CN113640442A

CN113640442A - Method for simultaneously measuring extractable Cr (III) and Cr (VI) in tipping paper for cigarettes

Info

Publication number: CN113640442A
Application number: CN202111014218.9A
Authority: CN
Inventors: 韩维岐; 王洋
Original assignee: Jilin Tobacco Industrial Co Ltd
Current assignee: Jilin Tobacco Industrial Co Ltd
Priority date: 2021-08-31
Filing date: 2021-08-31
Publication date: 2021-11-12

Abstract

The invention provides a method for simultaneously measuring extractable Cr (III) and Cr (VI) in tipping paper for cigarettes, which comprises the following steps: a) crushing the tipping paper for the cigarettes, mixing the crushed tipping paper with water, and performing ultrasonic extraction to obtain an extract liquid; mixing the extract with Triton X-114 solution and APDC solution, adjusting pH, adding water to constant volume, heating, centrifuging, adding methanol to constant volume, and filtering to obtain a sample to be detected; b) separating and measuring the sample to be measured obtained in the step a) by using HPLC (high performance liquid chromatography) to obtain the contents of extractable Cr (III) and Cr (VI) in the tipping paper for the cigarette. The invention establishes a method for simultaneously measuring extractable Cr (III) and Cr (VI) in tipping paper for cigarettes, namely a cloud point extraction-HPLC method; the method has the advantages of high detection sensitivity, low detection limit, good stability, good precision, high recovery rate and high enrichment factor, and is suitable for simultaneous determination of extractable Cr (III) and Cr (VI) in the tipping paper for cigarettes.

Description

Method for simultaneously measuring extractable Cr (III) and Cr (VI) in tipping paper for cigarettes

Technical Field

The invention relates to the technical field of chemical analysis and detection, in particular to a method for simultaneously measuring extractable Cr (III) and Cr (VI) in tipping paper for cigarettes.

Background

The chromium element is widely existed in nature, a plurality of raw materials, dyes, additives and the like can be used in the processing process of the cigarette tipping paper, and the tipping paper contains trace chromium due to environmental factors. During the smoking process of the cigarette, the tipping paper is directly contacted with the oral cavity, and trace chromium contained in the tipping paper can migrate into the human body to cause harm to the human body. Chromium exists mainly in the form of trivalent chromium (Cr (III)) and hexavalent chromium (Cr (VI)) in nature, and research shows that Cr (III) is a trace element necessary for human body, has important function in maintaining glucose balance of organism and metabolism of protein and fat, and hexavalent chromium has high toxicity, can cause diseases such as nephritis, anemia and neuritis when inhaled, and has strong carcinogenicity. Therefore, the accurate determination of the contents of different forms of chromium in the tipping paper has important significance for the harmfulness evaluation of cigarettes.

However, when the measurement is performed directly, different valence states interfere with each other, and the measurement must be performed after separation. The separation methods reported mainly include ion exchange chromatography, liquid-liquid microextraction, solid phase extraction, coprecipitation, liquid membrane extraction, etc. The cloud point extraction method is an environment-friendly extraction technology developed in recent years, which is based on the solubility and cloud point phenomenon of a surfactant micelle aqueous solution, enables the surfactant to generate a cloud point phase separation by changing parameters such as temperature, pH value, ionic strength and the like, separates hydrophilic substances from hydrophobic substances, does not use a volatile organic solvent, and has been successfully used for separating and enriching trace elements.

At present, the measurement methods disclosed in the prior art mainly include: industry standard-YQT 60-2015 cigarette tipping paper hexavalent chromium determination continuous flow method; the method comprises the following steps: and (3) activating the polyamide SPE column (firstly, eluting with 5mL of methanol, then eluting with 5mL of water, and then eluting with 5mL of dipotassium phosphate solution), oscillating and extracting the sample with the dipotassium phosphate solution for 30 minutes, filtering with filter paper to obtain filtrate, purifying the filtrate with the activated polyamide SPE column, and detecting on a computer. An inductively coupled plasma mass spectrometry method for measuring arsenic, lead, cadmium, chromium, nickel and mercury in YC316-2009 cigarette tipping paper and cigarette tipping paper base paper is adopted as an industrial standard; the method comprises the following steps: cutting the tipping paper sample into pieces, adding acid for microwave digestion, diluting to constant volume, and measuring the total chromium content by using inductively coupled plasma mass spectrometry.

However, the current standard can only measure the total content of chromium elements in the tipping paper sample or can only measure the content of hexavalent chromium in the tipping paper sample, and cannot simultaneously measure the contents of trivalent chromium and hexavalent chromium.

Disclosure of Invention

In view of the above, the invention aims to provide a method for simultaneously measuring extractable Cr (III) and Cr (VI) in tipping paper for cigarettes, the method adopts a cloud point extraction-HPLC method, can solve the problem of simultaneously measuring trivalent chromium and hexavalent chromium, and has the advantages of high detection sensitivity, low detection limit, good stability, good precision, high recovery rate and high enrichment factor.

The invention provides a method for simultaneously measuring extractable Cr (III) and Cr (VI) in tipping paper for cigarettes, which comprises the following steps:

a) crushing the tipping paper for the cigarettes, mixing the crushed tipping paper with water, and performing ultrasonic extraction to obtain an extract liquid; mixing the extract with Triton X-114 solution and APDC solution, adjusting pH, adding water to constant volume, heating, centrifuging, adding methanol to constant volume, and filtering to obtain a sample to be detected;

b) separating and measuring the sample to be measured obtained in the step a) by using HPLC (high performance liquid chromatography) to obtain the contents of extractable Cr (III) and Cr (VI) in the tipping paper for the cigarette.

Preferably, the crushing process in step a) is specifically:

the tipping paper for the cigarette is cut into pieces of 0.1 cm-1 cm multiplied by 0.1 cm-1 cm and evenly mixed.

Preferably, the process of mixing the crushed tipping paper for cigarettes with water in the step a) is as follows:

2g of the crushed tipping paper for cigarettes is put into a 50ml triangular flask, and 20ml of water is added.

Preferably, the time of the ultrasonic extraction in the step a) is 20min to 40 min.

Preferably, the addition amount of the extract in the step a) is 5 ml;

the concentration of the Triton X-114 solution is 0.5% v/v, and the addition amount is 1.5 ml-2.5 ml;

the concentration of the APDC solution is 0.1% m/v, and the addition amount is 2 ml-3 ml.

Preferably, the process of adjusting pH in step a) is specifically:

and adjusting the pH value of the system to 4-6 by using 0.2mol/L sodium acetate and 0.2mol/L acetic acid.

Preferably, the water in the step a) is used for metering to 10 ml; the heating mode is water bath heating, the temperature is 50-60 ℃, and the time is 25-40 min; the centrifugation is carried out while the mixture is hot, the rotating speed is 4000 rpm-6000 rpm, and the time is 3 min-7 min; the methanol is fixed to the volume of 1 ml; the filtration was performed using a 0.45 μm organic phase filter to a chromatography flask.

Preferably, the HPLC column in step b) is ZORBAX SB-C18; 4.6mm × 150mm, 5 μm.

Preferably, the conditions for separating and determining by HPLC in step b) are in particular:

the column temperature is 25-35 ℃;

the sample amount is 15-25 mul;

the detector is a DAD detector;

the detection wavelength is 210 nm-310 nm;

the flow rate is 0.5ml/min to 1.5 ml/min;

mobile phase: the phase A is water, and the phase B is methanol.

Preferably, the separation by HPLC and determination in step b) is carried out using a gradient elution, the time program being as follows: 0 min-8 min, A: b25: 75, 8.5-11.5 min, 100% B; 12min, A: b25: 75; operating time: and (5) 12 min.

The invention provides a method for simultaneously measuring extractable Cr (III) and Cr (VI) in tipping paper for cigarettes, which comprises the following steps: a) crushing the tipping paper for the cigarettes, mixing the crushed tipping paper with water, and performing ultrasonic extraction to obtain an extract liquid; mixing the extract with Triton X-114 solution and APDC solution, adjusting pH, adding water to constant volume, heating, centrifuging, adding methanol to constant volume, and filtering to obtain a sample to be detected; b) separating and measuring the sample to be measured obtained in the step a) by using HPLC (high performance liquid chromatography) to obtain the contents of extractable Cr (III) and Cr (VI) in the tipping paper for the cigarette. The prior art can only determine the total amount of chromium elements or can only determine the content of hexavalent chromium, and because the toxicity difference of different forms of the chromium elements is very large, the chromium with different forms is very necessary to be accurately determined, and the problem is well solved by the invention. Compared with the prior art, the invention establishes a method for simultaneously measuring extractable Cr (III) and Cr (VI) in the tipping paper for the cigarette, namely a cloud point extraction-HPLC method; in order to improve the sensitivity as much as possible, the invention adopts a cloud point extraction method which is more environment-friendly to enrich the chelate in the solution, obtains good enrichment effect, and further realizes the functions of separation and detection through HPLC (high performance liquid chromatography); the method has the advantages of high detection sensitivity, low detection limit, good stability, good precision, high recovery rate and high enrichment factor, and is suitable for simultaneous determination of extractable Cr (III) and Cr (VI) in the tipping paper for cigarettes.

Drawings

FIG. 1 is a graph showing the absorption curves of two ion chelates in an example of the present invention;

FIG. 2 is a graph showing the effect of pH on the results in examples of the present invention;

FIG. 3 is a graph showing the effect of APDC dosage in an embodiment of the present invention;

FIG. 4 is a graph showing the effect of Triton X-114 dosage in an embodiment of the present invention;

FIG. 5 is a graph showing the effect of reaction temperature in examples of the present invention;

FIG. 6 is a graph showing the effect of reaction time in examples of the present invention;

FIG. 7 is a standard curve of Cr (III) ion chelate according to an example of the present invention;

FIG. 8 is a standard curve of Cr (VI) ion chelate compound in the examples of the present invention;

FIG. 9 is an overall process flow diagram of the measurement method in the example of the present invention.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments of the present invention, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The method comprises the steps of firstly crushing the tipping paper for the cigarettes, mixing the crushed tipping paper with water, and carrying out ultrasonic extraction to obtain an extract liquid. The invention has no special limitation on the type and source of the tipping paper for the cigarette. In the present invention, the water is preferably ultrapure water, and the resistivity thereof is 18.2M Ω · cm.

In the present invention, the crushing process preferably includes:

cutting the tipping paper for the cigarettes into fragments of 0.1-1 cm multiplied by 0.1-1 cm, and uniformly mixing;

more preferably:

cutting the tipping paper for the cigarette into pieces of 0.5cm multiplied by 0.5cm, and mixing uniformly.

In the invention, the process of mixing the crushed tipping paper for cigarettes with water is preferably as follows:

In the present invention, the time of the ultrasonic extraction is preferably 20min to 40min, and more preferably 30 min.

After the extraction liquid is obtained, the extraction liquid is mixed with Triton X-114 solution and APDC solution, after the pH value is adjusted, the volume is determined by water, and then the sample to be measured is obtained by sequentially heating, centrifuging, determining the volume by methanol and filtering.

In the present invention, Triton X-114 (Triton X-114) is a nonionic surfactant; APDC is ammonium pyrrolidine dithiocarbamate; the invention takes APDC as a chelating agent and Triton X-114 as an extracting agent, simultaneously enriches Cr (III) and Cr (VI) in a sample, and is convenient for subsequent separation and determination by HPLC. The sources of Triton X-114 and APDC are not particularly limited in the present invention, and commercially available products known to those skilled in the art may be used.

In the present invention, the addition amount of the extract is preferably 5 ml; based on the above, the amount of the Triton X-114 solution is preferably 1.5ml to 2.5ml, more preferably 2ml, and the amount of the APDC solution is preferably 2ml to 3ml, more preferably 2.5 ml.

In the present invention, the concentration of the Triton X-114 solution is preferably 0.5% v/v, and is prepared according to the following method: transferring 5ml of Triton X-114, using ultrapure water to make the volume of the solution constant to 100ml, then transferring 10ml of the solution, using ultrapure water to make the volume of the solution constant to 100ml, so as to obtain 0.5% (v/v) Triton X-114 solution.

In the present invention, the APDC solution, preferably at a concentration of 0.1% m/v, is formulated as follows: 0.1g of APDC was weighed out and dissolved with ultrapure water to a volume of 100 ml.

In the present invention, the process of adjusting pH is preferably specifically:

adjusting the pH value of the system to 4-6 by using 0.2mol/L sodium acetate and 0.2mol/L acetic acid;

more preferably:

the pH of the system was adjusted to 5 with 0.2mol/L sodium acetate and 0.2mol/L acetic acid.

In the invention, the water is used for fixing the volume to be preferably 10 ml; the heating mode is preferably water bath heating, the temperature is preferably 50-60 ℃, more preferably 55 ℃, and the time is preferably 25-40 min, more preferably 30 min; the centrifugation is preferably carried out while the solution is hot, the rotation speed is preferably 4000 rpm-6000 rpm, more preferably 5000rpm, and the time is preferably 3 min-7 min, more preferably 5 min; after centrifugation, the methanol constant volume is firstly subjected to inclined separation to remove an upper water layer, and the remainder is subjected to constant volume by using methanol, preferably to 1 ml; the filtration is preferably performed using a 0.45 μm organic phase filter into a chromatography flask.

After the sample to be detected is obtained, the obtained sample to be detected is separated and measured by HPLC, and the contents of extractable Cr (III) and Cr (VI) in the tipping paper for the cigarette are obtained.

In the present invention, HPLC (high performance liquid chromatography) has a function of separation and detection; the chromatographic column of the HPLC is preferably ZORBAX SB-C18; 4.6mm × 150mm, 5 μm.

In the present invention, the conditions for separation and measurement by HPLC are specifically:

the column temperature is preferably 25 ℃ to 35 ℃, and more preferably 30 ℃;

the sample amount is preferably 15 to 25 mul, and more preferably 20 mul;

the detector is preferably a DAD detector;

the detection wavelength is preferably 210 nm-310 nm, and more preferably 254 nm;

the flow rate is preferably 0.5ml/min to 1.5ml/min, more preferably 1 ml/min;

mobile phase: the phase A is water, and the phase B is methanol; on this basis, the separation and determination by HPLC preferably employs gradient elution, with the following time course: 0 min-8 min, A: b25: 75, 8.5-11.5 min, 100% B; 12min, A: b25: 75; operating time: and (5) 12 min.

The invention establishes a method for simultaneously determining extractable Cr (III) and Cr (VI) in the tipping paper for cigarettes, namely a cloud point extraction-HPLC method, thereby realizing the application of the cloud point extraction method in the determination of the form of the chromium in the tipping paper for cigarettes and the application of the cloud point extraction method combined with the high performance liquid chromatography in the determination of the form of the chromium in the tipping paper; in order to improve the sensitivity as much as possible, the invention adopts a cloud point extraction method which is more environment-friendly to enrich the chelate in the solution, obtains good enrichment effect, and further realizes the functions of separation and detection through HPLC (high performance liquid chromatography); the method has the advantages of high detection sensitivity, low detection limit, good stability, good precision, high recovery rate and high enrichment factor, and is suitable for simultaneous determination of extractable Cr (III) and Cr (VI) in the tipping paper for cigarettes.

To further illustrate the present invention, the following examples are provided for illustration. The materials, instruments and reagents used in the following examples of the invention are as follows:

materials: the test material used in the following examples was tipping paper for cigarettes, each numbered A, B, C, D, E.

The instrument comprises the following steps: HY-8A digital display speed-regulating multi-purpose oscillator (Jiangsu province Jintanshi, nabobism manufacturing Co., Ltd.); DU-14 ultrasonic instrument (Clifton, UK); HB-03 heating pan (Beijing Laibuttaceae instruments, Inc.); TGL-16M desk-top high speed refrigerated centrifuge (Hunan instruments laboratory Instrument development Co., Ltd., Hunan); DMT-2500 multi-tube vortex mixer (Hangzhou Mioho instruments Co., Ltd.); Milli-Q10 Water purification apparatus (Millipore, USA); ORION STAR A214 pH meter (Thermo technologies, USA); agilent 1290 high performance liquid chromatography (Agilent, USA).

Reagent: acetic acid (chromatographically pure, fisher, usa); sodium acetate (analytically pure, alatin); methanol (chromatographically pure, fisher, usa); ultrapure water (resistivity 18.2M Ω · cm); triton X-114 (analytical grade, alatin); ammonium Pyrrolidine Dithiocarbamate (APDB) (analytical pure, alatin); hexavalent chromium standard solutions (1000 μ g/ml, national center for nonferrous metal and electronic material analysis and testing); trivalent chromium standard solution (1000. mu.g/ml, national center for analysis and test of nonferrous metals and electronic materials).

Examples

(1) Solution preparation:

0.5% (v/v) Triton X-114: transferring 5ml of Triton X-114, using ultrapure water to make the volume constant to 100ml, then transferring 10ml of the solution, using ultrapure water to make the volume constant to 100ml, so as to obtain 0.5% (v/v) Triton X-114 solution;

0.1% (m/v) APDC: 0.1g of APDC was weighed out and dissolved with ultrapure water to a volume of 100 ml.

(2) Sample preparation:

cutting the cigarette tipping paper sample into pieces of 0.5cm × 0.5cm, mixing, taking 2g (to the accuracy of 0.0001g) in a 50ml triangular flask, adding 20ml ultrapure water, and performing ultrasonic extraction for 30 min. 5ml of the extract was put into a 10ml centrifuge tube, 2ml of 0.5% (v/v) Triton X-114 solution and 2.5ml of 0.1% (m/v) APDC solution were added thereto, the pH of the system was adjusted to 5.0 with 0.2mol/L sodium acetate and 0.2mol/L acetic acid, and the volume was made to 10ml with ultrapure water. Placing in 55 deg.C constant temperature water bath for 30min, centrifuging (5000rpm) for 5min, obliquely separating to remove upper water layer, diluting the residue with methanol to 1ml, filtering with 0.45 μm organic phase membrane, and bottling.

(3) The instrument conditions were as follows:

a chromatographic column: ZORBAXSB-C18(4.6 mm. times.150 mm, 5 μm); column temperature: 30 ℃; sample introduction amount: 20 mu l of the mixture; a detector: a DAD detector; detection wavelength: 254 nm; flow rate: 1 ml/min; mobile phase: phase A is water, phase B is methanol, and gradient elution is carried out for the following time program: 0 min-8 min, A: b25: 75, 8.5-11.5 min, 100% B; 12min, A: b25: 75; operating time: and (5) 12 min.

(4) And (3) data analysis:

(4-1) selection of detection wavelength:

1ml of Cr (III) and Cr (VI) standard solutions with the concentration of 1mg/L are respectively taken to be placed in a 10ml centrifuge tube, 2.5ml of 0.1% (m/v) APDC solution and 2ml of 0.5% (v/v) Triton X-114 solution are added, a sample to be detected is obtained by the method, and a DAD detector is used for scanning in the wavelength range of 210nm to 640nm, so that absorption curves of the two are obtained (figure 1). As can be seen, both showed the absorption maximum at 254nm, and 254nm was selected as the detection wavelength.

(4-2) pH value optimization:

in the cloud point extraction process, the pH of the sample solution plays an important role in the formation and extraction of metal chelates, the influence of the pH in the range of 3.0-9.0 on the detection result is considered (0.5ml of Cr (III) and Cr (VI) standard solution with the concentration of 100 mu g/ml is operated according to the experimental method), and the result is shown in figure 2 (note: Relative peak area refers to the ratio of the chromatographic peak area to the maximum peak area under the same considered factor condition, and the same is used below). From the results, it can be seen that the results tend to increase and decrease with increasing pH, and at pH 5.0, the detection results of the two ion chelates reach the maximum, and pH 5.0 is selected as the optimal reaction condition.

(4-3) optimization of APDC dosage:

cr (III) and Cr (VI) ions can be subjected to chelation reaction with Ammonium Pyrrolidine Dithiocarbamate (APDB) to generate different organic chelates, so that the different chelates can be separated. Therefore, the amount of APDC can have a significant effect on the results. The invention investigates the influence of different APDC dosage (0.5ml of Cr (III) and Cr (VI) standard solution with the concentration of 100 mu g/ml is operated according to the experimental method, 0.1% (m/v) APDC solution is added in the volume range of 0.5 ml-3 ml), and the result is shown in figure 3. As can be seen from the results, the results of the detection of the two ion chelates increased with the increase in the amount of APDC, reaching a maximum at a volume of 2.5ml of 0.1% (m/v) APDC solution added. Therefore, an APDC addition of 2.5ml of 0.1% (m/v) was chosen.

(4-4) optimization of surfactant:

triton X-114 is used as a common surfactant and has friendly cloud point temperature (22-25 ℃) and is very convenient for experimental operation, the invention selects Triton X-114 as the surfactant, and the influence of the dosage on the result is considered (0.5ml of Cr (III) and Cr (VI) standard solution with the concentration of 100 mu g/ml is operated according to the experimental method, and the volume range of 0.5% (v/v) Triton X-114 is 1-4 ml), and the result is shown in figure 4. As can be seen from the results, an addition of 2ml of 0.5% (v/v) Triton X-114 was the optimum condition.

(4-5) reaction temperature optimization:

the temperature has important influence on the chemical reaction, the chelation reaction of metal ions is no exception, in order to obtain the best detection effect, the invention optimizes the reaction temperature range of 30-70 ℃ (0.5ml of Cr (III) and Cr (VI) standard solution with the concentration of 100 mu g/ml is operated according to the experimental method), and the result is shown in figure 5. As can be seen, the detection results increased with increasing temperature, and reached a maximum at 55 ℃ with the optimum reaction temperature being 55 ℃.

(4-6) reaction time optimization:

the reaction time also has important influence on the chelation reaction and the extraction of chelate, and the invention optimizes the reaction time (0.5ml of Cr (III) and Cr (VI) standard solution with the concentration of 100 mu g/ml is operated according to the experimental method, and the time range is 10 min-40 min), and the result is shown in figure 6. As can be seen, the peak area of the target increases with the reaction time, reaches a maximum value at 30min, and the optimal reaction time is 30 min.

(4-7) mobile phase optimization:

the target is a metal ion chelate, and the system contains Triton X-114, so that the method needs to use a mode of combining an organic phase and an aqueous phase to achieve the effect of separating the target and effectively removing the residue of the Triton X-114 in a chromatographic column. The invention considers the combination mode of methanol and acetonitrile as organic phase and ultrapure water, and a large number of experiments prove that the best mobile phase combination is methanol and ultrapure water, and the elution mode is gradient elution. Mobile phase: phase A is water, phase B is methanol, and gradient elution is carried out for the following time program: 0 min-8 min, A: b25: 75, 8.5-11.5 min, 100% B; 12min, A: b25: 75; operating time: and (5) 12 min.

(4-8) standard curve and detection limit:

the mixed standard solution of Cr (III) and Cr (VI) with the concentration of 5 mug/L, 10 mug/L, 20 mug/L, 50 mug/L, 100 mug/L, 200 mug/L and 500 mug/L is obtained by using ultrapure water and adopting a stepwise dilution method, and the measurement is carried out according to the optimized method. The standard curves (fig. 7, fig. 8) were obtained as Y ═ 3.2392X +37.3563, respectively; the correlation coefficients of Y-6.5753X +19.7262 are R2-0.9996 respectively; r2 ═ 0.9996; diluting the standard solution step by step, and taking the concentration corresponding to 3 times of signal to noise ratio as detection limit, wherein the detection limit of the determination method provided by the invention is 14 mug/kg respectively; 10. mu.g/kg.

(4-9) optimizing the extraction mode of the tipping paper sample:

cutting a cigarette tipping paper sample A into fragments of 0.5cm multiplied by 0.5cm, uniformly mixing, putting 3 parts of the sample into a 50ml triangular flask, adding 20ml of ultrapure water into 2g (accurate to 0.0001g) of each part, and respectively extracting for 30min by three modes of soaking, oscillating (180 r/min-200 r/min) and ultrasonic. Each 5ml of the solution was treated by an experimental method, and the content of the target substance was measured, and the results are shown in Table 1. From the results, it can be seen that the best extraction mode is ultrasonic extraction.

TABLE 1 Effect of the extraction mode in the examples of the present invention

Mode of extraction	Cr(Ⅲ)/(μg/kg)	Cr(Ⅵ)/(μg/kg)
			Soaking	-	35.67
Oscillation	-	77.25
			Ultrasound	-	115.38

(4-10) optimization of extraction time of tipping paper samples:

cutting the cigarette tipping paper sample A into pieces of 0.5cm multiplied by 0.5cm, mixing uniformly, taking 6 parts of sample, putting 2g (accurate to 0.0001g) of sample into a 50ml triangular flask, adding 20ml of ultrapure water, and carrying out ultrasonic extraction for 15min, 30min, 45min, 60min, 90min and 120 min. Each 5ml of the solution was treated by an experimental method, and the content of the target substance was measured, the results are shown in Table 2. As can be seen from the results, the measurement result of Cr (VI) tends to increase with the increase of the extraction time, and reaches the maximum value at 30min, and the extraction time is selected to be 30 min.

TABLE 2 Effect of extraction time in the examples of the invention

Extraction time/min	Cr(Ⅲ)/(μg/kg)	Cr(Ⅵ)/(μg/kg)
			15	-	37.64
30	-	116.29
			45	-	111.74
60	-	117.31
			90	-	115.67
120	-	118.49

(4-11) recovery, precision and enrichment factor:

tipping paper sample A was treated according to the above procedure, and spiked recovery experiments were performed at 3 concentration levels, each concentration being measured in parallel 6 times, and the results are shown in Table 3. The result shows that the recovery rate of Cr (III) is 96.2-103.6%, the RSD is 4.6-7.1%, the recovery rate of Cr (VI) is 94.7-104.4%, the RSD is 4.3-8.5%, and the trace analysis requirement is met.

Table 3 precision and recovery results in examples of the invention (n ═ 6)

The invention also considers the enrichment factor of the target object, selects 2 parts of mixed standard solution with the concentration of 20 mu g/L, adds 2 parts of Triton X-114 to carry out cloud point extraction, does not add one part of mixed standard solution, processes other conditions according to optimized experimental conditions, and obtains the enrichment factors of Cr (III) and Cr (VI) which are respectively 15.3 and 20.1 according to the detection result.

(4-12) sample measurement:

according to the experimental method of the present invention, 4 different tipping paper samples were measured, and the results are shown in table 4. From the results, some tipping paper samples contained extractable Cr (vi) but not extractable Cr (iii).

TABLE 4 results of measurement of samples in examples of the present invention

Sample (I)	Cr(Ⅲ)/(μg/kg)	Cr(Ⅵ)/(μg/kg)
			B	-	-
C	-	21.25
			D	-	-
E	-	16.34

(5) And (4) conclusion:

the invention establishes a cloud point extraction-HPLC method which is a method for simultaneously measuring extractable Cr (III) and Cr (VI) in tipping paper for cigarettes, and a specific process flow chart is shown in figure 9. The method uses ultrapure water to ultrasonically extract a tipping paper sample for 30min, uses pyrrolidine ammonium dithioformate (APDB) as a chelating agent, uses Triton X-114 nonionic surfactant as an extracting agent, simultaneously enriches Cr (III) and Cr (VI) in the sample, and separates and measures the Cr (III) and the Cr (VI) by HPLC. The method has the advantages of high detection sensitivity, low detection limit and good stability. Has good precision, recovery rate and higher enrichment factor, and is suitable for simultaneously measuring the extractable Cr (III) and Cr (VI) in the tipping paper for cigarettes.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for simultaneously measuring extractable Cr (III) and Cr (VI) in tipping paper for cigarettes comprises the following steps:

2. The method for simultaneously measuring extractable Cr (III) and Cr (VI) in tipping paper for cigarettes according to claim 1, wherein the crushing process in the step a) is as follows:

3. The method for simultaneously measuring extractable Cr (III) and Cr (VI) in tipping paper for cigarettes according to claim 1, wherein the step a) of mixing the crushed tipping paper for cigarettes with water comprises the following specific steps:

4. The method for simultaneously measuring extractable Cr (III) and Cr (VI) in tipping paper for cigarettes according to claim 1, wherein the ultrasonic extraction time in the step a) is 20-40 min.

5. The method for simultaneously measuring extractable Cr (III) and Cr (VI) in tipping paper for cigarettes according to claim 1, wherein the addition amount of the extract in the step a) is 5 ml;

6. The method for simultaneously measuring extractable Cr (III) and Cr (VI) in tipping paper for cigarettes according to claim 1, wherein the pH regulation in the step a) is specifically as follows:

7. The method for simultaneously measuring extractable Cr (III) and Cr (VI) in tipping paper for cigarettes according to claim 1, wherein the volume of water used in the step a) is up to 10 ml; the heating mode is water bath heating, the temperature is 50-60 ℃, and the time is 25-40 min; the centrifugation is carried out while the mixture is hot, the rotating speed is 4000 rpm-6000 rpm, and the time is 3 min-7 min; the methanol is fixed to the volume of 1 ml; the filtration was performed using a 0.45 μm organic phase filter to a chromatography flask.

8. The method for simultaneously measuring extractable Cr (III) and Cr (VI) in tipping paper for cigarettes according to claim 1, wherein the chromatographic column of the HPLC in the step b) is ZORBAX SB-C18; 4.6mm × 150mm, 5 μm.

9. The method for simultaneously measuring extractable Cr (III) and Cr (VI) in tipping paper for cigarettes according to claim 1, wherein the conditions for separating and measuring by HPLC in the step b) are as follows: