A reliable immunoturbidimetry method for immunoglobulin G in bovine colostrum

Figures & data

Table 1. The affection of different test volume to the test results.

	OD value
Test volume	1	2	3	4	CV (%)
200 µL	0.907	1.128	1.135	1.140	11.38
230 µL	1.018	1.190	1.195	1.199	8.84
250 µL	1.160	1.192	1.198	1.197	1.80
300 µL	1.166	1.178	1.181	1.182	0.74
500 µL	1.154	1.162	1.161	1.162	0.39

Figure 1.  Optimisation of reaction time.

Figure 2.  Optimisation of PEG's content. The concentration of IgG standard at 1.0 mg/mL and the concentration of Rabbit anti-bovine IgG at 0.1 mg/mL were selected as working concentration in the optimisation.

Figure 3.  Typical standard curves for IgG immunoassay. Data represent the means of four determinations.

Table 2. OD value of each determination.

Samples	OD value
IgG solution containing four proteins	0.4632	0.4585	0.4731	0.4772	0.4556	0.471
Controlled IgG solution	0.4481	0.4665	0.4587	0.4639	0.4508	0.4614

Table 3. OD value of each determination.

	Determinations of IgG solution containing inactive IgG^a
Determinations of controlled IgG solution	0.2 mg/mL	0.4 mg/mL	0.6 mg/mL	0.8 mg/mL
0.4234	0.4603	0.4665	0.4307	0.4593
0.4514	0.4628	0.441	0.4632	0.4374
0.4476	0.4371	0.4506	0.4494	0.4688
0.465	0.4579	0.4614	0.4795	0.4549
0.4573	0.458	0.4621	0.4518	0.449
0.4357	0.4473	0.4583	0.4667	0.4763
^aIn the OD values’ measurements of each reaction between IgG solution containing each concentration of pre-inactive IgG and rabbit anti-bovine IgG, 10 µL of corresponding concentrations of inactive IgG dissolved in 250 µL of PBS containing 4% PEG was set as calibration solution.

Table 4. Determinations and recoveries of IgG from spiked milk samples.

	0.200 mg/mL		0.500 mg/mL		0.800 mg/mL
No.	Determinations^a (mg/mL)	Recoveries (%)	Determinations^a (mg/mL)	Recoveries (%)	Determinations^a (mg/mL)	Recoveries (%)
1	0.1809	90.47	0.4836	96.71	0.8334	104.2
2	0.2043	102.2	0.4884	97.68	0.8070	100.9
3	0.2119	105.9	0.4983	99.66	0.7992	99.90
4	0.1922	96.10	0.5212	104.24	0.8028	100.35
5	0.1907	95.35	0.4849	96.98	0.7861	98.26
6	0.1876	93.80	0.4901	98.02	0.7849	98.11
7	0.1893	94.65	0.5283	105.7	0.7748	96.85
8	0.1964	98.20	0.4723	94.46	0.8102	101.3
9	0.1915	95.75	0.5358	107.2	0.7952	99.40
10	0.2079	103.9	0.4905	98.10	0.8164	102.1
^aIt represented the determination of post-calibration. It was the real determination minus 0.001 mg/mL, which was the original concentration in ordinary milk after the dilution of 200-fold.

Table 5. Determination of IgG's content in liquid bovine colostrum samples.

No.	Content of IgG [Xbar]±SD (mg/mL)
1	40.43±1.53
2	70.10±1.10
3	55.92±1.02
4	21.33±2.04
5	10.47±2.36

Table 6. Determination of IgG's content in bovine colostrum powder samples.

No.	Content of IgG [Xbar]±SD (g/100 g)
1	11.48±0.31
2	14.34±0.23
3	18.96±0.40
4	26.42±0.51
5	15.63± 0.36
6	24.12±0.61
7	28.15±0.78
8	20.14±0.62
9	8.290±0.20
10	23.57±0.81

Table 7. Repeatability results of the immunoassay.

No.	Content of IgG [Xbar]±SD (mg/mL)	CV (%)
1	0.580±0.020	3.50
2	0.547±0.020	3.60
3	0.624±0.020	3.15
4	0.582±0.012	2.03

Table 8. Reproducibility results of the immunoassay.

No.	Content of IgG [Xbar]±SD (mg/mL)	CV (%)
1	0.574±0.054	9.41
2	0.567±0.038	6.73
3	0.621±0.042	6.75
4	0.481±0.022	4.68
5	0.462±0.015	3.16
6	0.482±0.016	3.26
7	0.338±0.018	5.44
8	0.243±0.013	5.30

Figure 4.  Correlation between IgG concentrations measured by immunoturbidimetry method and by HPLC in bovine colostrum powder samples. y = 0.843x + 1.893, r ²=0.930, n = 20.