Acrylamide in Foods - Semantic Scholar

Acrylamide in Foods: Chemistry and Analysis. A Review

Food and Bioprocess Technology An International Journal ISSN 1935-5130 Volume 4 Number 3 Food Bioprocess Technol (2010) 4:340-363 DOI 10.1007/s11947-010-0470x

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Author's personal copy Food Bioprocess Technol (2011) 4:340–363 DOI 10.1007/s11947-010-0470-x

REVIEW PAPER

Acrylamide in Foods: Chemistry and Analysis. A Review Javad Keramat & Alain LeBail & Carole Prost & Nafiseh Soltanizadeh

Received: 13 February 2010 / Accepted: 3 November 2010 / Published online: 25 November 2010 # Springer Science+Business Media, LLC 2010

Abstract Acrylamide is a potential cause of a wide spectrum of toxic effects and is classified as probably “carcinogenic in humans”. The discovery of acrylamide in human foods has given rise to extensive studies exploring its formation mechanisms and levels of exposure and has spurred search into suitable analytical procedures for its determination in foodstuffs. However, the exact chemical mechanisms governing acrylamide formation are not yet known and cheap, convenient, and rapid screening methods are still to be developed. Acrylamide in food is produced by heat-induced reactions between the amino group of asparagine and the carbonyl group of reducing sugars along with thermal treatment of early Maillard reaction products (Nglycosides). Similarly, the decarboxylated Schiff base and decarboxylated Amadori compounds of asparagine as well as the Strecker aldehyde have been proposed as direct precursors and intermediates of acrylamide. Corresponding chromatographic methods are used to determine various structural groups present in Maillard reaction model systems. Gas chromatography-mass spectrometry and liquid chromatography with tandem mass spectrometry analysis are both acknowledged as the main, useful, and authoritative methods for acrylamide determination. This review is an attempt to summarize the state-of-the-art knowledge of acrylamide chemistry, formation mechanisms, and analytical methods. Special attention is given J. Keramat : N. Soltanizadeh (*) Department of Food Science and Technology, Isfahan University of Technology, Isfahan 84156, Iran e-mail: [email protected] A. LeBail : C. Prost ENITIAA, rue de la Geraudiere, BP 82225, 44322, Nantes, Cedex 3, France

to comparison of different chromatographic techniques, particularly the novel, simple, and low-cost methods of its determination. Keywords Acrylamide chemistry . Mechanism of acrylamide formation . Acrylamide analysis

Introduction In April 2002, the formation of acrylamide in starch-rich foods or high-temperature cooking, like with a variety of baked and fried foods cooked at high temperature, was reported by researchers from the Swedish National Food Administration (SNFA) and the University of Stockholm. Since the Swedish report, similar findings have been reported by numerous other countries, including, Norway, Switzerland, UK, and the USA (FAO/WHO 2004).Then, much interest was created about this compound, and moderate levels of acrylamide (5–50 ppb) in heated protein-rich foods and higher contents (150–4,000 ppb) in carbohydrate-rich foods such as potato, beetroot, and selected commercial potato products were reported. Median levels of acrylamide were found at 1,200 ppb in potato chips, 450 ppb in French fries, and 410 ppb in biscuits and crackers (Table 1; Tareke et al. 2002). Table 2 provides some information about contribution of food groups to acrylamide exposure. Acrylamide is a potential cause of a wide spectrum of toxic effects (Eriksson 2005; IARC 1994; European Union Risk Assessment Report 2002; Manson et al. 2005), including neurotoxic effects as has been observed in humans. Also, acrylamide has been found to be carcinogenic in animals, increasing incidences of a number of benign and malignant tumors identified in a variety of

Author's personal copy Food Bioprocess Technol (2011) 4:340–363

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Table 1 Acrylamide content of various food products Commodities

Reported maximum, μg/kg

Number of samplesa

3,304 (12,346)

343

156

7,834

Cereal and pasta, raw and boiled Cereal and pasta processed (toasted, fried, grilled) Cereal-based processed products, all Bread and rolls

113 (372)

15

71

47

200 (634)

123

110

820

2,991 (11,327)

366

151

7,834

1,294 (5,145)

446

130

3,436

Pastry and biscuits

1,270 (4,980)

350

162

7,834

Breakfast cereals

369 (1,130)

96

131

1,346

Cereal and cereal-based products

Pizza

Mean concentration, μg/kg

CV (%)

Food item

58 (85)

33

270

763

Fish and seafood (including, e.g., breaded, fried, baked)* Meat and offal (including, e.g., coated, cooked, fried) Milk and milk products

52 (107)

25

180

233

138 (325)

19

174

313

62 (147)

5.8

119

36

Nuts and oilseeds

81 (203)

84

233

1,925

Pulses

44 (93)

51

137

320 5,312

Root and tubers

2,068 (10,077)

477

108

Potato puree/mashed/boiled

33 (66)

16

92

69

Potato baked

22 (99)

169

150

1,270

Potato crisps (US=chips)

874 (3,555)

752

73

4,080

Potato chips (US=French fries)

1,097 (6,309)

334

128

5,312

Potato chips, croquettes (frozen, not ready to serve)

42 (48)

110

145

750

469 (1,455)

509

120

7,300

Coffee (brewed), ready-to-drink Coffee (ground, instant, or roasted, not brewed) Coffee extracts

93 (101)

13

100

116

205 (709)

288

51

1,291

20 (119)

1,100

93

4,948

Coffee decaffeinate

26 (34)

668

169

5,399

Coffee substitutes

73 (368)

845

90

7,300

Cocoa products

23 (23)

220

111

909

Green tea (roasted)

660

Stimulated and analog

29 (101)

306

67

Sugar and honey (mainly chocolate)

58 (133)

24

87

112

Vegetables

84 (193)

17

206

202

Raw, boiled and canned

45 (146)

4.2

103

25

Processed (toasted, baked, fried, grilled)

39 (47)

59

109

202

Fruits, fresh

11 (57)

90%). However, one drawback is the long extraction time of 10 days while no information is available on the potential acrylamide formation during the extraction (Wenzl et al. 2003). To overcome these problems, some researchers have extracted acrylamide selectively by using ASE without co-extracting the starch, which leads to the simultaneous simplification of the subsequent sample clean-up (Brandl et al. 2002). Although solubility of acrylamide in most organic solvents is lower than water, dichloromethane appears to be a promising extraction solvent, particularly addition of 2% ethanol as a modifier improves the results considerably. Re-extraction of the organic phase with water delivers an aqueous solution which is almost free of any interfering matrix components. For instance, fatty components remain in the organic phase; thus, defatting of the sample prior to extraction is not necessary any more. Applying this method, nearly all of the target foodstuffs could be analyzed in a similar fashion with satisfactory results (Brandl et al. 2002; Dionex 2004). In using the ASE method, pure water, 10 mM formic acid solution, and acetonitrile were tested as the extraction solvent in LC methods of acrylamide determination. Pure water extracts showed lower recoveries than the formic acid, but the formic acid extracts had a lower stability. Acetonitrile extracts were cleaner, as less material was coextracted from the sample matrix. With three extraction cycles of 4-min durations, a yield of 95% in the first extract and an additional 8% in the second extraction of the same sample using 10 mM formic acid were achieved (Dionex 2004). However, a mixture of water and acetone has also been reportedly used as the extractant (Takatsuki et al. 2003; Fauhl et al. 2002). Other researchers have also used the ASE device (Cavalli et al. 2002; Höfler et al. 2002). Different mechanical methods can be used for the initial extraction steps that include shaking at high speeds on a horizontal shaker (Becalski et al. 2003), using a rotating shaker (US Food and Drug Administration 2003), occasional swirling (Ahn et al. 2002; Takatsuki et al. 2003), and mixing with a blender or mixing on a vortex (Fauhl et al. 2002). After extraction, the aqueous phase is centrifuged and different laboratories have reported different centrifugation conditions, as described in Wenzl et al. (2003). Becalski et al. (2003) and FDA (2003) recommended combined centrifugation and filtration using a 5 kDa cut-off Centricon Plus-20 and 0.45 μm PVDF filters, respectively. Ono et al. (2003) used centrifugation filters with a 3 kDa cut-off after clean-up of the extract by SPE. To control the recoveries achieved and to keep track of possible losses during the extraction and purification steps, an internal standard is added to the food-extraction mixture. Similar to the GC-MS methods, isotopically labeled [13C3]acrylamide (Tareke et al. 2002; Becalski et al. 2003), [D3]-

Sample

[13C3]-acrylamide 16 g sample+IS+80 ml water+ 10 ml Becalski et al. Potato chips, dichloromethane, mixing (15 min), 2003 potato crisps, or [D3] centrifugation (2 h at 24,000×g), cereals, acrylamide centrifugation of 10 ml supernatant bread, coffee (4 h at 4,000×g) in 5 kDa centrifuge filter, passing 5 ml of filtrate through Oasis MAX cartridge connected with tandem with Oasis MCX cartridge, loading the elution onto the preconditioned ENVl-carb cartridge,

Hypercarb column, Mobile phase, 15% methanol in 50×2.1 mm 1 mM ammonium formate; 0.175 ml/min; Inj, 5–10 μl; column temperature, 28 °C

MS/MS; LOD, ~6 μg/kg

Ionization mode, positive; desolvation temperature, 250 °C; source temperature, 120 °C; desolvation gas flow, 525 L/h; cone gas flow, 50 L/ h; collision gas pressure, 2.6×10-3 mbar; ion energy, 10 V; MRM: dwell time; 0.3 s; cone voltage, 34 V; mass span, 0.1 Da;

Capillary voltage, 4.1 kV; cone voltage, 20 V; source temperature, 120 °C; desolvation temperature, 250 °C; m/z transitions (collision energy); AA, 72> 72 (5 eV), 55 (10 eV), 27 (19 eV); IS, 75>75 (5 eV), 58 (10 eV), 29 (19 eV)

350

–

Synergi Hydro-RP Mobile phase, 0.5% methanol/0.1% LC–ESI-MS/ MS; LOD, acetic acid in water; 0.2 mL/min; 80 A column, 10 μg/kg run-time, 10 min; Inj, 20μL 250 mm×2 mm

–

Roach et al. 2003

Ion spray voltage, 5.2 kV; turbo Mobile phase: methanol/water=10/ LC–MS/MS gas temperature, 450 °C; m/z LOD, 0.2 ng/ 90; 0.1 mL/min; run time, transitions (collision energy); mL LOQ, 10.2 min; Inj, 2 μL AA, 72>55 (18 eV); IS, 75> 0.8 ng/mL 58 (18 eV)

Atlantis dC18 column, 150 mm× 2.1 mm

–

[2 H3]acrylamide 50 g sample+IS+300–400 ml water, homogenization, centrifugation (20 min at 48,000×g), freezing and melting of supernatant, centrifugation (10 min at 21,700×g), fractionation of 0.5–2 ml supernatant on SPE cartridge, fraction collected and centrifugation (10 min at 27,000×g), filtration of supernatant through 0.22 μm syringe filters, centrifugation of filtration with cut-off of 3 kDa (50 min at 14000×g) 1 g sample+IS+ 9 ml water, mixing for [13C3]acrylamide Cereal, bread crumb, potato 20 min, centrifugation (15 min at 9,000 rpm), centrifugation of 5-ml chips, coffee aliquot in spin filtration tube (2– 4 min at 9,000 rpm), pretreatment of Oasis HLB SPE cartridges (3.5 mL of methanol followed by 3.5 mL of Water), extract loaded (1.5 ml) and collected

Ono et al. 2003

Various food products

Capillary voltage, 2 kV; cone Hypercarb HPLC Mobile phase, methanol/water=20/ LC–MS/MS; voltage, 20 V; source LOD, 80 (gradient); 0.4 mL/min; Inj, column, temperature, 125 °C; 58 (9 eV)

–

Mashed potato, 2–4 g sample+IS+40 ml water, [2 H3]acrylamide homogenization (2 min at 9,500 minrye flour, 1 crisp bread, ), centrifugation (3600×g, 10 min), potato crisps extra-centrifugation for potato chips (10 min at 16,800) after precipitation by freezing, pretreatment of SPE with 1 ml acetonitrile and washing with water, filtration through 0.22 μm Syringe filter

Sheath gas, 60 units; auxiliary gas, 10 units; corona current, 5 μA; vaporize temperature, 350 °C; capillary temperature, 150 °C; m/z transitions (collision energy); AA, 75>55; IS, 75>58

Detector parameters

Rosén and Hellenäs 2002

LC-MS/MS; LOD, 10 ng/ ml

Detector LOD and LOQ

Synergy Polar-RP Column, 150× 3 mm

Mobile phase: water containing 0.1% acetic acid; 0.5 ml/min; column temperature, 40 °C

Chromatography parameters

–

Derivatization Column

Accelerated sample extraction using dichloromethane containing 2% ethanol, 2 g sample+IS+200 μl water in five cycles (10 min each at 80 °C, 100 bar), mixing of combined extract with 5 ml water, using aliquot of aqueous extract

Internal standard


Extraction and clean-up

Brandl et al. 2002

Liquid chromatography methods

Study

Table 3 Chromatographic-based methods for the determination of acrylamide in food products


Breakfast cereal, crackers

French fries


Riediker and Stadler 2003

Mestdagh et al. 2004

Hoenicke et al. 2004

Andrzejewski Coffee et al. 2004

Sample

Study

Table 3 (continued)

Extraction with water, homogenization using a dispersing tool, centrifugation, mixed with acetonitrile to precipitate coextractives, acetonitrile evaporation, preconditioning with methanol and water (isolute multimode, 2, 2×2 mL; Accubond II SCX 1, 1 mL), residual water removal, extract (2 mL) loaded and collected, collected (1 mL) extract charged onto the latter cartridge, effluent collected, filtration through a syringe filter unit 1 g sample+IS+10 ml hexane, 10 min shaking, centrifugation (10 min at 4000 rpm), hexane removal, adding 10 ml Milli-Q water, 20 min shaking, centrifugation (20 min at 4,000 rpm), ultrafiltration through 0.45-μm membrane filter, preconditioning of cartridge (5 ml methanol and 5 ml water), loading on Oasis HLB and Varian Bond Elut Accurate cartridge Weighed into a filter, placed on a Witt'scher pot, equipped with a vacuum pump, defatted by adding iso-hexane (80 mL), spiked with IS, incubation (30 min), extraction with water (20 mL) in an ultrasonic bath (60 °C, 30 min) purification by adding acetonitrile (20 mL), Carrez I and Carrez II (500 μL each), centrifugation (4,500×g, 10 min), supernatant filtration through a membrane filter Spiked with IS, extraction with HPLC grade water, centrifuge tubes capped and shaken/vortexed (30 s), centrifugation, aliquot transfer to a Maxi-Spin PVDFb filtration tube (0.45 μm) and centrifugation Conditioning (Oasis HLB 6 cc cartridge) with methanol and water (3.5 mL each), filtered extract (1.5 mL) loaded, water (1.5 mL) elution and effluent transfer onto the second cartridge (Bond ElutAccucat), a mark placed on the

discarding first 1 ml and collecting remaining (f1), washing cartridge with 1 ml water (f2) and 1.5 ml 10% methanol (f3), analyzing f1, f2, f3



Electrospray voltage, 5.5 kV; Mobile phase, 50% acetonitrile in LC–MS/MS; Merck source temperature, 350 °C; LiChrospher 100 1% acetic acid isocratic for 5 min, LOD, 72, 55, 44 acetonitrile for 5 min, 0.7 mL/min 75, 58, 44 (spilt 1:5), runtime, 10 min; Inj, (18 eV) 10 μL or 40 μL

Synergi Hydro-RP Mobile phase, 0.5% methanol in 80A column, water, 0.2 mL/min; run time, 250 mm×2 mm 10 min; Inj, 20 μL

–

–

[13C3]acrylamide

LC–MS/MS; Capillary voltage, 4.1 kV; cone LOD, 10 μg/ voltage, 20 V; source kg; temperature, 120 °C; desolvation temperature, 250 °C; m/z transitions (collision energy); AA, 72> 72 (5 eV), 55 (10 eV), 27 (19 eV); IS, 75>75 (5 eV), 58 (10 eV), 29 (19 eV)

m/z transitions (collision energy); AA, 72>72 (5 eV), 72>55 (10 eV); IS, 75>58 (10 eV), 75>30 (20 eV)

[2H3]acrylamide

LC-MS/MS Mobile phase, 92% water (containing 0.1% acetic acid) and 8% water/methanol (35/65, with 0.3% fomaric acid); 0.15 ml/min

Atlantis dC18 column, 150 mm× 2.1 mm

–

[D3]acrylamide

interchannel energy, 0.05– 0.1 s; m/z transitions (collision energy); AA, 72> 55 (11 eV), 72>54 (11 eV), 72>44 (14 eV), 72>27 (16 eV); IS, 75>58 (11 ev)

Detector parameters

LC–ESI-MS/ Capillary voltage, 3.1 kV; cone MS; LOQ, 45 voltage, 22 V; source temperature, 100 °C; desolvation temperature, 350 °C; m/z transitions (collision energy); AA, 72> 55 (11 eV), 54 (20 eV), 27 (20 eV)


– Mobile phase, 0.01% aqueous Shodex RSpak formic acid/methanol =6/4, DE-613 polymethacrylate 0.75 mL/min split to 0.35 mL after the LC column using a gel column, PEEKb; T-piece, run time, 150×6 mm 12 min; Inj, 50 μL


[13C3]acrylamide

Internal standard

Author's personal copy

Food Bioprocess Technol (2011) 4:340–363 351

Sample


Rice, bread, corn chips, potato chips, biscuits, candy, coffee

Zhang, et al. 2007

Kim et al. 2007

Gökmen et al. Potato chips 2005

Study

Table 3 (continued) Internal standard

[13C3]acrylamide 1.5 g sample+IS, 10 min standing, adding 20 ml petroleum ether, 10 min shaking, removal of petroleum ether and repeating defatting, adding 7 ml NaCl (2 mol/L) and 20 min shaking, centrifugation (15 min at 15,000 rpm), extracting the residue with 8 ml NaCl, extracting the NaCl solution with 15 ml ethyl acetate for three times, drying organic phase under nitrogen, adding 1.5 ml water to residue, preconditioning of Oasis HLB cartridge (3.5 ml methanol and 3.5 ml water), loading (1.5 ml) and extracting 10 g sample+IS+ 98 ml water, 20 min [13C3]acrylamide shaking, centrifugation (10 min at 9,000 rpm), conditioning C18 solidphase extraction cartridge (5 ml methanol and 5 ml water), loading and collecting, filtration through 0.45 μm membrane

outside of the tube at a height equivalent to 1 mL of liquid above the sorbent bed, conditioning with methanol and water (2.5 mL each), sample loaded and collected [13C3]acrylamide 2 g sample+IS+10 ml methanol, mixture centrifugation (10 min at 11180×g), supernatant clarification with Carrez I and IIa and centrifugation, drying of 2.5 ml supernatant under nitrogen, resolving residue in 1 ml water, Oasis HLB cartridge preconditioning with 1 ml of methanol and 1 ml of water, extract loaded (1 ml) and collected, filtration through a 0.45 μm syringe filter


Atlantis dC18 column; 210× 1.5 mm

Aqua C18 HPLC column, 2× 250 mm

–

Synergi MAXRP, 250×4.6 mm

Luna C18, 250× 4.6 mm

HiChrom 5 C18, 300×4.6 mm

bond C18, 250× 4.6 mm

Zorbax Stable-

Zorbax SIL, 250× 4.6 mm

HILIC, 250× 4.6 mm

Atlantis

Atlantis dC18, 250× 4.6 mm

–

–


Detector parameters

226 nm with peak spectra 190– DAD, LOD, 350 nm 2.0 μg/ml, LOQ, 4.0 μg/ kg


Capillary voltage, 4.2 kV; source temperature, 120 °C; desolvation temperature, 240 °C; desolvation gas flow rate, 650 L/h nitrogen; argon gas pressure, 2.5 mbar; m/z transitions; AA,72>55; IS, 75>58

352

Mobile phase, aqueous 0.2% acetic LC-MS/MS; LOQ, 2 μg/ acid and 1% methanol; 0.2 ml/ kg min; run time, 14 min; Inj, 20 μl

Mobile phase, 10% methanol /0.1% HPLC-ESI-MS/ Capillary voltage, 3.5 kV; cone voltage, 50 V; source fomaric acid in water; 0.2 ml/min; MS temperature, 100 °C; column temperature, 25 °C desolvation gas temprature, 350 °C; desolvation gas flow, 400 L/h nitrogen; cone gas flow, 45 L/h nitrogen; argon collision gas pressure, 3×103 mbar; m/z transitions (collision energy); AA, 72> 72 (1 eV), 72>55 (6 eV), 72 >44 (9 eV), 72>27 (15 eV); IS, 75>75 (1 ev), 75>58 (6 eV), 75>30 (15 eV)

Mobile phase, 1.0 or 0.5 ml/min; column temperature, 25 °C; Inj, 20 μl



Sample


Internal standard

Fried food

Bromination 10 g sample+ 100 ml water, filtration of N,N-Dimethyl acrylamide extract through glass-fiber filter, purification on carbograph 4 column, addition of standard, bromination 10 g sample+ 100 ml water, filtration of N,N-dimethyl Protein-rich Bromination acrylamide or extract through glass-fiber filter, and [13C1]acrylamide purification on carbograph 4 column, carbohydrateaddition of standard, bromination rich foods Various food 50 g sample+IS+300-400 ml water, [2H3]acrylamide Bromination products homogenization, centrifugation

CP-Sil 24 CB Lowbleed/MS

BPX-10 column, 30 m×0.25 mm

HP PAS 1701 column, 25 m× 0.32 mm

85 °C held for 1 min, ramped at 25 °C/min to 175 °C, held for

65 °C held for 1 min, ramped at 15 °C/min to 250 °C, held for 10 min; Inj, 2 μL; splitless

65 °C held for 1 min, ramped at 15 °C/min to 250 °C, held for 10 min; Inj, 2 μL; splitless

Mobile phase, 10 mM fomaric acid; LC-MS, LOQ, 15 μg/kg 0.3 ml/min; column temperature, 25 °C

– Atlantis T3 column, 150 mm× 4.6 mm

ODS-C18 column, Mobile phase, 10% acetonitrile and LC-MS/MS; LOD, 1 ng/ 90% water containing 0.1% 250 mm× ml; LOQ, formic acid; 0.4 ml/min; Inj, 4.6 mm 5 ng/ml

–

GC–MS; LOD, m/z transitions; AA, 52, 150; 0.2 ng/mL IS, 155, 153

GC–MS; LOD, m/z transitions; AA, 152, 150, 5 μg/kg 106; IS, 180, 155

GC–MS; LOD, m/z transitions; AA, 152, 150, 5 μg/kg 108,106; IS, 180, 178

Capillary voltage, 2 kV; corona current, 5 μA; drying gas temperature, 350 °C; m/z transitions (collision energy); IS, 72

Capillary voltage, 1 kV; cone voltage, 20 V; 1source temperature, 110 °C; desolvation temperature, 400 °C; desolvation gas flow, 600 L/h nitrogen; cone gas flow, 50 L/h; argon collision gas pressure to 2×10-3 mbar; m/z transitions (collision energy)AA, 72>55 (13 eV); IS, 75>58 (13 eV)

200 nm Mobile phase: sulfuric acid (5 mM); HPLC-DAD; LOD, 30 μg/ 0.6 ml/min; Inj, 20 μl; column kg temperature, 50 °C

HC-75 H+ column, 305 mm× 7.75 mm

Detector parameters

–




Food Bioprocess Technol (2011) 4:340–363

Ono et al. 2003

Tareke et al. 2002

Tareke et al. 2000

Genga et al. 2008

acrylamide 2 g sample+ 10 ml methanol 75%, Fried potato treating with Carrez I and II, shaking chips, (45 mint 100 rpm), centrifugation biscuits, Chinese fried/ (10 min at 10000 rpm), evaporating 5 ml of supernatant to 1 ml under baked foods nitrogen, preconditioning Oasis HLB cartridge (5 ml methanol and 5 ml water), loading and eluting by 2 ml 10% methanol, filtration of extract with 0.45 μm syringe filter [13C3]acrylamide Liu et al. Tea 1 g sample+ IS+9 ml water, 20 min 2008 shaking, adding 10 ml acetonitrile +4 g anhydrous magnesium sulfate + 0.5 g of sodium chloride, 1 min shaking, centrifugation (5 min at 5,000 rpm), separating of acetonitrile layer and drying under nitrogen, dissolving the residue in 05 ml water, filtering through 0.45 μm syringe filter, preconditioning of Oasis MCX SPE cartridge (2 ml methanol and 2 ml water), loading and collecting, filtration through 0.22 μm syringe filter [13C3]acrylamide Gökmen et al. Cookie, potato Aqueous extraction, 1 g sample+IS+ 9 ml of 10 mM fomaric acid, treated 2009 crisp, bread with Carrez I and II, centrifugation crisp (10 min at 5,000 rpm), four stage extraction of supernatant without Carrez clarification, preconditioning Oasis MCX cartridge, extract loaded and collected, filtration through 0.45 μm nylon filter. Methanol extraction, 1 g sample+IS +9 ml methanol, centrifugation (10 min at 5,000×g), supernatant treated with Carrez I and II, centrifugation (10 min at 5,000 rpm), four stage extraction of supernatant, drying under nitrogen, reconstitution of residue in 1 ml water, elution through preconditioned Oasis MCX cartridge, filtration through 0.45 μm nylon filter. Gas chromatography methods

Study

Table 3 (continued)

Author's personal copy 353

Bread

[13C3]acrylamide Cereal products Weighted (15 g) into a 250 mL centrifuge bottle, spiked with IS, sample suspended in water (150 mL) and homogenized (30 s), suspension acidified to pH 4–5 by addition of glacial acetic acid (∼1 mL), treated successively with Carrez I and IIc (2 mL each), centrifugation (16,000g, 15 min), bromination, extract transferred onto a glass chromatography column containing calcinated sodium sulfate and activated Florisil (5 g each), using small aliquots taken from hexane (50 mL), acrylamide derivative eluted with acetone (150 mL), evaporated to ∼2 mL and then to dryness (N2), redissolved in EtAcd (400μL), triethylamine added (40μL)filtered through a 0.2 μm microfilter

Hamlet et al. 2004

Pittet et al. 2004

(20 min at 48,000×g), freezing and melting of supernatant, centrifugation (10 min at 21,700×g), fractionation of 0.5-2 ml supernatant on SPE cartridge, fraction collected and centrifugation (10 min at 27,000×g), filtration of supernatant through 0.22 μm syring filters, centrifugation of filtration with cut-off of 3,000 Da (50 min at 14,000×g) [2H3]Acrylamide Weighed into a filter, placed on a Witt’scher pot, equipped with a vacuum pump, defatted by adding iso-hexane (80 mL), spiked with IS, incubation (30 min), extraction with water (20 mL) in an ultrasonic bath (60 °C, 30 min) Purification by adding acetonitrile (20 mL), Carrez I and Carrez II (500 μL each), centrifugation (4500×g, 10 min), supernatant filtration through a membrane filter 5 g sample+IS+deionised water, 1 min [13C3]acrylamide shaking, adding 0.3 ml glacial acetic acid, treating with Carrez I and II, centrifugation (20 min at 1942 g)


Internal standard

Hoenicke et al. 2004


Sample

Study

Table 3 (continued)

Bromination

Bromination

–

65 °C held for 2 min, ramped at 15 °C/min to 250 °C, held for 5 min; Inj, 1 μl; splitless

70 °C held for 1 min, ramped at 20 °C/min to 230 °C, held for 10 min; Inj, 1 μL, splitless

6 min, ramped at 40 °C/min to 250 °C, held for 7.52 min


Detector parameters

GC-MS/MS; LOD; 0.01 ng/ml

Ionization mode, negative; argon collision gas pressure, 1.5 mTorr; m/z transitions (collision energy); AA, 149> 70 (10 eV), 151>70 (10 eV); IS, 152>73 (10 ev), 154>73 (10 eV)

m/z transitions;AA, 89>72, 55; GC–MS/MS; IS, 92>75 LOQ, 30 μg/ kg


GC–MS; LOD, m/z transitions; AA, 149, 70; ZB-WAX capillary 65 °C held for 1 min, ramped at IS, 154, 110 column, 30 m× 15 °C/min to 170 °C, 5 °C/min to 2 μg/kg; 0.25 mm 200 °C, 40 °C/min to 250 °C, held for 15 min; Inj, 2 μL, splitless

Rtx®-50 column, 30 m×250 μm

DB-WAX capillary column,30 m× 0.25 mm

column, 30 m× 0.25 mm



354 Food Bioprocess Technol (2011) 4:340–363

DB-WAX silica capillary column, 30 m× 0.25 mm

–

French fries, potato chips

Lee et al. 2007

Carrez I, potassium hexacyanoferrate (II) trihydrate solution; Carrez II, zinc sulfate heptahydrate solution

GC–HRTOF MS: high-resolution time-of-flight mass analyzer

SPME (Solidphase microextraction). The microextraction fibers tested herein were coated with 75μm carboxen/poly(dimethylsiloxane) (CAR/PDMS); 65μm carbowax/divinylbenzene (CW/ DVB); 85 μm polyacrylate (PA); 100 μm poly(dimethylsiloxane) (PDMS); 65 μm poly(dimethylsiloxane)/divinylbenzene (PDMS/DVB).

c

b

a

LOD limit of detection, LOQ limit of quantification, IS internal standard, Inj injection volume, AA acrylamide, SPE solid phase extraction, SPME solid-phase microextraction

The microextraction fibers tested herein were coated with 75–>μm carboxen/poly(dimethylsiloxane) (CAR/PDMS); 65 μm carbowax/divinylbenzene (CW/DVB); 85 μm polyacrylate (PA); 100 μm poly(dimethylsiloxane) (PDMS); 65 μm poly(dimethylsiloxane)/divinylbenzene (PDMS/DVB)

Mass-to-charge ratio (m/z) scan range from 40 to 100 u

HP INNOWAx capillary column, 30 m× 0.32 mm

Bromination

[13C3]acrylamide 1.5 g sample+ IS, 10 min standing, adding 20 ml petroleum ether, 10 min shaking, removal of petroleum ether and repeating defatting, adding 7 ml NaCl (2 mol/L) and 20 min shaking, centrifugation (15 min at 15000 rpm), extracting the residue with 8 ml NaCl – 10 g sample+100 ml water, centrifugation (10 min at 5000 rpm), dilution of 1.5 ml aliquot to 15 ml with water, mixing with 15 ml buffer (pH 7), immersing of SPME fiber


Zhang et al. 2007

Ramped at 15 °C/min from 80 °C GC-PCI-MS/ MS; LOD, to 220 °C, held at 220 °C for 2 min; carrier gas, helium, 1 mL/ 0.1 μg/L min; elution time, 9.88

GC-MS; LOD, Electron ionizing, 70 eV, m/z Isothermal for 0 min, ramped at transitions; AA, 71> 15 ng/g; 10 °C/min from 80 to 280 °C, LOQ; 50 ng/g 71,55,27; IS, 74, 58 Isothermal for 13 min; flow of carrier gas 1.0 ml/min; Inj, 1 μl; splitless Ionization mode, positive; m/z GC-MECD; 110 °C for 1 min, 10 °C/min to transitions; AA, 70, 149, 151; LOD, 10 μg/ 140 °C, 140 °C held for 15 min, IS, 110, 154 kg ramped at 30 °C/min to 240 °C, and finally isothermal at 240 °C for 7 min; carrier gas, nitrogen; Inj, 1 μL,

HP INNOWAX column, 30 m× 250 μm

–

2 g sample+IS+ 20 ml methanol, Carrez [13C3]acrylamide clarification, centrifugation (10 min at 10000 rpm) using 0.45 μm microspin PVDF centrifuge filter

Potato chips

Serpen and Gokmen 2007

Detector parameters

INNOWx capillary 70 °C for 1.0 min, 20ºCmin−1 to GC–HRTOF Acquisition rate, 2 Hz; pusher column, 30 m× 240 °C (held for 10.5 min); MSb; LOQ, interval, 33 μs (30303 raw 0.25 mm carrier gas, helium, 1.0 ml/min; spectra s−1); inhibit push 15 and 40 μg Inj, 1 μl; pulsed splitless 1.0 min, kg−1 value, 14; time-to-digital 4 ml/ min−1 converter (TDC), 3.6 GHz; mass range, m/z 45–500; ion source temperature, 220 °C; transfer line temperature, 240 °C; detector voltage, 2,600 V.


–


[D3] acrylamide 3 g sample+ IS+ 4.5 ml deionized water, 30 min ultrasonic bath, adding 24 ml n-propanol, centrifugation (5 min at 11000 g), adding 5 drop olive oil, drying, dissolving the residue in 2 ml MeCN, defatting with 10 and 5 ml n-hexane, mixing 1 ml MeCN with 60 mg PSA sorbent, centrifugation (1 min at 11000 rpm),


Potato crisps, breakfast cereals, crisp bread

Internal standard

Dunovska et al. 2006


Sample

Study

Table 3 (continued)


Food Bioprocess Technol (2011) 4:340–363 355


acrylamide (Becalski et al. 2003; Ahn et al. 2002; Rosén and Hellenäs 2002; Ono et al. 2003), and [13C1]-acrylamide (Takatsuki et al. 2003) have been used. Most purification procedures consist in combining several SPE. For instance, a combination of three different cartridges: mixed-mode anion exchange, mixed-mode cation exchange, and graphitized carbon have been used (Becalski et al. 2003). Takatsuki et al. (2003) also used a similar combination of SPE cartridges for the clean-up of samples, which were measured by LC-MS with column switching. Also, a combination of SPE and filtration and/or ultracentrifugation has been used to avoid blockage of the chromatographic system (Wenzl et al. 2003). However, Höfler et al. (2002) reported that both SPE and liquid– liquid extraction did not lead to any significant improvement in the analysis. Therefore, filtration through a 0.22μm nylon filter is the only sample treatment used as cleanup procedure after extraction and before applying to HPLC. In contrast, other laboratories added acetonitrile to the aqueous extract and pipetted 0.5 ml Carrez I and Carrez II onto the sample in order to obtain a clear sample (Wenzl et al. 2003). One special aspect of the extraction procedure involves the swelling of the matrix in order to provide better access for the extraction solvents to potentially adsorbed or enclosed acrylamide. However, the side-effect associated with swelling is that it provides some time for the development of matrix/internal standard interactions. For this reason, the homogenized sample is mixed with water and an internal standard solution and kept at a pre-specified temperature for 10–20 min. Depending on the matrix, swelling yielded an increase in analyte recovery of up to 100-fold (Biedermann et al. 2002b). Although extraction at room temperature provides satisfactory results, hot water (60–80 °C) can be used to enhance the extraction. Increased recovery has also been observed by treating the sample in an ultrasonic bath (30 min at 60 °C; Schaller 2003). Problems with the high viscosity of the sample/water extraction mixture have been reported to be solved by the addition of small amounts of amylase to the mixture. In derivatization methods, acrylamide is converted to 2,3-dibromopropionamide which is volatile and can be detected on a GC with an electron capture or an alkali flame detector (Tekel et al. 1989; United States Environmental Protection Agency 1996). This bromination is mostly performed by ionic reaction (Hashimoto 1976; Arikawa and Shiga 1980). The analysis has been suggested to be performed on the more stable 2-bromopropenamide obtained after debromination of 2,3-dibromopropionamide (Andrawes et al. 1987; Martin et al. 1990). Applications of SPE columns to obtain concentrated samples or utilizing a more sensitive derivatization technique may increase the


possibility for determination of residual acrylamide in many types of food (Kawata et al. 2001; Pérez and OstermanGolkar 2003). Bromination of acrylamide has the advantage that a more volatile compound is produced and the selectivity of determination is enhanced (Wenzl et al. 2003). However, some derivatization approaches are laborious and timeconsuming. The procedure first reported by Hashimoto (1976) is carried out by adding a pre-prepared bromination solution containing potassium bromide, hydrogen bromide, and bromine to either the pre-treated or raw aqueous extracts (Tareke et al. 2002; Ahn et al. 2002; Castle 1993; Castle et al. 1991; Ono et al. 2003). In this method, the yield of 2,3-DBPA is constant and >80% when the reaction time is more than 1 h (United States Environmental Protection Agency 1996). Nemoto et al. (2002) improved the method by using different derivatization reagents including potassium bromide and sodium bromate in an acidic medium. The necessity of additional sample pre-treatment depends upon the matrix. Matrices such as carbohydrate rich foods (e.g., potato crisps or bread) require additional fractionation steps (Tareke et al. 2002; Tareke et al. 2000). Usually, the raw extract is subjected to fractionation on a graphitized carbon black cartridge. Bromination is frequently carried out overnight at 0 °C or slightly above the freezing point of water. It has also been stated that application of isotopically labeled internal standards allowed a reduction in the reaction time from overnight to 1 h. This is in accordance with the methods proposed by other scientists (Ono et al. 2003; Nemoto et al. 2002). The excess of bromine is removed after the reaction by titration with sodium thiosulfate solution (0.7–1 M) until the solution becomes colorless. The brominated acrylamide is less polar compared with the original compound and, therefore, non-polar organic solvents (usually ethyl acetate or a mixture of ethyl acetate and cyclohexane) are used for the extraction of the analyte from the aqueous phase. Gertz and Klostermann (2002) reported that, on a DB-5 MS column, a transformation of 2,3-DBPA to 2-BPA does not take place, so that it is not necessary to transform the dibrominated compound into the more stable 2monobromopropenamide by adding triethylamine. However, more recent reports confirm that, in acrylamide analysis with bromination and detection by GC-ECD in HPINNOWAX capillary column, 2-BPA rather than 2,3-DBPA was chosen as the quantitative analyte because the peak response of former was nearly 20 times higher than that of the latter (Zhang et al. 2006). Defatting has to be included in some sample preparations because of the influence of high fat content on the analysis. In one method, the fatty compounds were removed by extracting with hexane or by using graphitized


carbon cartridges after swelling (Tareke et al. 2000; Tareke et al. 2002). Other methods include a phase separation by centrifugation followed by removal of the water fraction by azeotropic distillation (Biedermann et al. 2002b; Tateo and Bononi 2003). The effects of other factors, such as pH, on acrylamide extraction have been studied. Changes in pH have been found to have a significant effect on acrylamide extraction efficiency. A higher amount of acrylamide (three to four times) was observed in food samples by changing pH towards the alkaline pH (pH>12). One reason might be that, during normal water extraction, polyacrylamide sterically hinders all of the acrylamide from getting into the solution. Alkaline pH can change the structure of the matrix and facilitate the free acrylamide to get into the solution. Also, increasing pH releases the chemically bound acrylamide (bound with protein and carbohydrate) to become available for analysis with this extraction technique (Kim et al. 2001; Svensson et al. 2003). Phase separation is usually carried out by centrifugation of the sample. Further clean-up is also performed by fractionation of the organic extraction on silica–gel cartridges (Castle 1993; Castle et al. 1991). Since silica is of high water adsorptivity, ethyl acetate has to be dried or replaced by cyclohexane to avoid any change in silica activity. Florisil is also used as an adsorbent and a mixture of acetone and hexane as the elution solvent (Nemoto et al. 2002). Alternatively, gel permeation chromatography on Bio-Beads S-X-3 gel is performed as the final sample clean-up (Tareke et al. 2000). Recently, drying of the extract has been carried out by adding sodium sulfate (Tareke et al. 2002; Ahn et al. 2002). In addition, removal of residual water eliminates or decreases the effect of interferences from water-soluble co-extractants. The solvent volume has to be reduced to 30–200 μl to reach limits of detection in the range of 1–5 μgkg-1 before injection into the GC column (Tareke et al. 2002; Tareke et al. 2000; Castle 1993; Castle et al. 1991). Analyte Separation, Detection, and Quantification Owing to the higher polarity of the non-derivatized acrylamide, columns with polar phase, e.g., polyethylenglycol, have to be used. A total of 1–2 μl samples is usually injected in splitless mode, and analyte separation is performed on standard GC capillary columns with a length of 30 m and an internal diameter of 0.25 mm (standard in GC-MS). The initial oven temperature is normally adjusted to 60 °C to 85 °C, and the heating rate is 15 °Cmin-1. The final oven temperature is usually about 250 °C. This is while columns with middle to high polarity can be used in the case of derivatized acrylamide. However, it is possible to inject sample extracts into the GC in the split mode

357

(Biedermann et al. 2002b; Tateo and Bononi 2003; WiertzEggert-Jörissen (WEJ) GmbH 2003). The major drawback of GC analysis without derivatization is the lack of characteristic ions in the mass spectrum of underivatized acrylamide. In the electron ionization mode, the major fragment ions are at m/z 71 and 55, respectively, which are also used for quantification. Coextracted substances such as maltol or heptanoic acid produce almost the same fragmentation pattern and may, therefore, interfere. Selectivity can be increased by chemical ionization using methane as the reagent gas (Biedermann et al. 2002b). The original method using GC-MS with bromination is based on adding methacrylamide as an internal standard to the homogenized sample and then producing the derivative 2,3-dibromo-2-methylpropionamide (Castle et al. 1991). Alternatively, methacrylamide can be derivatized separately and added to the sample directly before the final adjustment of the solvent volume (Castle 1993). The latter is preferred because methacrylamide acts as a chromatographic internal standard, which means that it can monitor potential changes in the performance of the instrument. However, Castle (2003) reported a large difference between the reaction kinetics of the bromination reactions of acrylamide and methacrylamide. Quantification is performed by adding different kinds of internal standards, ranging from propionamide to isotropically labeled acrylamide. LOD is reported to be about 10– 50 mgkg-1. Acrylamide may also be determined by positive chemical ionization with ammonia as the reagent gas and tandem mass spectrometric detection of the daughter ions released from the single charged molecular ion adduct. Thus, LOD can be reduced by GC-MS/MS to 1–2 μgkg-1. The methods usually used for acrylamide quantification include external and internal standard methods. The external quantitative analysis, however, revealed poor reproducibility. Zhang et al. (2006) suggested an improvement of the quantitative method by introducing the internal standard, which is the most commonly used quantification method for acrylamide. The commonly used internal standards include isotope-labeled internal standard (e.g., 13 C3-acrylamide or 2H3-acrylamide, etc.) and non-isotopelabeled internal standards (e.g., methacrylamide, etc.). Although the isotope-labeled internal standards are the most ideal ones of the type, they can only be used in MSbased analysis and satisfactory repeatability cannot be achieved until isotope-labeled acrylamide is used. This could be due to the differing stability of the compounds and incomplete derivatization of structurally different internal standards. Due to the large differences reported between the reaction kinetics of the bromination reactions of acrylamide and methacrylamide, a long bromination reaction time is required when methacrylamide is used as the internal


standard (Wenzl et al. 2003; Castle and Eriksson 2005). The method of standard addition is also an accurate quantification method and especially useful when the matrix of the sample is very complex and extraction yields strongly vary (Basilicata et al. 2005; Ito and Tsukada 2001). In cases where isotopically labeled acrylamide is used, repeatability of results is achieved by adding N,N-dimethylacrylamide. The properties of N,N-dimethylacrylamide are obviously far different from those of acrylamide. Consequently, the coefficient of variation (CV) of the acrylamide recovery of spiked samples decreased from 26% to 7.5% when applying [13C3]-acrylamide (Tareke et al. 2002). Castle (1993) reported that 2,3-dibromopropionamide might eliminate hydrogen bromide during injection or chromatographic separation. Others used dehydrobromination instead of 2,3-dibromopropionamide (Andrawes et al. 1987; Nemoto et al. 2002; Takata and Okamoto 1991). Another reason for the large CVs might be incomplete derivatization of structurally different internal standards (methacrylamide and N,N-dimethylacrylamide). Meanwhile, most laboratories use [D3]-acrylamide, [13C3]-acrylamide or both together as internal standards. The quantification is usually performed by the method of standard addition as follows: a set of GC peak areas of the analyte obtained for each sample (one for unspiked and three for spiked portions with different levels of standard solutions) are plotted as along the y-axis, while the quantities of standard substances in the portions are plotted as the xaxis. A calibration curve is then prepared using the linear regression method to calculate the amount of the analyte in the spiked portion of the sample (Zhu et al. 2008). For the chromatographic separation of acrylamide, most scientists have used reversed-phase chromatography (different C18 columns; European Union Risk Assessment Report 2002; Rosén and Hellenäs 2002; Takatsuki et al. 2003). Different reversed-phase columns have been compared. Primisphere C18-HC is recommended because it provides sufficient retention time for acrylamide to minimize matrix interference. An alternative to reversed-phase columns is the IC. An IonPac column is a combined ion exchange with size exclusion chromatography. The advantage is that there is a good separation of acrylamide from matrix compounds of even untreated sample extracts (Ahn et al. 2002; Cavalli et al. 2002; Höfler et al. 2002). For detection of acrylamide after LC separation, tandem mass spectrometry is most often the method of choice. There are just a few exceptions in which UV at 202 nm (incurring a lack of selectivity) and single quadruple MS (in the single ion monitoring mode) are used (Höfler et al. 2002). This lack of selectivity would hamper the determination of acrylamide in complex matrices. A solution could be the use of two-dimensional (Fauhl 2003) and/or multidimensional LC (Takatsuki et al. 2003) that use four


different columns for separation of the analyte from the interference. LC-MS/MS, working in MRMs, in which the transition from a precursor ion to a product ion is monitored, has a high selectivity. MRM means that the transition from a precursor ion, which is separated in the first quadruple, to a product ion, generated by collision with argon in the second quadruple, is monitored in the third quadruple. The transition 72→55 has been usually selected for quantifying acrylamide because it shows a relatively high intensity (Becalski et al. 2003; Ahn et al. 2002; Rosén and Hellenäs 2002; Tareke et al. 2000). Other transitions, such as 72 → 54, 72→44, and 72→27, have been used in some cases for configuration. For the detection of the isotopically labeled acrylamide used as internal standard, the monitored transitions are 75→58 for [D3]- and [13C3]-acrylamide and 37→56 for [13C1]-acrylamide. Despite the selectivity offered by MS/MS, interference can still occur. Peaks showing identical retention times to acrylamide and deuterated acrylamide have been observed. This problem could be solved by increasing the pH of the solution from which acrylamide was extracted into an organic solvent (e.g., the ASE device used during extraction; Swiss Federal Office of Public Health 2002). Becalski et al. (2003) also reported the existence of an early eluting compound that interferes when transition 72→55 is used for the detection of acrylamide. Increasing the column length from 100 to 150 mm and applying Isolute Multi-Mode cartridges during sample preparation eliminated the problem. Further details on the chromatographic conditions and the optimum parameters used for the MS/MS and UV detectors are reported in Wenzl et al. (2003).

Strategies for Reduction of Acrylamide Levels in Food Different strategies for reducing acrylamide levels in food have been suggested. Removing or reducing of reactants is one of them. When one of the reactants (asparagine or glucose) is at lower concentration, formation of acrylamide will be reduced. Decreases in asparagine content may be achieved by: (a) selecting cultivars (e.g., potatoes, cereal grain) that contain lower levels of asparagine; (b) elimination of enzymes which control biosynthesis of asparagine by suppressing genes that encode them; (c) hydrolysis of asparagine to aspartic acid and ammonia by acid- and/or asparaginase/amidase-catalysis; (d) modification of asparagine to N-acetylasparagine via acetylation, so formation of N-glycoside intermediates, which form acrylamide, is prevented (Friedman 1978, 2001). Meanwhile, researchers have determined two possible ways to reduce the level of sugar in potatoes. During storage of potatoes, the amount of sugar increases, thus


using fresh potatoes could result in less acrylamide being formed. Also, storing potatoes below 8–10 °C can increase the formation of reducing sugars, and the presence of these reducing sugars together with asparagine may lead to acrylamide formation. The variety of potato with relatively lower amounts of reducing sugars and asparagine also affects the amount of acrylamide formation (FAO/WHO 2004). In another procedure, the formation of acrylamide will be reduced with disruption of reaction. There is a time– temperature relationship to the formation of acrylamide in food, thus changing the temperature or duration of cooking will affect the level of acrylamide. It has been suggested that, when the temperature of food rises above 120 °C, the rate of acrylamide formation increases rapidly with temperature over a limited range (Claus et al. 2008). Acrylamide formation in food is also pH-dependent and optimum pH for acrylamide formation in food is about 7. In acidic pH, acrylamide formation is inhibited. Lowering the pH of the food system to reduce acrylamide generation may attribute to protonating the α-amino group of asparagine, which subsequently cannot engage in nucleophilic addition reactions with carbonyl source (Zhang and Zhang 2007). Other inhibitors of acrylamide formation are the asparaginase enzymes that disrupt the formation of acrylamide. Another factor is water activity that seems to be a critical factor (Taeyman et al. 2004). Destroying and/or trapping of acrylamide after its formation is another strategy which can be done via (a) hydrolysis of the amide group of acrylamide to acrylic acid and ammonia by acid- or enzyme-catalysis; (b) polymerization of monomers of acrylamide to polyacrylamide in processed foods by means of using UV light or radiation (Friedman 1997); (c) reaction of acrylamide with SHcontaining amino acids, esters, peptides, and proteins (Friedman 1996). Also, some compounds like NaCl and CaCl2 could decrease the amount of acrylamide formed (Açar et al. 2010; Pedreschi et al. 2010).

Conclusion Only a limited number of methods have been so far proposed in the literature on the determination of acrylamide in food products. As for the recognition of methods, mainly two general methods of analysis (LC-MS/MS or GC-MS) are used, and it is still difficult to determine which one is more reliable. By comparing methodologies, large differences are found among the extraction procedures and clean-up strategies, e.g., variation in extraction, in swelling conditions, in temperature and time of extraction, in mechanical treatment, and in centrifugation or the use of SPE for

359

both GC- and LC-based methods, especially in LC sample preparation. GC-MS after bromination is the best approach so far, because this method is a relatively mature coupled technique with adequate sensitivity and multiple ion conformation. Application of GC-MS/MS or coupling to a highresolution MS would even further lower the detection limit of certain foods to 1–2 μg/kg. Determination of acrylamide using LC-MS/MS may avoid derivatization and has the advantages of rather high sensitivity and stability. Also, research should be focused on cheap, convenient, and rapid screening methods that are reliable and robust which could be employed in most laboratories. In this respect, GC-ECD method has been developed for identification and quantification of derivatized acrylamide in heatprocessed starchy foods, while it requires a relatively lowcost instrumentation to perform compared with MS detection-based methods. The ASE method provides a fast and efficient extraction of acrylamide from various food samples along with simple and rapid sample preparation without SPE clean-up and concentration prior to GC-ECD analysis. In addition, the standard addition method has been reported as a suitable quantification method for the determination of acrylamide in heat-processed foods.

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