.22 μm filter). | CZE: Fused-silica capillaries of 50 μm id with poly-(TEDETAMA-co-HPMA) 50:50 copolymer-coating. BGE: 35 mM NH4OAc (pH 4.8 adjust with HOAc). Injection and voltage: 0.5 psi (5s), −20 kV.ESI-MS: SC: DGF: 4 L/min, DGT: 200 °C, NP: 0.4 bar. | 93 |
| Baby foods | Nucleotides | SLE | 0.50 g + H2O (4.5 g), shaken manually, centrifuged (15 min @ 2800g, RT). 4.0-mL supernatant and passed through CUF device (30 min @ 2800g) previously conditioned with 5.0 mL H2O (15 min @ 2800g). 0.5 mL of H2O added to the CUF device and centrifuged again (30 min @ 2800g),filtrate directly analyzed by CE-MS. | CZE: Bare fused silica capillary, 50 μm I.D., BGE: 76 mM hexafluoro-2-propanol (pH 10 adjust with conc. NH4OH). Injection and voltage: 50 mbar (40s), +30 kV. SL: 1.6% (v/v) hexafluoro-2-propanol in H2O; 10 μL/min. ESI-MS: 3.5 kV, SC: DGF: 7 L/min, DGT: 350 °C, NP: 7 psi. | 94 |
| Onion fed rat’s liver | Metabolites | SLE | 50 mg liver tissue homogenized, cold MeOH/H2O (1:1, w/v) at 1:10 (w/v). 100 μL homogenate + 100 μL of 0.2 M formic acid (FA) centrifuged (10 min @16,000 x g, 4 °C) and added to a centrifree ultracentrifugation (30 kDa protein cutoff filter) for deproteinization by centrifu-gation (70 min @ 2000 x g, 4 °C). Filtrate dried (Speed-Vac Concentrator), resuspended in 100 μL of 0.1 M FA, 0.2 mM methionine sulfone (IS) before analysis. | CZE: Uncoated fused silica capillary (total length, 96 cm; i.d., 50 μm). BGE: 0.8 M formic acid in 190% MeOH. Injection and voltage: 50 mbar (50 s), +30 kV. SL: 10 mM formic acid in 1:1 (v/v) MeOH/−H2O; 6 μL/min. ESI-MS: Positive, +3.5 kV, SC:.5 kV, DGF: 10 L/min, DGT: 200 °C, NP: 10 psi. | 77 |
| Algae | Harmala alkaloids | Online-SPE | 0.1 g (±0.0001 g) of dried algae + 500 mL MeOH + 500 ml (3.5 M) HCl incubated (6 h @ 80 °C, Thermo-Shaker TS-100), vortexed (30 s) and centrifuged (15 min @ 10,000 g, 25 °C). Solid discarded and supernatant (approx. 950 ml) evaporated to dryness, reconstituted (H2O to a final volume of 250 mL) and filtered (0.22 μm nitrocellulose membrane) before ultrafiltration (3 KDa cut-off, 15 min @16,000 g, 25 °C). 50 ml H2O added to filtrate and centrifuged (10 min @12,000 g). Filtrate reconstituted with H2O to final volume of 100 ml and analyzed by SPE-CE-MS. | CZE: 60 cm total length, 75 μm id, and 360 μm od bare fused silica capillary. BGE: 10 mM NH4OAc, 10% MeOH (pH 7.8). Injection and voltage: 35 mbar (3 s), +20 kV. SL: 0.05% (v/v) FA in 60;40 (v/v) IPA/H2O; 3.3 μL/min. ESI-MS: +4 kV; SC: DGF: 4 L/min, DGT: 200 °C, NP: 5 psi. | 55 |
| Lobster | Neurotoxin (β-N-methylamino-L-alanine) | SPE | 50-mg freeze-dried samples hydrolyzed with 1 mL 6 M HCl in flame-sealed glass ampoule (16 h @ 110 °C). Hydrolysates dried (N2 @ 55 °C), spiked with BMAA-d3 and reconstituted in 2.5 mL (20 mM) HCl. A portion of this crude extract (25 mg tissue equivalent) loaded onto an Oasis-MCX cartridge (pre-conditioned with 3 mL MeOH and 3 mL (20 mM) HCl), washed (3 mL H2O and 4 mL MeOH) and BMAA eluted with 7 mL (5% w/v) NH4OH. Eluent dried (N2), reconstituted (0.5 mL of 2 mM HCl) and filtered (0.22 μm Ultrafree-MC filter) | CZE: The exit of the CE capillary was stripped of polyimide coating, heated, pulled and cut. The tapered section (ca. 4.5 μm long), 100 μm OD and 30 μm ID. BGE: 5 M formic acid in 9:1 (v/v) H2O/can. Injection and voltage: 50 mbar (60 s), + 15 kV to +30 kV. SL: 50;50:0.1 (v/v/v), MeOH/−H2O/formic acid; 1 μL/min. ESI-MS: 4.2 kV. | 64 |
| Head lettuce | Metabolites (50 target compounds (anions: organic acids, phosphorylated compounds, cations: amino acids) | SLE | 50 mg of frozen leaves grounded and homogenized in liquid N2. Samples mixed with 0.2 mL MeOH (100%) for enzyme inactivation. 0.2 mL H2O containing IS (50 μM (PIPES) and 50 μM methionine sulfone) added to homogenates, centrifuged (4 min @ 22,000g, 4 °C), supernatant ultrafiltered (3 kDa cut-off filter) with centrifugation (30 min @ 14,000g, 4 °C) and analyzed by CE-MS | CZE: For anions polyethylene glycol-coated capillary (DB-WAX, Agilent Technologies, Palo Alto, CA., USA, 100 cm , 50 μm i.d.) with 20 mM ammonium acetate (pH 8.5) as a running buffer. For cations, uncoated fused silica capillary (90 cm, 50 μm i.d.),1 M formic acid (FA) pH 1.9) as the running buffer. Injection and voltage: ±25 kV voltage was carried out for anions in negative mode or cations in positive mode. ESI-MS: + 3.5 kV for cations, −3.5 kV for anions. SL: 5 mM NH4OAc in 50% (v/v) MeOH(for anions); 0.1% FA in 50% (v/v) MeOH (for cations); 8 μL/min. SC: DGF: 8 L/min, DGT: 320 °C | 11 |
| Mussel | Saxitoxin monitored isotope (m/z): 151Eu; 153Eu; | SLE | 0.5 g vacuum freeze dried (−46°C) dried mussel powder mixed with 1.0 mL DMSO under ultrasonic oscillation (30 min @ 30°C). DMSO solution (with extracts) separated by centrifugation. DMSO extracting solution concentrated to 500 μL (N2-blowing concentrator) and used for CE-ICP-MS analysis | CZE: 60 cm length × 75 μm i.d. × 375 μm o.d. bare fused-silica capillary. BGE: 20 mM NaH2PO4 + 5 mM Na2B4O7 + 0.2 mM CTAB (pH 6 adjusted with 0.1 M HCl). Injection and voltage: ICP-MS: velocity: 20 μL/min (pump 1), 200 μL/min (pump 2); RF power: 1300 W; outer plasma gas: 15 L/min; auxiliary plasma gas: 0.9 L/min carrier gas: 0.8 L/min; makeup gas: 0.2 L/min; acq. mode: time-resolved mode; nebulizer: 60 psid, MCN (100-400 μL/min); DGF: 10 L/min. | 85 |
| Cabbage leaves | Zinc dimethyldithiocarbamate, zinc ethylenebisdithiocarbamate monitored isotope (m/z): Zn66; | SLE | 1.0 g sample + 5 mL (0.1 M) NaOH sonicated (20 min, 200 W), cooled to RT, and filtered (0.22 μm membrane filter) and diluted to desired volume with H2O (according to the zinc content in the sample), and final solution was used for CE–ICP-MS analysis. | CZE: 50 cm length × 75 μm id × 375 μm od fused silica capillary. BGE: 50 mM H4BO3 + 12.5 mM Na2B4O7 (pH 9). ICP-MS: velocity: 12 μL/min (pump 1), 240 μL/min (pump 2); RF power:1400W; outer plasma gas: 15 L/min; auxiliary plasma: 0.9 L/min carrier gas: 0.8 L/min; makeup gas: 0.2 L/min; 60 psi, MCN (100-400 μL/min), DGF: 10 L/min. | 43 |
| Cheese, coffee | Saturated fatty acids | SLE | 0.5 g cheese pulverized (liquid N2) + 1 mL H2O + 3 mL ACN sonicated (30 min @ 35 °C) and centrifuged (10 min @ 14,000 rpm). Supernatant filtered (3 kDa cutoff) by centrifugation (20 min @ 14,000 rpm). 0.5 g coffee + 5 mL H2O + 15 mL of ACN (treated as above). 100 mL of filtered aliquot used for CE-MS analysis | CZE: Fused-silica capillary (50 μm i.d. x 358 μm o.d., 85 cm in length). BGE: 30 mM NH4HCOO in 40% ACN (pH 10 adjust with 25% NH4OH). Injection and voltage: 50 mbar (20 s), +30 kV. SL: 250 μM ionic liquids as ion pairing reagent in 1:1 (v/v) MeOH/-H2O; 10 μL/min. ESI-MS: +3.5 kV; SC: DGF: 11 mL/min, DGT: 230 °C | 82 |
| Seaweed (O. japonicus A. Berger) | Metabolites (Anions and Cations) | LLE | Fermented samples (4 days) kept on ice (5±10 min) and centrifuged (20 min @ 3,000 rpm at 4 °C). Pellets retained for further processing. Supernatants mixed with equal volume EtOAc and shaken for 2 h (RT). EtOAc separated from supernatants using sep. funnel, and dried (rotary evaporator). Dried compounds dissolved (1.6 mL MeOH), stored on ice. Retained pellets washed with 10 mL H2O (vortex 30s), centrifuged (5 min @ 3000 rpm) and supernatant discarded. MEOH extract solution (1.6 mL) added to pellets , sonicated (30s) along with 1.1 mL IS solution. Mixture left at RT (30s), centrifuged (20 min @ 3000 rpm, 4°C). Supernatant transferred to ultra-centrifugal filter (5-kDa-cutoff), centrifuged (2±5 h @ 9,000 rpm, 4°C), dried under vacuum (3 h @ 1,500 rpm) | CZE: Cationic and anionic metabolites study were carried out with a fused silica capillary of 50 μm × 80 cm. BGE : cation buffer solution (p/n: H3301-1001), anion buffer solution (p/n: I3302-1023); Injection and voltage, 50 mbar for 10 s and 25 s using 27 kV and 30 kV, respectively. ESI-MS: Positive, 4.0 kV and Neaative, −3.5 kV for cations and anions. SL: HMT (p/n: H3301-1020) | 97 |
| Pork meat | Benzimidazole | DLLME | samples crushed and homogenized. Portions of 1 g (crushed/homogenized) sample + 1mL of H2O agitated (vortex) and 2mL ACN added (mix 30s). 0.5 g MgSO4 and 0.1 g NaCl added to mixture (agitate 5 min), centrifuged (10 min @ 9000rpm) and 1700 μL of upper phase mixed with 950 μL CHCl3 (extractant) and injected in 5mL of H2O for DLLME. Ternary system vigorously shaken by hand (60s) and stable cloudy solution formed centrifuged (2 min @ 5000rpm) for phase separation. CHCl3 layer collected and dried with N2. Residue reconstituted with 250 μL of 30:70 (v/v) ACN/H2O and filtered before injection into CE-MS | CZE: Uncoated fused-silica capillary (100 cm total length, 50 μm i.d., 375 μm o.d.). BGE: 500 mM formic acid (pH 2.2). Injection and voltage: 50 mbar (25 s), 25 kV. SL: 50:49.5:0.5 (v/v/v) EtOH/H2O/formic acid ; 0.1 mL/h. ESI-MS: −4.5 kV; SC: DGF: 8 L/min, DGT: 250 °C, NP: 6 psi | 44 |
| Fish | Metabolites | SLE | Fish feed pellet (20 mg) supplemented with or without probiotic crushed (mortar), mixed with 600 μL MeOH containing IS (50 μM) and homogenized (1,500 rpm, 120 sec × 2 times). CHCl3 (600 μL), H2O (240 μL) added to homogenate, mixed thoroughly, and centri-fuged (2,300 x g for 5min, 4 °C). H2O layer (200 μL × 2) filtrated (5-kDa cut-off filter). Filtrate centrifugally concentrated and re-suspended in 50 μL of H2O | CZE: A fused silica capillary with inner diameter and total length of 50 μm and 80 cm. BGE: electrophoresis buffer (Solution ID H3301-1001 for cation mode and H3302-1021 for anion mode; HMT Inc., Tsuruoka, Japan). Injection: 50 mbar (10 s) in cation mode and 50 mbar (25 s) in anion mode. ESI -MS operated in positive ion mode (4.5 kV) and negative ion mode (3.5 kV) for cat-ionic and anionic metabolites, respectively | 78 |
| Citrus tumida peel fed mice liver | Metabolites | SLE | 50 mg frozen liver sample immersed in 1800 μL 50% ACN in H2O containing IS (H3304-1002, HMT). Tissue homogenized (BMS-M10N21 homogenizer) and centrifuged (2300 g, 5 min,4 °C). 800 μL of the upper layer filtered by centrifugation (9100 g, 120 min, 4 °C) using (HMT 5-kDa cut-off filter). Filtrate resuspended in 50 μL H2O for CE-MS analysis | CZE: BGE: H3301-1001 for cation SL: 5 mM NH4OAc in 50% (v/v) MeOH/H2O; 10 μL/min. ESI-MS: 4.0 kV; SC: DGF: 10 L/min, DGT: 300 °C | 101 |
| Nutraceutical Tablets | Antihypertensive peptides | SLE | Nutraceutical tablets grounded (mortar and pestle) to fine powder. 0.15 g powder mixed with 1mL of warm H2O (at 45 °C), mixture shaken (1 h at 45 °C, 700 rpm) and centrifuged (7000 x g, 10 min, 25 °C). Supernatant filtered (a 0.22 μm nylon filter) before analysis by CE-MS | CZE: A 72cm total length x 75 μm id x 360 μm od bare fusedsilica capillary. BGE: 1 M HOAc (pH 2.3). Injection and voltage: 34 mbar (15s), +10 kV. SL: 0.05% fir nut in 60:40 (v/v) IPA/H2O; 3.3 μL/min. ESI-MS: +4.0 kV; SC: DGF: 4 L/min, DGT: 200 °C, NP: 7 psi. | 87 |
| Pork meat | Thiamine, thiamine phosphate | SLE | Frozen muscle tissue immediately plunged into MeOH containing 50 μM IS (H33041002) at 0 °C and homogenized 3 times (1500 rpm for 120 s). H2O and CHCl3 added at a ratio of 2:5 to the samples, mixed, and centrifuged (4 min at 2300×g, 4 °C). Upper aqueous layer centrifugally filtered (5-kDa cutoff filter) to remove proteins. Filtrate lyophilized and suspended in H2O before CE-TOFMS analysis | CZE: A fused silica capillary (50 μm i.d. ×80 cm total length), with commercial Cation and Anion electrophoresis buffers (Solution ID: H3301-1001 and H3302-1021 used. SL: cationic metabolites: MeOH/H2O (50% v/v) and 0.1 μM Hexakis, for anionic metabolites: 5 mM NH4OAc in MeOH/H2O 50% (v/v) containing 0.1 μM Hexakis; 10 μL/min SC: ESI-MS : Positive , 4.0 kV and Negative, 3.5 kV, DGF: 10 psi, DGT: 300 °C | 96 |
| Sea foods | Neurotoxin (β-N-methylamino-L-alanine) | Hydrolysis | Lysis buffer (1% sodium deoxycholate in 50 mM NH4HCO3, pH 7.5–8.0) added to 1 g seafood and homogenized. 1 mL of homogenate centrifuged (5 min @ 21,000×g), supernatant probe sonicated (20% amplitude, 20 s) twice and centrifuged (5 min @ 21,000×g). protein concentration measured (Nano-Drop 2000c, absorbance at 280 nm). Appropriate volume of sample containing 250 μg of protein transferred to a 10-kDa MWCO-filter unit (pre-washed with 200 μL H2O), centrifuged (14,000×g,15 min) and washed with 400 μL H2O (14,000×g and 20 °C) until <100 μL remained in filter unit. Eluate collected for free fraction analysis. Retained volume in filter unit washed with 100 μL H2O, filter unit inverted and spun (14,000×g and 20 °C) to collect protein fraction. Appropriate volume containing 250 μg sample added to clean vials for total sample analysis. Separated fractions stored at −20 °C until hydrolysis. Total and free protein fraction samples hydrolyzed with 40 μL of 6 N HCl and 5 μL of 4.7mM SIL-BMAA reconstituted in 50 μL H2O. Hydrolyzed samples incubated overnight (95 °C), lyophilized, and reconstituted in 50 μL of diluent (110 mM NH4OAc + 2% FA in 50% MeOH). Final samples diluted 1:100 prior to analysis | BGE: 2% FA in 50% MeOH in H2O | 47 |
| Coffee | Monosaccharides | Acid hydrolysis | 1.0 g dried coffee + 10 mL of 1 M H2SO4 heated (90 °C, 150 min) and manually stirred every 30 min. Solution cooled (tapwater) until RT, filtered, and the final volume make up to 10 mL H2O. 1 mL of 1 M Ba(OH)2 suspension added to 1 mL of sample solution for neutralization and sulfate precipitation (as BaSO4). Samples centrifuged (1 min @ 6000 rpm), filtered (0.2 μm PVDF/PPmembrane), diluted 10x before injecting | CZE: 90 cm long, 20 μm i.d. and 360 μm o.d. fused-silica capillary. BGE: 500 mM TEA (pH 12.3). Injection and voltage: 100 mbar (30s), +25 kV. SL: BGE diluted 50-folds with 1:1 (v/v) MeOH/H2O; 6 μL/min. ESI-MS: Positive, +4.5 kV; SC: ESI 4.5 kV, DGF: 6 L/min, DGT: 200 °C, NP: 10 psi | 48 |
| Fish | Hg and MeHg monitored isotope: 200Hg and 202Hg | MAE | Fish muscle sample extracted by MAE method reported in previous paper [Ref 21]. Extract filtered (0.22 μm membrane filter), evaporated to dryness (vacuum freeze drying, −46°C) and residue quantitatively dissolved into appropriate volume of BGE before analysis with CE–ICP-MS | CZE: a 70 cm length × 75 μm id × 365 μm od fused-silica capillary. BGE: 0.72 mM Tris + 0.72 mM H3BO3 + 16 mM EDTA + 0.3 mM CTAB (pH 8.0). Injection: −18 kV (10s), separation voltage: +20 kV. ICP-MS: velocity: 14 rpm (pump 1), 6 rpm (pump 2); RF power: 1500 W; outer plasma gas: 15 L/min; auxiliary plasma gas: 0.9 L/min carrier gas: 0.72 L/min; makeup gas: 0.27 L/min | 117 |
| Mussel | Paralytic shellfish toxins, tetrodotoxins, and domic acid | DE | Wet tissue homogenate + equal mass of 0.1 M HCl homogenized (10,000 rpm), boiled (water bath, 5 min), cooled to RT, centrifuged (6700 g, 10 min). Final volumes determined gravimetrically. A 100-μL sub-sample of supernatant vortexed with 300 μL of ACN insoluble protein, removed by spin filtration (0.22-μm polyvinylidene difluoride filter), at 2500 g for 5 min. 250 μL filtrate spiked with 16 μL (25 μM BMAA-d3) | CZE: Bare fused-silica capillary tubing with 100 cm total length (50-μm i.d., 363-μm o.d) BGE: 5 M formic acid in 10% (v/v) ACN/H2O. Separation and voltage: 50 mbar (30 s), +30 kV. SL: 0.1% FA in 1:1 (v/v) MeOH/H2O; 4 μL/min. ESI-MS: + 4 kV; SC: ESI 4000 V, CGP: 40 psi, DGT: 250 °C, NP: 4 psi. | 110 |
| Green/roasted coffee | Metabolites | SLE | 5 mg of grounded coffee mixed with 1.5mL 25% (v/v) MeOH in H2O and SLE carried out in Thermomixer Compact (700rpm, 15 min @ 25 °C). After centrifugation (3500 rpm, 10 min, 25 °C) the supernatant fraction directly analyzed by CE–MS | CZE: Uncoated fused-silica capillaries of 50 μm ID with a total length of 100 cm. BGE: 1 M formic acid (pH 1.8). Injection and voltage: +30 k 50 mbar (80 s), +30 kV. SL: 1 M HOAc in 50:50 (v/v) MeOH/H2O; 8 μL/min. ESI-MS: Positive, +3 kV., SC: DGF: 5 L/min, DGT: 180 °C, NP: 10 psi; SG (jet stream): 3 L/min, 150 °C | 79 |
| Corn | Pesticides | QuEChERS | 15-g homogenized sample (fortified with QC spiking solution (100 μL) if needed and vortexed for 1 min) + 15.0 mL ACN containing 1% (v/v) of HOAc added to each tube as well an Agilent-buffered QuEChERS extraction salt packet contenting 6 g MgSO4 and 1.5 g NaOAc. Sample tubes capped tightly, hand-shaken vigorously (1 min), and centrifuged (5000 rpm, 5 min). 1 mL supernatant diluted with BGE 1:1 (v/v), filtered (0.2 μm PVDF and PP membrane) and analyzed. | CZE: A 58-cm long, 50 μm i.d., 360 μm o.d. fused-silica capillary (Agilent, Redmond, OR, USA) with the inner wall coated with poly(vinyl alcohol) (PVA). BGE: 0.1 M formic acid (pH 2.4). Separation and voltage: 100 mbar (12 s), +28 kV. SL: BGE diluted 5x with 1:1 (v/v) MeOH/H2O; 5 μL/min ESI-MS: Positive, +4 kV; SC: DGF: 6 L/min, DGT: 250 °C, NP: 7 psi. | 7 |
| Barley grain and malt | Hordeins | SLE | 15 g barley grain/malt grounded in a coffee grinder and stored at RT. 250 mg ground sample mixed with 1 mL of 50:50 (v/v) IPA:H2O, incubated (30 min, constant shaking) and centrifuged (15,000×g, 5 min, RT). Supernatant filtered (0.20 μm nylon filter) before the analysis. | CZE: A 72 cm LT × 75 μm id × 365 μm od fused silica capillary coated with hydroxypropyl cellulose. BGE: 1 M HOAc (pH 2.3). Injection and voltage: 50 mbar (20 s), +25 kV. SL: 0.05% (v/v) FA in 60:40 (v/v) IPA/H2O; 3.3 μL/min. ESI-MS: +4 kV, SC: DGF: 4 L/min, DGT: 300 °C, NP: 7 psi. | 49 |
| Dry-cured ham | Metabolites (amino acids, organic acids and nucleotides) | SLE | Ham sample extracted by plunging the samples into 500 μL MeOH containing (20 μM each methionine sulfone, D-camphor-10-sulfonic acid, and 2-(N-morpholino) ethanesulfonic acid as IS. Samples homogenized (1,500 rpm, 5 min) using cell disruption device. Homogenized sample mixed with 500 μL CHCl3 and 200 μL H2O, centrifuged (4,600g, 15 min, 4 °C) and upper aqueous layer (300 μL) centrifugally filtered (5-kDa cutoff filter) at 9,100g for 4 h at 20 °C. Filtrate (300 μL) lyophilized and dissolved in 50 μL of H2O containing reference compounds (200 μM 3-aminopyrrolidine and trimesate) before analysis. | CZE: BGE: 1 M formic acid, 50 mM NH4OAc (pH 8.5) SL: 1:1 (v/v) MeOH/H2O + 0.1 μM Hexakis (cation analysis; 5 mM NH4OAc in 1:1 (v/v) MeOH/H2O + 0.1 μM Hexakis (anion analysis); 10 μL/min. ESI-MS: Positive, +4 kV; SC: DGF: 7 L/min, DGT: 300 °C. | 80 |
| Chili powder | Sudan dyes Sudan I, Sudan II, Sudan III and Sudan IV | Freeze-out cleanup | 2.0 g sample + 5 mL ACN sonicated 5 min (35 kHz, 120 W), centrifuged (4025×g, 5 min) and supernatant transferred to 15 mL centrifuge tube (solid residue reextracted). Combined supernatants mixed with 2.5 mL H2O and 1 g NaCl and placed at −20 °C for 3 h. 100 μL of the ACN layer diluted to 1:10 with 900 μL of 6:1:1:1 (v/v/v/v) H2O/ ACN/MeOH/THF mixture, resulting in final dilution of 1:50. Diluted solution filtered (0.22 μm nylon syringe filter) and analyzed by MEKC/MS/MS. | MEKC: BGE: 60:20:10:10 (v/v/v/v), 25 mM ammonium perfluorooctanoic acid; /ACN/MeOH/THF (pH 9.0); Injection and voltage: 5 kPa, 50s, +25 kV. SL: 50:49.9:0.1 (v/v/v) IPA/H2O/FA, 10 μL/min. ESI-MS: +3 kV; SC: DGF: 6 L/min; DGT: 250 °C; NP: 206.8 kPa | 89 |
| Plastic food packaging materials | Organotin | SPE | Food packaging sample rinsed (H2O), dried, and cut into small pieces (approx. 0.4 × 0.4 cm). 0.5 g sample extracted with 5 mL DCM (ultrasonic,30 min @ 25 °C), evaporated to dryness (rotary evaporator @ 45 °C) and residue reconstituted (3 mL of 10 : 90 (v/v) ACN/H2O). 30 mL extracts (pH 2 adjusted with 1 M HCl) passed (1 mL/min) through C18 SPE extraction column (pre-conditioned with 5 mL MeOH 5 mL H2O), rinsed (10 mL H2O), air dried, and eluted with 3 mL of 5% HOAc in ACN. Eluted analyte evaporated to dryness (N2) and reconstituted (200 μL of 5% HOAc in ACN) for CE-ESI-MS analysis. | CZE: A fused-silica capillary (30 μm i.d. and 150 μm o.d., with a length of 90 cm, smoothened with 2000 mesh sand paper and etched with HF solution to form a porous section of approximately 5 cm using a sheathless interface (made in house). BGE: 10% HOAc in 20:80 (v/v) MeOH/ACN. Sheathless ESI-MS: Positive, +1.6 kV; SC: DP: 60 eV, CGP:10 psi, interface heating: 50 °C | 32 |
Hexakis: hexakis (2,2-difluoroethoxy)phosphazene; PLE: pressurized liquid extraction; EAE: enzyme-assisted extraction; CTAB: cetyltrimethylammonium bromide; SA: sinapinic acid; TFA: trifluoroacetic acid; TEA: trimethylamine; IS: internal standard; MSLE: microwave-assisted solid-liquid extraction; AA: amino acid; FA: formic acid; DSPE: dispersive solid phase extraction; PSA: primary-secondary amine; UHT: Ultrahigh temperature; PST: paralytic shellfish toxins; MAE: microwave-assisted extraction; DE: dispersive extraction; CGP: curtain gas pressure: PIPES: 1,4-piperazine di-ethane sulfonic acid. AMP: adenosine 5-monophosphate; CMP, cytidine 5-monophosphate; CUF, centrifugal ultrafiltration; GMP: guanosine 5_-monophosphate; IMP: inosine 5-monophosphate; PNP, programmed nebulizer pressure; UHQ, ultra high quality; UMP, uridine 5-monophosphate