Method for measuring parameters of volatile organic compounds adsorbed and released by skin

Abstract

The invention belongs to the field of human health exposure research, and particularly relates to an efficient method for measuring adsorption and release parameters of volatile organic compounds (VOCs) of skin or artificial skin. The method comprises the following steps: designing a skin loader for bearing experimental skin and keeping the experimental skin in a hydration state in an experimental process; a testing system suitable for skin VOCs adsorption and release is developed; establishing a physical model for describing a skin VOCs release process; the skin to be measured is placed in the constant-temperature environment chamber, sufficient VOCs gas is injected to enable the skin to be adsorbed to a balanced state, then pure air is introduced to promote the skin to release VOCs, and meanwhile the gas-phase VOCs concentration in the chamber is measured. And carrying out nonlinear fitting on the concentration data by combining particle swarm optimization and an ant colony algorithm, and calculating diffusion coefficients (Dm) and distribution coefficients (K) of different VOCs in the skin. The testing system is low in cost, easy and convenient to operate, high in calculation method precision, good in expansibility, suitable for testing of other materials and capable of being widely applied to laboratories and engineering application.

Description

Technical Field

[0001] The invention belongs to the technical field of human health exposure, and in particular relates to an efficient and high-precision method capable of measuring parameters characterizing the adsorption and release of volatile organic compounds on skin or artificial skin. Background Art

[0002] People spend more than 90% of their time indoors and in cars every day. Volatile organic compounds (VOCs) in these environments enter the human body through inhalation, ingestion and skin contact, affecting human health. The health effects of VOCs exposure include headaches, dizziness, worsening asthma, and irritation of the nose and eyes, which are collectively referred to as "sick building syndrome". Among them, VOCs such as benzene, toluene, ethylbenzene, xylene and formaldehyde, especially formaldehyde and benzene, are identified as Class A carcinogens and pose a major risk to public health. Studies have shown that skin exposure can account for 30-40% of total VOCs exposure, which is equivalent to the amount of inhalation. Ignoring skin contact will underestimate the health risk, but compared with the inhalation route, the calculation of skin exposure is more complicated and often overlooked. Accurate assessment of skin exposure risk depends on the establishment of physical models and the measurement of their key parameters. Some researchers have proposed a transient mass transfer model suitable for different exposure scenarios, but this model only has a semi-analytical solution, the pollutant concentrations in the gas phase and the skin are coupled, and numerical techniques are required to determine the absorption rate. In addition, key parameters in the semi-analytical model are difficult to obtain. The process of VOCs adsorption and release from the skin is characterized by two key parameters: the partition coefficient (K) and the diffusion coefficient (D m ). Previous studies have mostly estimated these parameters based on empirical formulas, which may lead to parameter measurement deviations, thereby affecting the accuracy of skin exposure risk assessment. In addition, existing studies have mostly used the method of applying liquid pollutants to the skin to calculate the absorption amount and rate, but these experimental results are only applicable to specific pollutant concentrations and exposure methods and cannot be generalized to other concentration levels or exposure forms. Especially for gaseous pollutants that people are most commonly exposed to in their daily lives, the applicability of such methods is limited. The current challenge is to obtain the physical parameters of skin transmission under exposure to gaseous pollutants, which is the main research goal of this invention. Summary of the invention

[0003] The purpose of the present invention is to face the current situation that there is a lack of effective methods for measuring the key parameters of the mass transfer process of the adsorption and release of gaseous pollutants by the skin. The present invention proposes an innovative method for quickly and accurately measuring the key parameters that characterize the adsorption and release of volatile organic compounds (VOCs) in skin or artificial skin; the experimental system design of this method is simple, the solution accuracy is high, and it can be widely used in laboratory research and engineering practice.

[0004] In order to achieve the above purpose, the present invention designs a skin carrier specially used for carrying the experimental skin to ensure that the skin always remains hydrated during the experiment. At the same time, based on the small environmental chamber experimental system, a method is proposed that can quickly and accurately measure the diffusion coefficient (D m ) and the partition coefficient (K); this method can measure these key parameters under different temperature conditions and can be used in physical models exposed to different gas-phase VOCs concentrations under real environmental conditions to help predict exposure risks, including the following steps:

[0005] 1) Use a graduated rubber-tipped dropper to take a certain amount of several VOCs solutions and place them in different brown bottles, ensuring that there is enough free space above the brown bottles. Then seal the brown bottles and use labels to mark the names of the solutions in the brown bottles.

[0006] 2) Use acetone or alcohol to clean the inner wall of the small-sized environmental chamber, and then use clean air to blow away the remaining pollutants in the chamber;

[0007] 3) Set the gas temperature in the environmental chamber to the required value with a temperature control accuracy of ±0.5°C;

[0008] 4) Pour physiological saline into the skin carrier until it is full, seal the water inlet, and then fix the skin or artificial skin on the skin carrier so that the lower surface of the skin or artificial skin is always in contact with the physiological saline, thereby maintaining a hydrated state during the entire experiment;

[0009] 5) placing the carrier filled with physiological saline and skin or artificial skin into the small-sized environmental chamber after the purging, and sealing the environmental chamber;

[0010] 6) Use a syringe to extract VOCs from the brown gas cylinder and then inject it into the sealed environmental chamber;

[0011] 7) Keep the environmental chamber closed to allow the skin in the chamber to fully absorb VOCs until the VOCs concentration in the skin phase and the air phase reaches equilibrium. Use a dinitrophenylhydrazone adsorption tube DNPH or a Tenax-TA adsorption tube connected to a high-precision sampling pump at the air outlet of the environmental chamber to collect gas-phase VOCs to determine the gas-phase equilibrium concentration C of VOCs. equ ; Or use online monitoring equipment to directly measure the VOCs concentration in the environmental chamber;

[0012] 8) After sampling, open the high-pressure gas cylinder and introduce pure air into the environmental chamber. At this time, the skin begins to release VOCs. Then, select appropriate time intervals to collect VOCs gas at the air outlet of the environmental chamber using DNPH or Tenax-TA. The experiment ends when the gas phase VOCs concentration is basically reduced to a stable level.

[0013] 9) Then use high performance liquid chromatography HPLC or gas chromatography-mass spectrometry GC-MS for quantitative analysis to obtain the hourly concentration C of each VOCs in the environmental chamber. a ;

[0014] 10) Establish a physical model of the process of VOCs release from the skin in the environmental chamber; after the gas-solid two-phase VOCs in the environmental chamber reach equilibrium, when pure air is introduced into the environmental chamber, the VOCs concentration in the chamber can be described as:

[0015]

[0016] In this model: C a is the gas phase VOCs concentration in the environmental chamber, μg / m 3 ; C equ is the equilibrium concentration of gas-phase VOCs in the environmental chamber, μg / m 3 ; t is the release time, s; D m is the diffusion coefficient of VOCs in skin or artificial skin, m 2 / s; K is the distribution coefficient of VOCs in skin or artificial skin; A is the surface area of ​​skin or artificial skin, m 2 ; L is the thickness of the skin or artificial skin, m; V is the volume of the environmental chamber, m 3 ; β = AL / V, which represents the ratio of the volume of skin or artificial skin to the volume of the environmental chamber; q n About D m and K function; h m is the convective mass transfer coefficient, m 2 / s;Bi m =h m L / D m , is the mass transfer Biot number;

[0017] 11) The hourly concentration C of each VOCs obtained from the experimental test a and equilibrium concentration C equ The data was combined with equation (1) and nonlinear fitting was performed using a particle swarm coupled ant colony algorithm to obtain the diffusion coefficient D of VOCs in the skin or artificial skin phase. m and the distribution coefficient K.

[0018] Features and effects of the present invention:

[0019] The present invention has significant advantages in the field of determining key parameters of VOCs mass transfer in skin or artificial skin, solves the bottleneck problem in the prior art, and provides an effective tool for studying and controlling the impact of gaseous pollutants on human health. The present invention designs a simple and practical skin carrier and cleverly combines it with a small-sized environmental chamber test system to enable experiments on skin adsorption or release of VOCs. Based on this test system, an efficient method for determining parameters that characterize skin VOCs adsorption and release is proposed, providing a reliable basis for related exposure health research. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 System diagram for determination of VOCs adsorption and release parameters for skin or artificial skin

[0021] Figure 2 is the nonlinear fitting result of xylene concentration DETAILED DESCRIPTION

[0022] The method proposed by the present invention can quickly and accurately simultaneously determine the key parameters characterizing the adsorption and release of volatile organic compounds (VOCs) by skin or artificial skin, which is described in detail in conjunction with the accompanying drawings and examples as follows:

[0023] The test system of the present invention for the VOCs adsorption and release process of skin or artificial skin in a small-sized stainless steel environmental chamber is as follows: Figure 1 As shown, the test system consists of four parts: an air intake system, a temperature and humidity control system, a sampling system and a skin carrier. The air intake system consists of a high-pressure gas cylinder 1 with a pressure reducing valve, a valve 2 and a mass flow controller 3; the temperature and humidity control system consists of a closed cabin 4 filled with pure water, a three-way valve 5, an empty closed cabin 6, a temperature and humidity monitor 7, and a constant temperature water bath 12, which are used to adjust and control the temperature and humidity of the air inside the environmental cabin 16; the skin carrier 15 is made of glass products, the upper half of which is a detachable square glass sheet for fixing the experimental skin 13, and the lower half is used to hold physiological saline 14, and a water inlet is designed for it, so that physiological saline can be injected again after the experimental skin is fixed. , to ensure that the lower surface of the skin is in contact with physiological saline so that the skin or artificial skin can continue to remain hydrated during the experiment; a dinitrophenylhydrazone adsorption tube (DNPH, for aldehydes and ketones) or a Tenax adsorption tube (Tenax-TA, for non-aldehydes and ketones) 11 is connected to the air outlet of the environmental chamber, and the gas-phase VOCs in the environmental chamber are collected under the action of a sampling pump 10, and the sampling flow is further monitored using a flow detector 9 to guide the adjustment of the sampling pump flow; the gas-phase VOCs concentration in the environmental chamber can also be measured using an online monitoring instrument 8.

[0024] The artificial skin xylene adsorption and release parameter determination method of this example comprises the following steps:

[0025] 1) Use a graduated rubber dropper to take 2 ml of xylene solution and place it in a brown bottle, leaving enough free space above the brown bottle, and then seal the brown bottle;

[0026] 2) Use alcohol to clean the inner wall of the 30L stainless steel environmental chamber, and then use clean air at a flow rate of 500ml / min to blow away the remaining pollutants in the chamber for about 4-5h;

[0027] 3) Set the gas temperature in the environmental chamber to 25°C, with a temperature control accuracy of ±0.5°C;

[0028] 4) Fill the skin carrier with physiological saline until it is full, seal the water inlet, and then fix the artificial skin with a surface area of ​​5 cm×5 cm on the top of the skin carrier so that the lower surface of the artificial skin is always in contact with the physiological saline, thereby maintaining the hydration level during the entire experiment;

[0029] 5) placing the carrier filled with physiological saline and artificial skin into the small-sized environmental chamber after the purge, and sealing the environmental chamber;

[0030] 6) Use a syringe to extract xylene gas from the brown gas cylinder and then inject it into the sealed environmental chamber, injecting a total of 3L;

[0031] 7) Continue to seal the environmental chamber to allow the skin in the chamber to fully absorb xylene. After about 10 hours, the xylene concentrations in the artificial skin phase and the air phase reach equilibrium. Then, use the Tenax-TA adsorption tube connected to a high-precision sampling pump at the air outlet of the environmental chamber to collect xylene to determine the equilibrium gas phase concentration of xylene, C equ , is 19864μg / m 3 ;

[0032] 8) Open the high-pressure gas cylinder and introduce pure air into the environmental chamber at a flow rate of 500 ml / min, and the artificial skin begins to release xylene; then use Tenax-TA to collect xylene gas at the air outlet of the environmental chamber every 0.5-1 hour, and end the experiment after 8 hours;

[0033] 9) Then use gas chromatography-mass spectrometry GC-MS for quantitative analysis to obtain the hourly concentration C of xylene in the environmental chamber. a ;

[0034] 10) Establish a physical model of the xylene release process in the artificial skin in the environmental chamber; after the gas-solid two-phase xylene in the environmental chamber reaches equilibrium, pure air is introduced into the environmental chamber, and the xylene concentration in the chamber can be described as:

[0035]

[0036] In this model: C ais the concentration of gaseous xylene in the environmental chamber, μg / m 3 ; C equ is the equilibrium concentration of gaseous xylene in the environmental chamber, μg / m 3 ; t is the release time, s; D m is the diffusion coefficient of xylene in skin or artificial skin, m 2 / s; K is the distribution coefficient of VOC in skin or artificial skin; A is the surface area of ​​artificial skin, m 2 ; L is the thickness of the skin or artificial skin, m; V is the volume of the environmental chamber, m 3 ; β = AL / V, which represents the ratio of the volume of skin or artificial skin to the volume of the environmental chamber; q n About D m and K function; h m is the convective mass transfer coefficient, m 2 / s;Bi m =h m L / D m , is the mass transfer Biot number;

[0037] 11) The hourly concentration C of each VOCs tested a and equilibrium concentration C equ The data was combined with equation (1) and nonlinear fitting was performed using particle swarm coupled ant colony algorithm to obtain the VO diffusion coefficient D m and the distribution coefficient K are 2.00×10-13m 2 / s, 1.58×10 5 The nonlinear fitting results are as follows: Figure 2 shown.

[0038] The principle of the present invention is as follows: the skin or artificial skin in a hydrated state first adsorbs VOCs in an environmental chamber until the gas-solid two-phase concentration is balanced, and then pure air is introduced into the environmental chamber to make the skin or artificial skin release the adsorbed VOCs. The hourly concentration and equilibrium concentration data of various VOCs in the environmental chamber at different times are obtained by sampling. All the experimentally measured concentration data are combined with a physical model, and a particle swarm coupled ant colony algorithm is used for nonlinear fitting, so that the diffusion coefficient D characterizing the adsorption and release of VOCs on the skin or artificial skin can be quickly and accurately obtained at the same time. m and the distribution coefficient K.

Claims

1. A method for measuring the parameters of volatile organic compounds adsorbed and released by skin, comprising the following steps: 1) Use a graduated rubber-tipped dropper to take a certain amount of several volatile organic compound (VOCs) solutions and place them in different brown bottles, ensuring that there is enough free space above the brown bottles. Then seal the brown bottles and use labels to mark the names of the solutions in the brown bottles. 2) Use acetone or alcohol to clean the inner wall of the small-sized environmental chamber, and then use clean air to blow away the remaining pollutants in the chamber; 3) Set the gas temperature in the environmental chamber to the required value with a temperature control accuracy of ±0.5°C; 4) Pour physiological saline into the skin carrier until it is full, seal the water inlet, and then fix the skin or artificial skin on the skin carrier so that the lower surface of the skin or artificial skin is always in contact with the physiological saline, thereby maintaining a hydrated state during the entire experiment; 5) placing the carrier filled with physiological saline and skin or artificial skin into the small-sized environmental chamber after the purging, and sealing the environmental chamber; 6) Use a syringe to extract VOCs from the brown gas cylinder and then inject it into the sealed environmental chamber; 7) Keep the environmental chamber closed to allow the skin in the chamber to fully absorb VOCs until the VOCs concentration in the skin phase and the air phase reaches equilibrium. Use a dinitrophenylhydrazone adsorption tube DNPH or a Tenax-TA adsorption tube connected to a high-precision sampling pump at the air outlet of the environmental chamber to collect gas-phase VOCs to determine the gas-phase equilibrium concentration C of VOCs. equ ; Or use online monitoring equipment to directly measure the VOCs concentration in the environmental chamber; 8) After sampling, open the high-pressure gas cylinder and introduce pure air into the environmental chamber. At this time, the skin begins to release VOCs. Then, select appropriate time intervals to collect VOCs gas at the air outlet of the environmental chamber using DNPH or Tenax-TA. The experiment ends when the gas phase VOCs concentration is basically reduced to a stable level. 9) Then use high performance liquid chromatography HPLC or gas chromatography-mass spectrometry GC-MS for quantitative analysis to obtain the hourly concentration C of each VOCs in the environmental chamber. a ; 10) Establish a physical model of the process of VOCs release from the skin in the environmental chamber; after the gas-solid two-phase VOCs in the environmental chamber reach equilibrium, when pure air is introduced into the environmental chamber, the VOCs concentration in the chamber can be described as: In this model: C a is the gas phase VOCs concentration in the environmental chamber, μg / m 3 ; C equ is the equilibrium concentration of gas-phase VOCs in the environmental chamber, μg / m 3 ; t is the release time, s; D m is the diffusion coefficient of VOCs in skin or artificial skin, m 2 / s; K is the distribution coefficient of VOCs in skin or artificial skin; A is the surface area of ​​skin or artificial skin, m 2 ; L is the thickness of the skin or artificial skin, m; V is the volume of the environmental chamber, m 3 ; β = AL / V, which represents the ratio of the volume of skin or artificial skin to the volume of the environmental chamber; q n About D m and K function; h m is the convective mass transfer coefficient, m 2 / s;Bi m =h m L / D m , is the mass transfer Biot number; 11) The hourly concentration C of each VOCs obtained from the experimental test a and equilibrium concentration C equ The data was combined with equation (1) and nonlinear fitting was performed using a particle swarm coupled ant colony algorithm to obtain the diffusion coefficient D of VOCs in the skin or artificial skin phase. m and the distribution coefficient K.

2. The skin carrier according to claim 1, characterized in that: It is made of glass products, and its upper part is a removable circular / square glass piece for fixing the experimental skin. The lower part is a hollow cavity for holding saline solution. The side of the cavity is a water inlet. After the experimental skin is fixed, saline solution can be injected again to ensure that the lower surface of the skin is in contact with saline solution so that the skin or artificial skin can continue to remain hydrated during the experiment.

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