Biosensors

In the past 10 years, biosensor technology increasingly has been relied on for the sensitive and reliable monitoring of veterinary drug residues in food [212-215]. This technique typically relies on contacting the food sample or extract with a

Table 2 Biosensor veterinary drug residue methods

Drug class

Examples of compounds

Matrices

Sensitivity (limit of detection (LOD))

References

Sulfonamides

Sulfamethazine,

Milk, pig bile

1-23 mg/kg

[188,189,

sulfadiazine,

and muscle,

217,218]

sulfamethoxazole

chicken serum

and plasma

b-Lactams

Benzylpenicillin,

Milk

1.2-100 ng/mL

[219,220]

ampicillin,

amoxicillin,

cephapirin,

ceftiofur, etc.

Aminoglycosides

Gentamicin,

Milk powder,

15-70 mg/kg

[221,222]

neomycin,

milk, honey,

kanamycin,

pig muscle

streptomycin,

and kidney

dihydrostrepto-

mycin

Macrolides

Tylosin

Honey

2.5 mg/kg

[223]

Quinolones

Enrofloxacin,

Milk

2-3 ng/mL

[224]

ciprofloxacin

Phenicols

Chloramphenicol,

Milk, honey,

0.02-250 mg/kg

[191,225]

florfenicol,

chicken

thiamphenicol,

muscle,

florfenicol amine

shrimp

Coccidiostats

Nicarbazin

Eggs, liver

17-19 mg/kg

[226]

Anthelmintics

Ivermectin,

Milk, liver

0.5-16.2 mg/kg

[227]

levamisole

residue-specific antibody to form a drug-antibody binding pair. The binding reaction generates a signal that can be detected by various methods, e.g., optical, piezoelectric, etc. The inherent specificity of the binding reaction allows biosensors to offer many advantages over traditional analytical methods. Food matrices require only minimal sample preparation and the analytical signal is typically absent of background interference. As a result, biosensor methods are easy to use, fast and offer excellent sensitivity for high-throughput screening.

For veterinary drug residue analysis, most of the literature methods have been developed using optical biosensor instrumentation based on surface plasmon resonance. Methods have been developed for a broad range of the drug classes described previously in foods. A selection of recent methodology is summarized in Table 2. In addition, binding assay test kits are commercially available for sulfonamides, chloramphenicol, streptomycin and others [216].

Table 3 Multi-class veterinary drug residue methods

Matrix

Drug classes

Extraction

Detection

Number of residues

References

Eggs

Ionophores, macrolides

Silica SPE

Ion trap LC-MS

7

[104]

electrospray

Eggs

Fluoroquinolones, sulfonamides,

Succinate buffer extraction,

Ion trap LC-MS

29

[232]

tetracyclines,

polymeric SPE

electrospray

/i-lactams

Shrimp

Sulfonamides quinolones

Trichloroacetic acid

Ion trap LC-MS

19

[228]

tetracyclines, dyes

extraction, polymeric SPE

APCI / no-discharge-

APCI

Tissue,

Sulfonamides, benzimidazoles,

Acetonitrile extraction,

LC-UV / Fluorescence,

30

[233]

fish, eggs

tranquilizers, fluoroquinolones,

cation exchange SPE

LC-MS (APCI)

dyes

Milk

/i-Lactams, tetracyclines,

Trichloroacetic acid or acetonitrile

LC-MS-MS triple quad,

44

[234]

aminoglycosides, macrolides,

extraction

electrospray

quinolones, sulfonamides

Tissue

Macrolides, fluoroquinolones, etc.

Acetonitrile extraction, on

LC-MS-MS triple quad,

13

[229]

line polymer SPE

electrospray

Tissue

Quinolones, sulfonamides,

Acetonitrile/methanol (95:5

LC-MS-MS triple quad,

130

[231]

tetracyclines, macrolides,

extract), hexane wash

electrospray

benzimidazoles, /i-lactams, etc.

Fish

Quinolones, sulfonamides,

Acetonitrile/hexane

Ion trap LC-MS

35

[235]

tetracyclines, macrolides, dyes,

extraction, hexane wash

electrospray

imidazoles, /i-lactams, etc.

Tissue

Tetracyclines, sulfonamides,

70% methanol extract diluted with LC-MS-MS triple quad,

19

[236]

macrolides, quinolones, /i-lactams

water

electrospray

Milk

Tetracyclines, sulfonamides,

Trichloroacetic acid,

LC-MS (single quad)

10

[230]

pyrimethamine

polymeric SPE

electrospray

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