Quantitative Analysis of Chlorophyll Content in Tea Leaves by Fluorescence Spectroscopy

Fig. 8. Results of variable selection using SPA algorithm. (a) Relationship between number of selected variables and RMSEP; (b) locations of selected variables in processed spectra

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Fig. 9. Prediction results of simplified PLS model

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Table 1. Statistics on chlorophyll content
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Table 1. Statistics on chlorophyll content
Sample Maximum Minimum Mean SD CV
Tea leaf 87.0±0.3 61.6±0.3 78.93 5.09 0.06

Table 2. PLS values before and after chlorophyll relative content treatment
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Table 2. PLS values before and after chlorophyll relative content treatment
Evaluation index Before After
3 points 5 points
R_C 0.8339 0.9129 0.9162
RMSEC 2.2360 2.2776 0.2747
R_P 0.8820 0.8675 0.8989
RMSEP 1.8811 1.9199 1.4831

Table 3. Descriptive statistics for calibration set and prediction set
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Table 3. Descriptive statistics for calibration set and prediction set
Subset Number of samples Minimum Maximum Mean SD
Calibration set 80 61.6±0.3 87.0±0.3 78.56 5.80
Prediction set 40 70.9±0.3 85.8±0.3 79.66 3.16

Table 4. Descriptive statistics of calibration set and prediction set

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Table 4. Descriptive statistics of calibration set and prediction set

Method	Number of variable points	Calibration set		Prediction set
Method	Number of variable points	R_C	RMSE	R_P	RMSE
PLS	1044	0.9063	2.4359	0.9386	1.4871
UVE-PLS	160	0.9174	2.2208	0.9224	1.4073
SPA-PLS	10	0.9176	2.2896	0.9450	1.3069
BiPLS	280	0.9048	2.4545	0.9392	1.4861
BiPLS-SPA	14	0.9612	0.9483	0.9591	0.8863

Table 5. Results of selecting optimal intervals step by step

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Table 5. Results of selecting optimal intervals step by step

Numberintervalsin model	Selectedinterval	Numberofvariables	RMSECV	Numberintervalsin model	Selectedinterval	Numberofvariables	RMSECV
20	6	400	2.6825	10	11	200	2.3902
19	9	380	2.4252	9	5	180	2.3643
18	4	360	2.3616	8	14	160	2.3413
17	18	340	2.3325	7	3	140	2.3402
16	19	320	2.3269	6	1	120	2.4077
15	20	300	2.3222	5	2	100	2.4248
14	17	280	2.3212	4	10	80	2.3955
13	16	260	2.3221	3	13	60	2.7288
12	15	240	2.3333	2	12	40	2.7245
11	8	220	2.3684	1	7	20	2.4189

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Yande Liu, Xiaodong Lin, Haigen Gao, Xue Gao, Sun Wang. Quantitative Analysis of Chlorophyll Content in Tea Leaves by Fluorescence Spectroscopy[J]. Laser & Optoelectronics Progress, 2021, 58(8): 0830001

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