GB/T 18932.23-2003Method for the determination of oxytetracycline, tetracycline, chlortetracycline and doxycycline residues in honey -- LC-MS-MS method (English PDF)

4.17 Matrix mixed standard working solutions of oxytetracycline, tetracycline,

chlortetracycline and doxycycline. according to needs, pipette appropriate standard stock

solutions of oxytetracycline, tetracycline, chlortetracycline and doxycycline (4.16); use

blank sample extracting solution to dilute to be the matrix mixed standard working

solutions of appropriate concentrations; store the matrix standard solutions at 4°C; it may

be used in three days.

5.1 LC-tandem quadrupole mass spectrometer, equipped with electrospray ionization

source.

5.2 Analytical balances. 2 balances of which the sensitivity is 0.1 mg and 0.01 g

respectively.

5.3 Liquid mixer.

5.4 Solid phase extraction vacuum device.

5.5 Liquid reservoir. 50mL.

5.6 Micro-syringe. 25uL and 100uL.

5.7 Graduated sample tube. 5mL, precision is 0.1mL.

5.8 Vacuum pump. vacuum degree shall reach 80kPa.

5.9 Centrifuge tube. 50mL.

5.10 Flat-bottomed flask. 100mL.

5.11 pH meter. measurement precision is ±0.02.

6.1 Sample preparation

For non-crystallized laboratory sample, stir it evenly; For crystallized sample, in a

enclosed circumstance, place it in the water bath at not more than 60°C; warm it; oscillate

it; after it is totally melted, stir it; rapidly cool it to room temperature. Take 0.5 kg as the

sample. Place the prepared sample in the sample flask, seal and mark it.

oxytetracycline, tetracycline, chlortetracycline and doxycycline are shown in Table 3.

If the difference exceeds the repeatability limit, it shall discard the test results and carry

out two independent tests again.

9.2 Reproducibility

Under reproductive conditions, the absolute difference between two independent test

results shall not exceed reproducibility limit (R). The content range and reproducibility

equation of oxytetracycline, tetracycline, chlortetracycline and doxycycline are shown in

Table 3.

Table 3 Content range AND repeatability and reproducibility equations

Name Content Range (mg/kg) Repeatability Limit r Reproducibility Limit R

Oxytetracycline 0.002~0.100 lgr=0.9668lgm - 0.8686 lgR=1.0096lgm - 0.6597

Tetracycline 0.002~0.100 lgr=0.9484lgm - 0.8370 lgR=1.1611lgm - 0.2317

Chlortetracycline 0.002~0.100 lgr=0.8395lgm - 1.0872 lgR=0.9060lgm - 0.8136

Doxycycline 0.002~0.100 lgr=0.9209lgm - 0.8462 lgR=0.9899lgm - 0.6504

Note. m is the arithmetic mean value of two test results.

Annex B

(Informative)

Recovery rate

The test data od adding concentrations and average recovery rates of oxytetracycline,

tetracycline, chlortetracycline and doxycycline are shown in Table B.1.

Table B.1 Test data of adding concentrations and average recovery rates of

oxytetracycline, tetracycline, chlortetracycline and doxycycline

Drug Name Adding Concentration / (mg/kg)

Average Recovery Rate /

(%)

Oxytetracycline

0.002

0.010

0.050

0.100

88.0

95.3

93.6

95.8

Tetracycline

0.002

0.010

0.050

0.100

81.9

82.6

84.5

89.3

Chlortetracycline

0.002

0.010

0.050

0.100

87.2

86.0

86.6

90.8

Doxycycline

0.002

0.010

0.050

0.100

85.2

85.3

86.8

87.9

......