The effect of fish matrix on colloidal gold immunochromatographic assay of antibiotics: the source of interference and removal method

Figures & data

Figure 1. GICA results for PBS (a) and crude extracts of different negative fish samples (b). From left: PBS; 1, Scophthalmus maximus; 2, Cyprinus carpio; 3, Siniperca chuatsi; 4, Aristichthys nobilis; 5, Ctenopharyngodon idella.

Figure 2. GICA results for crude extracts after 5-sulfosalicylic acid treatment. From left: Blank control; 1, Scophthalmus maximus; 2, Cyprinus carpio; 3, Siniperca chuatsi; 4, Aristichthys nobilis; 5, Ctenopharyngodon idella.

Table 1. The protein content in different fish samples.

Concentration	Scophthalmus maximus	Cyprinus carpio	Siniperca chuatsi	Aristichthys nobilis	Ctenopharyngodon idella
Crude extract (mg/mL)	21.5 ± 0.7	18.4 ± 1.0	23.5 ± 0.9	24.6 ± 1.0	30.3 ± 0.4
Extract after acid treatment (mg/mL)	0.19 ± 0.02	0.16 ± 0.04	0.20 ± 0.02	0.20 ± 0.02	0.16 ± 0.04

Note: Data are presented as mean ± standard deviation (n = 3).

Figure 3. GICA results for sample extracts removed lipid component (a), and for fish polysaccharide simulated solutions (b). From left: PBS; 1, Scophthalmus maximus; 2, Cyprinus carpio; 3, Siniperca chuatsi; 4, Aristichthys nobilis; 5, Ctenopharyngodon idella.

Table 2. The lipid and sugar content in different fish samples.

Concentration	Scophthalmus maximus	Cyprinus carpio	Siniperca chuatsi	Aristichthys nobilis	Ctenopharyngodon idella
Lipid in crude extracts (mg/mL)	1.42 ± 0.05	2.39 ± 0.05	0.84 ± 0.05	0.52 ± 0.05	0.76 ± 0.05
Lipid in extract after diatomite filtration (mg/mL)	0.23 ± 0.05	0.14 ± 0.05	0.10 ± 0.05	0.31 ± 0.05	0.12 ± 0.05
Sugar in crude extracts (mg/mL)	0.98 ± 0.16	0.82 ± 0.27	1.59 ± 0.18	0.72 ± 0.40	1.39 ± 0.50

Note: Data are presented as mean ± standard deviation (n = 3).

Figure 4. GICA results for simulated total metal ions in PBS and their gradient solutions (a, from left: PBS; 1–5: diluted with PBS to 0, 10, 50, 100 folds), single salt in PBS (b, from left: PBS; 1–5: K⁺, Na⁺, Mg²⁺, Al³⁺, Ca²⁺), and gradient magnesium in PBS (c, from left: PBS; 1–5: 1 g/kg, 0.5 g/kg, 0.1 g/kg, 0.05 g/kg, 0.01 g/kg).

Figure 5. The proposed mechanism of the magnesium-induced interfere to GICA.

Figure 6. The efficiency of different pre-treatments to remove protein, magnesium and matrix interference of Scophthalmus maximus. 1–3: the pH of the samples was directly adjusted with NaOH, KOH, Ca(OH)₂ after acid extraction. 4–6: the pH of the samples was adjusted with NaOH, KOH, Ca(OH)₂ after acid extraction and centrifugation.

Figure 7. GICA results for different Scophthalmus maximus extracts. From left: PBS, crude extract, CIP of 10 ng/ml in PBS, samples extract after optimized pre-treatment and the corresponding blank control.